Reports

Effect of cooling and packaging methods on the quality deterioration of redfish fillets

Published:

01/09/2011

Authors:

Hélène L. Lauzon, Aðalheiður Ólafsdóttir, Magnea G. Karlsdóttir, Eyjólfur Reynisson, Björn Margeirsson, Sigurjón Arason, Emilía Martinsdóttir

Supported by:

EU IP Chill ‐ on (contract FP6‐016333‐2)

Contact

Aðalheiður Ólafsdóttir

Sensory evaluation manager

adalheiduro@matis.is

Effect of cooling and packaging methods on the quality deterioration of redfish fillets

The aim of the experiment was to evaluate the effect of slush ice cooling after filleting and / or packing in vacuum packaging on the deterioration of the quality of fresh redfish fillets. The fillets were stored at -1 ° C for 6 days to simulate well-executed sea transport in foam plastic boxes and then at 2 ° C, as happens after delivery abroad and storage in retail. Product and ambient temperature were monitored from packaging and sensory evaluation, microbial and chemical measurements were performed. The fish was caught in the spring and processed 6 days after fishing. The results show that the quality of the raw material was not the best during packaging as the development process (PV and TBARS) was well underway. This probably explains why none of these refrigeration methods led to an increase in shelf life. It was also found that there was no benefit in cooling the fillets unprotected in slush ice as the microbial growth and formation of TVB-N and TMA in the fillets was faster with further storage. However, it seems preferable to refrigerate vacuum packed fillets in ice cream as this method has led to slower growth of pest microorganisms, lower TMA levels and a slower development process. Photobacterium phosphoreum is important in the process of damaging fresh redfish fillets, regardless of the packaging method.

The aim of this study was to evaluate the effect of slurry ice cooling in process (post ‐ filleting) and packaging method (+/‐ oxygen) on the quality deterioration of skinned redfish fillets during storage in expanded polystyrene boxes simulating well ‐ performed sea freight transportation (6 days at ‐1 ° C) followed by storage at the retailer (2 ° C). Also, to assess the use of vacuum ‐ packaging to protect the fillets from direct contact with the cooling medium (slurry ice) and to achieve superchilling following extended treatment. Temperature monitoring as well as sensory, chemical and microbial analyzes were performed. The fish was caught in the spring and processed 6 days post catch. The results show that quality of the fillets was not optimal at packaging, due to the detection of primary and secondary oxidation products. This may have been the reason why shelf life extension was not achieved by any of the methods evaluated. Further, there was no advantage of cooling the fillets unpacked since this method stimulated microbial growth and formation of basic amines. On the other hand, slurry ice cooling of vacuum ‐ packaged fillets led to a slower microbial development, the lowest TMA level and delayed autoxidation. Finally, the importance of Photobacterium phosphoreum in the spoilage process of redfish fillets, independently of the packaging method, was demonstrated.

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Reports

Bacterial diversity in the processing environment of fish products

Published:

01/03/2010

Authors:

Eyjólfur Reynisson, Sveinn Haukur Magnússon, Árni Rafn Rúnarsson, Viggó Þór Marteinsson

Supported by:

Tækniþróunarsjóður, AVS

Contact

Viggó Marteinsson

Research Group Leader

viggo.th.marteinsson@matis.is

Bacterial diversity in the processing environment of fish products

The report seeks to address the diversity and species composition of micro-organisms in fish processing environments. The research work began with the installation and development of methods for scanning microbial composition using molecular biological methods, and then at a later stage, work began on examining selected environments from the fishing industry. Two fish processing plants were visited, each twice where an evaluation was made of the processing and approx. 20 samples taken in each trip. A diverse community of bacteria was found, where known harmful bacteria were usually in a high proportion along with various other species. Microbial counts showed high levels of bacteria on the surface of production lines during processing with few bacterial groups in excess but also numerous other species in smaller quantities. The main groups of bacteria found belong to Photobacterium phosphoreum, which was in the highest proportion overall throughout the study, along with Flavobacterium, Psychrobacter, Chryseobacter, Acinetobacter and Pseudoalteromonas. All of these species are known fish bacteria that live in the redness and intestines of live fish. This is the first known project where molecular biological methods are used to scan the bacterial ecosystem of fish processing plants. A knowledge base has therefore been laid here for bacterial ecosystems in different conditions in fish processing, which will be used permanently in research and development of improved processing processes and storage methods for fish.

In this report we seek answers on diversity and species composition of bacteria in fish processing environment. The study initiated method development to screen microbial systems using molecular methods followed by analysis of samples from 2 fish processing plants. This research shows the presence of a diverse microbial community in fish processing environment where known spoilage microorganisms are typically in high relative numbers along with various other bacterial species. Total viable counts showed the presence of bacteria in high numbers on processing surfaces during fish processing where few species typically dominated the community. Photobacterium phosphoreum was the most apparent species followed by genera such as Flavobacterium, Psychrobacter, Chryseobacter, Acinetobacter and Pseudoalteromonas. All these species are known fish associated bacteria that live on the skin and in the digestive tract of a living animal. To our knowledge, this is the first study where molecular methods are used to screen microbial communities in fish processing plants. This research has therefore contributed a database on bacterial diversity in fish processing plants that will be used in the future to improve processing and storage methods in the fish industry.

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Reports

24-hour detection of undesirable microbes in food / 24-hour detection of undesirable microbes in food

Published:

01/12/2009

Authors:

Eyjólfur Reynisson, Sveinn Haukur Magnússon, Árni Rafn Rúnarsson, Viggó Þór Marteinsson

Supported by:

Tækniþróunarsjóður, AVS

Contact

Viggó Marteinsson

Research Group Leader

viggo.th.marteinsson@matis.is

24-hour detection of undesirable microbes in food / 24-hour detection of undesirable microbes in food

The aim of the project was to develop and establish methods for rapid detection of undesirable bacteria in agricultural and marine products as well as other foods. With traditional methods as used today, results are obtained after 3 and up to 7 days, but with the methods developed in this project, it is possible to get results in a few hours or within 24 hours. The method is based on real-time PCR methodology and specific amplification of the genetic material of pathogenic bacteria and other undesirable bacteria. Diagnostic methods have been developed for major pathogens (Salmonella, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus) in milk, meat and fish products as well as for specific spoilage bacteria in food. The results of the project will improve services to the food industry in Iceland by detecting unwanted microorganisms much earlier so that it is possible to intervene in production processes and thereby increase consumer safety in agricultural and fish products.

The aim of this project was to develop and set up new methods for rapid identification of undesirable bacteria in food and feed. With today's conventional and accredited culture methods results can be expected after 3 and up to 7 days. With the new methods to be taken in use and was developed in this project, the time of diagnostic procedure will decrease to few hours or to one working day. The detection methods are based on real ‐ time PCR technology and a specific amplification of genetic material of the undesired bacteria. Diagnostic methods for the most common pathogens (Salmonella, Campylobacter, Listeria monocytogenes, Vibrio parahaemolyticus) in meat‐, milk and fish products were developed through as well as quantitative assays for the main spoilage bacteria in fish. The results of the project will be used to improve the service for the Icelandic food industry on the domestic‐ and overseas markets by having rapid diagnostic methods for bacterial contamination at hand.

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