Location: Cereal Crops ResearchTitle: Comparison of wort osmolyte concentration and malt extract to wort sugars from barley breeding lines undergoing development for malting and brewing
Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2021
Publication Date: N/A
Interpretive Summary: Barley malt quality is determined by several tests but the most critical test that establishes its value in the commercial markets is the measure of malt extract (ME), which is the measure of the mass of substances in a liquid extract known as the wort. Because the ME values are so critical to the success of a barley line being developed for malting purposes, plant breeders rely upon ME tests to evaluate the results of their breeding programs. Additionally, state agriculture agents rely upon ME tests of barley grown in their geographical regions to make recommendations to farmers about which barley varieties they should plant to increase their chances of being paid a premium for their crop. A new test has been developed in the past few years that measures osmolyte concentration (OC) and demonstrated to be of value in evaluating commercial barley varieties for malting purposes. The current study demonstrated that OC is also a useful test to evaluate barley in early cultivar stages that is being bred with the intent of being sold in the commercial malt market. OC is a quick, easy and inexpensive test that can be used to supplement or replace ME tests, which are more expensive and slower to perform and more valuable in later stages of breeding line development.
Technical Abstract: In 2008 wort osmolyte concentration (OC) was introduced as a new method of measuring malt quality. The OC, which is the molar concentration of solutes, of a mash is predominantly due to the conversion of starch to sugars and of storage proteins to smaller nitrogenous compounds. Malt extract (ME), the mass of material in wort, has been used since the 1700’s as the major measure for malt quality. Here we present a study comparing OC and ME to wort sugar concentrations in lines from 3 U.S. malting barley breeding programs. Each line was malted using standard CCRU protocols and the worts analyzed for OC with a vapor pressure osmometer, ME by the ASBC Method, and sugars by pulsed amperometric detection of HPLC separated sugars. The fermentable sugars produced from starch degradation during mashing are glucose, maltose, and maltotriose. Correlations between OC and the combined molar concentrations of fermentable sugars for lines from breeding programs A, B, and C were (A) r=0.930, P<0.0001, (B) r=0.584, P=0.0003, and C) r=0.526, P=0.0099. Correlations between ME and fermentable sugars were (A) r=0.0524, P=0.8078, (B) r=0.036, P=0.8388, and (C) r=0.578, P=0039. These data indicate that OC is far superior to ME in the prediction of fermentable sugars in mash for some breeders’ lines and about equal to ME for others. Maltose is the most abundant sugar in wort. Correlations between OC and wort maltose were (A) r=0.904, P=<0.0001, (B) r=0.106, P=5534, and (C) r=0.262, P=0.229. Correlations between ME and wort maltose lines were (A) r=0.0092, P=9661, (B) r=-0.0111, P=0.950, and (C) r=0.272, P=2270. Sucrose is the primary transport sugar in germination. Correlations between OC and sucrose were (A) r=0.6054, P=0.0017, (B) r=0.7095, P<0.0001, (C) r=0.3647, P=0.0871. Correlations between ME and sucrose were (A) r= -0.1098, P=0.6095, (B) r=0.1995, P=0.2579, and (C) r=0.1795. These data indicate that those lines that correlated well with fermentable sugars also correlated well with sucrose.