Abstract
The potential to utilize low nitrogen barley for production of distilling quality malt was studied. This presents an opportunity to reduce the environmental impact of nitrogen fertilizer applications. Malting barley (cv. Octavia) was grown without the application of inorganic nitrogen fertilizer, to produce grain with a relatively low nitrogen concentration (1.16%, dry weight basis). Following micro-malting trials, dextrinizing units (58 DU) obtained from low nitrogen malt were much higher than a typical specification of 45 DU for malt with a conventional nitrogen concentration (<1.5%). A higher soluble nitrogen ratio (SNR) or index of modification (IoM) of 49 indicated greater modification of the low nitrogen barley, resulting in higher extract released into the wort. Additionally, much lower levels of β-glucan were found in low nitrogen malt wort (64 mg/L compared with over 100 mg/L in wort of conventional nitrogen malt). Low nitrogen malt also produced higher predicted spirit yields following wort fermentation and wash distillation. These findings indicate that lower nitrogen concentration barley can be processed without negatively impacting malt quality for distilling applications. The implication of these findings to help realize more environmentally sustainable production of barley for malting and use in distilling is discussed.
Highlights
Different sectors of the alcohol industry have different malt-quality requirements resulting in different barley varieties being bred for each, whether that be for malt distilling, grain distilling or brewing
The higher soluble nitrogen ratio (SNR, soluble/total-nitrogen), known as index of modification (IoM) obtained from the lower nitrogen malted barley further confirmed that the test malt was well modified
It is salient to note that while the malting barley cultivar tested here is one of the main varieties in use by industrial distillers in the UK, and that the malting regime itself presents the major factors influencing the success of the malting process, future work might confirm this null hypothesis: that malting barley genotype does impact on these conclusions made here
Summary
Different sectors of the alcohol industry have different malt-quality requirements resulting in different barley varieties being bred for each, whether that be for malt distilling, grain (e.g. wheat) distilling or brewing. The optimal grain protein concentration is considered to be 9.4 % (equivalent to 6.25 x 1.5 % nitrogen [1]) and, as protein concentration is inversely related to grain starch concentration, represents the best balance for high starch concentration and potential alcohol yield [2]. These attributes are seen as critical determinants of alcohol yield following fermentation of the malted barley wort. Under-modification can lead to wort separation and filtration issues due to cross linking of non-degraded cell wall components such as β-glucans [9]
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