Evaluation of the Quality changes of Common Beans (Phaseolus vulgaris L.) varieties during storage in Hermetic Polyethylene Bags

Abstract

Common beans (Phaseolus vulgaris L.) are extensively cultivated in sub-Saharan Africa as a cheap source of proteins, starch, dietary fiber, and excellent mineral salts and vitamins. However,beans are lost due to poor post-harvest handling and storage practices that provide insufficient protection against storage insect pests. Therefore, farmers are forced to apply insecticides more than once in a storage period to achieve protection. Excessive use of chemicals is not safe for health and is uneconomical. Hermetic techniques for storage have attracted increasing attention in recent years as chemical-free methods to preserve food grains and protect them against storage insect pests. Whereas substantial research that evaluates how hermetic technologies can lower quantitative losses arising from insect damage exists, there are barely any investigations that assess the effect on the quality of the stored produce, especially in hot and humid regions. This study aimed to evaluate the impact of hermetic storage (PICS®) conditions on the quality of beans in chemical and biochemical composition, grain texture, hard-to cook-defect, in-vitro nutrient digestibility, and aflatoxin ontamination. Three varieties of common beans: Rosecoco,Nyayo, and small red, in three moisture levels (12%, 15%, and 18%) were stored hermetically for seven and a half months. Sampling and analyses were done every 45 days and PPB were used as control bags. The beans were analyzed for physicochemical properties, biochemical constituents, texture and cooking quality, moulds, and aflatoxin contamination using standard methods. Data analysis was done using Stata software to perform variance analysis while means were separated using the Least Square Difference at α=0.05. The Nyayobeans data were subjected to principal component analysis to validate the interrelationships between the variables and treatments of each experimental condition.PICS® bag was significantly different from PPB bags at p<0.001 in terms of preserving the quality of beans during storage: The PICS® had 22%, 23%, and 18% higher total soluble sugars, in-vitro starch, and protein digestibility respectively than the PPB bags during storage. The study found out that a hermetic bag was significant in reducing the bean hardness during cooking compared to the control bag. Similarly, the activation energy required during cooking was significantly higher in PPBs than PICS®. Furthermore, it was observed in the study that incidences of molds were higher in PPB bags than PICS bags for Aspergillus spp., Fusarium spp., Penicillium spp., and Rhizopus spp. Hermetic bag was better than the ordinary PPB bag in terms of nutrient and texture preservation as well as for mould and aflatoxin control, hence recommended for beans storage