Effect of Wheat Germ Heat Treatment by Fluidised Bed on the Kinetics of Lipase Inactivation

Abstract

Wheat germ is scrapped during milling due to their unfavourable baking properties and rapid deterioration. Although it is a low-cost by-product with remarkable nutritional features, its widespread utilisation is limited by the action of enzymes. On that basis, the effect of the germ stabilisation process by fluidisation with hot air was studied. Fluidisation, carried out with air between 90 and 150 °C, generated notable lipase inactivation, which reached a minimum residual activity of 15.5% from original. The total tocopherol contents of stabilised samples were not significantly affected. Colour attributes of treated samples showed slight changes compared with raw wheat germ. A mathematical model was fitted to colour data to predict the changes due to heat. A first-order kinetic model was applied to descript the thermal lipase inactivation. The inactivation rate constant, D value, Z value and the activation energy were calculated for this process. The results obtained in this study are expected to contribute to the optimisation of wheat germ stabilisation by fluidisation. This process may enable to obtain a food with good nutritional features for human consumption from a co-product of the wheat milling industry at a short time and high temperature.