Sustainable food processing: single and interactive effects of type and quantity of brewers' spent grain and of type of sweetener on physicochemical and sensory characteristics of functional biscuits

Barley brewers' spent grain (BSG), the main by-product of the brewing industry, can be conveniently used as supplement in nourishing and stable foods such as bakery products. This study was aimed to investigate the effects of three factors - namely amount (40 or 50%) and type of brewers spent grain (malt + durum or malt + common wheat), and type of sweetener (honey or brown sugar) - on the quality attributes of the biscuits, with particular attention to the functional aspects and sensory characteristics. The cereal mixtures (60% barley malt and 40% common or durum wheat) used in brewing and the corresponding BSG were analysed, too. BSG differed from the starting cereal mixtures for the lower concentration of gallic acid and the higher contents of vanillic acid, caffeic acid, ferulic acid, epigallocatechin gallate, quercetin, rutin, resveratrol, and kaempferol of the first. Biscuits fortified with 40% of BSG showed the highest total phenolic contents, received the highest overall quality scores if sweetened with brown sugar and, if formulated with RI, received significantly higher scores for flavour intensity, sweetness, crunchiness, and friability and significantly lower bitterness and fibrousness than those produced with DA.