Quality deterioration in tilapia during storage in refrigerated brine

During storage of Tilapia nilotica in refrigerated brine at 4°C, the whole (ungutted) fish had higher levels of free fatty acid and spoiled faster than the gutted fish. The shelf life of whole fish was 16 days and that of gutted 28 days; these values are, at least, as good as those reported for ice storage. Flavour of the cooked fish appeared to be the quahty-hm1tmg factor reducing the shelf-life of gutted tilapia to 28 days even though the raw gutted fish was judged acceptable, after 31 days retaining 65-70% freshness.

Management of Biesboch reservoirs for quality control with special reference to eutrophication

The three Biesbosch Reservoirs are pumped storage reservoirs, fed with rather polluted and highly eutrophic water from the River Meuse. Air injection at the bottom of the reservoirs prevents thermal stratification, which would otherwise result in serious water quality deterioration. Reservoir mixing also serves as an economic algal control measure; mixing over sufficient depth causes light to play the role of limiting factor and this, combined with zooplankton grazing, keeps the biomass of phytoplankton at acceptable levels. Special problems are caused by benthic, geosmin-producing Oscillatoria species growing on the inner embankment. Rooting up the bottom with a harrow is used as the method of control, based on underwater observations by biological staff trained as SCUBA-divers. With regard to pollutant behaviour the three reservoirs act as a series of fully mixed reactors. This enables the application of kinetic models to describe their behaviour and allows the use of a selective intake policy, e.g. for suspended solids with associated contaminants, ammonia and polynuclear aromatic hydrocarbons. A combination of selective intake and self- purification processes - enhanced by the compartmentalisation of the storage volume in three reservoirs - leads to a striking improvement for many water-quality parameters.

Change in quality of different variety of fish during long distance transportation

A study was conducted to investigate the quality of iced fish of different species during long distance transportation. Total bacterial counts showed different species to show different quality deterioration under similar handling conditions.

Feed utilization and wastage in semi-intensive pond culture of mahseer, Tor putitora. (Ham.)

Mahseer, Tor putitora with 12.75, 12.11, and 12.02g of initial weight were fou · J to attain a net weight gain of 12.0 kg, ll.5 kg, and 11.4 kg respectively in pond-1 (commercial feed), pond-2 (farm-made feed), and pond-3 (farm-made feed), respectively against 78.2 kg, 70.3 kg, and 68.1 kg feed fed. Gross energy contents in fish were 1359.3 Kcal/kg, 1281.5 Kcal/kg and 1266.6 Kcal/kg, respectively in pond-1, pond-2, and pond-3 against 3630.4, 3876.9 and 3570.5 Kcal/kg energy in the feed fed. Only 9.4%, 10.5% and 13.7% of the protein, and 8.9%, 3.4% and 3.3% of the lipid fed to fish were converted into muscle respectively in pond-1, pond-2 and pond-3. It was observed that the higher the protein content in feed, the lower the rate of conversion in muscle; the same was also true for lipid. It is supposed that feed derived wastes contribute potentially to water quality deterioration and eutrophication. Lower feed conversion, higher nitrogenous and phosphatic concentrations and higher plankton biomass in the ponds are all supportive to this observation.

Spoilage of spotted seer (Scomberomorous guttatus) during ice storage

Quality deterioration of seer held directly in contact with ice, in different forms, fillets and chunks, and of chunks held in ice but without direct contact, was studied for a period of 15 days. While the chunks held out of contact with ice were acceptable up to 13 days based on organoleptic evaluations, the chunks and fillets held in direct contact with ice were acceptable only up to 10 days. The order of preference of the samples at any interval of ice storage was chunks held out of contact with ice>chunks held directly in ice>fillets held directly in ice. The changes in the chemical quality of these samples were also in the same order, the deterioration being maximum in fillets and least in chunks kept out of contact with ice.

