Effect of traditional processing practices on the content of total carotenoid, β-carotene, α-carotene and vitamin A activity of selected Tanzanian vegetables

The α-carotene, β-carotene and total provitamin A carotenoids and the effect of traditional processing practices on the retention of these provitamins were studied using amaranth, cowpea, peanut, pumpkin and sweet potato leaves. Results of this study indicated that the content of total carotenoids, β-carotene and α-carotene were in the range of 26.79–44.74 mg, 4.16–19.12 mg, and 0.99–10.26 mg per 100 g of dry vegetables, respectively. The vitamin A activities were 4.042, 3.124, 0.829, 2.025 and 1.581 mg RE per 100 g of dry amaranth, cowpea, peanut, pumpkin and sweet potato leaves, respectively. The traditional processing practices of sun drying and storage in ventilated containers resulted in a significant (p<0.05) decrease in the concentration of total carotenoids, β-carotene and α-carotene for all the vegetables. Conventional blanching and cooking resulted in a significant (p<0.05) increase in the concentration of carotenoids in the cowpea, peanut and pumpkin leaves while in amaranth and sweet potato greens, thermal processing resulted in a significant (p<0.05) decrese in the concentration of these nutrients.