RESUMO
This study aimed at chemical characterization of Dovyalis caffra (Hook.f. & Harv.) Sim. and Dovyalis abyssinica (A. Rich.) Warb. fruits from Kinamba Town (KT) in Laikipia county and Gitoro Forest (GF) in Meru county of Kenya. All analysed fresh fruit samples had low pH values averaging at 2.67. Other tests showed D. abyssinica-GF to be significantly inferior to D. caffra-GF and D. caffra-KT in terms of TSS, TSS:TTA ratio, and ascorbic acid content. Based on these parameters, D. caffra-KT presents itself with a higher potential for direct consumption as compared to D. caffra-GF. Proximate analysis of dried fruit pulps demonstrated D. abyssinica-GF to be significantly higher in ash content and significantly lower in protein and fat contents compared to the other two samples. There were insignificant difference in the fibre and carbohydrate contents of all the fruit samples. In phytochemical analysis, D. caffra-GF recorded the highest total polyphenol content of 1845 mg Gallic acid equivalent (GAE)/100 g while D. abyssinica-GF reported the lowest figure of 1128 mg GAE/100 g. Flavonoid and simple phenols fractions were in the range of 18.15-26.85% and 73.15-81.85% respectively in all fruit samples. As for antioxidant activity, D. caffra-GF recorded significantly high scores in both DPPH and CUPRAC assays, and D. abyssinica-GF the lowest. The range of DPPH and CUPRAC scores for all samples was 1995-4993 mg l-ascorbic acid/100 g and 1384-2303 mg l-ascorbic acid/100 g respectively. The current study presents the nutritional and health potential of D. caffra and D. abyssinica fruits. This forms a good basis for future adoption and exploitation of these fruits.
RESUMO
The kinetics of the alkaline phosphatase catalyzed hydrolysis of disodium p-nitrphenyl phosphate was studied at 25 degrees C in the presence of the carbohydrates sucrose, fructose, lactose, maltodextrin (DE = 13-17), carboxymethylcellulose (CMC), and CMC-lactose (in 1:1 proportion) at different concentrations and in the presence of sucrose at two different concentrations in a temperature range between 25 and -10 degrees C in subcooled and frozen systems. The objective was to determine whether the reaction is diffusion-controlled, to gain an insight about the factors that determine the diffusion of the reaction species, to understand the mechanism through which the different carbohydrate additives affect the kinetics of the reaction, and to determine the effect of low temperature and freezing on the structural conformation of the enzyme. It was found that the alkaline phosphatase catalyzed hydrolysis of DNPP under the condition studied is at least partially diffusion-controlled. The results also indicate that the diffusion is not controlled by the macroviscosity of the reaction media. The concentration and type of the molecules that constitute the background matrix seem to be the main factors governing the reaction. The results indicate that the different carbohydrates affect the kinetics of the reaction through the excluded volume effect of molecular crowding and decreased substrate and product diffusion rate and not through nonspecific solute effects, which may cause protein denaturation and alteration in enzyme activity. Low temperature does not seem to affect the structural conformation of the enzyme in the temperature range studied, whereas freezing affected the catalytic properties of the enzyme perhaps through its effect on the structural conformation of the enzyme.
