Submitted to: Journal of American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2003
Publication Date: 10/7/2003
Citation: MUSLIN, E.H., KARPELENIA, C.B., HENSON, C.A. THE IMPACT OF THERMOSTABLE ALPHA-GLUCOSIDASE ON THE PRODUCTION OF FERMENTABLE SUGARS DURING MASHING. JOURNAL OF AMERICAN SOCIETY OF BREWING CHEMISTS. 2003. 61(3):142-145. Interpretive Summary: Mashing is the industrial process of extracting nutrients from brewer's grains into a liquid, known as the wort, that supports fermentation by yeast. The primary nutrients produced during mashing are fermentable sugars. Typically, mashing takes place at very high temperatures. It has long been known that some of the enzymes that convert starch to fermentable sugars have either no or very little activity at these elevated temperatures. It has been assumed that this reduces the efficiency of the mashing process. To determine if this presumed limitation exists and to remedy it if it does exist, we added a thermostable enzyme that degrades starch to the mashing system and quantified the fermentable sugars produced in the wort. The work presented here demonstrates that additions of thermostable alpha-glucosidase to mashing significantly increase the yield of fermentable sugars. This means that more product (fermentable sugar) can be extracted from the raw materials (malted barley and other cereal grains) than the currently used process extracts. Brewers specify the amount of fermentable sugars required in worts. The impact of this more efficient mashing process will be cost savings resulting from the reduced amount of raw materials needed to produce the desired amount of fermentable sugars in worts.
Technical Abstract: Alpha-glucosidase is one of the four carbohydrases present in malted barley that degrade starch. The thermostability of these carbohydrases is important because the industrial processes that convert starch to fermentable sugars typically take place at temperatures of 65-73C. At these temperatures alpha-glucosidase has less than 5% of the activity it has at 30C. We hypothesized that the thermolability of alpha-glucosidase could result in decreased production of fermentable sugars during mashing at these high temperatures. To test this hypothesis, experimental mashes were supplemented with either non-mutated recombinant alpha-glucosidase (control) or with recombinant alpha-glucosidase that had been mutated to have increased thermostability. The real degree of fermentation and the identity and quantity of maltodextrins produced were compared between these two mashes. The amounts of glucose, maltose and maltotriose and the real degree of fermentation were significantly increased in the mashes containing thermostable alpha-glucosidase. Hence, we conclude the presence of a thermostable alpha-glucosidase during mashing does increase the efficiency of the mashing process as more fermentable sugars are produced with no increase in the amount of malt or adjunct grain added to the mash.