EFFECT OF DIFFERENT POSTHARVEST TREATMENTS ON ANTINUTRITIONAL FACTORS IN SOME COMMONLY CONSUMED LEAFY VEGETABLES IN CAMEROON

Effect of squeeze-washing, boiling in kanwa (a local alkaline salt) and drying of the leaves of some leafy vegetables (Vernonia colorata, V. calvoana var. bitter, V. calvoana var. nonbitter and V. amygdalina) consumed in Cameroon on antinutritional factors were evaluated. Results show that values for polyphenols were high in the unprocessed leaves. These values were reduced by 84.5% in V. amygdalina during processing. Sun drying and oven drying at 75C also caused slight losses (P < 0.05) in polyphenols. Saponin values were high in these four species but were considerably reduced by processing, rendering the nutrients in these leafy vegetables more bioavailable. Reductions (P < 0.05) were also observed for proteins as a consequence of processing by squeeze-washing and use of kanwa. Similar trends were found for oxalic acids. Losses of up to 73% oxalic acids were observed in samples after processing. With the exception of drying, significant losses in minerals were observed due to these processes. This study, therefore, suggests the use of some of these different processing techniques to reduce the levels of antinutritional factors in these leafy vegetables. The different species of leafy vegetables (Vernonia) are potentially rich sources of provitamin A, vitamin C and minerals. Use of appropriate processing and preservation technology makes these vegetables available at off seasons and in cities of high demand and improves on the actual nutritional value to the consumers. Industrially, these vegetables can be processed by squeeze-washing and the use of minimal quantities of kanwa and possibly dried at 45C for use in urban centers.