Increasing the shelf life of millet flour by using heat-moisture and microwave treatments

Millet is one of the cereals that used in the preparation of gluten-free products for celiac patients. Physical modification methods such as heat-moisture treatments and microwave can be used to improve the performance of gluten-free flours in the baking industry. Millet seeds have limited shelf life in normal storage condition due to its relatively high fat content and high activity of lipase enzymes. In this study Heat-moisture treatments at different levels of moisture (11,15 and 20%) and two different temperatures (90 and 110°C) for 3 hours in oven and microwave treatment at different levels of moisture (11,15 and 20%) were used at different times (30,60 and 90S) with a constant power of 900 W. Then, in order to ensure the effect of the above treatments, the amount of free fatty acids of the treated flours was measured every 10 days as well as the level of lipase activity on the first day and after 30 days. In the heat-moisture treatment, the rate of inactivation of the lipase enzyme increased with simultaneous increase of moisture and temperature of the oven as well as in the microwave treatment with simultaneous increase of moisture and microwave time and the amount of free fatty acid flour during 30 days of storage was reduced. The highest rate of inactivation of lipase enzyme and the least change in the free fatty acid content of flour in heat-moisture and microwave treatments were observed in treatment with 20% moisture content and 110°C, and treatment with 20% moisture and 90S.