Impact of spontaneous fermentation and heat treatment on the physicochemical, functional and antioxidant properties of BSG

Brewers spent grain (BSG) is the main by-product in brewing, but due to its rapid decomposition it can become hazardous to the environment. It is a lignocellulosic by-product with a recalcitrant structure which must be modified to enhance its functionality; therefore, the objective of this study was to evaluate the impact of spontaneous fermentation and heat treatment on the physicochemical, functional, and antioxidant properties of BSG. Four treatments were evaluated: BSG without spontaneous fermentation and drying at 40 ºC (BSG_WEF40), BSG with spontaneous fermentation and drying at 40 ºC (BSG_EF40), BSG without spontaneous fermentation and heat treatment at 95 ºC (BSG_WEF95) and BSG with spontaneous fermentation and heat treatment at 95 ºC (BSG_EF95). The results demonstrated that spontaneous fermentation and heat treatment at 95 ºC had a significant impact (p ≤ 0.05) on the proximal chemical composition of the samples, with an increase in ethereal extract and a decrease in total carbohydrate content, as well as an improvement in water holding capacity, oil, and water solubility index. BSG_WEF95 and BSG_EF95 had the highest proportion of soluble to insoluble fiber, as well as the highest concentration of melanoidins and total polyphenols, which resulted in higher antioxidant activity against DPPH• and ABTS^•₊ radicals (p ≤ 0.05). The browning index decreased, while the lightness increased, thereby improving the color of the BSG variants. Therefore, this combination of applied treatments improves the techno-functional properties of BSG and broadens the diversity of food products in which it can be incorporated.