Impact of Mashing Conditions on Extract, its Fermentability, and the Levels of Wort Free Amino Nitrogen (FAN), β-Glucan, and Lipids

Abstract

In a small-scale protocol, the mashing conditions used were found to have important influences on malt quality parameters, including extract, fermentability, and the levels of wort free amino nitrogen (FAN) and β-glucan. Understanding this relationship is important in determining and prioritizing malt components for malt quality assessment. The impact of mash-in temperatures of 62.5–75.0°C was assessed on a modernized small-scale mash program whose key parameters included grist milling at 0.7 mm by disc mill, addition of CaSO4 (0.3 mM) to water, grist/water ratio of 1:3, 60 min duration of the initial phase of mashing, and the completion of mashing at 74°C. Wort β-glucan and total protein levels were relatively stable, whereas FAN progressively decreased across the temperature range studied. Maximal fermentability was obtained at a mash-in temperature of 65°C. It was observed that malts containing the most thermostable β-amylase type, Sd2H, produced more fermentable worts and that these mashes maintained a greater degree of fermentability at the higher mash-in temperatures. At mash-in temperatures greater than 65°C, extract slowly decreased, whereas the level of wort total fatty acids increased substantially. The levels of linoleic (C18:2) and linolenic (C18:3) acids increased, whereas the level of palmitic (C16:0) and stearic (C18:0) acids declined at mash-in temperatures above 65°C. For yeast fermentation performance, C18:2 is a key nutritive component provided by wort. It was observed that malt samples from different barley varieties produced a range of levels of wort total fatty acid contents, although the greater proportion of this variation could be attributed to between sample variation at mash-in temperatures below 65°C. However, at mash-in temperatures above 65°C, the varietal sample became substantially more important in determining fatty acid content and composition. In both small-scale and commercial worts, wort boiling and trub removal reduced the level of wort fatty acids by up to 85 percentage points and increased the proportion of C16:0 while decreasing the proportion of C18:2. This effect of wort boiling was more variable with commercial brewery worts that were also more variable in the initial levels of total fatty acids and were not as consistent with respect to the extent of trub removal. In particular, the level and composition of wort fatty acids is well known to impact on yeast fermentation performance and generation of flavor-active esters. As such, brewers with a greater understanding of the determinants of the level and composition of the fatty acids in the wort from which they were brewing could potentially produce beer more efficiently and closer to their desired quality specifications.