Investigation the Effect of Okara Flour and Protease Enzyme on Physicochemical and Sensorial Properties of Semi-Sweet Biscuit

Okara is the valuable by-product of soymilk industry that is a suitable source of protein, fiber and micronutrients in nutritional aspects. Therefore, its application in food industry is suitable in order to increase the nutritional value of food products and also to increase the added value of soybean processing industry. The aim of this study was to investigate the effect of wheat flour replacement by okara (0, 10, 20, 30 and 40%) in order to benefit its suitable nutritional characteristics and the utilization of protease enzyme (0, 60 and 120 ppm) in order to improve the qualitative properties of biscuit. In this regards, qualitative characteristics including dimensions and spread ratio, density, hardness, color and sensory properties were investigated. Results showed that thickness, density and hardness increased by increasing okara amounts and on the contrary the addition of protease had a reverse influence on the mentioned factors. Also the average diameter and spread ratio of the samples decreased by the addition of okara and increased by the addition of protease enzyme. Increasing okara and protease enzyme had similar effects on color characteristics so that redness and yellowness increased and the lightness decreased by increasing the percentage of replacement. According to the results of sensorial and instrumental analysis, the sample with 20% of okara and 60 ppm of protease enzyme was selected as the best sample. Finally, evaluation of nutritional properties of the best sample showed a significant enhancement in protein, crude fiber, total phenolic, calcium, magnesium as well as potassium content and significant reduction in carbohydrates content in comparison with the control.