Effect of liquid nitrogen freezing and subsequent storage on survival of Staphylococcus aureus and Streptococcus pyogenes in treated prawn meat

Prawn meat treated with Streptococcus pyogenes B-49-2 culture and Staphylococcus aureus ATCC-12598 culture were frozen in conventional plate freezer at -40°C and by spray type liquid nitrogen freezer. The frozen products were stored at -18°C. Streptococcus pyogenes B-49-2 showed low sensitivity to cold injury during freezing and frozen storage. Staphylococcus aureus ATCC-12598 survived during the entire storage period of 240 days. Total bacterial count of untreated prawn meat was found to be always lesser in liquid nitrogen frozen products than that in plate frozen products.

Delayed freezing on the quality and shelf-life of Kalawa (Epinephelus spp.)

Kalawa (Epinephelus spp.) caught on board FORV Sagar Sampada was frozen in the absolutely fresh condition as well as after keeping for 5 and 10h at ambient temperature. Evaluation of changes in the quality of these samples during storage at -20°C indicated appreciable difference between the fresh frozen and delayed frozen fish during the initial stages of storage. Fresh frozen and 5h delayed froze fish samples had a shelf-life of more than 62 weeks, whereas the 10h delayed frozen fish had a shelf-life of about 48 weeks.

Effects of gamma radiation and freezing on the chemical and sensory changes in shrimp Penaeus monodon (Fabricius, 1978)

Gamma radiation (3, 6 and 9 kGy) in combination with low temperature (-20°C) were applied to retain the quality and shelf-life of shrimp, Penaeus monodon for a longer period. The quality was assessed by monitoring the chemical (TVN, TMA) and sensory changes in irradiated and non-irradiated (control) samples. Among chemical indicators of spoilage, total volatile nitrogen (TVN) values for irradiated shrimps were found to be 2.26, 2.18 and 1.57 mg N/100g of sample at 3, 6 and 9 kGy respectively after 90 days whereas for non-irradiated samples it was found 2.45mg N/100 g of sample. Trimethylamine (TMA) value for non-irradiated samples after 90 days were found 2.30mg N/100 g sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 2.10, 2.08 and 1.98 mg N/100 g sample respectively. The sensory scores of control sample were gradually decreased with the progress of storage period. From this study, it was clear that gamma radiation in combination with low temperature showed shelf-life extension (90 days) in each dose of radiation used but during the use of 9 kGy radiation, P. monodon showed best quality.

Effect of gamma radiation in combination with freezing on the microbiological changes in frozen shrimp Penaeus monodon

In this study gamma radiation (3, 6 and 9 kGy) in combination with low temperature (-20°C) were applied to retain the quality and shelf-life of shrimp, Penaeus monodon for a longer period. The quality was assessed by monitoring microbiological changes (TBC, TMC, TYC, TCC and Salmonella count) in irradiated and non-irradiated (control) samples. Among microbiological indicators of spoilage, total bacterial count (TBC) values for irradiated shrimps were found to be 1875, 1625 and 1525 cfugˉ¹ of sample at 3, 6 and 9 kGy respectively after 90 days whereas for non-irradiated samples it was found 2475 cfugˉ¹ of sample. Total moulds count (TMC) value for non-irradiated samples after 90 days were found 425 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 275, 250 and 200 cfugˉ¹ sample respectively. Total yeast count (TYC) value for non-irradiated samples after 90 days were found 4125 cfugˉ¹ sample whereas that for irradiated shrimps at 3, 6 and 9 kGy were found to be 2850, 2150 and 1725 cfugˉ¹ sample respectively. Total coliform count and Salmonella count showed that those were absent during 90 days storage period. From this study, it was clear that gamma radiation in combination with low temperature showed shelf-life extension (90 days) in each dose of radiation used but during the use of 9 kGy radiation, Penaeus monodon showed best quality.

