Postscript on the degradation of spent grain
We’ve done just a quick web search for ‘degradation of spent grain’ and encountered this – an extract from a World Intellectual Property Organization site concerning the invention of a process to isolate a protein concentrate and a fibre concentrate from fermentation residue, in particular from fermentation residue that is obtained from an ethanol producing fermentation of a cereal selected from the group consisting of barley, corn, rice, wheat, rye, oat or combinations thereof. Here’s the relevant extract:
(WO/2005/029974) METHOD OF ISOLATING A PROTEIN CONCENTRATE AND A FIBRE CONCENTRATE FROM FERMENTATION RESIDUE
In conventional processes of making commercial beer, barley malt is mixed with water to form a mash. The enzymes present in the malt are then allowed to break down the barley protein. Next, adjuncts such as cooked corn or rice, are added to the mash, to provide additional starch. Subsequently, enzymatic conversion of the starch to sugar is permitted to take place. After the starch conversion is more or less complete, the aqueous extract or wort is separated by filtration from the spent solids, which are commonly known as” brewer’s spent grain”. The wort continues through the brewing process and eventually becomes beer.
Substantial quantities of brewer’s spent grain are produced in the commercial production of beer. Typically, for each hectolitre of beer about 15-20 kg of wet spent grain is produced. The breweries usually dispose of the spent grain by selling it for cattle feed.
The brewer’s spent grain contains all the solids that have been separated from the wort by filtration; it includes what is left of the barley malt and the adjuncts. The spent grain consists mainly of the pericarp and hull portions of the barley….. Although “spent” in terms of carbohydrate, brewer’s spent grain is higher in protein, lipids, and fibre than was the original barley-adjunct mixture.
The crude fibre content of brewer’s spent grain is approximately 150 g/kg dry matter, making it unsuitable as a feed for non-ruminant animals, e. g. pigs or chickens. Furthermore, spent grain as obtained from the brewery or distillery is a very bulky material due to the high water content (70-80% w/w), making handling and transport inefficient. The high water content also makes the spent grain material vulnerable to microbiological decay.
So, as well as being used as fodder or for making biscuits/bread the spent grain from the brewing process consists of a water heavy mush which is vulnerable to rapid (?) decay.