High-intensity ultrasound treatment for prolongation of wheat bran oxidative stability

Abstract

Wheat bran has a short shelf life, which could be prolonged by reducing the activity of enzymes in lipid degradation. In this study, high-intensity ultrasound treatment (400 W, 80% amplitude, 15 min), with or without cooling, was investigated for reducing the activity of lipase and peroxidase of wheat bran. Lipid stability parameters (free fatty acid content, peroxide value, anisidine value) of bran with coarse and reduced particle size (median 50th percentile diameter 503 and 177 μm, respectively) were followed under ambient or refrigerated storage conditions. Ultrasonic treatment without accompanying cooling inactivated 63% of lipase and 90% of peroxidase, but also decreased the antioxidant activity of bran by 13%. Compared with the untreated bran, the ultrasound-treated bran was darker, redder, and yellower. When ambiently stored, the critical anisidine value (10) of the unprocessed bran was exceeded after only 2 months, whereas the ultrasound-treated bran had an acceptable anisidine value for almost 12 months. Cooling during ultrasonication limits the ability to inactivate enzymes, and the reduction in bran particle size promotes its oxidative deterioration. The application of high-intensity ultrasound without cooling is beneficial for prolonging the oxidative stability of wheat bran compared to refrigerated storage.