The improvement of aging time on adhesive performance of wheat starch paste for restoration of Chinese ancient books

The improvement of aging time on adhesive performance of wheat starch paste for restoration of Chinese ancient books | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The improvement of aging time on adhesive performance of wheat starch paste for restoration of Chinese ancient books Changwei Wang, Yuqi Yao, Yue Zhang, Xiao Yao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3855470/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In the restoration of Chinese ancient books, wheat starch paste is used as a paper adhesive, and its performance directly affects the quality of the restoration work. Allowing the starch slurry to stand for several days until it becomes slightly acidic can enhance the adhesive performance of the paste. However, the entire process relies on the manual experience of craftsmen. The study reproduces the process of making wheat starch paste for the restoration of traditional ancient books and investigates the effects of aging time on the apparent viscosity, rheological properties, and adhesive performance of the paste. The results indicate that the aging process has minimal impact on the apparent viscosity and rheological properties of starch paste. However, it significantly enhances adhesive performance, with optimal results observed after aging for approximately three days. This is attributed to the reduction in residual protein content in starch and a significant improvement in starch gelatinization capability. Infrared spectroscopy and XRD test results reveal that there are no significant changes in the molecular and crystalline structures of starch during the aging process. The acidic environment produced by starch fermentation promotes protein hydrolysis, emerging as the primary reason for the improved adhesive performance of the paste. Ancient books restoration Paper adhesive Wheat starch paste Adhesive property Protein hydrolysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction China is one of the world's oldest civilizations, and over the course of its long history, the invention and widespread use of paper played a revolutionary role in the realms of writing and information dissemination, significantly advancing the progress of civilization. The extensive collection of ancient books represents not only precious cultural heritage but also a vital medium for recording the history of material and spiritual civilizations(Ou 2017 ). However, due to various natural and societal factors, ancient books have suffered a degree of damage, and the responsibility for restoring these ancient books bears the crucial task of prolonging their longevity and safeguarding their invaluable contents. The principle of ancient book restoration work is "restore it as it was," meaning that when restoring ancient books, the goal is to preserve their original state as much as possible. Before and after restoration, efforts are made to maintain the original appearance. Wheat starch paste, as an adhesive used in the restoration of ancient books, plays a crucial role in bonding pages and supporting painting cores. It can be said that the quality of the restoration of ancient books depends on the appropriate use of starch paste. Therefore, there are strict performance requirements for the starch paste used in ancient book restoration. First and foremost, it must be reversible, meaning that pages repaired with starch paste can be unmounted without any negative effects. Industrial paper adhesives such as CMC (carboxymethyl cellulose) and PVA (polyvinyl alcohol) do not meet this requirement. Although they can be produced on a large scale with standardized equipment, they do not exhibit the reversible adhesive properties similar to starch paste. Secondly, the starch paste should have a clean and white texture, strong adhesive properties, adjustable thickness, and its adhesive properties should not diminish over time. It should be storable for an extended period without deterioration(Wang 2010 ). The reversibility of the items mounted using starch paste is related to the hydrogen bonding strength within their molecular structure. The polar hydroxyl groups in the chain-like starch molecules readily form hydrogen bonds with water molecules, making the starch paste highly hydrophilic, resulting in a "swelling" phenomenon, and the adhesive action between the starch paste and the bonded material is desorbed by water(Gong and Fan 2022 ).The desorption process of the starch paste adhesive structure by polar water molecules is illustrated in Fig. 1 . Due to the intrusion of water molecules, the distance between starch molecules in the adhesive structure increases from L to L + 2ΔL, disrupting the hydrogen bonds formed between the starch paste and the bonded material. This results in the creation of free hydroxyl groups that become new water molecule attraction points, leading to the infiltration of more water molecules. As a result, the hydrogen bonds within the adhesive structure gradually break, leading to a reduction in adhesive strength. Fan(2010) provides a detailed introduction to the preparation, storage, and usage of wheat starch paste, but does not explain the role and purpose of the aging process. The production of paste largely relies on the artisan's manual experience, without any relevant standards to refer to. The primary objective of this study was therefore to reproduce the production of wheat starch paste based on existing literature and practical experience, and systematically analyze the purposes and functions of each step in the process. This work aimed to promote the scientific and standardized production and use of wheat starch paste, thereby enhancing the quality of ancient book restoration. 2. Materials and methods 2.1. Materials Wheat flour, a commercial product with 11%wt gluten (Yihai Kerry Arawana Holdings Co., Ltd., China). Xuan paper, made of ∼80% fibers of sandalwood and ∼20% straw fibers (Jing County, Anhui province). Damask silk, made by Huzhou Yunhe Shuanglin Damask Silk Co., Ltd., China. 2.2. Sample preparation (1) Paste preparation The preparation of wheat starch paste was shown in Fig. 2 , which mainly included the following four steps: Step Ⅰ. Gluten removal The traditional extraction method was employed to extract wheat starch. Wheat flour and water were mixed in a 2:1 ratio to form a dough, which was then allowed to stand for 20 minutes. Water was added, and the dough was kneaded and washed repeatedly until no starch precipitated. Then, an 80-mesh filter was used to filter the starch slurry. The main purpose of removing gluten is to eliminate the insoluble proteins in flour, as the proteins can affect the gelatinization of starch and make the paste prone to deterioration. Step Ⅱ. Aging The cleaned starch slurry from step Ⅰ was placed in a constant temperature and humidity curing box at 20 ℃ and stood for aging. The starch naturally settled, while the upper liquid turned yellow with a slight acidic taste. The aging period ranged from 0 to 7 days, with 0d representing unaged starch. Separating the liquid phase from the solid phase, the precipitated solid was dried to obtain starch with different aging periods, while the supernatant was dried to obtain yellow colloidal substances containing different hydrolysis products of starch. The average moisture content of starch was about 11.8% Step Ⅲ. Paste preparation The starch obtained from step Ⅱ was mixed with water in a 1:4 ratio and heated in an 80 ℃ water bath. The slurry was continuously stirred until it thickened from a thin consistency to a semi-transparent one (cooked pulp), indicating the completion of starch gelatinization (Li 2011 ). Step Ⅳ. Paste application The cooked pulp would cool into a solid and needed to be diluted with water before use. A suitable amount of it was mixed with water in a 1:3 ratio to obtain a starch paste with moderate viscosity for ancient book restoration. (2) Gelatinization process of starch The preparation of starch paste essentially involves the process of starch gelatinization at high temperatures(Goesaert et al. 2005 ). As depicted in Fig. 3 , starch is insoluble in cold water, but as the temperature increases, the order of starch granule molecules is disrupted. This leads to a rapid increase in the viscosity of the starch suspension, and after stirring, it forms a semi-transparent, viscous colloidal substance. Starch granules (Ⅰ) are generally insoluble in cold water, forming only a suspension. When the starch suspension is heated, the starch granules undergo a process of water absorption and swelling in a wet and hot environment (Ⅱ). Once a certain temperature, known as the gelatinization temperature, is reached, the starch granules accelerate their expansion, and the outer layers of branched starch around the granules crack open (Ⅲ). This causes the volume to increase to several tens or even hundreds of times its original size, transforming the suspension into a semi-transparent, viscous colloidal substance. During cooling, linear starch molecules regenerate and form ordered or crystalline branched starch molecules (Ⅳ)(Han et al. 2019 ). (3) Xuan paper and damask silk samples To characterize the adhesion performance of the paste, the surfaces of paper and damask silk were coated for testing its tensile strength and peel strength. The surface of Xuan paper was evenly coated and naturally dried. A piece of damask silk was coated, then another piece of damask silk was covered and compacted to ensure a tight fit and natural drying at room temperature. 