Reports

Effect of temperature control on the efficiency of modified atmosphere packaging of cod loins in bulk

Published:

01/06/2011

Authors:

Hélène L. Lauzon, Kolbrún Sveinsdóttir, Magnea G. Karlsdóttir, Eyjólfur Reynisson, Björn Margeirsson, Emilia Martinsdóttir

Supported by:

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

contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Effect of temperature control on the efficiency of modified atmosphere packaging of cod loins in bulk

The aim of the experiment was to compare the freshness, quality and shelf life of sub-chilled (CBC) cod necks in air storage and in aerated packages (MAP) at controlled temperatures to simulate temperature fluctuations during transport and distribution in the European market. Changes in the composition of the gas in the packages were monitored and sensory assessments and microbial and chemical measurements were performed. The fish was caught in bottom trawls in the spring and processed three days after fishing. There was a two-day prolongation during the freshness period and one day for the shelf life of fish in aerated packages (2.7 kg in a tray) compared to air (3.1 kg) in foam plastic, despite a 0.5 ° C difference in the average temperature of the groups and the air group was stored at lower temperatures (‐0.3 ± 0.9 ° C). The greatest temperature fluctuations led to the greatest shortening of the freshness time in air-conditioned packages. Cod saddles stored subcooled at -1.1 ± 0.1 ° C had a shelf life of 13 days. The results of microbial counts and chemical measurements showed the importance of Photobacterium phosphoreum in the formation of TMA in the process of damaging cod necks during both air and air exchange packaging. MAP and subcooling slowed down and changed the damage process. MAP increased drip by 2% in the later stages of storage.

The aim of this study was to compare freshness, quality deterioration and shelf life of CBC (combined blast and contact) ‐treated cod loins packaged in bulk under different atmospheres (air or modified atmosphere, MA) and stored under different temperature profiles to mimic temperature changes during transport and distribution to European markets. Sensory, chemical, microbial and headspace gas composition analyzes were performed regularly. The fish was caught by trawler in the spring and processed 3 days post catch. Following simulation of current sea freight conditions and distribution to European markets, a 2 ‐ day and 1 ‐ day increase in freshness period and shelf life of MA ‐ packaged fish (2.7 kg in trays), respectively, was observed compared to air ‐ stored loins (3.1 kg in EPS boxes). This is despite a mean product temperature difference of 0.5 ° C between the products, being lower (‐0.3 ± 0.9 ° C) for air ‐ stored fish. Abusive conditions had the greatest impact on the reduction of the freshness period for MAP fish. Superchilled storage of MAP loins (‐1.1 ± 0.1 ° C) resulted in a 13 ‐ day shelf life. Evaluation of microbial and chemical indicators emphasized the importance of Photobacterium phosphoreum and TMA formation in the deterioration of cod loins stored in air or MA, while superchilled MAP storage delayed as well as modified the spoilage pattern. MAP increased drip loss by about 2% at late storage.

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Reports

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

Published:

01/12/2009

Authors:

Emilia Martinsdóttir, Cyprian Ogombe Odoli, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Hannes Magnússon, Sigurjón Arason, Ragnar Jóhannsson

Supported by:

Technology Development Fund

contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

The purpose of the experiments was to find the best storage conditions for fresh tilapia fillets by determining the shelf life by sensory evaluation, microbial counts and physical and chemical measurements. Nile tilapia (Oreochromis niloticus) raised in a renewable water cycle system was filleted and packed in 100% air and aerated packages 50% CO2: 50% N2 MA for storage at 1˚C and -1˚C. The development of the QIM rating scale and the sensory evaluation properties of fresh and cooked tilapia fillets and the use of the scale in shelf life testing are described. A linear relationship was found between the quality factor and the storage time (r> 0.93) for all storage groups. The results of sensory evaluation and microbial counts showed that fillets packed in air had a shelf life of 13-15 days at 1˚C and 20 days at -1˚C. At the end of shelf life in air packs, the total number of micro-organisms and the number of pseudomonads micro-logs were 7 CFU / g in meat. In fillets in aerated packages, the coating phase was longer and the total number of microorganisms was below log 4 CFU / g after 27 days of storage at both 1˚C and -1˚C. However, aerobic conditions adversely affected the color of the fillets shortly after packing, but the color of the fillets significantly affected buyers' choices. Chemical measurements such as TVB-N and TMA were not a good measure of damaged fillet fillets. The best storage conditions for tilapia fillets are air packing and storage at a constant low temperature of -1 ° C. This report is based on the main findings of Cyprian Ogombe Odoli's master's project.

