Phytic Acid Content and Phytase Activity of Barley Malt

The phytic acid content of nine North American six- and two-rowed barley varieties ranged from 0.95 to 1.11%. There was a marked increase in phytase activity during four days of germination, which was accompanied by a concomitant decrease in phytic acid content. Phytic acid levels in malt ranged from 0.67 to 0.88%, representing about 74% of the phytic acid content of unmalted barley. Approximately 75% of the phytase activity of green malt was lost during kilning. Phytase activity declined 20% during the 45°C hold in an ASBC mash, and an additional 55% by the time the temperature reached 55° C during the rise to 70° C. Only about 6% of the original activity remained as the temperature reached 70° C and none was observed after 30 min at this temperature. The partially purified enzyme had a pH optimum of 5.0 and a temperature optimum of 40° C. The enzyme was slightly inhibited by nickel and cobalt and highly inhibited by mercury, silver, zinc, iron, and copper.