Evaluation of the antioxidant and antimicrobial activity of extracts obtained from four agro-industrial residues after different pretreatments

Agro-industrial wastes are not of interest to the industry that generated them; however, they can be used for the extraction of high value-added compounds. Compounds with antimicrobial and antioxidant activity can be recovered from residues generated by different industries. Jalisco is a large agri-food producer therefore resides generated by established or growing industries in the state were selected. However, the extraction of the compounds of interest from residues cannot be carried out directly, they must be subjected to different treatments that break the matrices to release the components of interest and increase the extraction yield. In this study, aqueous, enzymatic, chemical-enzymatic and ethanolic extractions were used to evaluate the antioxidant and antimicrobial capacity of the extracts. As residues, agave bagasse and brewers spent grain were evaluated, as well as blackberry and raspberry, both showing the first stages of spoilage. For the evaluation of antioxidant capacity ABTS and DPPH techniques were used. The antimicrobial capacity was evaluated by observing the inhibition halo caused by the extracts, and the inhibition percentage using different concentrations of the extracts, with three Gram-positive bacteria, three Gram-negative bacteria and three yeasts. The techniques used for the recovery of compounds with antioxidant and antimicrobial activity were adequate, and it was possible to observe differences between pretreatments for the different residues. It should be mentioned that inhibition was observed in the growth of Gram-positive and Gram-negative bacteria using low concentrations (10% of extracts).