Jasper K. Imungi

Carotenoid contents in fresh, dried and processed sweetpotato products

In order to understand the effects of drying and processing sweetpotato storage roots into traditional baked food products on their pro‐vitamin A contents, total carotenoids and s‐carotene were colorimetrically determined. Fresh and cooked storage roots, dried and stored chips, and sweetpotato processed products were used. Flesh colors of the storage roots were white, yellow, cream, orange, and purple. Total carotenoids ranged from trace to above 9 mg s‐carotene equiv./100 g of fresh storage root. Storage roots of high carotenoid content cultivars had consistently orange flesh; those with low to very low carotenoid contents were yellow or white. Hunter “b” values were high and consistent for flours from orange‐ and cream‐fleshed root cultivars, which could easily be used to predict total carotenoid and s‐carotene contents. Drying sweetpotato storage roots at 65°C for 12 h reduced total carotenoid contents by 30%. Storing dried chips in ambient conditions for 11 months induced a 10% loss. Incorporation of ...

Antioxidant and Antidiabetic Properties of Condensed Tannins in Acetonic Extract of Selected Raw and Processed Indigenous Food Ingredients from Kenya

Recently, tannins have received considerable attention as health-promoting component in various plant foods and several studies have reported on its nutraceutical properties. However, no study has established the role of condensed tannins in indigenous foods of Kenya. Therefore, this study was designed to evaluate the antioxidant activity (DPPH and FRAP) and antidiabetic effects (α-amylase and α-glucosidase inhibition activities) of condensed tannins in some selected raw and traditionally processed indigenous cereals, legumes, oil seeds, and vegetables. The condensed tannin content of the grains and vegetables ranged between 2.55 and 4.35 g/100 g DM and 1.53 and 5.73 g/100 g DM, respectively. The scavenging effect of acetonic extract on DPPH radical ranged from 77% to 90% while the reducing power was found to be 31 to 574 mmol Fe(II)/g DM in all the investigated food ingredients. The condensed tannin extracts of the analyzed samples showed promising antidiabetic effects with potential α-amylase and α-glucosidase inhibition activities of 23% to 44% and 58% to 88%, respectively. Condensed tannins extracted from the amaranth grain, finger millet, field bean, sunflower seeds, drumstick, and amaranth leaves exerted significantly higher antioxidant and antidiabetic activities than other food ingredients. Among the traditional processing methods, roasting of grains and cooking of vegetables were found to be more suitable mild treatments for preserving the tannin compound and its functional properties as opposed to soaking + cooking and blanching treatments. The identified elite sources of optimally processed indigenous food ingredients with promising results could be used as health-promoting ingredients through formulation of therapeutic diets.

Some chemical characteristics and availability of vitamin A and vitamin C from Kenyan varieties of papayas (Carica papaya L.).

Papayas from 14 Kenyan varieties were analysed for dry matter, pH, titratable acidity, total soluble solids, total sugar, vitamin C, total carotenoids and β‐carotene. There were significant varietal differences (p < 0.05) among the levels of dry matter, titratable acidity, total soluble solids, total sugar, vitamin C, total carotenoids and β‐carotene, but no significant differences among pH values.

Ascorbic acid changes in three indigenous Kenyan leafy vegetables during traditional cooking

The ascorbic acid (vitamin C) contents in three fresh green leafy vegetables commonly consumed in Kenya namely, Amaranthus hybridus, Gynandropsis gynandra and Solanum nigrum L. and the changes during traditional cooking were measured. In the fresh leaves, the ascorbic acid varied from 123.8 mg/100 g fresh weight in A. hybridus to 189.2 mg/100 g fresh weight in G. gynandra. Cooking for 20 min in boiling water led to losses of between 75 and 89%. Smaller losses in ascorbic acid were observed when the leafy vegetables were cooked in two and four volumes of water. The loss in ascorbic acid as a function of cooking time was highest in S. nigrum while its loss as a function of volume of cooking water was highest in A. hybridus. Using loss in ascorbic acid as an index, it is proposed that controlling the time and amount of water used in cooking without sacrificing palatability could help, at least in part, in preventing loss in other essential nutrients during traditional cooking of the vegetables.

The prevalence and nutritional value of some Kenyan indigenous leafy vegetables from three locations of Machakos District

A survey was carried out to determine the locally available leafy vegetables in three locations of Machakos District, Kenya. The most common vegetables were analyzed for vitamin C, beta‐carotene calcium, iron and oxalate. Consumption of wild and semi‐wild leafy vegetables was found to be common in the three locations especially during the dry seasons. Results of laboratory analyses revealed high levels of beta‐carotene and vitamin C, and iron, and moderate levels of the mineral calcium, in the majority of the vegetables. Most vegetables were found to satisfy more than 100% of the daily requirements for vitamins A and C and more than 50% of the mineral calcium for an adult male. Three of the vegetable species analyzed had high levels of oxalate.

