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In development of fermented dairy products and protein hydrolysates with high inhibitory activity towards angiotensin-converting enzyme (ACE), it is crucial to have a reliable assay for measuring the ACE activity. In the present study, the performance of two commonly used assays based on synthetic N-derivates of tripeptides as substrates were tested with respect to reliability in determination of ACE activity per se and to the inhibitory effect of a tryptic whey protein digest and captopril. In one test, the ACE activity was calculated from the amount of hippuric acid liberated from hippuryl-His-Leu (HHL) during 30 min of incubation with ACE, as quantified after HPLC separation of reaction products. In the other assay, the ACE activity was measured directly as the rate of decrease in the absorbance at 340 nm during the first 30 min of ACE catalysed hydrolysis of furanacroloyl-Phe-Glu-Glu (FA-PGG). Both assays, in the absence of inhibitor, showed a good performance with relative standard deviation between replicate samples around 7%. In the presence of inhibitor solutions, relative standard deviations for both assays varied between 1 and 18% for the variously diluted inhibitors. Both assays gave values for the concentration of inhibitor needed to inhibit ACE by 50% similar to those previously reported for whey protein digests and captopril. Different results from the two assays, however, emphasize the importance of controlling the actual ACE-activity for comparison between assays. The limitations of each assay are discussed. Considering the fewer steps in the assay using FA-PGG as substrate, and thus less time and chemicals consumed per sample, and the simpler equipment needed, this assay is recommended for the screening of clear peptide samples.

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Background and Objective: The benefits of using natural colors in foods are many such as they are strong antioxidant, safe and get from renewable sources. Generally natural pigments do not cause any health problems; conversely, they may act as a health improvement. So, the objectives of this study are using natural colors and antioxidant from aqueous extracts of red cabbage and turmeric in the preparation of stirred yogurt. In addition, study the effects of these extracts on the quality characteristic of the obtained stirred yogurt. Methodology: Four natural extracts were prepared by using only distilled water; red cabbage juice, aqueous extracts of anthocyanin, aqueous extracts of turmeric and aqueous extract of curcumin. The inoculated milk was dived into five portions, control and four treatments fortified with 10% of prepared natural color extracts. All samples were incubated at 43°C until full coagulation and the containers were transferred to the refrigerator overnight. The yogurt samples then stirred and stored in the refrigerator at 7° ± 1°C. Chemical, microbiological, antioxidant activity and organoleptic evaluations were carried out after that. Results and Conclusion: The inclusions of red cabbage and turmeric extracts in the stirred yogurt resulted in products with appropriate and acceptable physicochemical, microbiological and sensory attributes. Aqueous extract of anthocyanin from red cabbage is the best extract, followed by the curcumin extract. These extracts were best known for their health benefits for humans and recommended to use in stirred yogurt and another dairy products.

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Abstract:This study aims to evaluate the effect of different graded levels of local yeast (Saccharomyces cerevisiae) on the growth performance of Africancatfish, Clarias gariepinus. At the start of the experiment, a total number of 140 healthy fish were chosen. The fish were weighed and then divided into seven experimental groups of 10 fish per 70 -L aquarium. The water was replaced every day, but the fecal matters were siphoned out daily. Each aquarium was supplied with dechlorinated water and aerated continuously by an air compressor, so that oxygen levels were kept close to saturation. Dissolved oxygen, pH and total NH3-N were monitored in each aquarium during the experimental period. Dissolved oxygen levels were monitored close to air saturation (5.6mg/L) and pH was always on the alkaline side (7.9), while NH3-N not more than 0.097mg/L and temperature 25.5co as well as photoperiod12:12 Light: Dark). One control and six experimental diets duplicate (B2%, B1%, B0.5%, B0.2%, B0.1%&B0.05%) were arranged. Baker yeast (Saccharomyces Cerevisiae) was not included to the control group; however a (B2% at B0.05%) group was supplemented with baker yeast at 20.0, 10.0, 5.0, 2.0, 1.0and 0.5 g per kg diet respectively.The experimental diets were formulated to contain approximately 33.64 % crude protein. The feed was provided two times a day (10:00 am and 2:00 pm). All the experimental groups were fed the experimental diets at a rate of 3% of the live body weight of the fish. The experimental aquaria were inspected daily to remove food wastes and dead fish. The conclusion from the economic point of view the use of cheap local baker's yeast for African catfish increases their growth and production under farming conditions. The present study indicates that live baker's yeast positively enhance some hematological and physiological parameters as a results of the feed utilization, growth and production performance of African catfish. 176

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