Nutritional quality, bioactive compounds and antioxidant activity of selected african indigenous leafy vegetables as influenced by maturity and minimal processing

Abstract

The African indigenous vegetables (AIVs) are excellent sources of β-carotene, vitamin C, iron as well as protein, minerals, fiber and bioactive compounds. In the recent past, AIVs have gained commercial importance as a result of increased awareness of their nutritional and health benefits and are now produce in both formal and informal marketing channels. One of the challenges in production, marketing and consumption of AIVs is that they are highly perishable and there is inadequate capacity for their storage in fresh state. This is because most storage techniques require low temperatures, which are nonexistent for AIVs in Kenya. Minimal processing can enable AIVs produced in far flung locations to be stabilized and transported to the markets in the urban centres. However, this can affect the color, texture, flavor, and nutritional quality of AIVs. This study aimed at examining the influence of harvest maturity and minimal processing techniques on the nutritional, phytochemical and anti-oxidant capacity in stinging nettle, amaranth and black nightshade. The results indicated significant differences between treatments and stages of maturity. Results further show that the highest contents of β-carotene in fresh state, at young stage was 47.82 mg/100g in amaranth and mature stage was 71.22 mg/100g in black night shade. For vitamin C, the highest content was 142.06 mg/100g in stinging nettle at young stage while amaranth had the highest content of vitamin C at mature stage as 193.52 mg/100g. The highest phenol content in fresh state was in black night shade at 1.09 g/100g and 1.29 g/100g at young stage and mature stage respectively. Among the processed, the highest content of vitamin C was seen in Freeze-Dried Unsliced Unblanched black nightshade at both young and mature stage as 86.64mg/100g and 111.14mg/100g respectively. For β-carotene, the highest content was reported on Freeze-Dried Unsliced Blanched in amaranth as 30.24mg/100g at young stage and mature stage had 57.12mg/100g in black nightshade.

Keywords: Minimal processing, blanching, drying, African indigenous vegetable, maturity

Afr. J. Food Agric. Nutr. Dev. 2019; 19(3): 14769-14789