2.3. pH determination During the aging process of starch slurry, the increase in the acidity of the slurry is mainly caused by the substantial proliferation of microorganisms resulting from starch fermentation. A pH meter (model PHS-25, China) was used to measure the pH of the supernatant and the paste made from aged starch at 25℃. An acidic environment could accelerate cellulose degradation(Ahn et al. 2012 ), so the acidity of the adhesive may also promote the acidification of paper. The pH of the paper samples was measured using a cold extraction method according to ISO 6588–1(2021). 2.4. Tensile strength Tensile strength refers to the maximum tension that a paper sample can withstand per unit width before breaking. The paper samples were cut into test strips measuring 150 mm in length and 15 mm in width, with 10 strips each for horizontal and vertical directions testing according to ASTM D828(2022). The average maximum tensile strength and elongation were measured using a horizontal computerized tensile tester (model WZL-B, China) with a pulling rate of 20 mm/min. 2.5. Peel strength For artworks composed of non-rigid materials such as paper and damask silk, peel strength can be used to evaluate the adhesive bonding strength(Wu et al. 2014 ). The fiber strength in paper material is lower compared to the silk protein in silk material. During the peeling process, the paper sample often does not separate at the bonding interface, but rather the paper itself undergoes delamination and damage, making it difficult to analyze the peel strength of the paper sample. Therefore, damask silk is chosen as the base material to analyze the peel strength. The damask silk samples were cut into strips measuring 200 mm in length and 15mm in width for peeling tests by a horizontal computerized tensile tester (model WZL-B, China) according to ASTM D903(1998), with a stretching rate of 20 mm/min. 2.6. Apparent viscosity and rheological properties The apparent viscosity of the paste was directly measured using a digital viscometer (model NDJ-8S, China) at 25℃, while the rheological properties were obtained using a six-speed rotational viscometer (model ZNN-D6, China). Experimental data of the flow curve were fitted using the power-law model (Wang et al. 2018 ): $$\tau =K\bullet {r}^{n}$$ where τ is the shear stress (Pa), γ is the shear rate(s − 1 ), K is the consistency coefficient (Pa • s n ) and n is the flow behavior index. 2.7. Starch gelatinization ability Wheat flour contains about 11% protein, which significantly reduces the starch's gelatinization ability. In section 2.2 , the process of gluten removal can only remove the insoluble proteins in the flour, mainly including glutenin and gliadin. A portion of the water-soluble proteins, however, remains in the aged starch after drying. The determination of protein content uses the Kjeldahl method for nitrogen determination(Zhang et al. 2020 ). The swelling power and solubility of starch were determined according to the method described by Shang et al.(Shang et al. 2020 ) with modification. 2% (w/v) starch suspension (50 mL) was maintained at 80°C for 30 min, cooled, and then centrifuged at 3000 rpm for 20 min. The supernatant was placed in glass dishes and dried. The swelling power was evaluated as the wet sediment weight divided by initial dry matter weight excluding water-soluble starch. The solubility was expressed as the percentage of dried solid weight based on the weight of dry sample. 2.8. FT-IR spectroscopy The chemical characteristics of wheat flour, aged starch, and starch slurry supernatant were investigated using Fourier-transform infrared spectroscopy (FT-IR)(Koohkesh et al. 2020 ). All spectra were collected in the spectral range of 4000 − 400 cm − 1 using a Bruker Tensor-27 spectrometer (Germany) at room temperature, with an average of 16 scans and a spectral resolution of 4 cm − 1 . All spectra were baseline-corrected and normalized. 2.9. X-ray diffraction X-ray diffraction patterns of the starch with different aging periods were obtained using an X-ray diffractometer (Ragaku Ultima IV, Japan). The diffractometer was operated using Cu-Kα radiation (λ = 0.15406 nm) at 25 mA and 35 kV with the scanning speed of 5°/min from 5 to 40°, and step intervals was 0.02°. Relative crystallinity (%) was calculated as the percentage ratio of the diffraction peak area to the total diffraction area(Li et al. 2013 ). 3. Result and discussion 3.1. pH During the aging periods of starch slurry, starch fermentation leads to the proliferation of microorganisms, which produce organic acids. The organic acids cause the pH of the slurry to decrease continuously, as shown in Fig. 4 . At aging 0d, the pH of the paste is 6.41, close to neutral. But at days 2–3 of aging, the acidity noticeably increases. By aging 4d, the pH drops to 4.04, with a slight further decrease observed thereafter. Similarly, the pH of the starch also decreases with prolonged aging time. Before aging 3d, there is little change in pH, remaining close to neutral. However, after 3 days, the pH decreases from 6.58 to 5.42. An acidic environment will accelerate paper acidification, so adhesives used for paper should ideally be as close to neutral as possible(Borges et al. 2018 ). The pH of the reference paper is 8.10, indicating weak alkalinity. This is due to the addition of fillers such as calcium carbonate in the manufacturing process of Xuan paper(Zhang et al. 2023 ). The acidity of the paste can affect the pH of the paper sample. The paste before aging 3d has almost no impact on the pH of the paper sample, whereas paste after 3 days of aging will lower the pH of paper sample. Although the decrease of the pH is only 0.05 in numerical value, it has a certain negative impact on the long-term stability of the paper, making it unfavorable for prolonged preservation. This suggests that despite the increase in acidity during the aging process, the impact on the starch paste and paper is relatively minimal before aging 3d. 3.2. Apparent viscosity and rheological properties The starch paste used in the restoration of ancient books has quite high requirements for its apparent viscosity. If the paste is too thick, it is not easy to spread, and the adhered pages are prone to hollowing and deformation, causing secondary damage to the ancient books. On the other hand, if the paste is too thin, containing too much water, its adhesive properties will be poor, and the repaired pages may detach on their own after some time. The study discusses obtaining the moderate viscosity pastes by controlling the ratio of starch to water in the gelatinization and dilution steps, and testing its apparent viscosity at 25℃ as shown in Fig. 5(a). Overall, there is not a significant difference in apparent viscosity among them. The paste aged for 0 days has slightly higher apparent viscosity, while the apparent viscosity of pastes aged for 1–7 days fluctuates around 35 to 39 mPa•s. However, for polymer fluids like pastes, which typically exhibit some degree of pseudoplasticity, there may be fluctuations in measurements, so further rheological properties are measured. The steady flow behaviors of pastes were investigated, and the results are shown in Fig. 6(b) and Table 2. According to Fig. 6(b), the flow behavior profile of each sample is well fitted by the power-law model ( R 2 = 0.9988–0.9991). The consistency coefficient ( K ), flow behavior index ( n ), and coefficients of determination ( R 2 ) for each flow curve are