CHARACTERIZATION OF POSTHARVEST PHYSIOLOGY ATTRIBUTES OF SIX COMMERCIALLY GROWN TOMATO VARIETIES IN KENYA

Tomato ( Lycopersicon esculentum Mill) is the leading vegetable in terms of production in Kenya. The Kenyan local market has a wide variety of tomato cultivars with a wide range of morphological and sensorial characteristics. However, information on the nutritional and postharvest quality of these varieties is lacking. The aim of this research was to investigate and identify tomato varieties of superior postharvest quality and recommend them to small and medium scale farmers. In this study, six tomato varieties were grown in a greenhouse and analyzed at three maturity stages (mature green, turning and red ripe). The tomatoes were analyzed at specific days after harvest and storage at room temperature (25o C). Percentage weight loss, color, respiration and ethylene production rates were analyzed to assess the postharvest quality of the tomatoes. The color was measured using a Minolta Chromameter while the respiration rate and ethylene production rates were determined using the static system approach. Color, weight loss, respiration and ethylene production rates were positively affected by storage time when harvested at the three maturity stages. The percentage weight loss of the tomato fruits was higher in the determinate varieties, and at the turning stage of maturity (3.8 %). Minor color changes were observed after storage of the tomatoes harvested at red stage for six days. Both rates of respiration and ethylene production were low, with the respiration rate ranging between 56-10 ml CO2 Kg-1h-1. The Chonto F1 variety had the highest rate of ethylene production (5.4 μL C2H4 Kg-1h-1) on the 4th day of storage after harvest at the red ripe stage. Overall, the indeterminate tomato varieties displayed better postharvest quality that can prolong the fruits shelf life for marketing. In turn, the turning stage of maturity proved to be a better stage to harvest tomatoes as the color development was more uniform.

STANDARDIZATION OF CASSAVA MAHEWU FERMENTATION AND ASSESSMENT OF THE EFFECTS OF IRON SOURCES USED FOR FORTIFICATION

Cassava root is the main staple for 70% of the population in Mozambique, particularly in inaccessible rural areas, but is known to be low in iron. Anaemia is a public health problem in mothers and preschool children in Mozambique and up to 40% of these cases are probably due to dietary iron deficiency. The World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO) recognize the fortification of foodstuff as an effective method to remedy dietary deficiencies of micronutrients, including iron. Cassava mahewu, a non-alcoholic fermented beverage is prepared at subsistence level from cassava roots using indigenous procedures. The aim of the study was to standardize mahewu fermentation and investigate if the type of cassava fermented, or the iron compound used for fortification affected the final product. Roots of sweet and bitter varieties of cassava from four districts (Rapale, Meconta, Alto Molocue and Zavala) in Mozambique, were peeled, dried and pounded to prepare flour. Cassava flour was cooked and fermented under controlled conditions (45°C for 24 h). The fermentation period and temperature were set, based on the findings of a pilot study which showed that an end-point pH of about 4.5 was regularly reached after 24 h at 45°C. Cassava mahewu was fortified with ferrous sulfate (FeSO4.7H2O) or ferrous fumarate (C4H2FeO4) at the beginning (time zero) and at the end of fermentation (24 h). The amount of iron added to the mahewu was based on the average of the approved range of iron used for the fortification of maize meal. The mean pH at the endpoint was 4.5, with 0.29% titratable acidity. The pH and acidity were different to those reported in previous studies on maize mahewu, whereas the solid extract of 9.65% was found to be similar. Lactic acid bacteria (LAB) and yeast growth were not significantly different in mahewu fortified with either of the iron compounds. There was no significant difference between cassava mahewu made from bitter or sweet varieties. A standard method for preparation and iron fortification of cassava mahewu was developed. It is recommended that fortification occurs at the end of fermentation when done at household level.

MORPHOLOGICAL DIVERSITY OF MANGO GERMPLASM FROM THE UPPER ATHI RIVER REGION OF EASTERN KENYA: AN ANALYSIS BASED ON NON- FRUIT DESCRIPTORS

Phenotypic variation in plants can be evaluated by morphological characterization using visual attributes. Fruits have been the major descriptors for identification of different varieties of fruit crops. However, even in their absence, farmers, breeders and interested stakeholders require to distinguish between different mango varieties. This study aimed at determining diversity in mango germplasm from the Upper Athi River (UAR) and providing useful alternative descriptors for the identification of different mango varieties in the absence of fruits. A total of 20 International Plant Genetic Resources Institute (IPGRI) descriptors for mango were selected for use in the visual assessment of 98 mango accessions from 15 sites of the UAR region of eastern Kenya. Purposive sampling was used to identify farmers growing diverse varieties of mangoes. Evaluation of the descriptors was performed on-site and the data collected were then subjected to multivariate analysis including Principal Component Analysis (PCA) and Cluster analysis, one- way analysis of variance (ANOVA) and Chi square tests. Results classified the accessions into two major groups corresponding to indigenous and exotic varieties. The PCA showed the first six principal components accounting for 75.12% of the total variance. A strong and highly significant correlation was observed between the color of fully grown leaves, leaf blade width, leaf blade length and petiole length and also between the leaf attitude, color of young leaf, stem circumference, tree height, leaf margin, growth habit and fragrance. Useful descriptors for morphological evaluation were 14 out of the selected 20; however, ANOVA and Chi square test revealed that diversity in the accessions was majorly as a result of variations in color of young leaves, leaf attitude, leaf texture, growth habit, leaf blade length, leaf blade width and petiole length traits. These results reveal that mango germplasm in the UAR has significant diversity and that other morphological traits apart from fruits can be useful in morphological characterization of mango.