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 total extract in the spent grain using the diastase method
Wet spent grain, dry spent grain
The total extract is obtained through boiling the spent grain followed by enzymatic digestion with diastase obtained from malt. The available residual extract represents the difference between total extract and soluble extract.