A systematic micro-dissection of brewers’ spent grain

Brewers’ spent grain (BSG), one of the co-products of the brewing industry, has been mainly used as cattle feed. Spent grain was shown to contain a number of potentially high-value components such as feruloylated arabinoxylan and protein, as confirmed by microscopy and chemical analysis. A significant quantity of starch was also identified, a polysaccharide generally considered to be removed through the malting and mashing steps of brewing. As part of a study to increase the exploitation of spent grain, five separate fractions were prepared through combined milling and vibratory sieving and characterised in terms of chemical composition (polysaccharide composition and linkage; phenolic composition) and by fluorescence microscopy. Material retained on sieve mesh plates of 500, 250 and 150 μm consisted mainly of arabinoxylan-rich palea and lemma, while material passing through 106 and 55 μm sieves was fine, crumb-like material enriched in protein and starch. Lignin was present in all fractions, and originated from the fragmented palea and lemma. The results are discussed in relation to the potential for whole BSG exploitation.