The influence of ethanol and vacuum on okara drying

Abstract

Okara is a coproduct of processing soy milk and tofu. It is often discarded but has a great potential for use in the food industry due to its high content of fiber and protein. The aim of this study was to evaluate the drying of okara by natural convection and by vacuum drying (10 kPa). The tested temperatures were 80 and 100 °C. The samples were fresh, or their surface was pretreated with ethanol. The kinetics of drying were fitted with empirical models from the literature. The following three factors improved drying and reduced drying time, 1) the use of ethanol as pretreatment, 2) vacuum application and 3) temperature. Among these factors, a greater reduction in time was observed when ethanol was used, followed by temperature and vacuum, in this order. Page’s model showed the best fitness (r²>0.98, RMSE<0.05 and MAE<0.11).