Sourdough: a tool for non-conventional fermentations and to recover side streams

The world population growth trend and the necessity to provide a nutritionally balanced diet and to reduce greenhouse gas emissions require relevant production increases of vegetables, as well as the transition to a diet higher in plant rather than animal proteins (Banovic et al. Appetite 125:233–243, 2018; Hayes et al. Child Obes 14(1):11–17, 2018). Aiming at either addressing environmental concerns and meeting nutritional deficiencies and recommendations, staple foods fortification has been recently identified as an effective and promising intervention (Mannar and Hurrell. Food fortification in a globalized world. 1st ed. Academic Press, Cambridge, 2018). To date, several studies investigated the nutritional value of additional ingredients to be used as wheat-substituting in cereal-based products. Legumes and pseudo-cereals, side-streams of the cereal industry including bran, germ, and brewer’s spent grain, are excellent sources of proteins with high biological value or dietary fibers, and supply relevant levels of vitamins, minerals, oligosaccharides, and phenolic compounds. Nevertheless, the high content of fibers, the absence of gluten, and the peculiar sensory characteristics may impair their high nutritional values worsening the technological and organoleptic profiles of the products. Moreover, the presence of anti-nutritional factors (ANF) further limited the use of such ingredients by the food industry. Different biotechnological options, such as air fractionation, roasting, soaking, germination, and fermentation were already proposed to decrease the ANF level, and to improve technological properties and sensory profile of non-wheat flours and cereal side-streams. Among these options, sourdough fermentation, often driven by the use of selected lactic acid bacteria (LAB) has largely been recognized as a suitable tool to improve the overall quality of these alternative matrices. Fermented ingredients can thus be used for staple food fortification, exploiting more of their potential.