The development of the freezing and export of prawns in India

The paper deals with an overview on the preservation of fish by freezing process. Until a few years ago the surplus catches of fish, prawns were being dried, salted or pickled. The Kerala coast had always yielded large catches of prawns and about 5000 tons of dried prawns were annually exported to Burma and other Eastern countries. The Government of India looking at the great potential of this industry, has now, with a view to encourage exports, provided a series of incentives towards this end.

Some aspects of freezing and frozen storage of pomfrets

It has been observed that a better frozen product can be obtained by freezing good quality pomfrets transported in insulated containers with sufficient quantity of ice. To enhance the keeping quality and to prevent dehydration and discoloration, a dip in B H A (0.005%) for 15 minutes and subsequent storage in polythene lined gunny bag at -15°c to -I8°c can be recommended. The products treated in the above manner can be stored well over six months. Periodical glazing at an interval of 3 weeks will also prevent the dehydration to a greater extent.

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.

Preservation of fish by freezing and glazing. Pt. 1. Bacteriology of fresh, frozen and glazed fish

Microbiological investigation of fresh and frozen fishes such as pomfret, surmai and mackerel was carried out under various conditions of preservation. Glazing, block-freezing and preservation in gunny bag were affected. Determination of bacterial load and isolation, identification and classification of the resistant bacteria were made. Spore-formers of Subtilis mesentericus group were found to be resistant to freezing as well as glazing by ascorbic acid, citric acid and sodium nitrite except a mixture of sodium chloride and glucose. Bacterial load was reduced to a good extent and maintained low till the end of frozen storage period.

Preservation of fish by freezing and glazing. Pt. 2. Keeping quality of fish with particular reference to yellow discolouration and other allied organoleptic changes on prolonged storage

Organoleptic observations of quick, slow and block frozen, glazed and stored fish were recorded at regular intervals. Glazing was renewed at intervals of four weeks. Development of yellow discolouration in the case of white pomfret was followed. Keeping quality of glazed fish was better than unglazed frozen fish. Yellow discolouration could be controlled by ascorbic acid for 42 months and by a mixture of sodium chloride and glucose for 52 months.

Preservation of fish by freezing and glazing. Pt. 3. Effect of freezing, glazing and frozen storage on the B-vitamins and essential minerals present in the fish flesh

The changes occurring in moisture, thiamine, riboflavin niacin, phosphorus, iron and calcium in pomfret, surmai and frozen mackerel, glazed with ascorbic acid, citric acid, sodium chloride, glucose, sodium nitrite and kept under frozen storage were studied up to 6 months and results reported.

Freezing and cold storage of cat fish fillets

The freezing and cold storage changes occurring in skinless fillets of cat fish and the effect of packaging on the quality of frozen fillets during storage at -18°C were studied. Maximum shelf-life of 27 weeks was shown by fillets frozen as glazed (water) blocks and packed in polythene lined waxed cartons.

Freezing characteristics of tropical fishes 1. Indian oil sardine

The influence of different pre-freezing ice storage periods on the biochemical and organoleptic qualities of Indian oil sardines (Sardinella longiceps) in the individual quick frozen (IQF) and block frozen (BF) forms and frozen storage at temperatures of -12°C and -23°C was studied. The shelf-life of the sardines varied between 24 and 2 weeks for samples iced for 0 to 5 days prior to freezing. The deterioration in quality was accompanied by considerable increase in the peroxide value (PV) and free fatty acid (FFA) content and decrease in salt extractability of the proteins. These changes were more rapid at -12°C than at -23°C. BF sardines appeared to be better than IQF samples with respect to the biochemical changes although the differences in overall organoleptic quality were not significant.

Freezing characteristics of tropical fishes 2. Tilapia (Tilapia mosambica)

Tilapia from fresh water and brackish water-sources behaved differently during iced and frozen storage. The former showed an ice storage shelf life of about 13 days while the latter showed signs of spoilage beyond 10 days. In their respective freezing characteristics, the samples from the two sources exhibited far more significant variations. The fresh water type iced for 13 days preserved well for over 24 weeks when frozen and kept at a temperature of -18° C, while the brackish water variety held in ice for 10 days and subsequently frozen gave a shelf life of only 8 weeks under similar conditions.

Technological aspects of preservation and processing of edible shell fishes III. Factors influencing the keeping quality of crab (Scylla serrata) during freezing and frozen storage

The possible factors leading to the loss of flavour and general quality of crab during freezing and frozen storage have been studied. The preprocess ice storage condition of the raw material was found to be one such important factor while the fresh frozen crab meat remained in good organoleptic condition for about 51 weeks at -23°C, the 7 days iced material held frozen was found to have a shelf life of about 21 weeks. The fall in myofibrillar protein noted during frozen storage together with the loss of myosin ATPase activity correlated well with the loss of organoleptic qualities.

Preliminary studies on freezing characteristics of Bombay duck (Harpodon nehereus)

Fresh Bombay duck (Harpodon nehereus) can be quick frozen at -40°C and stored at -l0°F for about 3 months in a very fair and acceptable condition. The maximum drip loss observed was about 24%. Rapid decrease in the extractable protein nitrogen of the fish muscle was noted during the frozen storage.

Quality loss in prawns due to double freezing

Icing is the practice for preserving prawns on board fishing boats in India. Majority of these boats need to preserve the catch only for a few hours because of the short duration of the fishing trip. However, with the anticipated introduction of a considerable number of bigger fishing vessels which can remain in the fishing ground for longer periods, more than fortnight, preservation methods, other than icing are required to retain prime quality. Freezing and cold storage of whole prawns on board followed by thawing and processing on land is a possible proposition. The extent of quality loss in prawns during these operations is one of the important points to be considered. Hence, laboratory scale studies were undertaken on double freezing of prawns and the results are dealt within this communication.

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.

A study on the average yield of different species pf prawns used for freezing and canning

The paper deals with the average yield of four spp of prawns viz. Metapenaeus dobsoni, Metapenaeus affinis, Parapenaeopsis stylifera and Penaeus indicus on conversion to peeled and deveined (PD), cooked and peeled (CP) and head less shell on (HL) forms in the different months of a year and the likely variations observed in the average yield.