Study of physicochemical, microbial and sensory properties of surimi produced from black mouth croaker (Atrobucca nibe) at freezing condition (-18ºC)

Black mouth croaker (Atrobucca nibe) is considered as a new valuable fish stock in the Oman Sea. In this study, surimi was manufactured from nonmarket size of the fish, manually and different cryoprotectant agents were added to the surimi. Finally changes in physiochemical, microbiological and sensory quality, characteristics of the surimi and kamaboko gel samples were assessed during 6 months at freezing storage (-18ºC). Surimi samples with the addition of Iranian tragacanth gum (TG), xanthan gum (XG), chitosan (CS) and whey protein concentrate (WPC) at 1% (w/w) were prepared to evaluate their impacts as a cryoprotectant on the surimi, individually. The results showed that the whiteness and lightness indexes in all surimi samples were gradually decreased during frozen storage. This trend of decreasing was more intensity in the control sample from 61.08±0.131 to 54.21±0.067 was recorded (p<0.05). Water holding capacity (WHC) in all treatments was decreased during 6 months. The lowest WHC (g/g) was obtained in the surimi without cryoprotectants and maximum WHC was measured in Tcs and Twpc samples, respectively (p<0.05). The lowest breaking force was calculated in Txg (166.00±22.627 g) and Tc (271.50±263.16 g) during 6 months at frozen storage, respectively (p<0.05), while Twpc treatment with slight variations showed the highest breaking force (p<0.05). Also, the lowest gel strength was obtained in Txg (68.22±6.740 g.cm) after 6 month of frozen storage (p<0.05). All Kamaboko surimi gels texture profile analysis parameters decreaced with increasing shelf life. This decreasing trend in the control sample was more severe. Floding results were reduced in all samples during storage (p<0.05). The best protective results probably were obtained in WPC, chitosan and commercial cryoprotectant agents, respectively due to protein stabilization of myofibrillar proteins and the protein-protein network structure, leading to the formation of surimi gel with strong textural properties during frozen conditions. The average number of surimi polygonal structures were significantly decreased (number per mm2) and their area were significantly increased (μm2) in all treatments (p<0.05). With increasing storage time, moisture, protein contents and pH were decreaced. Maximun TVB-N index was calculated in Tc (7.93±0.400 mg/100g) and Txg (7.88±0.477), respectively (p<0.05). TBRAs index was increased in all treatments during frozen storage, while this trend was reached in maximum value in Tc (p<0.05). Sensory evaluation of the fish finger quality characteristics (color, odor, texture and overall acceptability) preapare from frozen black mouth croaker surimi was decreaced during 6 month frozen storage. After the period of frozen storage the highest quality scores were measured in Twpc, Tcs and Tcc samples, respectively (p<0.05). In this study, coliform bacteria were not found in all treatments during frozen storage. The surimi sample containing chitosan showed lower mesophilic and psychrotropic bacteria (log cfu/g) than other treatments during frozen storage (p<0.05). Salt-soluble proteins extractions of all treatments were decreased during frozen storage. This decreacing trend was highest in Tcs (45.74±0.176%) and lowest in Tc treatments after 6 month of frozen storage (29.92±0.224%) (p<0.05). Although commercial cryoprotectant agents were successful in limiting the denaturation of proteins but sugar contents were not accepted for diabetics or those who disagree with the sweet taste and high calorie food. Hence, commercial cryoprotectant agents can be replaced with whey protein concentrate and chitosan at 1% level (w/w) consider that they were showed proper protection of the surimi myofibrillar proteins during storage.

