The effects of malting on b-glucan and phytate were investigated in one naked and one covered barley by a full factorial experiment with three factors (steeping temperature, moisture content and germination temperature) each with two levels. Analysis of total content of b-glucan in the malted samples showed small changes after steeping at the high temperature (48°C), while steeping at the lower temperature (15°C) gave a signi®cantly lower content. This trend was even stronger for b-glucan unextractable at 38°C. Analysis of the activity of b-glucanase for the samples steeped at 15°C showed a strong increase over the time of germination, while those steeped at 48°C had a much slower development. The other two factors in¯uenced the outcome to a small extent, mainly because the steeping temperature was the most important factor overall where any changes in b-glucan and b-glucanase were observed. When b-glucan was extracted at 100°C, a larger yield was obtained, and this was in¯uenced by the steeping temperature in a much stronger way than for b-glucan extracted at 38°C. Determination of average molecular weight for b-glucan extracted at 100°C gave a lower value for samples steeped at 15 than at 48°C. The design did not have any large effects on phytate degradation and phytase activity. However, it indicated that selective control of the enzymes might be possible, since phytase activity was barely affected by the parameters studied, while b-glucanase was heavily affected.

The effect of different steeping conditions on phytate, β-glucan and vitamin E in barley during malting was studied by a full factorial experiment with three variables (steeping temperature, barley variety and steeping additions). Addition of lactic acid to the steeping water induced a reduction of phytate during steeping and germination, especially in combination with the high steeping temperature (48 • C). Furthermore, lactic acid and high temperature steeping inhibited β-glucanase development, resulting in a well-preserved β-glucan content after germination. When steeping was conducted without addition of lactic acid, the low steeping temperature (15 • C) promoted development of both phytase and β-glucanase activity during germination. A slightly higher level of tocopherols and tocotrienols was observed in samples steeped at 15 • C than in samples steeped at 48 • C. However, addition of lactic acid reduced the amount for both temperatures. When lactic acid bacteria were added to the steeping water none of the parameters studied differed from samples steeped with water only. The results show the possibility of combining phytate degradation with a preserved β-glucan content during malting and can thus be of interest for development of cereal products with improved nutritional value.

Hydrolysis of extracellular phytate (InsP(6)) by high-phytase yeast strains and survival of yeast cells were studied at simulated digestive conditions using yeast peptone dextrose growth medium and wheat gruel as model meals. An in vitro digestion method was modified to better correlate with the gastric pH gradient following food intake in vivo. High-phytase yeast gave a strong reduction of InsP(6) (up to 60%) in the early gastric phase, as compared to no degradation by wild-type strains. The degree of InsP(6) degradation during digestion was influenced by the type of yeast strain, cell density, and InsP(6) concentration. Despite high InsP(6) solubility, high resistance against proteolysis by pepsin, and high cell survival, degradation in the late gastric and early intestinal phases was insignificant. Dependency on pH for phytase expression and/or activity seemed thus to be an important limiting factor. Although further studies are needed, our results show the potential of using yeast as a phytase carrier in the gastrointestinal tract.

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