Chemical and functional properties of ten sweetpotato varieties were investigated. The sweetpotato were of various flesh colours which included orange, yellow, cream and white with dry matter content ranging from 30.2% - 39.2%. The sweetpotato varieties varied significantly (p < 0.05) in total amylase activity, total starch and amylose content whose value ranges were 0.256 - 0.570 mg/ml/min 68.4% - 73.6%, 16.2% - 23.4% respectively. The pH of flours from the different sweetpotato varieties ranged from 6.01 - 6.64. The pasting behaviours of the sweetpotato flours also showed significant differences (p < 0.05) in the individual parameters (peak time, pasting temperature, peak viscosity, trough viscosity, final viscosity, breakdown and setback) among the different varieties. The results revealed the influence of variety on the chemical composition of sweetpotato and their pasting properties. Correlations were also revealed among different components of the sweetpotatoes which would be a basis in selection of the varieties for processing into different products
Sweetpotato varieties (five) were investigated for changes in <i>α</i>- and <i>β</i>-amylase activities during root development and on subjection of harvested roots to different postharvest handling and storage conditions. Changes in <i>α</i>- and <i>β</i>-amylase activities in development were monitored from 10 weeks after planting. At physiological maturity, sweetpotato roots were harvested and subjected to various conditions: freshly harvested roots and cured roots (spread under the sun for four days at 29℃ - 31℃ and 63% - 65% relative humidity), stored at ambient conditions (23℃ - 26℃ and 70% - 80% relative humidity) and in a semi-underground pit (19℃ - 21℃ and 90% - 95% relative humidity). Generally <i>α</i>- and <i>β</i>-amylase activities increased during development with NASPOT 9 and 10 consistently registering the highest activities and NASPOT 1 the lowest activity. Generally, maximum <i>α</i>-amylase activities were achieved at week 3 in ambient stores for NASPOT 9 and NASPOT 10 at 0.930 and 0.897 CU/g, respectively. Maximum <i>β</i>-amylase activity was achieved in ambient stores at week 3 and 4 for fresh and cured NASPOT 9 at 806 and 782 BU/g, respectively. Generally, curing and storing sweetpotatoes in ambient conditions registered the highest amylase activity. Maximum <i>α</i>- and <i>β</i>-amylase activities were registered at 67℃ - 68℃ and 58℃ - 60℃, respectively. These findings provide information for controlled modification of amylase activities of these sweetpotato varieties for product development efforts and monitoring the shelf life of the roots during storage
Changes in total starch and reducing sugar content in five sweetpotato varieties were investigated weekly during root development and following subjection of the roots to different postharvest handling and storage conditions. Freshly harvested (noncured) roots and cured roots (spread under the sun for 4 days at 29–31°C and 63–65% relative humidity [RH]) were separately stored at ambient conditions (23°C–26°C and 70–80% RH) and in a semiunderground pit (19–21°C and 90–95% RH). Changes in pasting properties of flour from sweetpotato roots during storage were analyzed at 14‐day intervals. Significant varietal differences (p < .05) in total starch, sucrose, glucose, maltose, and fructose concentrations were registered. The total starch and sucrose content of the roots did not change significantly (p < .05) during root development (72.4 and 7.4%, respectively), whereas the average concentrations of glucose, maltose, and fructose decreased markedly (0.46–0.18%, 0.55–0.28%, and 0.43–0.21%), respectively. Storage led to decrease in total starch content (73–47.7%) and increase in sucrose and glucose concentrations (8.1–11.2% and 0.22–1.57%, respectively). Storage also resulted in reduction in sweetpotato flour pasting viscosities. Curing resulted in increased sucrose and glucose concentrations (9.1–11.2% and 0.45–0.85%, respectively) and marked reduction (p < .05) in total starch content (72.9–47.6%). This resulted in low pasting viscosities compared to flour from storage of uncured roots. These findings show that significant changes occur in the carbohydrate components of sweetpotato roots during storage compared to development and present an opportunity for diverse utilization of flours from sweetpotato roots in the food industry.
Wild edible mushrooms, Termitomyces microcarpus are widely consumed in Uganda, partly because of their taste, flavour and because they are believed to have medicinal benefits. This study investigated the nutrient composition of the Termitomyces microcarpus mushrooms and the effect of the mushroom on feed intake, weight gain, serum cholesterol and triglycerides of male albino rats. Semi-dried mushrooms collected from Kyenjojo District in western Uganda were analyzed for nutrient composition using standard procedures. To determine the effect of dietary intake of mushrooms, a completely randomized study design was used with experimental treatments having diets containing 25, 45 and 60% air -dried mushroom flour mixed with the basal feed and 0.5% cholesterol. These were compared to a control diet consisting of only commercial (basal) feed and to a diet containing basal feed and 0.5% cholesterol. The rats were fed on the five diets for ten weeks and were monitored for changes in feed intake and weight at weekly intervals for six weeks and in serum total cholesterol, High Density Lipoprotein (HDL)-cholesterol, Low Density Lipoprotein (LDL)-cholesterol and triglycerides at two weeks intervals for ten weeks. Proximate analysis revealed that the mushrooms contained 25.5% protein, 2.3% fat, 11.2% dietary fibre, 48.37% available carbohydrates and 12.67% water. The mushrooms were also found to contain 61 mg/100g of iron, 156 mg/100g of calcium and a number of other dietary minerals. Dietary inclusion of Termitomyces microcarpus mushrooms significantly reduced the feed intake and weight gain of the rats by up to 36.8 and 29.5%, respectively. The reduction increased with the proportion of dietary mushroom. Inclusion of mushrooms in the diets of rats also lowered their total serum cholesterol, LDL-cholesterol and triglycerides by up to 15.6, 28.3 and 29.9%, respectively. Reduction in serum lipids did not, however, show a clear relation to the quantity of mushrooms in the diet. The reduction in the total serum cholesterol, LDL-cholesterol and triglycerides may be attributed to the high quantities of fibre in the mushrooms. These results suggest that consumption of T. microcarpus mushrooms could contribute to reducing the prevalence of diseases linked to high blood lipids.
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