Effect of microwave treatment on the alkaline extraction of proteins and phenolics from perilla seed meal in varying pH conditions: An optimization study using multicomponent analysis

Perilla seed meal (PSM) is a by-product rich in proteins and bioactive compounds obtained by cold pressed oil extraction method. Microwave is an efficient nonconventional technology usually used to accelerate the recovery of the extracts. In this study, pH, microwave power and treatment time were optimized to maximize the recovery of targeted compounds using Box–Behnken design. The pH was found to be the most significant variable affecting the yield followed by microwave power and treatment time (based on F-value). Compared to conventional alkaline extraction, an increase in the yield of protein content by 10.58%, antioxidant activity by 7.48% and total phenolic content by 21.59% was recorded at the optimal values of pH (11.5) microwave power (160 W) and treatment time (30 s). Moreover, principle component analysis revealed opposite correlation between antioxidant activity and extraction of protein/phenolics suggesting the loss of bioactivity at the higher yield of extracts. Also, from the clustering analysis, the effect of microwave treatment found to be lower in more extreme alkaline conditions compared to lower pH values. Hence, lower alkaline conditions are suggested for the microwave treatment to develop better control system in the extraction industry.