Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2007
Publication Date: 4/27/2007
Citation: Edney, M.J., Rossnagel, B.G., Raboy, V. 2007. Effect of low-phytate barley on malt quality including mineral loss during fermentation. Journal of American Society of Brewing Chemists. 65: 81-85
Interpretive Summary: Low-phytate crops are in development primarily because, in terms of grain phosphorus, they are more nutritious when used in feeds for non-ruminant animals such as poultry and swine. Barley is an important feed grain in many parts of the world but is also used in malting and brewing. Therefore it is important to study the quality of low-phytate barleys when used in malting and brewing. One aspect of quality for malting and brewing is the efficient fermentation of brewing "wort" and this may be effected both by the change in seed phosphorus chemistry in low-phytate barley and its effect on mineral utilization, such as zinc and magnesium utilization, during fermentation. Four barleys were evaluated: normal barley and three low-phytate barleys that have 50%, 30% and 5% of normal barley's level of phytic acid. Higher levels and usage of zinc and magnesium were observed in the worts and during fermentation of the low-phytate barleys as compared with normal barley. With the measurements used here, no significant effect on fermentation was observed with the low-phytate barleys. These results indicate that low-phytate barleys may be produced primarily for use in feeds but could also be used without major negative effect in malting and brewing.
Technical Abstract: The efficient fermentation of brewing wort is dependent on the adequate supply of a range of nutrients including minerals. Zinc and magnesium are two minerals that are often limiting and zinc supplementation is frequently required to achieve efficient fermentation. The recent development of low phytate barley offered the possibility of improving fermentation efficiency and reducing the need for mineral supplementation in the brew house. Phytic acid, an endogenous barley chemical that binds minerals rendering them nutritionally unavailable, has been genetically reduced in barley as a means of decreasing the need for phosphate supplementation in animal feeds as well as lowering the mineral content of manure. Three barley lines were developed with approximately 50%, 30% and 5% of normal phytate . The low phytate lines were developed in a Harrington background which increased the possibility of producing good malting quality from the lines. A study, therefore, was conducted with samples of the three low phytate lines and Harrington that had all been grown in Saskatoon, Saskatchewan in 2002. The samples were malted and tested for malting quality including zinc and magnesium usage during fermentation. Effects of zinc supplementation at mashing-in and at wort boiling were also compared among the lines. The low phytate lines were all found to have adequate malt quality being similar to Harrington, although, all 4 malts were only of fair to average quality due to severity of weather in the 2002 crop year. The 5% normal phytate wort (not supplemented) did have significantly higher levels of zinc and magnesium than the other three samples. Worts from the 50% and 30% normal phytate lines also had significantly higher levels of magnesium than the Harrington wort. The 5% normal wort, both the control and the mash supplemented, also had significantly greater use of zinc during fermentation than all the others. In the mash supplemented worts, the 5% and 50% normal phytate worts both used significantly more zinc during fermentation than did the 30% normal phytate or the Harrington worts. There were no significant differences in zinc usage among the worts supplemented at wort boiling as phytate would have been removed with the spent grains prior to supplementation. The low phytate trait had no significant effect on fermentation as measured with apparent attenuation limit at the lab bench. The results support the potential use of low phytate malts to improve mineral usage and fermentation efficiency. This potential will be further investigated using pilot scale brewing facilities and higher gravity worts where minerals would more likely be limiting.