Nutritional and physicochemical properties of stored solar-dried cowpea leafy vegetables

Abstract

Preservation techniques for cowpea (Vigna unguiculata L.) leaves, a green leafy vegetable mainly
consumed in the eastern and northern parts of Uganda, are still lacking. The study aimed at
determining the effect of blanching, open sun and solar-drying on the nutrient content,
organoleptic acceptability and physicochemical properties of cowpea leafy vegetables (CLV) during
storage. Proximate composition, sensory quality and colour of the CLV were determined. No
significant differences (p < 0.05) in nutrient composition were observed between drying methods,
except the dietary fibre, zinc and total carotenoid content. Blanched-solar dried CLV showed
higher dietary fibre and total carotenoid content compared to raw dried CLV. No significant
differences (p > 0.05) in appearance, taste, flavour, and texture of dried CLV were observed, except
for the fresh CLV (control). Water activity levels ranged from 0.34 to 0.54 indicative of storage
stability. Positive ‘L’ colour values (37.90 to 44.95) indicative of light green to green, negative ‘a’
values (-7.28 to -4.15) for greenishness and positive ‘b’ values (3.45 to 9.25) for yellowishness for
raw-dried and blanched green leafy cowpea vegetable, respectively, were obtained. Marked
increases in browning index and total colour difference were observed in the dried CLV during
storage. Blanching and solar drying treatment formed stable and highly acceptable vegetables
during storage, which could be recommended for market.