LIPOLYTIC AND OXIDATIVE CHANGES OF BARLEY LIPIDS DURING MALTING AND MASHING

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Abstract
Lipolytic and oxidative changes of barley lipids were studied during malting and mashing. The amount of lipid decreased by 23% during malting and changes in the composition of lipid classes were minor. On the other hand, during mashing the amount of free fatty acids (FFA) increased which indicated, that lipid hydrolysis had occurred. The same phenomenon was seen when malt flour was soaked in water at 23°C. The triglyceride (TG) and polar lipid (PL) contents were reduced and the proportion of FFA in total lipids was increased. Following similar soaking of barley flour, TG and PL were reduced but the accumulation of FFA and especially linoleic acid (LA) was slight. The results were consistent with the data on lipoxygenase activity (LOX) during malting. During steeping LOX decreased and was 15–20% of the activity of raw barley at the beginning of germination. The activity remained low during germination but rose sharply in the middle of kilning only to decrease again to a very low level at the end of kilning (5%). This in combination with the fact that the proportion of FFA remained high in the soaked malt samples suggests that the oxidation by LOX is negligible in the malt samples. However, the data suggest that mashing of barley, but not that of malt, includes the potential for the formation of highly polar lipid oxidation products.

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