Some processing and preservation methods for indigenous leafy vegetables (ILVs) and the effects of the methods on some nutrients and anti-nutrients
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Date
2004-11-24
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Abstract
Seven species of indigenous leafs’ vegetables (ILVs) namely Solanurn macrocarpon, Talinuni iriangulare, Hibiscus sahdarffjà, Corchorus olitoris, Colocasia esculenta, Xanthosonia sagil4,fhliuni and Arnaranthus cruenius were processed (by sun-drying, solar-drying, steam blanching followed by solar drying and hot water blanching followed by solar drying), packaged (in different colours of polyethylene; black, brown and colourless) and stored (for 20 weeks) and the effects of processing, packaging and storage on some nutrients, anti-nuthents and sensory characteristics were studied. The methods of processing had no significant effect on the levels of ash and calcium. The effect of processing on the provitamin A carotenoid (J3 -carotene and a — carotene) levels of the ILVs was species-dependent. In some of the ILVs (Solanuin inacrocarpon, Thhnzirn iriangulare, Corchorzt.c ohtorzus and Xanthosoma sagii,fhliuni), processing resulted in an increase in the levels of provitamin A carotenoids (by 7 — 342 %) but in others (Hibiscus sahdari/j, Colocasia esculenia and Mnaranlhus cruenlus) the provitamin A carotenoid levels were reduced (by 8 — 99 %) as a result of processing. Methods of processing however reduced the levels of iron (by 3.3 — 64.9 %) and vitamin C (by 87 — 100 %). Processing methods significantly reduced the levels of total phenol (by 0.0 —74.3 %) but did not significantly affect the levels of oxalate. Generally, processing methods did not eliminate alkaloids and they did not change the overall palatability of Solanuin sp, Co/ocasia sp, Xanlhosorna sp, Amaranthus sp and sun-dried and solar-dried Corchorus sp. Some methods of processing (sun drying and solar drying) increased the green colour of the ILVs, but others (blanching and drying methods) reduced greenness. in storage however the colour of the ILVs was best retained by the hot water blanched and dried samples. Black, high-density polyethylene packaging material best retained the green colour of the ILVs. Storage did not generally affect the levels of moisture and total phenol but it reduced the levels of vitamin C (by 19 — 100 %). The nutritional values of the seven ILVs were found to be high. Amaranthus cruentus leaves had the highest levels of most nutrients; ash, calcium, iron, s-carotene, lutein and vitamin A activity. The selected leaves were free from cyanogenic glucosides.
Description
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology in partial
fulfilment of the requirements for the award of Master of Science degree in Food Science and Technology, 2004