Processing of brewing by-products to give food ingredient streams

Very large amounts of brewer's spent grains (BSG) are produced in the world which is usually considered as a waste, or animal feed, rather than food for humans. Here, we report, for the first time, a new process at pilot scale for the separation of brewer's spent grain and trub to solid and liquid streams that can be used in foods. A new type of continuous rotary drum press was used to process hot BSG to produce a liquid filtrate and a filter cake stream. Analysis showed that of the starting mass of BSG (ca. 120kg), the liquid filtrate composed 50% of the mass, and the filter cake fraction composed 50% of the mass. The dry weight (DW) content of the BSG increased from 23 to over 35%. This led to concentration of insoluble dietary fibre (from 38 to 54%) and phenolics in the filter cake (from 102 to 150mg/100g DW as gallic acid equivalents). No fractionation of soluble species such as proteins occurred. Centrifugation of the filtrate from the rotary drum press led to a clarified supernatant stream and a paste. Concentration of insoluble dietary fibre and phenolics occurred in the paste (from 5 to 14% of DW and 61 to 114mg/100g DW as gallic acid equivalents), whereas soluble fibre and protein did not selectively partition. Given that the unit operations used here are scaleable and approved for food production, an industrially feasible route now exists to process brewers spent grains to ingredients.