Brewing By-Products as a Source of Natural Antioxidants for Food Preservation

Brewer's spent grain (BSG) and brewer's spent hops (BSH) are the major solid by-products of the brewing industry. The present work evaluated their potential as an alternative source of natural antioxidants. The efficacy of different solvents (MilliQ water, 0.75% NaOH, 50% MeOH, 50% MeOH + 0.3% HCl and 50% Acetone) for extracting polyphenols of these by-products was firstly evaluated, with NaOH showing the best results. The extraction conditions were optimized using the response surface methodology, and were determined to be 1.45% NaOH and 80 & DEG;C. BSG extracts showed the highest total polyphenol content (24.84-38.83 mu mol GAE/g), whereas the BSH showed the lowest value (24.84 & PLUSMN; 1.55 mu mol GAE/g). In general, BSG extracts presented significantly higher antioxidant capacity (ABTS, ORAC). Ferulic acid was the main polyphenol in all BSG extracts (156.55-290.88 mg/100 g), whereas in BSH, this compound was not detected. The addition of 10% BSG extract in o/w emulsions (stored 14 days) showed a reduction in the formation of primary oxidation products of 97%. In the emulsions covered with polylactic acid active films (1% BSG), this reduction corresponded to 35%. Hence, this study demonstrates the potential of these by-products as natural antioxidant sources for protecting food systems against oxidation.

Automated summary

This study evaluated the potential of brewer's spent grain and brewer's spent hops as natural antioxidant sources, with brewer's spent grain extracts showing higher total polyphenol content and antioxidant capacity. The main polyphenol in brewer's spent grain extracts was ferulic acid, which was not detected in brewer's spent hops extracts. Additionally, the addition of brewer's spent grain extracts in emulsions resulted in a significant reduction in the formation of oxidation products.