Fermented blend from sunflower seed press-cake and bovine sweet whey: Protein breakdown during in vitro gastrointestinal digestion

Sustainable food production implements circular economic system, valuing side streams and minimizing waste. This study was aimed to develop a new food by fermenting a blend of dehulled sunflower seed protein powder (SSPP) and reconstituted bovine sweet whey powder (RSWP). Blends were inoculated with <i>Lactococcus lactis</i> B12 alone or in association with <i>Saccharomyces cerevisiae</i> L12, and fermentation proceeded until reaching pH 4.8. After <i>in vitro</i> static gastrointestinal digestion, RSWP and SSPP proteins were highly proteolyzed and the soluble nitrogen content was 69-71% of total nitrogen. In digests, 42-75 unique peptides were identified, and most of them weighed 500-1000 Da. Free amino acids accounted for 202-228 mg/g protein in digests. Few bioactive peptides derived from RSWP were identified. These findings demonstrated strong degradability of RSWP and SSPP proteins during digestion and shed light on nutritional properties exploitable for food applications of the developed fermented blend.