The effect of traditional handling, processing and storage methods on the quality of dried fish in small scale fisheries in Nigeria

Most of the fish marketed throughout Nigeria are in either smoked or dried form. The technological requirement for other forms of preservation like chilling and freezing cannot be afforded by the small scale fisher folk. Considerable quantities of fish processed for distant consumer markets are lost at handling, processing, storage and marketing stages. Significant losses occur through infestation by mites, insects, fungal infestation and fragmentation during transportation. This paper attempts to describe the effect of these losses on fish quality and suggests methods of protecting fish from agents of deterioration

Approval of systems of Biological Indication of Water Quality under the auspices of the Severn-Trent Water Authority, UK

In accordance with the plan for joint Anglo-Soviet scientific and technical collaboration on environmental problems, the comparative evaluation of systems of hydrobiological analysis of the surface water quality started in 1977 at the Regional Laboratory of the Severn-Trent Water Authority in Nottingham were continued in the spring of 1978. The investigations were carried out under the auspices of the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR. Hydrobiological and hydrochemical samples were collected by Soviet and British specialists from the Kiev reservoir and the rivers Dnieper, Sozh, Desna and Snov. The possible approved methods to be adopted were evaluated from the samples using the phytoperiphyton, phytoplankton, zooplankton and zoobenthos against a background of hydrochemical characteristics.

Effects of water quality in Bassenthwaite Lake on anglers' catches of salmon and sea-trout in the River Derwent

This is the report on the Effects of Water Quality in the Bassenthwaite Lake on Anglers Catches of Salmon and Sea-trout in the River Derwent April 1993 by the Institute of Freshwater Ecology. An analysis of the catch statistics for salmon and sea-trout in the Rivers Derwent and Cocker was undertaken in relation to available information on the algal water quality in Bassenthwaite Lake to test the hypothesis that poor catch returns were associated with a deterioration of water quality within the lake. Analysis of the catch statistics failed to reveal any correlation between water quality and catch returns for either species of fish and it is concluded that any water deterioration in Bassenthwaite Lake has not caused any major damage to the salmon and sea trout fisheries of the Derwent/Cocker system. This conclusion is supported by the analysis of the Windermere/Leven and Crake system, where no correlation could be found between lake water quality and downstream catches of migratory salmonid fish. However, the possibility still exists and such an effect might be detected by further field work on the macroinvertebrates and on the composition of potential salmonid spawning in the area.

Influence of muscle fats on the quality of intermediate moisture fish

Chrysicthys nigrodigitatus with 12.95% fat having an iodine value of 74.8 and a saponification number of 198.48 and Citharinus citherus containing only 3.25% fat with iodine value of 67.8 and a saponification number of 145.86 were studied as examples of fatty and lean fishes respectively. The intermediate moisture (IM) products of both fish types compared with normal cooked samples, were evaluated as of acceptable colour, odour, texure and juiciness but of inferior taste due to the glycerol impact. However, during storage at 30°C the IM products became increasingly less acceptable with the deterioration being greater in the fatty fish than in the lean fish, although the fatty IM fish was superior to the IM lean fish with regard to water retention and juiciness. Overall quality differences were most apparent in colour and odour with the fatty IM fish being worse. The fatty fish had also greater evolution of TEA-reactive carbonyl breakdown products of lipid oxidation which were subsequently used up in non-enzymic browning producing the correspondingly darker fish colour and greater off odour.

Preservation of Indian oil sardine (Sardinella longiceps) in iced and chilled seawater. Part 2 - Changes during storage with particular reference to salt penetration and lipid deterioration during CSW holding

Oil sardines in prime condition were chilled on board. Two lots were chilled in CSW (samples C & CI), one lot ice (sample I) and a fourth lot was left un-iced on deck (sample AI). Sample AI was iced after landing and sample CI was taken out of the chilled seawater and. iced. All the four samples were kept in a chilled room for storage studies. Sample C, chilled and stored in CSW, recorded a gradual gain in weight and an increase in salt content of the muscle. Presence of salt did not seem to cause any excessive protein denaturation. Salt extractability decreased at a gradual rate in all cases. Presence of salt seemed to wield no noticeable influence on lipid hydrolysis and subsequent peroxidation. Results of chemical and sensory evaluations highlight this. Holding sardines in CSW gave a product of excellent quality for the first four to five days of storage. Beyond the fifth day of storage quality deteriorated rapidly and there was no noticeable superiority for this sample (sample C) over the on board iced fish. This was evident in the sensory evaluation as well. However, a storage life of five days in a readily acceptable state is sufficient for the fish to be disposed in the market at a premium sale price over other landings of the same species.

Effect of chilled sea water storage of oil sardine (Sardinella longiceps) on quality changes during frozen storage

The shelf-life of frozen oil sardine (Sardinella longiceps) can be improved by preserving the fish immediately after catch in chilled sea water before freezing. Delayed icing caused considerable deterioration in quality and reduced frozen shelf-life. Oil sardine preserved in chilled sea water were found to be suitable for freezing up to 5 days whereas iced samples could be frozen only up to 2 days.