Preparation of commercial products from brewer's waste grain and trub.
Processes are being developed for converting spent grains and trub into human food. Initially the spent grains were fractionated on a Kason vibrating screen separator into 3 fractions: a coarse fraction containing mainly husk, a finer fraction which passed through 10 mesh but not 40 mesh screens, and a water suspended fraction which passed through both screens but quickly settled on standing. The second and third fractions, containing 27 and 49% protein respectively, were processed further by drying and grinding to form a flour which was tested for use in baking bread, cakes and biscuits with successful results in a number of cases. The flour was a light tan colour and therefore could only be used in darker coloured products. High levels of addition caused undesirable changes in flavour and physical properties of the products. Whirlpool trub was pressed and then extracted with isopropyl alcohol to remove hop bitter substances which were then recovered. The solids remaining after extraction were dried to give a protein rich product which was also incorporated into bakery products. But these products had a very bitter flavour, were very dark coloured and emitted undesirable volatiles during baking. The hop bitter substances recovered from the trub were successfully used to bitter a home brewed ale.
Keywords: brewery by product food protein separation trub waste