Assessment of some traditional leafy vegetables of Upper East Region and influence of stage of harvest and drying method on nutrients content of spider flower (Cleome gynandra L.)

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Traditional leafy vegetables eaten in the Upper East region of Ghana were assessed. A survey was carried out to determine consumer perception of indigenous vegetables in the Upper East Region of Ghana. The survey was aimed at cataloguing a list of commonly eaten leafy vegetables in the Region and also obtaining information on level of production, harvest and postharvest practices such as: harvesting methods, transportation to market centres, level of losses to diseases and pests, processing and packaging methods used as well as its implication on quality. The research also studied the effect of stage of harvesting and drying method on nutritional composition of Cleome gynandra (Spider flower) grown in two (2) ecological zones. The study recorded 11 cultivated and 10 wild leafy vegetables commonly consumed in the region. The results of the survey indicated that majority of the leafy vegetable farmers (50.3 %) in the region had no formal education and were predominantly female (83.3%).The results also showed that traditional leafy vegetables are produced by 72.3 % and consumed by 98.3% of respondents in the region as against the exotic leafy vegetables. Harvesting of vegetables is done using varying methods (as indicated by 42 % of the respondents), and was mainly transported to and from the marketing centres using donkey carts (60 %). It was noted that vegetable farmers in the region lose up to 20 % of their vegetables to pests and diseases. Sun-drying (98.6 %) is the main method used in the region to process leafy vegetables to keep for future use. Processed leafy vegetables were mainly stored in polypropylene sacks (60 %). A common practice at the marketing centres was sprinkling of water (70.6 %) on the vegetables to maintain their freshness. In the second phase of the study, Spider flower (Cleome gynandra L.) was chosen due to its widespread use in the region at the beginning of the rainy season when grain stocks are depleted and grown in two different locations (Kumasi and Bolgatanga), harvested at two different harvest times (6 weeks and 7 weeks of age), processed with two different processing methods (sun and oven drying) and analyzed for proximate and mineral nutrients The study recorded varying results for proximate nutrient content in samples from the two locations. Harvesting at 6 weeks of age from both locations gave significantly (P< 0.05) higher levels of moisture (15.90 % and 16.47 %) on fresh weight basis for both locations (Kumasi and Bolgatanga) respectively than the 7th week harvest (14.57 %). Significantly higher levels were also recorded for crude fibre (15.67g/100g) in samples harvested in the 6th week from Kumasi and dried in the oven as well as carbohydrate (33.90 g/100 g) in samples harvested from Kumasi at week 6 and dried in the sun. Crude protein (29.80 g/100 g) in samples harvested from Kumasi at week 7 and dried in the oven, crude fat (3.50 g/100 g) in samples harvested from Kumasi at week 7 and dried in the sun and ash content (10.75 g/100 g) in samples harvested from Kumasi at week 7 all showed significant interaction. Analysis of spider flower harvested from Bolgatanga indicated significantly (P<0.05) higher levels of crude protein (32.10 g/100 g) and crude fat (3.50 g/100 g) in harvests at 6th week dried in the oven as well as ash content (13.50 g/100 g) in samples harvested at week 7 and dried in the oven, fibre (19.29 g/100 g) and carbohydrates (28.84 g/100 g) in that harvested at week 7 and dried in the sun as compared to the other treatments. Differences in time of harvest as well as drying method were not significant (P<0.05) with respect to mineral composition except for phosphorus content in the samples produced at Bolgatanga. Ranges recorded for the other test minerals in the study were; potassium (2.83 – 3.08 g/100 g), calcium (2.37 – 3.17 g/100 g), magnesium (1.72 - 2.17 g/100 g) and iron (3.3 - 13.8 mg/100 g). Generally oven drying resulted in better preservation of nutritional components (protein and crude fibre). The results of this study suggest that oven-drying should be the method of choice when it comes to protein and fibre preservation. However, as far as mineral content was concerned the drying method did not matter and that sun-drying was as good as oven-drying. Producers of C. gynandra could therefore use either drying methods for drying the vegetable without significant variation in mineral composition.
A Thesis Submitted to the Department of Horticulture, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana in partial fulfillment of the requirements for the Master of Science Degree in Post Harvest Physiology