Re-assessment of the half-grain modification method for assessing malt modification

The half-grain mashing (modification) method proposed by Palmer (J. Inst. Brew., 1975, 81: 408) was reassessed. The intention was to quantify the differences in malt modification in terms of ß-glucan breakdown and clarify the relationship between ß-glucan breakdown and overall modification of the endosperm during malting. This was carried out at 45°C as well as at 65°C, the percentage of weight loss was recorded and the endosperm residue was analysed for ß-glucan content. In general, weight loss was related to modification. Samples, which were modified at higher levels, lost significantly more material during the half-grain mashing procedure than those which were under-modified. At a malting process time of 96 h all the varieties had similar weight loss. After mashing the half grains, the ß-glucan contents of the grain residues showed an apparent increase because of loss of non-ß-glucan materials. However, over the malting period ß-glucan decreased. Chariot malted faster than the other varieties studied. The ß-glucan levels of this variety were reduced by 78% between 48 and 72 h of germination. Significant levels of ß-glucan were degraded and large quantities of starch and protein were released. During the same period of germination, the corresponding samples of Decanter did not show a significant reduction in ß-glucan levels. In contrast, Brazilian variety MN698 lost endosperm material and ß-glucan rapidly by 48 h. These early results suggest that during malting, extract solubilization may or may not accompany ß-glucan breakdown. Therefore, ß-glucan levels in malt cannot be used as an overall index of modification of the endosperm. © 2005 The Institute of Brewing & Distilling.