Effect of delayed icing on quality changes and shelf-life of some freshwater fish from Bangladesh

The quality and shelf-life of three freshwater fish species of Bangladesh, catla (Catla catla), magur (Clarias batrachus) and tilapia (Oreochromis niloticus) stored at room temperature and ice were evaluated. Live fishes were killed by cranial spiking and stored at room temperature (27-30 °C), ice stored immediately after death, 5 hr after death and 10 hr after death. The shelf-life and quality of the fishes were evaluated by organoleptic method, rigor-mortis studies and bacteriological assessment. Fishes kept at room temperature became organoleptically unacceptable within 16-20 hr duration. Ice stored fishes showed considerable differences in their shelf-life when icing was delayed for different duration. Shelf-life of catla ice stored immediately after death was 20 days but shelf-life reduced to 12 days when icing delayed for 10 hr after death. Similar trend was observed for two other fish species magur and tilapia. Rigor-index of the fishes stored under different conditions also considerably varied among the three fish species, particularly effect of delayed icing was very much evident. Bacteriological study showed patterns of Aerobic Plate Count (APC) at the end of shelflife study when fishes became organoleptically unacceptable were more or less similar for all the three fish species stored under different conditions. No definite pattern was observed in the generic distribution of bacteria in different fish species under different storage conditions. Micrococcus, Coryneforms, Pseudomonas and Achromobacter were the dominant groups of bacteria isolated from the fishes spoiled at room temperature and ice stored condition.

New approaches to materials education for students of engineering

A novel approach to the teaching of materials to engineering students is outlined. It starts from the overview of the "world" of materials made possible by material property charts, and develops both an understanding of material properties and skills in selecting materials and processes to meet design specifications. It is supported by extensive computer-based methods and tools, and is well adapted both for elementary and for advanced courses.

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.

On the comparative efficiency of trawls made of cotton, polyethylene and combination of both the materials

The merits and demerits of cotton, polyethylene and combination of the two materials ascertained on the basis of cost, wear and tear, maintenance, total catch and qualitative analysis of the catch are discussed by making comparative fishing experiments with the three trawl gears made of these materials. The study can be concluded with a suggestion for switching over to polyethylene twisted monofilaments for better, in case of bottom trawls without in any way adversely affecting the catch of shrimps and at the same time for enhanced fish catch. Even though the combination net is found to be equal in efficiency as the polyethylene net this idea cannot be conveniently adopted from the point of view of economy.

A wider choice of construction materials for the modern fishing boats

An account of fishing vessel construction materials is given, with information on essential features, and a material account. Materials discussed in detail are steel, wood, aluminium, glass reinforced plastic, and ferro-cement.

Load-displacement behavior during sharp indentation of viscous-elastic-plastic materials

A constitutive equation is developed for geometrically-similar sharp indentation of a material capable of elastic, viscous, and plastic deformation. The equation is based on a series of elements consisting of a quadratic (reversible) spring, a quadratic (time-dependent, reversible) dashpot, and a quadratic (time-independent, irreversible) slider-essentially modifying a model for an elastic-perfectly plastic material by incorporating a creeping component. Load-displacement solutions to the constitutive equation are obtained for load-controlled indentation during constant loading-rate testing. A characteristic of the responses is the appearance of a forward-displacing "nose" during unloading of load-controlled systems (e.g., magnetic-coil-driven "nanoindentation" systems). Even in the absence of this nose, and the associated initial negative unloading tangent, load-displacement traces (and hence inferred modulus and hardness values) are significantly perturbed on the addition of the viscous component. The viscous-elastic-plastic (VEP) model shows promise for obtaining material properties (elastic modulus, hardness, time-dependence) of time-dependent materials during indentation experiments.

Selection of materials for marine instruments

The paper describes the selection of materials for the reliable operation of oceanographic instruments. For selecting the material, raft immersion tests were carried out for one year. Results of the tests are presented. Comparisons between metals were discussed.

Effect of delayed icing on the quality of tiger shrimp (Penaeus monodon Fab.)

Effect of delayed icing on the quality of Penaeus monodon iced after three hours of harvest was studied in plastic and bamboo baskets. After harvest of three hours at ambient temperature (28°-32°C), ice was added to the shrimp at a ratio of 1:1 (shrimp:ice) and stored for 21 hours in both the baskets. Quality evaluation was carried out through visual assessment, biochemical analysis and microbial analysis for 24 hours. The organoleptic evaluation and scoring was done from the time of harvest treated as 0 hour and the average score was 10. At 9th hour after iced condition quality of shrimp was found reduced to the next stage (acceptable) with a score ranged from 8.4-6.5 in both baskets. This acceptable stage was observed throughout the experiment for bamboo basket whereas in the plastic basket the quality was reduced to a small extent with a score of 6.4 (moderately acceptable). Till the end point of the experiment the quality of shrimp was acceptable in respect to biochemical analysis. The microbial load was found log sub(10) 3.99±0.12 cfu/g to log sub(10) 4.33±0.21 cfu/g and log sub(10) 4.01 ±0.12 cfu/g to log sub(10) 4.83±0.19 cfu/g in the bamboo and plastic basket respectively. The importers or buyers suggests for immediate icing to maintain good quality but results of the present experiment suggest that the quality does not vary drastically for first three hours.