A study on the quality of prawns during processing in prawn-freezing factories

A study on the occurrence of defective pieces of prawns at three different stages of processing of headless shell on and peeled and deveined varieties was undertaken, each in one freezing factory. The average percentages of the defective prawns together with the standard deviation observed over a period of one year at the three stages are mentioned. Correlation is indicated between the occurrence of the defective pieces at the pre-freezing stage and those of earlier stages.

Experiments in constituting a taste panel for canned and frozen prawn products

With a view to constituting a taste panel in the laboratory for detecting the flavor changes in canned and frozen prawn, three methods of panel selection (scalar scoring method, range and deviation method and triangular method) were tried. Out of the three, triangular method was found to be suitable for panel formation in canned and frozen prawn. Using this method a panel of six members was formed for detecting flavor changes in the two products.

Factors controlling drained weight in canned prawn

The paper gives an account of factors controlling the drained weight in canned prawn. The most important among them are concentration of brine used for blanching and blanching time which are found to be fixed and specific for different sizes of prawn irrespective of the quality of the material used. Other factors such as, acidity of brine used for filling the can, volume of brine, time of sterilization and time of cooling the blanched meat are also to some extent found responsible for fluctuations in drained weight.

Seasonal variability in penaeid prawn larval abundance in the Mandovi and Zuari estuaries, Goa

Seasonal variations in the occurrence and abundance of penaeid prawn larvae in the Mandovi and Zuari estuaries of Goa were studied. Larvae and post-larvae of commercially important species viz. Metapenaeus dobsoni (Miers), M.affinis (H. Milne Edwards). M. Monoceros (Fabricius), Penaeus merguiensis de Man and Parapenaeopsis stylifera (H. Milne Edwards) were recorded in that order of abundance. Protozoea and mysis stages were dominant in surface zooplankton collections while the post-larvae were more in the bottom samples. Based on larval density, M. dobsoni appeared to be a continuous breeder. The active spawning periods in other species were during the late post-monsoon and pre-monsoon seasons varying with the species. Peak recruitment of post-larvae in the estuaries was observed mostly during southwest monsoon months (June to September). Penaeid prawn larval ingression was more in the Zuari estuary compared to the Mandovi estuary. Their numerical abundance gradually decreased towards the upstream areas. The feasibility of large scale collection of penaeid prawn larvae for aquaculture is indicated.

Investigation on bacterial flora of farmed freshwater prawn (Macrobrachium rosenbergii de Man) in Bangladesh

Total bacterial load in the haemolymph of freshwater prawn Macrobrachium rosenbergii varied from 6.2x10⁴ to 1.9x10⁷ CFU/ml whereas in the hepatopancreas, bacterial load varied from 1.9x10³ to 2.9x10⁵ CFU/g. The total bacterial load in the pond water varied from 2.6x10² to 4.1x10⁵ CFU/ml. The isolated bacterial genera in the haemolymph and the hepatopancreas of prawn were Streptococcus, Acinetobacter, Micrococcus, Aeromonas, Vibrio, Flavobacterium, Staphylococcus and Pseudomonas, whereas the detected bacterial genera in pond water were Micrococcus, Streptococcus, Vibrio, Flavobacterium, Staphylococcus, Pseudomonas and Aeromonas. Among the detected genera, Vibrio and Staphylococcus were found to be dominant genera in the haemolymph of the sampled prawn throughout the study period whereas Staphylococcus and Pseudomonas were dominant in pond water.

Effects of supplementary feeds on growth and survival of freshwater giant prawn (Macrobrachium resenbergii [i.e. rosenbergii] deMan)

Highest growth of prawn was obtained with Feed B (743 kg/ha) with highest survival rate (60.88%) followed by Feed A where production and survival rate was 659 kg/ha and 53.50%, respectively. Feed A contained 30% dry ground cow viscera, 40% oil cake, 20% rice-bran and 10% heat bran. Feed conversion ratios were found to be 7.60:1 for Feed A and 6.46:1 for Feed B, which indicated that Feed B was more efficiently utilized by the prawn than Feed A. Statistical analysis revealed that the differences in production of prawns among the treatments were highly significant (P< 0.01).