presented in Table 1 . All pastes have a pseudoplastic flow behavior for n values < 1 (0.8534–0.8565), indicating a shear-thinning behavior, that is viscosity decreases with frequency or increasing shear rate. The n values remain almost unchanged, while the consistency coefficient K initially decreases, followed by a slight subsequent rise This indicates that the aging time has no significant impact on the apparent viscosity and rheological properties of the paste. Table 1 The Power-law parameters of starch pastes (25℃) Samples Formula K /Pa•s n n R 2 Aging 0d τ = 0.1137r 0.8534 0.1137 0.8534 0.9988 Aging 3d τ = 0.0895r 0.8565 0.0895 0.8565 0.9991 Aging 7d τ = 0.0972r 0.8552 0.0972 0.8552 0.9990 3.3. Tensile strength Coating pastes with different aging periods were applied on paper samples to compare the tensile strength, and the results are shown in Fig. 6. There are certain differences in the mechanical properties of the paper in the transverse and longitudinal directions. In the transverse direction, both tensile strength and elongation are higher than in the longitudinal direction, indicating that the flexibility of the paper is greater in the transverse direction. This is attributed to the unique papermaking process of Xuan paper, which determines the orientation of the paper fibers(Han et al. 2006 ). In the transverse direction, the fiber orientation is dominant, resulting in strength significantly greater than the bonding strength between fibers. The tensile strength of paper samples coated with starch paste is significantly higher than that of the reference. The paste infiltrates the pores of the paper, and as the moisture evaporates, the paste dries to form a film, thereby significantly improving the paper's tensile strength and elongation, greatly enhancing the flexibility of the paper. The tensile strength of the paper shows a trend of initially increasing and then stabilizing. Before aging 3d, the tensile strength of the paper gradually increases. At aging 3d, the paper exhibits the highest tensile strength. Compared to aging 0d, the transverse tensile strength increased by 79.6%, elongation increased by 61.0%, longitudinal tensile strength increased by 42.9%, and elongation increased by 25.3%. After aging 3d, there is little change in the tensile strength and elongation of the paper. 3.4. Peel strength The peel strength characterizes the adhesive strength of the adhesive. If the paste has strong adhesive strength, the bonding is less likely to loosen, which is beneficial for the long-term preservation of ancient books. As shown in Fig. 7 , peel strength shows an initial increase followed by stabilization, consistent with the trend observed in the tensile strength of the paper. Before aging 3d, peel strength gradually increases, reaching its maximum at aging 3d with a 23.9% improvement compared to aging 0d. 3.5. Starch gelatinization ability According to existing research reports, proteins tend to envelop the surface of starch granules, thereby inhibiting starch swelling(Baxter et al. 2014 ). Additionally, proteins can lead to the souring and spoilage of starch paste, making it susceptible to insect infestation. The results of protein content in starch determined by the Kjeldahl method are shown in Fig. 9(a). Removal of insoluble glutenin and gliadin proteins from wheat flour can reduce the protein content in starch from approximately 11–1.92%, leaving behind soluble proteins within the starch. During the aging process, there is a significant decrease in protein content, reaching around 1.5% after aging 3d, indicating a decrease of 21.9% compared to aging 0d. Swelling power and solubility reflect the gelatinization capability of starch. The stronger the gelatinization capability of starch, the more it expands and dissolves in water(Zhuang et al. 2024 ). The swelling power and solubility of starch at different aging periods are depicted in Fig. 8. The swelling power and solubility of starch gradually increase before aging 3d, reach their maximum at 3 days, and remain relatively constant after 3 days. As described in Section 3.1 , the adhesive strength of the paste is derived from the gelatinization of starch. The adhesive performance of the paste is positively correlated with its starch gelatinization capability and negatively correlated with protein content. The enhanced gelatinization capacity of aged starch may be associated with the hydrolysis of water-soluble proteins in an acidic environment. 3.6. FT-IR spectroscopy The FT-IR spectra of wheat flour, aged starch, and starch slurry supernatant are shown in Fig. 9. From the magnified view of Fig. 9(b), it can be observed that only wheat flour exhibits distinct absorption peaks around 1663 cm − 1 and 1604 cm − 1 , which are associated with the amide I band in the secondary structure of proteins(Unbehend et al. 2003 ). This indicates that gluten removal effectively eliminates insoluble proteins from wheat flour. As shown in Fig. 9(a),the infrared spectrum of flour and starch granules shows a characteristic broad stretching peak of hydroxyl groups near 3400 cm − 1 , and the small band at around 2926 cm − 1 is attributed to the C-H stretching of CH 2 groups(Zha et al. 2012 ). The absorption peak near 1656 cm − 1 corresponds to the amorphous region's absorption peak of water adsorbed by starch. The peak around 1435 cm − 1 is attributed to the CH 2 bending vibration, while the absorption peak near 1370 cm − 1 corresponds to the bending vibration of the CH 2 bond. The absorption peak around 1157 cm − 1 is assigned to the stretching vibration of C-O and C-C bonds, and the peak near 1017 cm − 1 is associated with the stretching vibration of the C-O bond and the bending vibration of C-OH. The absorption peak near 764 cm − 1 is attributed to the stretching vibration of the C-C bond, and the peak around 576 cm − 1 is assigned to the skeletal mode vibration of starch(Du et al. 2015 ). The infrared spectra of starch at different aging periods show almost no variation, indicating that the aging process has minimal impact on the functional groups of starch. On the other hand, the supernatant containing various hydrolysis products exhibits an infrared spectrum distinct from that of starch. There is a strong absorption peak around 3422 cm − 1 , which includes N-H (amide A band) and sugar hydroxyl stretching vibrations. The absorption peak near 2930 cm − 1 is associated with the C-N stretching vibration (amide B band), and the absorption peak near 1636 cm − 1 is attributed to the stretching vibration of C = O stretching vibration (amide I band). The peak around 1422 cm − 1 is assigned to both the C = O stretching vibration and the N-H bending vibration (amide III band), and the absorption peak near 1057 cm − 1 is associated with the stretching vibration of the C-O bond(Chen et al. 2017 ).This indicates that the supernatant not only contains glucose or polysaccharides as hydrolysis products of starch but also includes amino acids or peptides from the hydrolysis of proteins. 3.7. X-ray diffraction The X-ray diffraction patterns and relative crystallinity of starch at different aging periods are presented in Fig. 10 . All starch granules show strong diffraction peaks at 15°, 17°, 18° and 23°, and there are two connected double peaks at 17° and 18°, indicated that starches are all typical A-type crystal structure, as reported by previous researchers(Zhang et al. 2016 ). In addition, a minor diffraction peak appeared at 20°, which is the characteristic of amylose-lipid complex. The relative crystallinity of starch is slightly reduced, and the decrease in crystal order can enhance the gelatinization ability of starch to a certain extent. However, overall, the aging time does not have a significant impact on the X-ray diffraction pattern of starch. It implies that the crystalline structure of starch remains nearly unchanged during the aging periods. 