β-carotene losses due to handling and cooking in Kenyan leafy vegetables connote no comparative nutritional superiority over kales.

Abstract

African leafy vegetables (ALVs) are known to be high in β-carotene content and are preferred over kales due to this nutritional superiority. Ten different vegetables were collected from farm and market locations and analyzed for β-carotene content. Cooked vegetables (in single or in combination) as well as solar dried samples were prepared by the community members in the study area in the usual way and without any instruction or conditions given. β-carotene content was analyzed using a High Performance Liquid Chromatography (HPLC). The results provided new representative β-carotene content of the fresh, marketed, cooked and dried vegetables without controlling or simulating the household handling or processing methods in a laboratory. While edible portions of kales are relatively inferior as a β-carotene source as compare to ALVs when in raw form, this is not the case at market place where kales exhibit comparable level of the β-carotene. As much as 280 μRE/100 g (a dietarily significant amount) can be lost through β-carotene oxidation before farm-fresh ALVs are sold in the market place with the losses severe in some ALVs and only subtle and relatively lower in kales. Post-cooking, kales had statistically comparable β-carotene content to ALVs save for when compared with purple amaranths and blacknight shade. Due to losses experienced in ALVs, kales are not comparatively inferior vegetables in terms of β-carotene content. Measures to prevent β-carotene losses in ALVs between the farm and market, during cooking and drying should be instituted in order to benefit from their high β-carotene content.