Valorisation Process Using Lactic Acid Bacteria Fermentation Induces Significant Changes in the Physical and Functional Properties of Brewers Spent Yeast

Brewer's spent yeast (BSY) is a plentiful by-product of the brewing process. Currently regarded as a waste product, this low-value material is used in animal feed formulations or disposed of. However, BSY is known to be nutritionally dense, particularly regarding high-quality proteins, fibre, vitamins, and minerals. Previous work has examined the effect of a process including fermentation with Lactobacillus amylovorus FST 2.11 on BSY and indicates a reduction in bitterness intensity and an increase in sour and fruity flavours. The current study expands on this previous work, examining the changes in composition and functionality resulting from this upcycling process. The major changes include protein degradation and a decrease in pH, leading to increased protein solubility by 41%, increased foam stability by up to 69% at pH 7, and improved emulsion stabilising characteristics as well as differences in rheological behaviour during heating. Compositional changes are also detailed, with evidence of glucan and trehalose degradation. These changes in the physical and functional properties of BSY provide useful information, particularly with regard to the incorporation of BSY into food products for human consumption.