4. Conclusion It is concluded from the results found in this study that the optimal aging time for starch paste production is around 3 days at 20°C, exhibits optimal tensile strength and peel strength. At this point, the acidity of the paste is relatively low, resulting in minimal impact on the pH value of the paper. Additionally, the apparent viscosity is moderate, facilitating to mount. These characteristics align perfectly with the requirements for use in the restoration of ancient books. Removing gluten can eliminate most of the proteins in wheat flour, primarily comprising gliadin and glutenin proteins, yet there remains 1.92% of water-soluble protein residues. During the aging process, starch hydrolysis triggers substantial microbial proliferation, gradually increasing the acidity of the slurry. This has minimal impact on the apparent viscosity and rheological properties of the starch paste but significantly enhances its tensile and peel strengths. The adhesive strength of the paste derives from starch gelatinization, where its bonding performance correlates positively with the starch gelatinization capacity and negatively with the protein content. Analysis based on infrared spectroscopy and XRD reveals that there are almost no significant changes in the molecular and crystalline structures of starch granules. However, it was found in the supernatant that, in addition to the starch hydrolysis products such as glucose or polysaccharides, there were also protein hydrolysis products such as amino acids or peptides. This indicates that the hydrolysis of residual proteins under acidic conditions is the fundamental reason for the significant improvement in the adhesive performance of the starch paste. Declarations Acknowledgements The authors are grateful to the support of this work by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). Funding This work was supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). Author contributions CW : Conceptualization, Methodology, Data curation, Writing - review & editing. YY : Investigation, Formal analysis, Writing - original draft. YZ : Investigation, Resources, Data curation. XY : Conceptualization, Resources, Supervision. 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Journal of Cultural Heritage 64:42-48. https://doi.org/10.1016/j.culher.2023.08.012 Zhang K, Zhao D, Zhang X, Qu L, Zhang Y, Huang Q (2020) Effects of the Removal of Lipids and Surface Proteins on the Physicochemical and Structural Properties of Green Wheat Starches. Starch - Stärke 73(1-2). https://doi.org/10.1002/star.202000046 Zhang Y, Guo Q, Feng N, Wang J-r, Wang S-j, He Z-h (2016) Characterization of A- and B-type starch granules in Chinese wheat cultivars. Journal of Integrative Agriculture 15(10):2203-2214. https://doi.org/10.1016/s2095-3119(15)61305-3 Zhuang Y, Wang Y, Yang H (2024, Feb 15) Effects of cation valence on swelling power, solubility, pasting, gel strength characteristics of potato starch. Food Chem 434:137510. https://doi.org/10.1016/j.foodchem.2023.137510 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3855470","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":267469031,"identity":"1a1550db-c055-4ea3-87aa-e009aedaa64d","order_by":0,"name":"Changwei Wang","email":"","orcid":"","institution":"Nanjing Tech University","correspondingAuthor":false,"prefix":"","firstName":"Changwei","middleName":"","lastName":"Wang","suffix":""},{"id":267469032,"identity":"eaa56f96-cf0e-41cc-954d-7a85828fae23","order_by":1,"name":"Yuqi Yao","email":"","orcid":"","institution":"Nanjing Tech University Library","correspondingAuthor":false,"prefix":"","firstName":"Yuqi","middleName":"","lastName":"Yao","suffix":""},{"id":267469033,"identity":"f1222532-8b9c-4a94-a7ef-4cd50b2be1b0","order_by":2,"name":"Yue Zhang","email":"","orcid":"","institution":"Mochou Vocational School","correspondingAuthor":false,"prefix":"","firstName":"Yue","middleName":"","lastName":"Zhang","suffix":""},{"id":267469034,"identity":"fa64919a-8431-47eb-91df-9d2cf26eb250","order_by":3,"name":"Xiao Yao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYLCCBAYGOQaGAwwMjA0MYJooLcYMDIdJ0QIEiQ0MzERqMTh++JjEgxqb9O2M5w8++LmDQY7vRgLj5wJ8Ws6kJRskHEvL3dlwmNmw9wyDseSNBGbpGfi0HMgxfJDAdjh3w4HDbNKMbQyJG24ksDHz4NNy/o3BgYR/h9MNDhxm/w3UUk9Yyw2gLYlthxOAWtiYgVoSDAhpkbzxLNkgsS/NEOgwY8neNgnDmWceNkvj08J3PvmY5I9vNvIGNw4+/PCzzUae73jywc/4tCgcgLEkwCwJBmjs4AbycGl+/ApHwSgYBaNgBAMA0vFVOcOeRjkAAAAASUVORK5CYII=","orcid":"","institution":"Nanjing Tech University","correspondingAuthor":true,"prefix":"","firstName":"Xiao","middleName":"","lastName":"Yao","suffix":""}],"badges":[],"createdAt":"2024-01-12 03:14:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3855470/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3855470/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49791370,"identity":"c00dceba-ca4f-473c-80af-8fa9837cd7f1","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":168003,"visible":true,"origin":"","legend":"\u003cp\u003eThe desorption process of water molecules in paste adhesive structure.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/2c26a8de183809abde3169d4.png"},{"id":49792065,"identity":"158b76dd-fcf0-43c2-9649-c59af54a487b","added_by":"auto","created_at":"2024-01-18 05:49:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":870713,"visible":true,"origin":"","legend":"\u003cp\u003eWheat starch paste preparation process\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/02173a7ff04b2a0f05fa8e9a.png"},{"id":49792068,"identity":"90721beb-4e0e-427c-bd52-757de3097f0d","added_by":"auto","created_at":"2024-01-18 05:49:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":179284,"visible":true,"origin":"","legend":"\u003cp\u003eHigh temperature gelatinization process of starch\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/eb5aa2a2c6dba37ec1f8a55d.png"},{"id":49791367,"identity":"4e215ef3-615c-4f3b-8958-421c091f408b","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":74456,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of aging time on the pH of starch slurry, paste and paper sample (25℃)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/84de46d26c972634a2487c77.png"},{"id":49791369,"identity":"3eb923aa-d250-4279-acb2-68e7727396c6","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":110988,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of aging time on apparent viscosity and rheological properties (25℃)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/6a46c7a5dbc6281ff339e773.png"},{"id":49792066,"identity":"d81ad3e3-20f7-4675-b17f-f6e461dd07fa","added_by":"auto","created_at":"2024-01-18 05:49:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":302448,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of aging time on tensile strength\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/b8e4d549b8f691874de33014.png"},{"id":49791376,"identity":"073b8148-190e-4fb1-92e2-2751a86feda9","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":45349,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of aging time on peel strength\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/bb3f6eee6addabd75f56e72b.png"},{"id":49791373,"identity":"6c878ae6-3f9d-4d86-acc7-e69bd572b6b8","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":100686,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of aging time on protein content and starch gelatinization ability\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/f0c389695d986d89aeb95248.png"},{"id":49792270,"identity":"86bf5e6f-fa84-4f8a-bb3d-1b8cf0846a70","added_by":"auto","created_at":"2024-01-18 05:57:41","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":172426,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra of wheat flour, aged starch and supernatant\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/3ac737d2244f16c8a31c809b.png"},{"id":49791374,"identity":"4efcb1b0-3266-4f21-b514-25ccf571a742","added_by":"auto","created_at":"2024-01-18 05:41:41","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":109364,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray diffraction patterns of aged starch\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/6df438c45db72e88329b5aa7.png"},{"id":53314819,"identity":"a98af2eb-195b-4244-a345-6e7295b53c5b","added_by":"auto","created_at":"2024-03-23 17:22:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2261811,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3855470/v1/68d6d4f1-359e-4976-a60b-d69ef3ac88de.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The improvement of aging time on adhesive performance of wheat starch paste for restoration of Chinese ancient books","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eChina is one of the world's oldest civilizations, and over the course of its long history, the invention and widespread use of paper played a revolutionary role in the realms of writing and information dissemination, significantly advancing the progress of civilization. The extensive collection of ancient books represents not only precious cultural heritage but also a vital medium for recording the history of material and spiritual civilizations(Ou \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). However, due to various natural and societal factors, ancient books have suffered a degree of damage, and the responsibility for restoring these ancient books bears the crucial task of prolonging their longevity and safeguarding their invaluable contents.