Use of onion extract to prevent enzymatic browning of frozen Agaricus bisporus mushrooms

The present work evaluated the use of aqueous extract of onion to inhibit enzymatic browning of Agaricus bisporus mushrooms during 8-month frozen storage at -25 degrees C. The material frozen consisted of mushrooms previously vacuum soaked in solutions containing sodium metabisulphite, citric acid and L-ascorbic acid and aqueous extract of onion. Mushroom colour was assessed using the CIELAB colour system and sensory profiling; sensory quality was evaluated using a 5-point scale. In addition, determinations were made of certain indicators of chemical composition, antioxidant activity and the activity of total polyphenol oxidase, monophenolase, diphenolase, peroxidase and catalase. Onion extract inhibited enzymatic browning of mushrooms more effectively than the solution containing organic acids, but less effectively than that containing sodium metabisulphite. Applying onion extract resulted in reduced polyphenol oxidase activity, the reductions being greater in monophenolase than in diphenolase. Mushrooms soaked in onion extract had better flavour and aroma than the other products examined. (C) 2015 Elsevier Ltd and IIR. All rights reserved.