Effect of Hot-Air Oven and Vacuum Pretreatment Methods on Oil Recovery Efficiency and Energy Usage on Flax and Hemp Oilseeds under Linear Pressing Process

Bulk flax and hemp oilseeds were evaluated under oven and vacuum heating temperatures con-cerning the percentage oil yield and energy demand under linear compression approach. The heating temperatures ranged from 40 oC to 90 oC at a constant drying time of 60 min. The oven pretreatment increased the oil yield of bulk flax oilseeds by 1.02% compared to the vacuum method. This increment resulted in a higher energy requirement of 23.06 J. The oil yield of bulk hemp oilseeds increased by 0.49 % resulting in a higher energy usage of 65.03 J. It was found that bulk hemp oilseeds produced a higher percentage oil yield of 23.86 ± 0.11% with a higher energy demand of 1641.66 ± 35.66 J than bulk flax oilseeds producing an oil yield of 17.52 ± 0.29 % and energy need of 1014.84 ± 52.26 J under both drying conditions. The established regression models for predicting the percentage oil yield and energy demand of the examined oilseeds dependent on heating temperature under both drying conditions were significant based on the P-value of the lack of fit which was greater than 0.05 indicating the reliability of the established regression models.