Twenty-seven barley (Hordeum vulgare L.) samples collected from growing sites in Scandinavia in 2001 and 2002 were examined to study the effect of endosperm structure on malting behavior. Samples were micromalted, and several malt characteristics were measured. Samples were classified as having a mealier or steelier endosperm on the basis of light transflectance (LTm). Because endosperm structure is greatly dependent on protein content, three barley sample pairs with similar protein contents were chosen for further analysis. During malting, the steelier barley samples produced less root mass, but showed higher respiration losses and higher activities of starch-hydrolyzing enzymes. Malts made from steelier barley had a less friable structure, with more urea-soluble D hordein and more free amino nitrogen and soluble protein. The reason for these differences may lie in the structure or localization of the hordeins as well as the possible effects of endosperm packing on water uptake and movement of enzymes.

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.Key Words: Barley, malting, lipids, lipase-lipoxygenase Introduction In the initial stages of malting, water activates the barley embryo and the hydrolysis of biopolymers begins with the rise of the activities of hydrolytic enzymes. However, lipid metabolism of germinating barley differs from that of other macromolecules. Lipase activity is already present in barley" and the activity is known to increase by over fourfold during malting1. Lipoxygenase activity has also been reported to increase during germination of barley4-10. Lipases and phospholipases act in concert with lipoxygenase: the polyunsaturated fatty acids released from triglycerides and phospholipids are preferentially oxidized by lipoxygenase. However, only minor differences exists between barley and malt lipids1.During mashing up to 30% of malt lipids may be oxidized2 even though only 2-4% of initial lipoxygenase activity has been reported to be present in malt after kilning4-12. It is surprising that such a low lipoxygenase activity would be responsible for the oxidation of such a high amount of lipid. A more detailed understanding of this anomaly would be valuable since the lipoxygenase activity of malt is closely related to the nonenal potential of wort5. We approached the problem by parallel determinations of changes in lipid composition and lipoxygenase activity during the malting process and under conditions simulating mashing. Materials and Methods BarleyThe malting barleys chosen for the lipoxygenase assays were the Finnish varieties Ingrid, Kilta, Kustaa, Kymppi, Pirkka, Pokko, and Porno harvested in both 1990 and 1991, and the other varieties Etu (1989), Elo (1990), Plaisant (1990), Ariel (1989), Formula (1989...

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A mathematical model was developed for water uptake during the steeping of barley. The model is based on laboratory scale experiments with various steeping programmes. The model consists of two compartments, and the rate of total water uptake is assumed to depend on the distribution of water in the grain. The root mean square error of the predicted process moistures was 0.61% in the in dependent validation data set (N = 20). The model can also be used for analysing the steeping process and for the planning of steeping programmes in the malthouse.