The main aim was to establish optimal storage conditions for fresh tilapia fillets by determining its shelf life by sensory and microbiological evaluation, as well as monitoring its physical-chemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted and packaged in 100% air and 50% CO2: 50% N2 MA prior to storage at different temperature; 1˚C and -1˚C. This report further describes the development of a Quality Index Method (QIM) scheme and a sensory vocabulary for fresh and cooked tilapia fillets accordingly and application in a shelf life study. The application of the QIM scheme for tilapia fillets showed a linear relationship between QIM scores and storage time (r> 0.93) for all samples. The results from sensory analysis of cooked samples as well as microbial growth indicated that fillets packaged in 100% air had a shelf life of 13-15 days during storage at 1˚C and 20 days during storage at -1˚C. At the end of shelf life in 100% air packaged groups, TVC and pseudomonads counts reached log 7 CFU / g in flesh. In MA packaged fillets, the lag phase and generation time of bacteria was extended and recorded total counts below the limit for consumption (<log 4 CFU / g) up to 27 days of storage at both 1˚C and -1˚C. However, MA packaging negatively affected the color characteristics of the fillets soon after packaging (as from d6) but color is an important indicator of quality and a major factor in influencing retail purchase decisions. Chemical analyzes (TVB-N and TMA) were not good indicators of spoilage of tilapia fillets in the present study. 100% air packaging at -1˚C storage temperature is the optimal storage conditions for fresh tilapia fillets. The report is based on the master thesis of Cyprian Ogombe Odoli.

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Reports

Shelf life tests on cod pieces: Effects of supercooling, pickling and gas packaging on the physical and chemical properties of cod muscles

Published:

01/12/2007

Authors:

María Guðjónsdóttir, Hannes Magnússon, Sigurjón Arason, Guðrún Ólafsdóttir, Sigurður Bogason

Supported by:

AVS, Rannís Technology Development Fund, Rannís Research Fund

contact

Sigurjón Arason

Chief Engineer

sigurjon.arason@matis.is

Shelf life tests on cod pieces: Effects of supercooling, pickling and gas packaging on the physical and chemical properties of cod muscles

An integrated refrigeration study was carried out on the effect of salting, different packaging methods and salting methods as well as the effect of subcooling on the quality and shelf life of cod muscles. The results show that storage is a more desirable salting method than injection salting from a microbiological point of view and with regard to drip and boiling efficiency. However, if the salinity during storage becomes too high, the muscle will gel. In the experiment, it was not considered to improve the quality of the fish to inject proteins into the muscle in addition to the salt. Microbial growth and the amount of wandering alkali decrease with decreasing temperature, so it is desirable to keep the temperature as low as possible, without the fish freezing. At -4 ° C, the surface of the fish in all groups, regardless of salinity, was frozen and the ice crystal formation increased with storage time. This ice crystal formation took place much more slowly at -2 ° C and is therefore considered a desirable storage temperature for lightly salted cod muscles. Air-packed packaging (MAP) also proved to be a more desirable storage method than foam packaging, as microbial growth and increase in erratic base was slower in the MAP packaging, which led to longer shelf life.

A combined cooling experiment was performed upon the effect of salting, different packaging and salting methods as well as the effect of superchilling on the quality and shelf life of cod muscle. The results show that brining is a better salting method that brine injection in terms of bacterial growth as well as increased yield. On the other hand, if the salt concentration becomes too high, gelation of the muscle proteins begins. The study also showed that injection of proteins along with salt injection did not improve the quality of the muscle. Microflora and the formation of volatile nitrogen bases decreased with lowering temperatures. It is therefore preferred to store fish at as low temperatures as possible, without letting the muscle water freeze. At -4 ° C the water at the muscle surface was frozen in all groups, independent of salt content, and the ice crystallization increased with storage time. This crystallization was much slower at -2 ° C and therefore this temperature is recommended for storage of light salted cod muscle. Modified Atmosphere Packaging (MAP) turned out to be a better packaging method than Styrofoam packaging, since the increase in bacterial growth and volatile nitrogen bases was slower in the MAP. This also lead to increased shelf life.