\u003c/p\u003e \u003cp\u003eThe principle of ancient book restoration work is \"restore it as it was,\" meaning that when restoring ancient books, the goal is to preserve their original state as much as possible. Before and after restoration, efforts are made to maintain the original appearance. Wheat starch paste, as an adhesive used in the restoration of ancient books, plays a crucial role in bonding pages and supporting painting cores. It can be said that the quality of the restoration of ancient books depends on the appropriate use of starch paste. Therefore, there are strict performance requirements for the starch paste used in ancient book restoration.\u003c/p\u003e \u003cp\u003eFirst and foremost, it must be reversible, meaning that pages repaired with starch paste can be unmounted without any negative effects. Industrial paper adhesives such as CMC (carboxymethyl cellulose) and PVA (polyvinyl alcohol) do not meet this requirement. Although they can be produced on a large scale with standardized equipment, they do not exhibit the reversible adhesive properties similar to starch paste. Secondly, the starch paste should have a clean and white texture, strong adhesive properties, adjustable thickness, and its adhesive properties should not diminish over time. It should be storable for an extended period without deterioration(Wang \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe reversibility of the items mounted using starch paste is related to the hydrogen bonding strength within their molecular structure. The polar hydroxyl groups in the chain-like starch molecules readily form hydrogen bonds with water molecules, making the starch paste highly hydrophilic, resulting in a \"swelling\" phenomenon, and the adhesive action between the starch paste and the bonded material is desorbed by water(Gong and Fan \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).The desorption process of the starch paste adhesive structure by polar water molecules is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Due to the intrusion of water molecules, the distance between starch molecules in the adhesive structure increases from L to L\u0026thinsp;+\u0026thinsp;2ΔL, disrupting the hydrogen bonds formed between the starch paste and the bonded material. This results in the creation of free hydroxyl groups that become new water molecule attraction points, leading to the infiltration of more water molecules. As a result, the hydrogen bonds within the adhesive structure gradually break, leading to a reduction in adhesive strength.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFan(2010) provides a detailed introduction to the preparation, storage, and usage of wheat starch paste, but does not explain the role and purpose of the aging process. The production of paste largely relies on the artisan's manual experience, without any relevant standards to refer to. The primary objective of this study was therefore to reproduce the production of wheat starch paste based on existing literature and practical experience, and systematically analyze the purposes and functions of each step in the process. This work aimed to promote the scientific and standardized production and use of wheat starch paste, thereby enhancing the quality of ancient book restoration.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eWheat flour, a commercial product with 11%wt gluten (Yihai Kerry Arawana Holdings Co., Ltd., China). Xuan paper, made of \u0026sim;80% fibers of sandalwood and \u0026sim;20% straw fibers (Jing County, Anhui province). Damask silk, made by Huzhou Yunhe Shuanglin Damask Silk Co., Ltd., China.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Sample preparation\u003c/h2\u003e \u003cp\u003e(1) Paste preparation\u003c/p\u003e \u003cp\u003eThe preparation of wheat starch paste was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, which mainly included the following four steps:\u003c/p\u003e \u003cp\u003eStep Ⅰ. Gluten removal\u003c/p\u003e \u003cp\u003eThe traditional extraction method was employed to extract wheat starch. Wheat flour and water were mixed in a 2:1 ratio to form a dough, which was then allowed to stand for 20 minutes. Water was added, and the dough was kneaded and washed repeatedly until no starch precipitated. Then, an 80-mesh filter was used to filter the starch slurry. The main purpose of removing gluten is to eliminate the insoluble proteins in flour, as the proteins can affect the gelatinization of starch and make the paste prone to deterioration.\u003c/p\u003e \u003cp\u003eStep Ⅱ. Aging\u003c/p\u003e \u003cp\u003eThe cleaned starch slurry from step Ⅰ was placed in a constant temperature and humidity curing box at 20 ℃ and stood for aging. The starch naturally settled, while the upper liquid turned yellow with a slight acidic taste. The aging period ranged from 0 to 7 days, with 0d representing unaged starch. Separating the liquid phase from the solid phase, the precipitated solid was dried to obtain starch with different aging periods, while the supernatant was dried to obtain yellow colloidal substances containing different hydrolysis products of starch. The average moisture content of starch was about 11.8%\u003c/p\u003e \u003cp\u003eStep Ⅲ. Paste preparation\u003c/p\u003e \u003cp\u003eThe starch obtained from step Ⅱ was mixed with water in a 1:4 ratio and heated in an 80 ℃ water bath. The slurry was continuously stirred until it thickened from a thin consistency to a semi-transparent one (cooked pulp), indicating the completion of starch gelatinization (Li \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eStep Ⅳ. Paste application\u003c/p\u003e \u003cp\u003eThe cooked pulp would cool into a solid and needed to be diluted with water before use. A suitable amount of it was mixed with water in a 1:3 ratio to obtain a starch paste with moderate viscosity for ancient book restoration.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(2) Gelatinization process of starch\u003c/p\u003e \u003cp\u003eThe preparation of starch paste essentially involves the process of starch gelatinization at high temperatures(Goesaert et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, starch is insoluble in cold water, but as the temperature increases, the order of starch granule molecules is disrupted. This leads to a rapid increase in the viscosity of the starch suspension, and after stirring, it forms a semi-transparent, viscous colloidal substance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eStarch granules (Ⅰ) are generally insoluble in cold water, forming only a suspension. When the starch suspension is heated, the starch granules undergo a process of water absorption and swelling in a wet and hot environment (Ⅱ). Once a certain temperature, known as the gelatinization temperature, is reached, the starch granules accelerate their expansion, and the outer layers of branched starch around the granules crack open (Ⅲ). This causes the volume to increase to several tens or even hundreds of times its original size, transforming the suspension into a semi-transparent, viscous colloidal substance. During cooling, linear starch molecules regenerate and form ordered or crystalline branched starch molecules (Ⅳ)(Han et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e(3) Xuan paper and damask silk samples\u003c/p\u003e \u003cp\u003eTo characterize the adhesion performance of the paste, the surfaces of paper and damask silk were coated for testing its tensile strength and peel strength. The surface of Xuan paper was evenly coated and naturally dried. A piece of damask silk was coated, then another piece of damask silk was covered and compacted to ensure a tight fit and natural drying at room temperature.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. pH determination\u003c/h2\u003e \u003cp\u003eDuring the aging process of starch slurry, the increase in the acidity of the slurry is mainly caused by the substantial proliferation of microorganisms resulting from starch fermentation. A pH meter (model PHS-25, China) was used to measure the pH of the supernatant and the paste made from aged starch at 25℃. An acidic environment could accelerate cellulose degradation(Ahn et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), so the acidity of the adhesive may also promote the acidification of paper. The pH of the paper samples was measured using a cold extraction method according to ISO 6588\u0026ndash;1(2021).