Study the physical properties of normal and hard seeds of Mung bean (Vigna radiata) and impact of different storage conditions on its hardness.

Abstract

Mungbean (Vigna radiata) plays a vital role in the Sri Lankan human diet, which contains a rich source of protein (14.6–33.0 g/100 g) and iron (5.9–7.6 mg/100 g). Under the current food crisis, mungbean is an ideal substitute to fulfill the country’s protein requirement. Currently, the Sri Lankan government has imposed policies to limit importation and popularize mungbean cultivation in the country. Therefore, an increase in mungbean production can be expected in the near future. In Sri Lanka, mungbean is used in the form of boiled, spiced curry, confectionary, etc. However, hardseededness (yak ata), is a major problem for consumers as well as farmers. Hardseededness is a physiologically or genetically determined trait that results in seeds being impervious to water and remaining hard even after cooking. There are no proper criteria to separate mungbean hard seeds currently in the country. Therefore, this study was done to compare the physical properties (length, width, thickness, weight of 100 seeds, true density, and color), and cooking properties (boiling time) of both normal and hard seeds for the variety MI-5 and to explore the impact of various storage environments on the hardness. Hard seeds were identified by soaking for 12 hours in water, where soft/swollen seeds were categorized as normal seeds and hard/non-swelled seeds were categorized as hard seeds. Comparatively lower seed length (4.65±0.17 mm), width (3.34±0.07 mm), thickness (3.37±0.05 mm), 100 seed weight (5.55±0.10 g), and true density (1.55±0.08 kg/m3) were obtained for hard seeds than normal seeds even if the values were not significant (p>0.05). Therefore, seed size, 100 seed weight, and true density are not reliable parameters to separate hard seeds for the variety MI-5. Color values indicated significantly (p<0.05) higher b* value for hard seeds. Therefore, further studies should be done to identify proper criteria for separating mungbean hard seeds. The storage trial was conducted at room (30±2 ⁰C) and cold (4 ⁰C) temperature for 6 months. The results revealed that the development of hard seeds tends to decrease with storage time, while room temperature was more effective to store mungbean than refrigerated conditions.