CHANGES IN BETA-CAROTENE, ASCORBIC ACID AND SENSORY PROPERTIES IN FERMENTED, SOLAR-DRIED AND STORED COWPEA LEAF VEGETABLES

This study was conducted to determine the effect of fermentation, solar drying and packaging on the nutritional, sensory and keeping properties of cowpea leaf vegetables. The cowpea leaves were purchased from the local markets, sorted to remove the blemished, leaves and foreign materials, washed in running tap water then drained. The vegetables were divided into three batches of 16kg. One batch was heattreated in hot water for 3 minutes then cooled to ambient temperatures, drained and solar-dried. The second portion was acidified to a pH of 3.8, heat-treated, and then solar dried. The third portion was fermented for 21 days, heat-treated, and then solar dried. The three batches of vegetables were spread at different times on drying trays at the rate of 4kg/m2 and dried in a solar drier to approximate moisture content of 10%. The dried vegetables were packaged in either polyethylene bags or Kraft company paper bags and stored for three months at 18°C, 22°- 26°C or 32°C.
Fermentation, heat-treating and drying of vegetables retained substantial levels of the vitamins: beta-carotene 91% and ascorbic acid 15%. Storage of the dried vegetables led to loss in both vitamins. The retention of beta-carotene and ascorbic acid at the end of storage, were 23% - 52% and 4% - 7% respectively, depending on storage conditions. Samples stored at 32°C had the highest losses, while those stored at 18°C had the lowest in both vitamins. Samples stored in Kraft paper bags had the highest losses in both vitamins. The duration and temperature of storage and the packaging material did not have significant effect on the sensory attributes of the dried vegetables. Increased acceptability of the fermented-dried vegetables in rural communities would assist in alleviating micronutrient malnutrition, help in dealing with the issue of seasonality and increase food security especially during the dry season.