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Tensile strength\u003c/h2\u003e \u003cp\u003eTensile strength refers to the maximum tension that a paper sample can withstand per unit width before breaking. The paper samples were cut into test strips measuring 150 mm in length and 15 mm in width, with 10 strips each for horizontal and vertical directions testing according to ASTM D828(2022). The average maximum tensile strength and elongation were measured using a horizontal computerized tensile tester (model WZL-B, China) with a pulling rate of 20 mm/min.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Peel strength\u003c/h2\u003e \u003cp\u003eFor artworks composed of non-rigid materials such as paper and damask silk, peel strength can be used to evaluate the adhesive bonding strength(Wu et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The fiber strength in paper material is lower compared to the silk protein in silk material. During the peeling process, the paper sample often does not separate at the bonding interface, but rather the paper itself undergoes delamination and damage, making it difficult to analyze the peel strength of the paper sample. Therefore, damask silk is chosen as the base material to analyze the peel strength. The damask silk samples were cut into strips measuring 200 mm in length and 15mm in width for peeling tests by a horizontal computerized tensile tester (model WZL-B, China) according to ASTM D903(1998), with a stretching rate of 20 mm/min.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Apparent viscosity and rheological properties\u003c/h2\u003e \u003cp\u003eThe apparent viscosity of the paste was directly measured using a digital viscometer (model NDJ-8S, China) at 25℃, while the rheological properties were obtained using a six-speed rotational viscometer (model ZNN-D6, China). Experimental data of the flow curve were fitted using the power-law model (Wang et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\tau =K\\bullet {r}^{n}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere τ is the shear stress (Pa), γ is the shear rate(s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), \u003cem\u003eK\u003c/em\u003e is the consistency coefficient (Pa \u0026bull; s\u003csup\u003en\u003c/sup\u003e) and \u003cem\u003en\u003c/em\u003e is the flow behavior index.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7. Starch gelatinization ability\u003c/h2\u003e \u003cp\u003eWheat flour contains about 11% protein, which significantly reduces the starch's gelatinization ability. In section \u003cspan refid=\"Sec4\" class=\"InternalRef\"\u003e2.2\u003c/span\u003e, the process of gluten removal can only remove the insoluble proteins in the flour, mainly including glutenin and gliadin. A portion of the water-soluble proteins, however, remains in the aged starch after drying. The determination of protein content uses the Kjeldahl method for nitrogen determination(Zhang et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe swelling power and solubility of starch were determined according to the method described by Shang et al.(Shang et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) with modification. 2% (w/v) starch suspension (50 mL) was maintained at 80\u0026deg;C for 30 min, cooled, and then centrifuged at 3000 rpm for 20 min. The supernatant was placed in glass dishes and dried. The swelling power was evaluated as the wet sediment weight divided by initial dry matter weight excluding water-soluble starch. The solubility was expressed as the percentage of dried solid weight based on the weight of dry sample.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8. FT-IR spectroscopy\u003c/h2\u003e \u003cp\u003eThe chemical characteristics of wheat flour, aged starch, and starch slurry supernatant were investigated using Fourier-transform infrared spectroscopy (FT-IR)(Koohkesh et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). All spectra were collected in the spectral range of 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e using a Bruker Tensor-27 spectrometer (Germany) at room temperature, with an average of 16 scans and a spectral resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. All spectra were baseline-corrected and normalized.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9. X-ray diffraction\u003c/h2\u003e \u003cp\u003eX-ray diffraction patterns of the starch with different aging periods were obtained using an X-ray diffractometer (Ragaku Ultima IV, Japan). The diffractometer was operated using Cu-Kα radiation (λ\u0026thinsp;=\u0026thinsp;0.15406 nm) at 25 mA and 35 kV with the scanning speed of 5\u0026deg;/min from 5 to 40\u0026deg;, and step intervals was 0.02\u0026deg;. Relative crystallinity (%) was calculated as the percentage ratio of the diffraction peak area to the total diffraction area(Li et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Result and discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. pH\u003c/h2\u003e\n \u003cp\u003eDuring the aging periods of starch slurry, starch fermentation leads to the proliferation of microorganisms, which produce organic acids. The organic acids cause the pH of the slurry to decrease continuously, as shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. At aging 0d, the pH of the paste is 6.41, close to neutral. But at days 2\u0026ndash;3 of aging, the acidity noticeably increases. By aging 4d, the pH drops to 4.04, with a slight further decrease observed thereafter. Similarly, the pH of the starch also decreases with prolonged aging time. Before aging 3d, there is little change in pH, remaining close to neutral. However, after 3 days, the pH decreases from 6.58 to 5.42.\u003c/p\u003e\n \u003cp\u003eAn acidic environment will accelerate paper acidification, so adhesives used for paper should ideally be as close to neutral as possible(Borges et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). The pH of the reference paper is 8.10, indicating weak alkalinity. This is due to the addition of fillers such as calcium carbonate in the manufacturing process of Xuan paper(Zhang et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The acidity of the paste can affect the pH of the paper sample. The paste before aging 3d has almost no impact on the pH of the paper sample, whereas paste after 3 days of aging will lower the pH of paper sample. Although the decrease of the pH is only 0.05 in numerical value, it has a certain negative impact on the long-term stability of the paper, making it unfavorable for prolonged preservation. This suggests that despite the increase in acidity during the aging process, the impact on the starch paste and paper is relatively minimal before aging 3d.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Apparent viscosity and rheological properties\u003c/h2\u003e\n \u003cp\u003eThe starch paste used in the restoration of ancient books has quite high requirements for its apparent viscosity. If the paste is too thick, it is not easy to spread, and the adhered pages are prone to hollowing and deformation, causing secondary damage to the ancient books. On the other hand, if the paste is too thin, containing too much water, its adhesive properties will be poor, and the repaired pages may detach on their own after some time.\u003c/p\u003e\n \u003cp\u003eThe study discusses obtaining the moderate viscosity pastes by controlling the ratio of starch to water in the gelatinization and dilution steps, and testing its apparent viscosity at 25℃ as shown in Fig.\u0026nbsp;5(a). Overall, there is not a significant difference in apparent viscosity among them. The paste aged for 0 days has slightly higher apparent viscosity, while the apparent viscosity of pastes aged for 1\u0026ndash;7 days fluctuates around 35 to 39 mPa\u0026bull;s. However, for polymer fluids like pastes, which typically exhibit some degree of pseudoplasticity, there may be fluctuations in measurements, so further rheological properties are measured.