Drying kinetics and quality of okara dried in a jet spouted bed of sorbent particles

Okara or soy residue is a byproduct of soymilk and tofu production process. Okara has high protein content and can be used as an ingredient in many food products or can be used as animal feed. However, okara deteriorates rapidly; hence raw okara must be dried as early as possible under appropriate conditions. Drying could also help eliminating undesirable antinutritional factors in okara. The present study investigated the feasibility of drying okara using a combined convection-sorption drying, i.e., the use of a jet spouted bed of sorbent particles. The effects of various parameters such as drying air temperature and velocity, mass ratio of sorbent particles to okara, and initial bed height of okara on the drying kinetics were investigated. Also, various quality attributes of okara viz. color, oxidation level, rehydration ability, urease activity and protein solubility as well as the specific energy consumption during drying were investigated in both low- and high-temperature ranges. (c) 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.