Abstract:We used 95% ethanol to extract residual oils in perilla cake meal to reduce residues and contamination by toxic organic solvents, as well as to obtain low-fat, high-protein perilla cake meal. Univariate analysis was performed to determine the optimal extraction temperature, number of extractions, liquid-solid ratio, and extraction duration. The processing conditions optimized through orthogonal experimental design were as follows: extraction temperature, 75℃; 5 extractions; liquid-solid ratio, 3.5:1; and time, 3 h. Using this process, the extraction rate of residual oil from perilla cake meal was 96.04%, oil content of perilla cake meal was reduced to 0.51%, and protein enrichment rate was increased to 57.90%. The physical and chemical properties of perilla seed pressed oil, perilla cake meal ethanol extract, and petroleum ether extract were compared. The three oils met national standards with respect to acidity, peroxide content, iodine content, and saponification. Among them, the acidity and peroxide content of petroleum ether extract oil were relatively high, with maxima of 3.65 (KOH)/(mg/g) and 5.96 (mmol/kg), respectively, followed by those for ethanol extract oil and low-temperature pressed oil (3.30 (KOH)/(mg/g) and 5.22 (mmol/kg), respectively). There was no significant difference in the iodine content, and the degree of saponification of the extract oil was greater than that of the low-temperature pressed oil. Gas chromatography analysis showed that the relative content of linolenic acid and proportion of unsaturated fatty acids in total fatty acids in ethanol extract oil were 59.60% and 89.31%, respectively, which are slightly lower than those observed for low-temperature pressed oil (61.09% and 90.33%, respectively) and higher than those observed for petroleum ether extract oil (57.29% and 86.10%, respectively). Overall, the quality of ethanol extract oil is higher than that of petroleum ether extract oil and slightly lower than that of low temperature pressed oil.