Effects of the quick and slow freezing on the quality of Nile Tilapia fillets (Oreochromis niloticus) and Red Tilapia fillets (O. niloticus and Tilapia mosambicus)

In this study, quality of fresh, slow frozen and quick frozen tilapia fillets and its changes during storage at -18C° were investigated. For preparation the samples, fresh tilapia fillets were frozen by slow and quick frozen methods. Slow frozen samples were prepared by storing the packed fillets directly in the -18 C°. The sprila freezing tunle with -30C° was also used for preparation the quick frozen sample. The quick frozen samples were then stored at -18C°for six months. Proximate composition, fatty acid profiles, TBA, PV, TVN, Total cuont, Drip loss, and sensory evaluation of the samples were determined in every month. Scanning Electron Microscopy (SEM) was used for study on the effects of the frozen condition on the microstructure of the fillets. Results indicated that two different frozen methods had significantly different effects on the quality of the fillets. Most of the proximate composition (protein, moistre and fat) reduced during the storage. Quick frozen filets had significantly (P<0.05) lower reduction than slow frozen samples. All of the chemical quality indexes (PV, TBA, and TVN) increased during the storage as compered to the fresh samples. In these paramethers, the slow freezing had higher changes than quick freezing metods (P<0.05). The microbial properties of the samples showed decrese during the storage. Lower amont of total cuont was observed at the end of the storage time in the quick frozen samples than slow frozen once (P<0.05). The large changes in the fatty acid profiles of the sample were fond in all samples. During the storage SFA and MUF of the samples increased however, the PUFA decresed. A lower change was obseved in the quick frozen samples than slow frozen samples (P<0.05). Drip loss was increased in both frozen samples during the storage period. The percentage of the drip in the slow frozen samples was significantly higer than quick frozen samples (P<0.05). SEM micrographs were also showed that the chnges in the microstructur of the samples was different in the slow and frozen samples. Slow freezing methods had higher damge in the microstructure of the sample then quick freezing mathods. Sensory evaluation of the samples indicated that a better acceptability in the quick frozen samples than slow frozen sample (P<0.05).

Entwicklung einer einfachen und schnellen Analysenmethode für Kohlenmonoxid in Fisch und Durchführung orientierender Untersuchungen

Treatment with gases containing CO, misleadingly called “tasteless smoke” or “clear smoke”, prior to freezing of fish like tuna, tilapia and swordfish (to name only a few of these species that are characterised by an intensive coloration of flesh) stabilise the fresh red colour of muscle also after thawing and suggest consumers non-existing freshness. In the European Union, carbon monoxide is excluded from being a permitted additive and therefore this handling is not allowed. Notwithstanding of the clear legal position, producers and traders are trying to establish CO treated fish on the market. In the case of taking legal measures the food control laboratories have to provide evidence that fish has been treated by CO and therefore a respective method is necessary. The method of determination of carbon monoxide in fish flesh presently applied requires considerable material and mechanistic effort to detect CO by GC after catalytic transformation into methane. The aim of our work was a direct detection of CO using suitable sensor technology. Mechanistic requirements and results of preliminary investigations to detect carbon monoxide in fish flesh will be described.

Qualitätsvergleich zwischen maschinen- und handgeschälten Nordseegarnelen

After the evaluation of 48 samples consisting of hand and machine-peeled sand shrimps it can be stated that there was no significant difference in quality between both. The quality of the sand shrimps was evaluated by sensorially performed paired comparison as well as by estimating the microbial load and the volatile amines (MMA, DMA, TMA). Additionally, the colour characteristics were measured instrumentally. To characterise the influence of the technological regime measurements of pH and of the salt content were performed. The quality of sand shrimp is further influenced by technological steps as freezing, cooking procedure and preservatives used. From the hygienic point of view the machine-peeling was without any objections. The microbial load was small and below the limit set by EC. Measurement of volatile amines was not suited to make visible difference created be the various peeling methods.

