Lawton, M.1 and Alcaine, S.1, (1)Cornell University, Ithaca, NY, USA
Poster
Lactose, milk sugar, is commonly used in beer as a non-fermentable sugar. It is a disaccharide composed of glucose and galactose, but brewer’s yeast, Saccharomyces cerevisiae, does not have the enzymatic ability to break the beta-1,4 bond linking the monosaccharides. A beta-galactosidase with activity against lactose has been isolated from barley; however, it rapidly loses activity at typical mash temperatures of >50°C. A modified mash profile, with a lower initial temperature, could allow this enzyme to hydrolyze lactose into glucose and galactose for utilization by S. cerevisiae. This would allow for the incorporation of lactose as a fermentable adjunct sugar in beer production. The objective of this study was to evaluate whether a barley mash with a step at the beta-galactosidase optimum temperature of 40°C would result in the detectable hydrolysis of added lactose. A 250 mL mash containing 65.9 g of barley meal and 25 g of lactose was stirred constantly at 40°C for 3 hr. A control mash consisting of barley meal and water, with no lactose added, was used to determine the amount of free glucose in the grain or glucose released from potential amylase activity. Samples were taken at 0, 10, 60, 120, and 180 min and heated to 70°C for 5 min to stop any further enzymatic activity. Levels of glucose in the samples were then analyzed via an enzymatic assay. Triplicate samples were taken at each time point, and the experiment was repeated three times. The pH of the wort was also taken at each sampling period. Statistical analysis (t test) was conducted to determine significant differences in glucose levels between the mash containing glucose and the control. Glucose analysis showed a significant increase in glucose levels over time compared to the control. The control (no lactose added) started at 0.01 g/L of glucose and increased to 0.79 g/L over the 3 hr. The treatment (lactose added) started at 0.02 g/L of glucose and increased to 9.2 g/L of glucose over the 3 hr. The level of glucose after 3 hr was significantly different between the control and the treatment. These results indicate that barley contains an endemic beta-galactosidase in sufficient quantities that a mash profile incorporating a step at the enzyme’s optimum temperature results in significant lactose hydrolysis. This opens the possibility of utilizing lactose and lactose-containing foods, such as acid whey, as fermentable adjuncts in brewing and lays the foundation for new potential beer styles. Further research will look into further mash optimization for enzyme activity, as well as whether enzyme activity varies among grain varieties.
Marie Lawton is a graduate student at Cornell University. She completed her bachelor’s degree in 2016 at the University of Massachusetts Amherst. Currently she is studying food microbiology and investigating new techniques in food safety.
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