No abstract

Fishes are the cheapest source of animal protein and it plays an important role in the diet of many people in both developed and developing countries. It is an important ingredient in the Nigerian traditional cuisine, cat fish being one of the most valued and very diverse groups of bony fish. The catfishes are a monophyletic group, belonging to the super-order called the Ostariophysi. Freshly caught fish spoil easily and therefore requires adequate preservation and storage. Of all flesh foods, fish is the most susceptible to tissue decomposition, development of rancidity, and microbial spoilage. Fish begin to deteriorate as soon as they leave the water. The preservation of fish is therefore considered to be a major hindrance to its production and utilisation especially in the tropical countries in Africa. The four most popular methods of fish preservation are freezing, canning, smoking and pickling, the major preservation method being pickling or salting, which has been used for centuries. In this present study, the effect of extracts from three indigenous spices; Piper guinensis (uziza), Xylopia aethiopicum (okada) and Myrustica monodora (ehuru) on the preservation of smoked-dried catfish stored for six weeks were evaluated using brine solution as control. Samples treated with uziza showed the lowest moisture content of 6.5% and lowest mean FFA formation of 0.55%, which was significantly different (p<0.5) from the other spices. The mean peroxide value range of 5.8-15.1 meq/kg was observed throughout the storage period for all the spices used. Thiobarbituric acid values ranged from 0.6mg/kg-1.4mg/kg with the lowest mean value of 0.37 mg/kg recorded in fish samples treated with uziza while the highest mean TBA value of 1.14mg was obtained in ehuru treated samples. This new research reveals that the three indigenous spices used, including Piper guinensis, Myristica monodora and Xylophia aethiopicum had chemical preservative and antioxidant properties. Among the three spices, Piper guinensis (uziza) was found to have the most effective preservation potential of smoked-dried fish during storage. This new result is anticipated to provide a simple, cheaper, healthier and safer method of fish preservation in developing countries.

Full-fat and defatted coconut protein concentrates containing 27.80% and 30.20% proteins (on a dry weight basis), respectively, were prepared from freeze-dried coconut meal samples. Selected functional properties such as: nitrogen solubility, emulsion and foaming properties were determined. Nitrogen solubility was measured in the range of P H 2.0-12.0 in three dispersion media including water, 0.1M NaCl (low salt) and 1.0M NaCl (high salt). The emulsion properties of the protein concentrates were measured at varying P H values (2.0-10.0) and sample concentrations.Foaming properties were determined using same parameters including the use of additives (NaCl solutions and carbohydrates). Below and above the isoelectric P H (4.0-5.0) the nitrogen solubility increased. The coconut protein samples showed a fairly high solubility (more than 54.0% and 53.0%) for full-fat coconut protein concentrate (FFC-PC) and defatted coconut protein concentrate (DFC-PC), respectively at pH 2.0. FFC-PC sample had maximum solubility (more than 73%) at 10.5 and minimum solubility (13.2%) at P H 4.0. On the alkaline P H scale, FFC-PC sample had maximum solubility of more than 43% at P H 10.5 in high salt (1.0M NaCl) solution while DFC-PC sample had maximum solubility of 50.2% in 1.0M NaCl solution and more than 80% in low salt (0.1M NaCl) dispersion medium.The emulsions prepared had good stability. A maximum of 92.5ml/g protein of emulsification capacity, at P H 10.0 and minimum of 45.3ml/g protein at P H 4.0 were obtained for FFC-PC while DFC-PC had a maximum EC of 86.4ml/g protein. FFC-PC samples produced significantly (P≤0.05) higher emulsion capacities than DFC-PC samples at all the dispersion P H and sample concentrations investigated. The FFC-PC samples had a significantly low foaming capacity than the DFC-PC samples at all the tested P H values. Similarly, the foaming capacities of FFC-PC and DFC-PC decreased with increasing P H of the sample medium. Both FFC-PC and DFC-PC foams collapsed completely, after 3hr standing at ambient temperature. Foaming was concentration dependent. The FFC-PC and DFC-PC foams increased sharply at 0.2% NaCl content of the sample slurries and progressed steadily to a peak of 92.0% and 113% in FFC-PC and DFC-PC samples respectively in 0.8% NaCl solution and then declined gradually with increased salt concentration. Addition of polymeric carbohydrates (sucrose, corn starch, gum acacia and pectins) significantly improved foaming properties of the protein concentrates but the foam stabilities were not significantly affected.