\u003c/p\u003e\n \u003cp\u003eThe steady flow behaviors of pastes were investigated, and the results are shown in Fig. 6(b) and Table 2. According to Fig. 6(b), the flow behavior profile of each sample is well fitted by the power-law model (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.9988\u0026ndash;0.9991). The consistency coefficient (\u003cem\u003eK\u003c/em\u003e), flow behavior index (\u003cem\u003en\u003c/em\u003e), and coefficients of determination (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e) for each flow curve are presented in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. All pastes have a pseudoplastic flow behavior for \u003cem\u003en\u003c/em\u003e values\u0026thinsp;\u0026lt;\u0026thinsp;1 (0.8534\u0026ndash;0.8565), indicating a shear-thinning behavior, that is viscosity decreases with frequency or increasing shear rate. The \u003cem\u003en\u003c/em\u003e values remain almost unchanged, while the consistency coefficient \u003cem\u003eK\u003c/em\u003e initially decreases, followed by a slight subsequent rise This indicates that the aging time has no significant impact on the apparent viscosity and rheological properties of the paste.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThe Power-law parameters of starch pastes (25℃)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSamples\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFormula\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e/Pa\u0026bull;s\u003csup\u003en\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAging 0d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026tau;\u0026thinsp;=\u0026thinsp;0.1137r\u003csup\u003e0.8534\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1137\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8534\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9988\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAging 3d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026tau;\u0026thinsp;=\u0026thinsp;0.0895r\u003csup\u003e0.8565\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0895\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8565\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9991\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAging 7d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026tau;\u0026thinsp;=\u0026thinsp;0.0972r\u003csup\u003e0.8552\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0972\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8552\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9990\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Tensile strength\u003c/h2\u003e\n \u003cp\u003eCoating pastes with different aging periods were applied on paper samples to compare the tensile strength, and the results are shown in Fig. 6. There are certain differences in the mechanical properties of the paper in the transverse and longitudinal directions. In the transverse direction, both tensile strength and elongation are higher than in the longitudinal direction, indicating that the flexibility of the paper is greater in the transverse direction. This is attributed to the unique papermaking process of Xuan paper, which determines the orientation of the paper fibers(Han et al. \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e). In the transverse direction, the fiber orientation is dominant, resulting in strength significantly greater than the bonding strength between fibers.\u003c/p\u003e\n \u003cp\u003eThe tensile strength of paper samples coated with starch paste is significantly higher than that of the reference. The paste infiltrates the pores of the paper, and as the moisture evaporates, the paste dries to form a film, thereby significantly improving the paper\u0026apos;s tensile strength and elongation, greatly enhancing the flexibility of the paper. The tensile strength of the paper shows a trend of initially increasing and then stabilizing. Before aging 3d, the tensile strength of the paper gradually increases. At aging 3d, the paper exhibits the highest tensile strength. Compared to aging 0d, the transverse tensile strength increased by 79.6%, elongation increased by 61.0%, longitudinal tensile strength increased by 42.9%, and elongation increased by 25.3%. After aging 3d, there is little change in the tensile strength and elongation of the paper.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4. Peel strength\u003c/h2\u003e\n \u003cp\u003eThe peel strength characterizes the adhesive strength of the adhesive. If the paste has strong adhesive strength, the bonding is less likely to loosen, which is beneficial for the long-term preservation of ancient books. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e, peel strength shows an initial increase followed by stabilization, consistent with the trend observed in the tensile strength of the paper. Before aging 3d, peel strength gradually increases, reaching its maximum at aging 3d with a 23.9% improvement compared to aging 0d.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5. Starch gelatinization ability\u003c/h2\u003e\n \u003cp\u003eAccording to existing research reports, proteins tend to envelop the surface of starch granules, thereby inhibiting starch swelling(Baxter et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). Additionally, proteins can lead to the souring and spoilage of starch paste, making it susceptible to insect infestation. The results of protein content in starch determined by the Kjeldahl method are shown in Fig.\u0026nbsp;9(a). Removal of insoluble glutenin and gliadin proteins from wheat flour can reduce the protein content in starch from approximately 11\u0026ndash;1.92%, leaving behind soluble proteins within the starch. During the aging process, there is a significant decrease in protein content, reaching around 1.5% after aging 3d, indicating a decrease of 21.9% compared to aging 0d.\u003c/p\u003e\n \u003cp\u003eSwelling power and solubility reflect the gelatinization capability of starch. The stronger the gelatinization capability of starch, the more it expands and dissolves in water(Zhuang et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e). The swelling power and solubility of starch at different aging periods are depicted in Fig. 8. The swelling power and solubility of starch gradually increase before aging 3d, reach their maximum at 3 days, and remain relatively constant after 3 days. As described in Section \u003cspan class=\"InternalRef\"\u003e3.1\u003c/span\u003e, the adhesive strength of the paste is derived from the gelatinization of starch. The adhesive performance of the paste is positively correlated with its starch gelatinization capability and negatively correlated with protein content. The enhanced gelatinization capacity of aged starch may be associated with the hydrolysis of water-soluble proteins in an acidic environment.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6. FT-IR spectroscopy\u003c/h2\u003e\n \u003cp\u003eThe FT-IR spectra of wheat flour, aged starch, and starch slurry supernatant are shown in Fig.\u0026nbsp;9. From the magnified view of Fig.\u0026nbsp;9(b), it can be observed that only wheat flour exhibits distinct absorption peaks around 1663 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1604 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which are associated with the amide I band in the secondary structure of proteins(Unbehend et al. \u003cspan class=\"CitationRef\"\u003e2003\u003c/span\u003e). This indicates that gluten removal effectively eliminates insoluble proteins from wheat flour.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;9(a),the infrared spectrum of flour and starch granules shows a characteristic broad stretching peak of hydroxyl groups near 3400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the small band at around 2926 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the C-H stretching of CH\u003csub\u003e2\u003c/sub\u003e groups(Zha et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). The absorption peak near 1656 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the amorphous region\u0026apos;s absorption peak of water adsorbed by starch. The peak around 1435 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the CH\u003csub\u003e2\u003c/sub\u003e bending vibration, while the absorption peak near 1370 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the bending vibration of the CH\u003csub\u003e2\u003c/sub\u003e bond. The absorption peak around 1157 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to the stretching vibration of C-O and C-C bonds, and the peak near 1017 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with the stretching vibration of the C-O bond and the bending vibration of C-OH. The absorption peak near 764 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the stretching vibration of the C-C bond, and the peak around 576 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to the skeletal mode vibration of starch(Du et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). The infrared spectra of starch at different aging periods show almost no variation, indicating that the aging process has minimal impact on the functional groups of starch.