Qualitätsvergleich zwischen panierten Filetportionen aus einfach- und doppelgefrorenen TK-Blöcken

Single and double frozen fillet blocks of Alaska pollack and cod both commercially processed of unknown shelf life were further processed to breaded battered portions. The quality of these fillet portions were compared using sensory (QDA), physical and chemical methods. It was difficult to differentiate between SF and DF fillets by sensory method because of the absence of differences in flavour attributes. While no differences could to be found in the texture of cod fillets, in Alaska pollack fillets some texture attributes were significantly different. These differences could not be verified by instrumental texture measurement. In all cases the lightness was different between SF and DF fillets. Probably, after having fixed L* values for SF fillets of commercially important fish species as limit this could be employed in the future to differentiate between single and double frozen products. Due to the unknown shelf life it is difficult to evaluate the results. Therefore, the investigation of the influence of double freezing on the quality needs a special sample preparation. The use of randomly taken commercially processed samples seems not to be useful.

Vergleichende Texturuntersuchungen an Filets von Kliesche (Limanda limanda) und Scholle (Pleuronectes platessa) in Abhängigkeit von Eislagerzeit post mortem, TK-Lagerung und Erhitzen

Instrumental investigations of texture have been performed using texture profile analysis. The following textural parameters have been assessed: hardness, gumminess, chewiness, springiness, cohesiveness and adhesiveness. The fillets of both species have been prepared from deep frozen headed and gutted raw material without fins after frozen storage of 0, 23 and 34 weeks, respectively. Deep freezing of fishes has been performed on board immediately after hauling or after 6 day’s storage in ice. Before texture measurement the raw material has been thawed and the measurement was carriedout on both thawed and microwave-heated fillets. In general, it can be concluded that both fish species are comparable in their texture parameters. The hardness of heated dab has been slightly higher comparing with that one of plaice. All other texture parameters showed a fairly good conformity between both species. While the hardness of dab increased during heating, it was decreasing in plaice. This was the only one significant difference between both fishes during heating. Adhesiveness as well as cohesiveness increased remarkably during heating. Changes effected by ice storage were only slight. Frozen storage, in contrast, caused a significant decrease of adhesiveness measured after heating the fillets of both species.

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

Einfluß von Eis- und Tiefgefrierlagerung/Auftauen auf die Länge von Seefischfilets

The objective was to study the influence of biological and processing conditions on the evaluation of a conversion factor between fillet length and fish size. This paper presents changes of the length and weight of skinless fillets from various marine fish species in relation to the ice storage time and to the deep freezing / thawing process. The biochemical changes during rigor mortis lead to considerable reduction in length of skinless fillets during ice storage and deep freezing / thawing of fillet blocks. The investigations were undertaken during various cruises of the FFS „Walther Herwig III“.

Fischerei und fischereibiologische Untersuchungen im Nordost-Atlantik im 1. Halbjahr 1996

Biological investigations were carried out onboard the commercial freezing trawler "KIEL" off the Norwegian coast in February/March and in the Bear Island area in May 1996. Data will be used as German contribution to the assessments of the ICES "Arctie Fisheries Working Group". Informations about the fishery and the concentrations of cod, haddock, saithe and redfish in the areas between Röst-, Nordvest-, Fuglöy-Bank and Bear Island are given. Length - and age distributions as well as preliminary results of stomach- and gonad investigations are represented.

Gute Kabeljau- und Schellfischvorkommen bei der Bären Insel

Biological investigations were carried out onboard the commercial freezing trawler "Kiel" in the Bear Island area in May/June 1995. Data will be used as German contribution to the assessments of the ICES "Artic Fisheries Working Group". Concentrations of cod were found southwest of Bear Island. Catches ammounted to 5-60 t/haul. Relatively good catches (5-25 t) with high proportions of haddock (40-80 %) were observed to the northwest of the island. Length- and age distributions as well as preliminary results of stomach- and gonad- investigations are presented.

Algae from the inland ice of Greenland. [Translation from: Kongl.Vetenskaps-Akademiens Forhandlingar 1871(2) 293-296, 1871.]

On the large inland ice cover of Greenland, where the temperature even during the short summer, falls below freezing some time during the daily 24 hours, it is still possible to find organic life. The author found in melted ice water several species of algae on his ”walk” in the latter part of July 1870. The article describes the finds and tries to identify the algae to family level.