Comparison of Wort Osmolyte Concentration and Malt Extract to Wort Sugars from Malting Barley Breeding Lines

Abstract

In 2007 wort osmolyte concentration (OC) was introduced as a method of measuring malt quality. The OC (molar concentration of solutes) of a mash is predominantly due to the conversion of starch to sugars and storage proteins to smaller nitrogenous compounds. Malt extract (ME) (mass of material in wort) has been used since the 1700’s as a measure for malt quality. Here we compare OC and ME to wort sugar concentrations in lines from three U.S. barley breeding programs. Lines were malted using standard protocols. Worts were analyzed for OC with a vapor pressure osmometer, ME by the ASBC Method, and sugars by pulsed amperometric detection of HPLC separated sugars. Correlations between OC and the combined molar concentrations of glucose, maltose, maltotriose, fructose and sucrose (TFS) for lines from breeding programs A, B, and C were (A) r = 0.930, P < 0.0001, (B) r = 0.625, P = 0.0014, and C) r = 0.667, P < 0.0001. Correlations between ME and TFS were (A) r = 0.408, P = 0.850, (B) r = 0.646, P = 0.0009, and (C) r = 0.081, P = 0.650. Correlations between OC and wort maltose were (A) r = 0.904, P= <0.0001, (B) r = 0.262, P = 0.2279, and (C) r = 0.105, P = 0.5534. Correlations between ME and wort maltose lines were (A) r = 0.009, P = 0.966, (B) r = 0.272, P = 0.2094, and (C) r= −0.011, P = 0.9504. This study indicates that OC is far superior to ME in the prediction of fermentable sugars in wort for some breeders’ lines and about equal to ME for others. These data also indicate that those lines that correlated well with fermentable sugars also correlated well with sucrose.

Keywords:

• Glucose
• maltose
• maltotriose
• total fermentable sugars

Acknowledgements

We thank Joseph T. Dietrich, Charles B. Karpelenia and Andrew J. Standish for expert technical assistance and Christopher H. Martens for providing malts and malt quality data. We thank the three anonymous breeding programs for producing and submitting the barley lines used in this study and for location information provided by each breeder. Mention of a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other suitable products.