\u003c/p\u003e\n \u003cp\u003eOn the other hand, the supernatant containing various hydrolysis products exhibits an infrared spectrum distinct from that of starch. There is a strong absorption peak around 3422 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which includes N-H (amide A band) and sugar hydroxyl stretching vibrations. The absorption peak near 2930 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with the C-N stretching vibration (amide B band), and the absorption peak near 1636 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the stretching vibration of C\u0026thinsp;=\u0026thinsp;O stretching vibration (amide I band). The peak around 1422 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to both the C\u0026thinsp;=\u0026thinsp;O stretching vibration and the N-H bending vibration (amide III band), and the absorption peak near 1057 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with the stretching vibration of the C-O bond(Chen et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e).This indicates that the supernatant not only contains glucose or polysaccharides as hydrolysis products of starch but also includes amino acids or peptides from the hydrolysis of proteins.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7. X-ray diffraction\u003c/h2\u003e\n \u003cp\u003eThe X-ray diffraction patterns and relative crystallinity of starch at different aging periods are presented in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e. All starch granules show strong diffraction peaks at 15\u0026deg;, 17\u0026deg;, 18\u0026deg; and 23\u0026deg;, and there are two connected double peaks at 17\u0026deg; and 18\u0026deg;, indicated that starches are all typical A-type crystal structure, as reported by previous researchers(Zhang et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e). In addition, a minor diffraction peak appeared at 20\u0026deg;, which is the characteristic of amylose-lipid complex.\u003c/p\u003e\n \u003cp\u003eThe relative crystallinity of starch is slightly reduced, and the decrease in crystal order can enhance the gelatinization ability of starch to a certain extent. However, overall, the aging time does not have a significant impact on the X-ray diffraction pattern of starch. It implies that the crystalline structure of starch remains nearly unchanged during the aging periods.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIt is concluded from the results found in this study that the optimal aging time for starch paste production is around 3 days at 20\u0026deg;C, exhibits optimal tensile strength and peel strength. At this point, the acidity of the paste is relatively low, resulting in minimal impact on the pH value of the paper. Additionally, the apparent viscosity is moderate, facilitating to mount. These characteristics align perfectly with the requirements for use in the restoration of ancient books.\u003c/p\u003e \u003cp\u003eRemoving gluten can eliminate most of the proteins in wheat flour, primarily comprising gliadin and glutenin proteins, yet there remains 1.92% of water-soluble protein residues. During the aging process, starch hydrolysis triggers substantial microbial proliferation, gradually increasing the acidity of the slurry. This has minimal impact on the apparent viscosity and rheological properties of the starch paste but significantly enhances its tensile and peel strengths. The adhesive strength of the paste derives from starch gelatinization, where its bonding performance correlates positively with the starch gelatinization capacity and negatively with the protein content.\u003c/p\u003e \u003cp\u003eAnalysis based on infrared spectroscopy and XRD reveals that there are almost no significant changes in the molecular and crystalline structures of starch granules. However, it was found in the supernatant that, in addition to the starch hydrolysis products such as glucose or polysaccharides, there were also protein hydrolysis products such as amino acids or peptides. This indicates that the hydrolysis of residual proteins under acidic conditions is the fundamental reason for the significant improvement in the adhesive performance of the starch paste.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are grateful to the support of this work by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCW\u003c/strong\u003e: Conceptualization, Methodology, Data curation, Writing - review \u0026amp; editing. \u003cstrong\u003eYY\u003c/strong\u003e: Investigation, Formal analysis, Writing - original draft. \u003cstrong\u003eYZ\u003c/strong\u003e: Investigation, Resources, Data curation. \u003cstrong\u003eXY\u003c/strong\u003e: Conceptualization, Resources, Supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eAll data and materials were included in the manuscript and provided upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAhn K, Hennniges U, Banik G, Potthast A (2012) Is cellulose degradation due to \u0026beta;-elimination processes a threat in mass deacidification of library books? Cellulose 19(4):1149-1159. https://doi.org/10.1007/s10570-012-9723-3\u003c/li\u003e\n \u003cli\u003eASTM D828 (2022) Standard Test Method for Tensile Properies of Paper and Paperboard Using Constant-Rate-of-Elogation Apparatus. ASTM International.\u003c/li\u003e\n \u003cli\u003eASTM D903 (1998) Standard Test Method for Peel or Stripping Strength of Adhesive Bonds. ASTM International.\u003c/li\u003e\n \u003cli\u003eBaxter G, Blanchard C, Zhao J (2014) Effects of glutelin and globulin on the physicochemical properties of rice starch and flour. Journal of Cereal Science 60(2):414-420. https://doi.org/10.1016/j.jcs.2014.05.002\u003c/li\u003e\n \u003cli\u003eBorges I d S, Casimiro M H, Macedo M F, Sequeira S O (2018) Adhesives used in paper conservation: Chemical stability and fungal bioreceptivity. 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Food Chem 434:137510. https://doi.org/10.1016/j.foodchem.2023.137510\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ancient books restoration, Paper adhesive, Wheat starch paste, Adhesive property, Protein hydrolysis","lastPublishedDoi":"10.21203/rs.3.rs-3855470/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3855470/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn the restoration of Chinese ancient books, wheat starch paste is used as a paper adhesive, and its performance directly affects the quality of the restoration work. Allowing the starch slurry to stand for several days until it becomes slightly acidic can enhance the adhesive performance of the paste. However, the entire process relies on the manual experience of craftsmen. The study reproduces the process of making wheat starch paste for the restoration of traditional ancient books and investigates the effects of aging time on the apparent viscosity, rheological properties, and adhesive performance of the paste. The results indicate that the aging process has minimal impact on the apparent viscosity and rheological properties of starch paste. However, it significantly enhances adhesive performance, with optimal results observed after aging for approximately three days. This is attributed to the reduction in residual protein content in starch and a significant improvement in starch gelatinization capability. Infrared spectroscopy and XRD test results reveal that there are no significant changes in the molecular and crystalline structures of starch during the aging process. The acidic environment produced by starch fermentation promotes protein hydrolysis, emerging as the primary reason for the improved adhesive performance of the paste.\u003c/p\u003e","manuscriptTitle":"The improvement of aging time on adhesive performance of wheat starch paste for restoration of Chinese ancient books","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-18 05:41:36","doi":"10.21203/rs.3.rs-3855470/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a75ab515-4ca3-486b-8338-c4bc1aa664f2","owner":[],"postedDate":"January 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-23T17:14:34+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-18 05:41:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3855470","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3855470","identity":"rs-3855470","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}