Studies on the post-mortem changes in shrimp and prawn during ice storage. Pt. 1. Organoleptic and physical changes

The organoleptic characteristics such as appearance, textural condition, colour and odour indicated that the M. rosenbergii stored in ice for 5-6 days was acceptable for processing in the industry while P. monodon under similar ice storage condition was acceptable for 8-9 days. In both species, samples stored in headless condition in ice had longer shelf life than that of stored in head-on condition. Physical changes were evaluated by determining expressible moisture and breaking strength of sample of muscles. The expressible moisture increased continuously in both samples with the lapse of storage period. The expressible moisture increased up to around 44% in 4-5 days of ice stored M. rosenbergii muscle while it was around 40% in 8-9 days ice stored P. monodon. At the end of 9 days of ice storage, the expressible moisture content in M. rosenbergii increased up to 60%, while it was up to 47% in P. monodon after 11 days of ice storage. The breaking strength declined from 0. 78 kg/cm² to 0.53 kg/cm² in tiger shrimp after 8 days of ice storage, while in case of immediately killed prawn, the breaking strength of muscle was 0.8 kg/cm² which declined to 0.43 to 0.35 kg/cm².

Studies on the post-mortem changes in shrimp and prawn during ice storage. Pt. 2. Biochemical aspects of quality changes

Studies were conducted on biochemical changes in P. monodon and M. rosenbergii during ice storage. At the end of 10 days of ice storage, moisture and protein content of freshwater prawn slightly decreased from 78.34 to '77.35% and 18.46 to 17.10, respectively, while lipid and ash content slightly increased. The moisture, crude protein, lipid and ash content of one day ice stored tiger shrimp samples were 78.07, 18.06, 1.3 and 1.29% respectively. The protein composition of freshwater prawn immediately after killed were 36.51% sarcoplasmic, 44.63% myofibrillar, 8.12% stroma and 6.44% alkali soluble protein. At the end of 10 days of ice storage, sarcoplasmic and stroma protein slightly decreased while there was little or no changes observed in myofibrillar and alkali soluble protein. In case of one day ice stored tiger shrimp, the composition of protein were 35.32% sarcoplasmic, 46.29% myofibrillar, 7.86% stroma protein and 7.08% alkali soluble protein. At the end of 10 days in ice, sarcoplasmic protein decreased from 35.32% to 32.16% while there was slight change in other protein fractions. The TVB-N value of 1 day ice stored shrimp was 10.5 mg/100g of sample. It increased gradually with the lapse of storage period and at the end of 10 days storage in ice, the value increased up to 60 mg/100g sample. The tiger head on shrimp in ice storage were found organoleptic acceptable condition for 8 days and at that time the TVB-N values were 32.2 mg/100g which is slightly above the recommended limit for TVB-N for export.

Development of low-cost feed for culture of giant freshwater prawn (Macrobrachium rosenbergii de Man) in ponds

An experiment was conducted for 105 days in 12 earthen mini ponds of each 30m² size. Five different experimental diets containing 32% protein were formulated and prepared using fishmeal, shrimp meal, soybean meal, mustard oil cake, sesame meal, wheat bran and rice bran. A commercial shrimp diet (SABINCO starter-III) was assigned to treatment six and considered as the control. Prawns were stocked at the rate of 2.5 fry/m² and feed twice daily at the rate of 10% at the beginning and reduced to 8% for the last two months. The results of the experiment showed that prawn fed diets 1, 2, and 6 (control) showed significantly (P<0.05) highest weight gain among the dietary groups, while prawn fed diet 5 showed significantly lowest weight gain. The FCR values of diets ranged between 3.06 to 4.85. Prawns fed diet 1 and 6 showed significantly higher SGR, survival (%) and production among the dietary groups. The survival (%) of the prawns ranged between 46.6 to 66.6% and the production ranged between 304.5 to 563.3 kg/ha/105 days. The result of the study showed that diet containing 30% fishmeal, 5% shrimp meal, 5% soybean meal, 10% mustard oil cake, 10% sesame meal, 20% wheat bran, 18% rice bran, 1% oyster shell and 1% vitamin premix may be recommended for monoculture of M. rosenbergii.

