Effect of pretreatments and processing conditions on anti-nutritional factors in climbing bean flours

It is difficult for many Rwandans to utilize climbing bean seeds (Phaseolus vulgaris L.) mainly because of longer cooking time (2 hours) and the high consumption of basic fuel. Climbing beans also contain anti-nutritional factors such tannins, phytates, trypsin inhibitors and phytohemagglutinins that limit nutrient absorption. One way to solve this problem is to utilize the flour of climbing beans made from different treatments and processing methods. In this study, climbing beans were pre-treated by soaking them in water for 24 hours, soaking in 2% sodium bicarbonate solution and steam blanching for 10 minutes. After that, pre-treated climbing beans were processed into flours by processing methods such as roasting, cooking and germination where anti-nutritional factors were reduced. The pretreatments did not significantly (p > 0.05) affect phytates in climbing bean flours but processing conditions significantly (p < 0.05) reduced it. Pretreatments and processing conditions significantly (p < 0.05) reduced tannin content. The pretreatments followed by different processing conditions significantly (p < 0.05) decreased trypsin inhibitors content. The great significant decrease in phytohemagglutinins content was observed in pretreatment followed by different processing methods. All pretreatments and processing conditions effectively decreased anti-nutritional factors at low level. However, pretreatments or untreated followed by germination and roasting were found to be the most and the least effective respectively. Making flour from germinated climbing bean seeds is a good option for sustainable food processing as it reduces anti-nutritional factors. It is an inexpensive method in terms of time, energy and fuel for Rwandan households, restaurants and industries where climbing bean seeds are integral part of daily meal.