Impacts of Pasteurisation Temperature, Preservatives, Storage Duration and Soursop Puree Substitution for Sugar on Physicochemical, Antioxidant and Microbial Properties of Set-Type Yoghurt

Abstract This study aimed to evaluate the impacts of pasteurization temperature (80°C, 90°C and 100°C), soursop puree substitution for sugar (0%, 25%, and 50%), storage duration (7, 14 and 28 days) and preservatives (potassium sorbate, sodium benzoate and no preservative) on the physicochemical, antioxidant and microbial properties of set-type yoghurt. The water holding capacity and syneresis of the yoghurt varied as the soursop puree to sugar ratio increased. Replacement of sugar with 50% soursop puree increased ash, protein, carbohydrate, vitamin C, total phenolic content and DPPH of the yoghurt to 0.69%, 4.02%, 29.26%, 58.50%, 1.25 mg GAE/l and 34.40%, respectively and no coliform was detected. Lactic acid bacteria counts decreased as the storage duration increased while sodium benzoate inhibits mould and yeast counts more than the potassium sorbate. The soursop puree substitution with up to 50% of sugar could be used to produce yoghurt with potential health benefits and increased shelf life.