Evaluating technological quality of okara flours obtained by different drying processes

Okara has high nutritional value but its high moisture value is a large problem for use as ingredient for food development. The objective of this work was to evaluate the physicochemical characteristics and technological functional properties of okara flours (OFs) obtained by different drying processes in forced air oven (FAD at 40, 50, 60, and 70 °C), microwave (MWD), and freeze drying (FRD). The OFs showed acidity range of 3–5.7 mEq NaOH/100 g, pH of 5.4–5.9, soluble solid of 0.6–1.3 °Brix, luminosity of 78–85, and good technological functional properties (MWD-OF and FRD-OF showed ↑oil absorption capacity, and ↑emulsifying capacity, and FRD-OF showed foam capacity). The FAD70-OF, MWD-OF, and FRD-OF showed 58–63 g/100 g of dietary fiber and 28–30 g/100 g of protein content, antioxidant activity of 0.21–0.31 mM Trolox/100 g, amount of aglycone isoflavones between 1.5 and 1.9 μmol/g, and good source of iron (3.8–4.2 g/100 g), calcium (63–70 g/100 g), and zinc (1.4–1.6 g/100 g). Therefore, considering the growing interest in the preparation of functional foods (high dietary fiber and aglycone isoflavones contents), the conventional method of drying by the convection oven was the one that produced the okara flour of better nutritional quality.