Effect of pre-processing on the physico-chemical properties of morama bean (Tylosema esculentum) milk

Abstract

Morama bean (Tylosema esculentum) is an indigenous bean of the Kalahari region of Botswana. It has high nutritional content and is believed to also contain high levels of phytonutrients. The bean is traditionally eaten roasted as a snack but there is increasing emphasis to develop other innovative high value morama products, while maintaining its healthful properties. The effect of pre-processing treatments including salt-water-blanching, sodium-bicarbonate-blanching, hot-water-blanching on the proximate composition, total solids non-fat, colour, viscosity, sediments, pH and titratable acidity of morama milk was assessed. Consumer preference of the morama milk was also studied, using a soymilk control. Milk extracts were stored at 4°C for up to 24 hours and analyses conducted using standard methods. The findings indicated that the pre-processing treatments produced significant differences (p < 0.05) in protein (1.50 ± 0.18g/100g) and carbohydrate (1.09 ± 0.94g/100g) composition of the baking soda blanched milk sample. The viscosity of the baking soda blanched milk (18.91 ± 3.38cps) was significantly higher than that of the other milk samples, while the sediments of the salt water blanched milk (14.01 ± 1.63%) was significantly higher (p < 0.05) than the others. Baking soda blanching resulted in the highest pH (7.31 ± 0.32) and lowest titratable acidity levels (0.45 ± 0.24). The hot water blanched and baking soda blanched samples were slightly darker in colour, while the baking soda blanched sample had more greenness and less yellowness characteristics than the other two samples. Baking soda blanched pre-treated morama milk was the preferred morama milk by over 85% of the consumers; they also preferred it over soymilk. This is the first reported study on the processing of morama beans into milk and it demonstrated that it was possible to process high quality and acceptable morama milk, which can be utilized as a supplement to the dairy industry.Key words: morama, milk, physico-chemical, sensory, nutrition