ASSESSMENT OF THE EFFECT OF PRETREATMENTS AND DRYING METHODS ON THE NUTRITIONAL QUALITY OF OKARA, AND OKARA-MAIZE COMPOSITED TUO ZAAFI

Abstract

Animal proteins are becoming largely expensive, hence the daily protein needs of low-income earners are unmet. This has triggered the need to explore rich but less expensive protein sources of plant origin such as okara, a soy residue to meet the protein needs of the consumer. One effective way of ensuring that consumers benefit from these less-expensive protein sources is their incorporation into frequently consumed diets. Therefore, this study sought to assess the effect of pretreatments (no pressing, 12 hours pressing and 24 hours pressing) and drying methods (sun drying, hot air drying and solar drying) on the nutritional quality of okara (soy residue) and maize-okara tuo zaafi. To accomplish the objective of the present study, the drying characteristics and proximate composition of the okara, the consumer acceptability and proximate composition of maize-okara tuo zaafi were determined using widely accepted scientific protocols. The study revealed that hot air drying (8.67±0.52 hours) presented the best drying condition of the okara samples, followed by the open sun (9.33±0.52 hours) and then the solar drying (14.33±1.51 hours) in that order. The drying methods had a significant (p<0.001) effect on the proximate composition of the okara samples. In contrast, the pretreatment had a significant effect on all the proximate parameters except the moisture and ash contents. However, the solar drying method resulted in the highest protein values compared to the open sun and the hot air drying methods. The unpressed okara samples dried using the solar drying method recorded the highest protein value (33.14 %) whiles, the 12 hours pressed samples dried using the hot air method recorded the lowest protein value (20.72 %). The acceptance of the sensory attributes of the tuo zaafi products decreased as the okara inclusion level increased. Hence, the tuo zaafi prepared using a 10 % okara inclusion level had similar sensory attributes as the maize-only tuo zaafi, while the other products (20 %, 30 % and 40 % okara inclusion level) were generally not accepted. The nutritional quality of the tuo zaafi products correspondingly increased with an increased inclusion level of the okara flour. Length of pressing and the drying techniques used greatly influenced the nutritional properties of the okara and okara-enriched tuo zaafi. Hence, for consumer acceptance of the okara-enriched TZ, 10 % okara flour inclusion level is recommended.