Microwave-Vacuum Extraction Technique as a Green and Clean Label Technology: Kinetics, Efficiency Analysis, and Effect on Bioactive Compounds

Grape pomace is a rich source of bioactive compounds and dietary fiber. This study aims to valorize the grape pomace by microwave-vacuum-assisted drying and extraction, which is a novel, green, and clean label technology. The drying and extraction of bioactive compounds from the grape pomace was optimized using response surface methodology. Box-Behnken design was used for three process variables, i.e., time, power, and vacuum levels. The highest drying rate was observed (5.53 g/100 g min after 10 min of drying) at the combination of 80 W and 20 inHg. This combination significantly reduced the drying time (25%) and resulted in the highest yield (64.5%) of bioactive compounds. Equally, changes in moisture ratio behavior were rapid under these processing conditions. Furthermore, Midilli model (R-2 = 0.999, RMSE = 0.002, SSE = 3.71 x 10(-6)) was the best to justify the fitness of experimental values with predicted values. In addition, the diffusion coefficient, activation energy, and extraction yield were increased with increase in power and pressure. The concentration of bioactive components was higher in dried pomace compared to the extract. The extraction was successfully achieved without the use of solvent and the characteristics of extracted phenolics remained unaltered. Based on these findings, the microwave-vacuum-assisted drying and extraction process can be claimed as a sustainable approach.

Automated summary

This study aimed to valorize grape pomace through microwave-vacuum-assisted drying and extraction, optimizing the process variables using response surface methodology and Box-Behnken design. The combination of 80 W and 20 inHg resulted in the highest drying rate, reduced drying time by 25%, and yielded the highest concentration of bioactive compounds. The Midilli model proved to be the best fit for the experimental values. The microwave-vacuum-assisted process showed increased diffusion coefficient, activation energy, and extraction yield with higher power and pressure, and the dried pomace exhibited higher concentration of bioactive components compared to the extract, preserving the characteristics of the phenolics.