| dc.description.abstract | A household survey was carried out in Luanda division of Vihiga district to establish the extent of
production, time taken before first harvest and the common cooking methods of two traditional
vegetables; Cleome gynandra and Corchorus olitorius.
The two vegetables were harvested from Maseno university's experimental plots. Cleome gynandra
was harvested at the 3rd
, s", ih and 9thweeks from planting while Corchorus olitorius was harvested
at the 4th, 6th, 8th and io" weeks from planting. The vegetables were analysed to establish the best
time to harvest. The fresh vegetables were analyzed for proximate composition, ascorbic acid, betacarotene,
the minerals, iron and calcium and the anti-nutrients total oxalates, total phenols and nitrates.
The leaf samples were cooked by boiling in distilled water and by steaming then analysed for ascorbic
acid, beta-carotene, iron, calcium, total oxalates, total phenols and nitrates.
Finally samples of fresh vegetables were dipped in a solution of hypochlorite, and stored in perforated
and non perforated polythene bags at 22°C and in domestic refrigeration at 4°C for a total of seven
days. The hypochlorite acted as an anti-microbial compound. The stored vegetables were analysed
initially then on the fourth and seventh days for ascorbic acid and beta-carotene.
Results indicate that 99% of the households grow and consume both vegetables. Harvesting of Cleome
gynandra begins at between 3 to 4 weeks from planting. Majority of the households cooked the
vegetable by boiling in water, as the cooking method reduces the bitterness in the vegetable. The
proportion of cooking-water averaged 616.8millilitres while the cooking time averaged 53 minutes.
Harvesting of Corchorus olitorius starts at 4 weeks from planting. The method of choice for cooking
of the vegetable is boiling in plain water. The average proportion of cooking was 875 milliliters, while
the cooking-time averaged 40 minutes. About 27% of the households, however, reported adding some
ash from bean trash to the boiling water. This helped to bring out the sometimes desired slimy taste of
the cooked vegetables.
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Results from the laboratory analyses indicate that Cleome gynadra showed gradual increases in dry
matter, crude protein, crude fiber, soluble carbohydrates, ascorbic acid, beta-carotene, calcium, iron,
anti-nutrients; total phenols, while the vegetables showed gradual decrease in crude lipid and total
oxalates during growth. Corchorus olitorius on the other hand showed gradual increase in dry matter,
crude fiber, total ash, calcium and iron and gradual reduction in crude lipid, and crude protein, during
growth. Soluble carbohydrates, ascorbic acid, beta-carotene, nitrates, total phenols and total oxalates
did not show any definite trend.
Boiling and steaming of both vegetables resulted in significant (P<O.05) increases in carotene but
reduction in ascorbic acid contents. There was a significant reduction (P<O.05) in the iron contents of
both vegetables and calcium content of Corchorus olitorius on boiling and steaming. Cleome
gynandra did not show significant changes in calcium contents when boiled and steamed. There was a
significant reduction (P<O.05) in the levels of total phenols for both vegetables on boiling and
steaming, but steamed vegetables were slightly higher in total phenols that the boiled. The levels of
oxalates in the two vegetables were not significantly affected by both boiling and steaming.
It was observed that the vegetables could be stored in perforated and non perforated bags for only four
days at ambient temperature (22±2°C), but for up to seven days at (4± 1°C). During the storage
however, the time, packaging and storage effected significant (P<O.05) reductions in ascorbic acid of
the vegetables. The treatment, packaging and storage conditions effected significantly (P<O.05) the
beta-carotene whereas, the treatment of the leaves with chloral a disinfectant did not affect betacarotene
contents.
This study showed that stage of harvest influenced the nutritional value of the two vegetables. Cleome
gynandra showed gradual increases in dry matter, crude protein, crude fiber soluble carbohydrates,
ascorbic acid, beta-carotene, calcium and iron and decreases in crude lipid and total oxalates. The
increase in the proximate chemical composition with age and decreases in oxalates is important
nutritionally. These samples showed gradual increase in total phenols. Corchorus olitorius showed
gradual decreases in crude lipid and crude protein. Therefore in order to maximize on these nutrients
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the vegetable should be harvested early. The vegetable also showed increases in dry matter, crude
fiber, total ash, calcium and iron with increase in age this is positive for health.
Cooking methods led to the reduction in ascorbic acid and minerals. It is therefore important to
standardize the methods involved in cooking this vegetable. Cooking also led to loses of anti nutrients.
Anti-nutrients have negative impact nutritionally in that some bind important minerals in the
vegetables, thus making them unavailable in the cooked vegetables. For example oxalates bind
calcium whereas tannins bind protein
Raw vegetables could be stored in polythene bags for up to four days at ambient temperatures and up
to seven days in a domestic refrigerator, without appreciably losing their consumer appeal. | en |
