A spent grain analysis provides more accurate insight into brewhouse operations than the conventional calculation involving wort volume and extract content of the cast-out wort. The total extract (remaining extract) in spent grain consists of soluble extract and available residual extract. The soluble extract is that which can be washed out of the spent grain and is usually determined from the liquor squeezed or pressed from spent grain. The total extract is determined by boiling the spent grain and then performing an enzymatic digestion. The difference between the total extract and the soluble extract represents the available residual extract captured in the spent grain. These results indicate whether a low brewhouse yield is due to a less than optimal grist composition, an ineffective mashing procedure or incorrect lautering practices.
Determination of the moisture content in the spent grain
Spent grain
The moisture content is determined by means of the loss in mass during a standardized drying process. For this purpose, the spent grain is dried at a defined temperature over a set time in an electrically heated air drying oven. The moisture content is determined by the difference in weight before and after drying.
If the barley possesses a moisture content of more than 17 % w/w, the whole kernels shold be dried prior to grinding them and determining the moisture content in the (coarsely ground) spent grain. The moisture content of the finely ground spent grain is subsequently determined and the total moisture content calculated from both values.