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.
Spectrophotometric determination of the iodine value of brewery spent grain
Brewery spent grain, wet spent grain, dry spent grain
High molecular weight dextrins and starch present in the wort extracted from brewery spent grain are precipitated through the addition of ethanol, centrifuged and dissolved in phosphate buffer, followed by the addition of an iodine solution. Depending on the molecular weight and degree of branching, a red to blue color forms, the intensity of which is measured spectrophotometrically at 578 nm.