Abstract

This study evaluated and endorsed optimal processing methods for Vernonia amygdalina Delile with the dual objective of producing a palatable, de-bittered vegetable (ndole) for human consumption and a nutrient-rich co-product (Vernonia amygdalina Wash-water-VaWW) for livestock feed. What distinguishes this study is its comprehensive, side-by-side evaluation of both edible and co-product streams from 21 debittering protocols, a level of comparative detail not presented in prior research. Nutritional values and antioxidant trade-offs are quantified for the first time across washing, abrasion, boiling, and potash-based methods. Twenty-one traditional processing methods from existing literature were first standardized under laboratory conditions and then scaled up to household conditions. Six most suitable methods—selected for their de-bittering effectiveness and efficiency—were subsequently evaluated for their impact on nutrient and antioxidant retention in both the final product and the wash-water. Results revealed a significant trade-off between processing time and nutrient retention. While Method 21 (heating with potash and water) was significantly (P < 0.05) the most time-efficient, requiring just 5 minutes to process 1000g of leaves, it resulted in significant (P < 0.05) nutrient and antioxidant loss in the final product. Conversely, Method 4 (ordinary abrasion until foaming stops) was found to be the superior (P < 0.05) processing method for nutrient retention. Method 4 consistently resulted in the highest retention of protein (content statistically similar (P > 0.05) to unprocessed leaves), Vitamin C, and minerals in the de-bittered ndole. Boiling methods (Methods 9 and 14) led to a greater loss (P < 0.05) of nutrients in the ndole but, consequently, produced VaWW with a higher nutrient content, confirming the transfer of these compounds from the leaves to the VaWW. In conclusion, this research identifies a superior processing method that maximizes nutrient retention for human food while simultaneously generating a valuable co-product for livestock. The utilization of Vernonia amygdalina wash-water as an animal feed additive provides a sustainable strategy to mitigate competition for this valuable food source. Policy adoption of abrasion-based protocols is recommended for communities prioritizing nutritional retention. Wash-water co-products should be promoted as sustainable livestock supplements, reducing feed costs and food competition.

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