The Physico-Chemical Characteristics and Some Nutritional Values of Vegetable Amaranth Sold in Nairobi-Kenya

Twenty one major supermarkets and ten independent green grocers in the city of Nairobi were surveyed for types of vegetable amaranths sold and their post harvest handling. The nutrient composition of the vegetables was also analyzed. In addition, information on three other traditional leafy vegetables (TLVs) namely, Cleome gynandra, Solanum nigrum, and Vigna unguiculata was obtained. All the vegetables were sold in bundles of average weight 0.45 kg. The edible fraction per bundle averaged 38.9%. Chemical analyses showed that vegetable amaranth had a moisture content of 85.5%, therefore a dry matter content of 14.5%. Expressed on dry matter basis, the mean total ash content was 19.2%, crude protein content 26.1% and the crude fiber content 14.7%. The mean ascorbic acid content was 627 mg/100 g, zinc content 5.5m g/100 g and iron content 18 mg/100 g. The men nitrate content was 732.5 mg/100 g, total oxalates 5830 mg/100 g and soluble oxalates 3650 mg/100 g, while the lead content averaged 1.03 mg/100 g. The study concludes that vegetable amaranth has potential as popular vegetable in the diets of Kenyans to significantly contribute to provision of micronutrients, particularly iron and zinc.

Antioxidant and Type 2 Diabetes Related Functional Properties of Phytic Acid Extract from Kenyan Local Food Ingredients: Effects of Traditional Processing Methods

Emerging scientific evidences reveal that phytic acid has several positive effects on human health. The antioxidant and type 2 diabetes related enzyme inhibition properties of phytic acid extract prepared from raw and traditionally processed local grains and vegetables collected from Kenya were evaluated. Phytic acid content of raw grains and vegetables ranged between 2.81–3.01 and 0.29–3.23 g/100 g DM, respectively. The phytic acid extract from raw samples revealed 59%–89% of DPPH radical scavenging capacity, 27–3,526 mmol Fe(II)/g extract of reducing power, 20%–72% of α-amylase inhibition activity and 8%–91% of α-glucosidase inhibition activity. Cooking and roasting improved the antioxidant and health relevant functionality of phytic acid extracts obtained from Kenyan local vegetables and grains, respectively.

Risk factors for symptoms of gastrointestinal illness in rural town Isiolo, Kenya.

This study assesses risk factors for food‐borne gastrointestinal illness indicated by diarrhoea and/or vomiting using 14‐day recalls among children and young adults. The study was set in Isiolo, a rural town of Kenya, inhabited mainly by pastoralists of different ethnic groups. The preparation methods of milk at the household level were also investigated. The study was cross‐sectional and involved 900 participants from randomly selected households. They were interviewed using a structured questionnaire. An unmatched nested case‐control study was constructed by randomly selecting three controls for each case. Potential risk factors for gastrointestinal illness were analysed using both univariate and multivariate logistic regression models with random effect on ethnic groups. The study results showed that consumption of mutton, carrots, Irish potatoes, raw camel milk, boiled camel milk and fermented camel milk were important risk factors for diarrhoea and/or vomiting, whereas the consumption of boiled goat milk, boiled cow milk, spinach, washing of hands with soap and the presence of proper drainage system had protective effects (odds ratio < 1). We conclude that in this setting, primarily vegetables and the camel milk market chain pose the greatest risks for symptoms of food‐borne gastrointestinal illness.

Changes in leaf yield and nutritive quality of the black nightshade (solarium nigrum) as influenced by nitrogen application

The effect of nitrogen application rates on the leaf yield and nutritive quality of the black nightshade (Solatium nigrum L.), an indigenous Kenyan leafy vegetable was investigated. Application of 5 g N per plant gave the highest fresh leaf yield of 19 and 40 tons/ha after 10 and 12 weeks of growth, respectively. The dry matter and crude fibre contents decreased with increasing nitrogen rates. With a supply of 5 to 15 g N per plant, the dry matter and crude fibre contents were on average 8.3% and 17.8 g/100 g dry matter. The crude fat and protein contents increased with nitrogen supply. Plants treated with N fertilizer yielded about 60% more proteins than the control plants grown with zero g N. The level of (5‐carotene in the leaves increased by about 60% from 63 mg/100 g fresh weight with zero g N to 103 mg/100 g fresh weight with 5 g N per plant. Although, the ascorbic acid content increased by over 100% in plants grown with 5 g N per plant, thereafter, a declining trend was observed with higher rates o...

Proximate chemical composition of street foods and their energy and protein contribution to the nutrition of manual workers in Nairobi

Street foods were sampled from 12 vending sites around construction sites and industrial areas in Nairobi. The foods were analyzed for proximate composition and assessed for their contribution to energy and protein RDAs to the manual workers. It was established that the foods were sold mainly as meals which could be described as githeri‐based, ugali‐based or rice‐based and that the main side dishes were matumbo, bean stew, greengram stew, potato/beef stew and stewed vegetables. The meals were of diverse energy contents and provided energy RDAs between 16.8–36.7% for age group 18–30 years and 17.8–38.3% for age group 30–60 years. Except for chapati+stewed vegetables all the meals provided more than 50% protein RDA to all consumers.