On the trend of prawn catches in bottom trawls in inshore waters off Kakinada (Andhra Pradesh)

From the results of fishing operations during 3 years (from August 1963 to July 1966) attempts were made to study the extent of availability of prawns for bottom trawls. It was found that prawns formed 22.5% of the total catch on an average of the catch rate of 12.3 kg per trawling hour. The prawns were found to be abundant during two periods from November to February and again from April to July. The depth range of 11-15 m yielded better catch rate with best frequency of the optimum catch per hour.

Phosphate treatment of frozen prawns. Pt 2. Frozen storage characteristics of prawn meat treated with polyphosphates

This communication reports the changes in physical, organoleptic and biochemical characteristics of prawn meat dip-treated with alkaline and neutral solutions of polyphosphates during frozen storage. Results are presented on changes in thawed and cooked yields, water extractable nitrogen, non-protein nitrogen, free amino-nitrogen, salt solubility, myosin and moisture in the muscle and loss of soluble nitrogenous constituents in thaw drip during frozen storage up to seven months. The salt solubility remained unchanged during storage in samples treated with neutral polyphosphate solutions and the organoleptic quality was superior to control sample. It is concluded that dip treatment with neutralized solutions of tripolyphosphate not only maintains correct drained weight and improves cooked yield during prolonged frozen storage but also protects the frozen product from denaturation as measured by the salt solubility of the proteins.

Factors controlling sterility in canned prawn

Probable sources of contamination of raw, blanched and processed meat at various stages of handling and methods for their rectification have been described in the paper. Inter-relationship between absolute sterility and commercial sterility with particular reference to the sanitation of the factory has been discussed.

Blackening of canned prawn and its prevention

The paper gives an account of the types of blackening associated with canned prawn in brine and their control. It was found that blackening caused by iron sulphide could be controlled by maintaining proper titratable acidity of fill brine in cans. The paper also elaborates on the factors responsible for or governing this critical titratable acidity. In regard to copper sulphide blackening, control was found to be difficult by maintaining the acidity or by additives such as EDTA when the copper content in the material went above the critical level.

Further observations on a newly located prawn fishery off Saurashtra coast

The abundance of prawns in a newly located ground off Saurashtra has been described. Catch composition showed that Metapenaeus affinis formed the bulk of the catches. Previously this species was thought to be of not much commercial importance in this region. The peak of the fishery lasted from September to November. Observations on the biology of this species showed that it occurs as an independent stock in this region. The significance of the gear employed in fishing is also emphasized.

Performance of paddy-cum-prawn culture in rainfed low land ecosystem of Sunderbans

Performance of both paddy (Var. NC 492) and prawn Penaeus monodon were assessed for two years during wet-season in rainfed lowland ecosystem with a view to study the economic viability of paddy-cum-prawn culture in the coastal saline zone of West Bengal. Both mono and dual culture of paddy and prawn were tried in the study. Fingerlings of prawn (α 35,000 haˉ¹) of 10-15 mm size were reared for about three and half months with and without fish feed. It was observed that addition of fish feed resulted in higher (57.7%) production of prawn (2.65 mg/haˉ¹) but not rice. Such increase in prawn production was 1.6 times higher when no feed was provided and 1.4 times higher when grown as sole crop. However, paddy, whether grown as mono or mixed culture, did not differ in yield significantly. In dual culture, the benefit - cost ratio was higher (6.83) when prawn was grown with feed and it was maximum (36.0) when grown without feed as sole crop. The study, therefore, indicates that paddy-cum-prawn culture under low land ecosystem of the coastal saline zone is enterprising particularly for small and marginal farmers who fear to take risk of growing prawn alone at the cost of paddy.