Microwave pretreatment to improve extraction efficiency and polyphenol extract richness from grape pomace. Effect on antioxidant bioactivity

Abstract

Microwave assisted extraction advantages are widely recognised. However, its implementa-tion at industrial scale is restricted due to microwave limitations. In this work, a microwavepretreatment is proposed as an easy scale-up alternative for grape pomace polyphenolextraction, especially for anthocyanins. The double effect of this pretreatment on extractionyield and on product richness is assessed. Microwaves accelerate the extraction kineticsof most compounds, but their effect on polyphenols is more pronounced than in othersubstances (like sugars and fibres). These differentiated rates are exploited to improve thepolyphenol richness of the final dry product. By selecting the appropriate operating condi-tions, polyphenol yield was increased by 57% and, simultaneously, dry product richness wasenhanced by 32%. Also, anthocyanin extraction boost was remarkable. Its content in the finaldry product was 85% higher than the one obtained without the microwave pretreatment.The cellular bioactivity of these extracts was improved by 83% and 133%.