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Reports

Shelf life tests on cod pieces: Effect of supercooling, pickling and gas packaging on quality changes and shelf life / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

Published:

01/05/2007

Authors:

Hannes Magnússon, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Ása Þorkelsdóttir, Birna Guðbjörnsdóttir, Emilia Martinsdóttir, Guðrún Ólafsdóttir, María Guðjónsdóttir, Sigurður Bogason, Sigurjón Arason

Supported by:

AVS Fisheries Research Fund, Technology Development Fund (Rannís)

contact

Kolbrún Sveinsdóttir

Project Manager

kolbrun.sveinsdottir@matis.is

Shelf life tests on cod pieces: Effect of supercooling, pickling and gas packaging on quality changes and shelf life / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

The aim of these experiments was to evaluate the effect of supercooling, aerated packaging (MAP) and brine on quality changes and shelf life of cod pieces. The effects of gas packaging and different storage temperatures on the growth of several pathogens and pointing organisms were also investigated. The experiment was carried out in October 2006 at Samherji in Dalvík. After storage (0.6 and 2% salt), the fish was trimmed and the neck pieces were packed in standard 3 kg foam packs (air packs) and in air-conditioned packaging. The gas mixture was adjusted to 50% CO2, 5% O2 and 45% N2. Three pieces (350- 550g) were placed in each tray with a drying mat. After packing, the samples were placed in Matís freezer simulators set at 0 ° C, -2 ° C and -4 ° C. The samples were examined over a four-week storage period. Sensory evaluation, microbial counts and chemical measurements were used to assess quality changes and shelf life. Pickled (2% salt) fish were stored shorter than uncooked (0.6% salt). A comparison of the number of micro-organisms the day after packing showed that the pickled fish contained ten times more cold-resistant micro-organisms than the non-pickled ones. According to sensory evaluation, the shelf life of the pickled fish at -2 ° C was 12-15 days in both air- and gas-packed pieces. In the blunt fish, the effects of gas packaging and supercooling were evident. The shelf life of air-packed pieces was about 11 days at 0 ° C and 14-15 days at -2 ° C. The shelf life of gas-packed pieces, on the other hand, was about 15 days at 0 ° C and about 21 days at -2 ° C. Supercooling of fresh uncooked fish products in air-conditioned packaging can therefore significantly increase shelf life. Gas packing significantly reduced the growth rate of pathogens and microorganisms at low temperatures. Salmonella was most affected, then Escherichia coli and Listeria monocytogenes the least. Under air conditions, L. monocytogenes grew at -2 ° C, but E. coli began to multiply at 5 ° C and Salmonella at 10 ° C.

The aim of these experiments was to evaluate the effect of superchilling, modified atmosphere packaging (MAP) and brining on the quality changes and sensory shelf-life of cod loins. The effect of MAP and different storage temperatures on some pathogenic and indicator bacteria was also tested. These experiments were initiated in October 2006 at Samherji, Dalvík. After brining (0.6 and 2% salt) the fish fillets were trimmed, and loins packed on one hand in 3 kg styrofoam boxes (air) and on the other in MA. The gas mixture used was 50% CO2, 5% O2 and 45% N2. Three pieces (350-550 g) were placed in each tray with an absorbent mat. After packaging the samples were placed in 3 coolers at Matís which were adjusted to 0 ° C, -2 ° C and -4 ° C. Samples were examined over a four-week period. Sensory analysis, microbial counts and chemical measurements were used to determine the quality changes and shelf-life. Brined loins had a shorter shelf-life than unbrined (0.6% salt). Comparison on numbers of microorganisms the day after packaging revealed that the brined pieces contained ten times more microbes than the unbrined ones. According to sensory analysis the shelf-life of the brined loins at -2 ° C was 12-15 days for both air- and MA-packed fish. In the unbrined loins the effects of superchilling and MAP were obvious. The shelf-life of air-packed loins was about 11 days at 0 ° C and 14-15 days at -2 ° C. The shelf-life of MA-packed loins was about 15 days at 0 ° C but 21 days at -2 ° C. Superchilling of unbrined fish under MA can therefore increase the keeping quality considerably. MA packaging clearly decreased the growth rate of pathogenic and indicator bacteria at low storage temperatures. Most effects were seen with Salmonella, then Escherichia coli but least with Listeria monocytogenes. In fact, L. monocytogenes could grow at -2 ° C under aerobic conditions, while proliferation of E. coli was first observed at 5 ° C but 10 ° C for Salmonella.

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