Effect of Processing Methods on Physical Properties of Gum Extracts from Selected Legume Seeds

Abstract

The use of legume seed flours as emulsifiers and flavouring agents in traditional soups is a function of the high level of their gum contents. The method of processing of legumes generally affects the physical behavior when applied to subsequent food processing. Generally, legume seed flours are obtained after some level of heat treatments (boiling and roasting) for a period of 10 min. Extraction of gums from tropical legume seeds has not been a common practice. This work was therefore designed to determine the effect of various processing methods on the physical properties of gum extracts of selected legume seeds. The various seed gums were extracted from de-coated Afziela africana “akparata”, Mucuna. sloanei “ukpo”, Brychestegia eurycoma “achi” and Detarium microcarpum “ofor” seeds after being processed as follows: boiling at 100°C for 10, 20, 30 min; roasting at 130°C for 10, 20, 30 min and soaking at ambient temperature for 8, 16, 24 h. Flours from each of the raw seeds served as control. The flours were de-fatted using petroleum ether and gums extracted using propan-2-ol. The functional properties of the seed gums were determined. D. microcarpum seed gums had the highest swelling indexes for all the processing methods adopted. Generally, gums from roasted seeds had the highest bulk density (0.60 g/ml), water absorption capacity (5.25 g/ml), oil absorption capacity (4.64 g/ml), gelation temperature (74.56°C), wettability (26.44 s) and swelling index (5.30) though lowest foaming capacity (15.43%), foaming stability (15.32%) and emulsion capacity (25.77%). The result showed that the legume seed gums could be useful raw material in food industry such as: bakery and dairy industries, especially in the use of non-wheat flour in baking, the gum could be a substitute for gluten in wheat. The results from this research will also help to reduce cost of importation of commercially available food gums and hydrocolloids.