Truffling through the special issue of African Journal of Food Agriculture Nutrition and Development about African Leafy Vegetables, one paper caught my eye: Changes in Beta-Carotene, Ascorbic Acid and Sensory Properties in Fermented, Solar-Dried and Stored Cowpea Leaf Vegetables, by Muchoki, Imungi and Lamuka. But only because a couple of days ago a different story — Sunlight Reduces the Value of Moringa Leaves — had done the same. Both tell the same basic story, that even all-powerful traditional leafy vegetables need care in their preparation if they are to deliver the nutritional benefits they are capable of.
Unfortunately I have been unable to find a copy of Ritah Namutebi’s poster on Moringa oleifera, so I have only the newspaper report to go on. Namutebi picked Moringa leaves in the morning, at midday and in the evening and dried them in direct sunlight or in the shade. Those dried in direct sunlight lost 35-60% of their vitamin A, while those dried in shade lost less, 11-15%. ((Actually there’s a conflict in the report. One paragraph gives the figures I have quoted. The following one says that shade drying loses up to 25%, rather than 15%)) There is no information on the effect of time of picking; presumably it made no difference.
The cowpea paper is a whole heap more detailed, with three different treatment methods and six different storage regimes. Bottom line:
- Fresh leaves contain roughly six times more ascorbic acid (vitamin C) than dried leaves, but the type of drying makes no difference.
- Drying makes no difference to the amount of beta-carotene, a precursor of vitamin A.
- During storage, both the container (polyethylene bags vs Kraft paper) and the temperature affect the levels of vitamins in a manner that depends on how the leaves were initially prepared.
- At each temperature, polyethylene preserved the vitamins better than Kraft paper.
There’s more, I’m sure, to be gained from this work, but the crucial point is that it is as important to devise appropriate methods of preserving neglected and underutilized species as it is to promote their use in the first place.
GRAIN, an NGO, has published a photo essay that shows a mobile seed festival that took place from 14 January to 13 February 2007 in Andhra Pradesh, India. While GRAIN’s web technology is a lot cruder than Time magazine‘s, and the content is occasionally a little harder to swallow then even the Mexican family‘s fondness for a certain fizzy carbonated drink, it does offer a useful insight into seeds and agricultural biodiversity and what they mean to one local community.