Drying of fish--factors to consider

Although one of the best possibilities for raising the animal protein of the diets of Nigerian is to increase the consumption of fish; particularly through the use of several methods of long term preservation techniques, such as drying, no radical approach has yet emerged. Although, a great deal of the artisanal fish catch is dried for the huge consumer and distant markets, the traditional methods of fish preservation need improvements to cope with demand for increased quantity, shelf-stable, and improved quality of fish products. The paper discusses drying requirements, heat and mass transfer, consumer acceptance, fuel sources, storage and marketing of dried fish products; and suggest ways and means of structurally transforming the artisanal technology of fish drying

Effects of different types of drying on the nutritive value of proteins in the fishmeals

A comparative study on the effect of different types of drying on the nutritive value of the proteins in the different fishmeals of known history was made. From the observations, it is clear that the mode of drying has got little or no effect on the nutritive value of the meal as revealed by the chemical indices of available lysine and pepsin digestibility, provided enough precautions were taken to avoid scorching during drying process. Sun dried meals are in no way inferior to the meals prepared by hot-air, steam or vacuum drying.

An accelerated method of hot air drying of fish

The effects of temperature and relative humidity on the rate of drying of split open fish and salted fish in a tunnel dryer have been studied at a constant air velocity. By a judicious combination of these two, the rate of drying could be considerably accelerated, 10 to 12 hours only being required for drying to moisture levels below 30% in the case of mackerel, lactarius, otolithes and kilimeen (Nemipterus japonicus)

On sun-drying of Bombay duck

Sun-drying of Bombay duck by hanging on scaffolds gave better products than those obtained by drying them in trays. Optimum rate of drying and quality of dried product were obtained when the fish were suspended at the rate of 50 to 60 per meter length of the rope. The quality of the raw material as affected by the delays in different hauls in the fishing trip was reflected in the dried products also.

Investigations on wooden floating materials: the loss of buoyancy under continuous immersion in water and the rate of its redemption by drying

A wooden fishing float under immersion in water for long periods is liable to absorb water, the quantity of water absorbed possibly being dependent upon the physical factors like the specific gravity and the inherent property of the material, the time of soaking and the pressure acting on it. Consequently a wooden float is likely to become heavy and loss its original buoyancy. However, when the float is removed from water and dried, the lost buoyancy is regained on complete drying. The present paper is an attempt to elucidate these two important characteristics of some of the chief wooden floating materials used on the West Coast of India.

Freeze drying of fishery products: Part IV - Biochemical changes occurring in prawn muscle during freezing, freeze drying and prolonged storage of the freeze dried product

The changes occurring in water and salt extractable protein and non-protein fractions in prawn muscle of different species during freezing, freeze drying and subsequent prolonged storage have been studied. There is no denaturation of water extractable proteins, whereas salt extractable proteins were rendered insoluble to the extent of 21% due to freeze drying. The freeze dried products remained in good edible condition for 32 months of storage up to which storage characteristics were followed.

Freeze drying of fishery products: Part V - Storage characteristics of ready-to-serve freeze dried foods

Behaviour of freeze dried ready-to-serve fish based food preparations during prolonged storage at room temp has been studied and reported in this paper. Storage life of such products under the conditions employed in this study can be reckoned in years at our ambient temps.

Preparation of mussel meat by drying

The paper describes a simple and cheap process for the preservation of mussel meat by drying. The method involves blanching the mussel meat shucked from purified live mussels in 5% boiling brine for 5 min followed by drying to moisture of 10 to 15%. The product stored in glass bottles or polythene bags suitably sealed, has a storage life of about six months after which the organoleptic qualities begin to deteriorate. No preservative is used at any stage of processing and the yield of the product is approximately 20%. The major type of spoilage during storage is brown discoloration. Spoilage due to insect infestation is also common unless packed properly.

Comparative efficiency of different surfaces for drying fish

The efficiency of four different drying surfaces, namely, cement platform, palmyrah leaf mat, aluminum tray and stretched net for drying fish were studied using sciaenids, mullet and perch. All the drying surfaces were found to be equally efficient. The cheaper and locally available palmyrah leaf mat or stretched net can replace costly cement platform and aluminium tray for efficient drying of fish.

Modified water spray chumming system for pole and line fishing of tuna

A water spray chumming system consisting of a 65 x 50 mm centrifugal pump driven by the propulsion engine through a PTO clutch and 'V' pulley power transmission system has been developed for the pole and line fishing of tuna. Water is sprayed through pipe loop system fitted on the edge of the fishing platform of the boat through small holes. The distance of the spray length can be adjusted by controlling the flow of the pump discharge water through a wheel valve.

Effect of cooking and drying on carbonyls of oil sardine

Changes in the total as well as major individual carbonyls of oil sardine during steam cooking, oven drying, sun drying and freeze drying are presented. Carbonyls extracted with hexane were converted to their 2:4 dinitro phenyl hydrazone (DNPH) derivatives and were separated into major classes by column chromatography on celite/magnesia. Individual carbonyls were then identified by capillary gas chromatography of the DNPH derivatives. Dehydration and heating increase the carbonyl production from highly unsaturated fish lipids. The carbonyls produced react with other muscle constituents leading to complex changes. The influence of the mode of dehydration on these different aspects and their net effect on flavour are discussed.