Physicochemical and functional characterisation of three lablab bean(Lablab purpureus L. (Sweet) varieties grown in Kenya

Abstract

The Lablab bean can significantly enhance the Food and nutrition security situation, particularly among the communities in the ASAL areas. However, the different varieties of Lablab beans grown in Kenya have received little research attention in comparison to other food crops. The objective of this study was to assess the physical properties, nutritional composition, cooking characteristics and the protein functional properties of three Lablab varieties (KAT/DL-1, KAT/DL-2 & KAT/DL-3) and compare them with that of KAT/X69 Phaseolus vulgaris variety (Rosecoco). Samples were obtained from KALRO-Katumani Dryland Research Station. The beans were evaluated for their physical characteristics, proximate composition, minerals, anti-nutrients and bioactive components, cooking characteristics, and functional properties of proteins. A fermented product, tempeh was developed and evaluated for its nutrition quality. The data was subjected to analysis of variance and Duncan Test used for mean separation at 5% significant level. The results showed that KAT/DL-1 had significantly higher seed weight and seed porosity (29.0g; 42.8) compared to KAT/DL-2 and KAT/DL-3. KAT/DL-3 had significantly higher hydration and swelling capacities (192.9 and 143.9 respectively) compared to the other two varieties. The three lablab beans had protein content of (25%,24%,22% while KAT/X69 had 21%... Linoleic acid was the most abundant fatty acid. KAT/DL-2 had significantly higher content of phytic acid (723mg/100g), tannins (0.33g/100g) and trypsin inhibitor (13 TIU/mg) compared to the other two lablab beans. Cooking and germination reduced the anti-nutrients significantly. KAT/DL-3 was adequately cooked at 140 minutes while KAT/X69 was cooked at 120 minutes. KAT/DL-1 had better taste compared to KAT/DL-2 KAT/DL-3 and KAT/X69. In conclusion, KAT /DL-1 had significantly higher seed weight and porosity, while KAT/DL 3 had significantly higher sphericity and hydration capacity. The lablab beans had significantly higher protein content compared to KAT/X69. KAT/DL-1 had significantly higher protein and starch digestibility compared to the other two varieties. KAT/ DL-2 had significantly higher levels of phytic acid and tannins, while KAT/DL-1 had significantly higher flavonoids than the other two varieties. All the lablab bean varieties had significantly lower trypsin inhibitory activity and tannins than the common Rosecoco bean. Cooking and germination were found to significantly reduce anti-nutrient levels in the bean varieties. KAT/DL-3 had a significantly shorter cooking than the other varieties. time to cook. It is therefore recommended that Lablab bean utilization should be up-scaled particularly in the arid and semi-arid regions due to its nutritional value. Breeding of easy to cook and low ant-nutrient beans need to be encouraged while more research is required on other Lablab varieties found in Kenya.