Storage duration and conditions change the phytate content and phytase activity of wheat grains

Abstract

Background:The degree to which storage conditions and duration affect phytase activity and inositol phosphates (InsP) was evaluated in wheat. Three wheat cultivars were stored as whole or ground kernels at 20, 7, and À18 C for 13, 48, 118, 188, 265, and 349 days. Samples were analyzed for InsP 3-6 concentration and phytase activity. Results:The InsP 6 concentration of whole wheat kernels stored at À18 and 7 C did not differ from that at time point 0. Storage of whole kernels at 20 C significantly reduced the InsP 6 concentration at days 48, 188, 265, and 349, by up to 8.4%. The InsP 6 concentration of ground wheat samples was reduced by up to 23.6% until day 349. The lower InsP isomers Ins(1,2,3,4,5)P 5 and Ins(1,2,4,5,6)P 5 were detected only at a storage temperature of 20 C and at day 118 or later. Phytase activity did not change over time in ground kernels stored at À18 and +7 C but was decreased in ground kernels at 20 C and in whole kernels independent of temperature. Probable cultivar effects were found regarding phytase activity over time, dependent on grinding and storage temperature. Conclusion:To avoid loss of InsP 6 content, wheat samples should be stored as whole kernels at or below 7 C. Phytase activity is more stable in ground samples than in whole kernels. However, some cultivars likely are more prone than others to storage effects.