Influence of sea buckthorn pomace pre-treatment and drying conditions on the drying kinetics, quantity and quality of seed oil

摘要

Sea buckthorn (Hippophae rhamnoides L.) pomace was pre-treated by sonication or freezing and a thin layer of pre-treated or untreated pomace was dried under various conditions. The seeds separated from dried pomace were ground and subjected to batch extraction using hexane as a solvent. Effects of process factors, i.e. drying temperature (40℃ and 50℃), pomace layer thickness (3 mm and 10 mm), ultrasound amplitude (0% and 20%) and pre-treatment temperature (-20℃ and 20℃), on the drying kinetics, quantity and quality of seed oil were evaluated. Performance of air drying and oil extraction were correlated with the process factors by multiple regression equations, which highlighted a significant effect of pomace layer thickness. A thicker layer led to higher levels of effective diffusivity ((0.141-1.484)× 10~(-9) m~2-s~(-1)), oil yield (13.1-14.5%) and extraction efficiency (90.5-93.5%) as well as to lower values of mean drying rate (0.144-0.354 kg·kg~(-1)·h~(-1)). Mean mass percentages of fatty acids found in the oils extracted from the seeds separated from the pomace dried at 50℃, i.e. 26.8% α-linolenic, 38.9% linoleic, 22.7% oleic, 0.9% palmitoleic, 7.9% palmitic and 2.8% stearic acid, were almost invariant with the process factors.