Prediction of Wort Fermentability in Two-Rowed Barley Genotypes

• Main Author: Huerta Zurita, Ramon
• Format: Others
• Published: North Dakota State University 2016
• Online Access: http://hdl.handle.net/10365/25707

Fermentability is the parameter that describes the ability of yeast to turn sweet wort into alcohol. As the efficiency of this process is related with alcohol yield, it will regulate the amount of beer produced from a given amount of malt. Considering that fermentation efficiency is influenced by the concentration of fermentable sugars in wort, the diastatic power (DP) of malt has long been associated with fermentability. However, research studies have shown that DP alone can not explain much of the observed variability (R2≤0.50) between malt samples. Some reports suggest that the separate determination of the activity and thermal stability of some of the enzymes contributing to DP and some malt modification parameters can considerably improve prediction (R2=0.91). On the other hand, few studies have focused on measuring fermentability variation in barley breeding. The objective of this study was to determine the effect of standard and non-standard malt quality parameters on the fermentability of different barley breeding lines, and to select the best multi-linear regression model for predicting this trait. Malts of 90 barley genotypes, grown in different locations of North Dakota during two years, were used in this study. Assays of the DP enzymes alpha-amylase, beta-amylase, alpha-glucosidase, and limit dextrinase, as well as their thermal stabilities (determined at 65°C for 10 min), were performed and adapted to a microplate reader format. Fermentability was determined as the real degree of fermentation (RDF) considering that the apparent degree of fermentation (ADF) showed strong alcohol dependence (R2=0.87), which could give false differences when comparing breeding lines in a population with high genetic variability. Results showed that, contrary to other reports, DP and beta-amylase and its thermostability are not highly associated with fermentability when the hot water extract (HWE) is used as the mashing method. Alpha-amylase and limit dextrinase though, had a more significant influence. The malt quality parameters: wort glucose, wort maltose, limit dextrinase, free amino nitrogen, soluble protein, alpha-amylase, and maltotriose, are considered the most significant factors for predicting fermentability as determined by the regression model (R2=0.71). === Mexican Council of Science and Technology (CONACyT) === National Institute for Forestry === Agriculture, and Livestock Research (INIFAP, Mexico) === American Malting Barley Association, Inc. === North Dakota Barley Council