Growing fish consumption worldwide has driven fish processors to introduce innovative seafood products with extended shelf-life and desirable organoleptic properties. This study investigates the impact of freezing deep-skinned Atlantic mackerel fillets before and after smoking, prior to canning. Physicochemical and organoleptic properties of canned fillets were evaluated after 1 and 12 months of storage at room temperature. The formation of primary oxidation products (PV) was similar in both cases, while the secondary oxidation products (TBARS) were significantly lower when the fillets were smoked before freezing. PV and TBARS were significantly lower in all canned mackerel samples after prolonged canned storage compared to the shorter storage. However, lipid oxidation and hydrolysis were very limited after both treatments and, therefore, do not constitute an issue in these products. Results of product evaluation and instrumental texture analysis of canned mackerel indicated more beneficial characteristics (firmer fillets, nor mushy) when fillets were frozen first and then hot-smoked (FSC). Fillets that were smoked first and then frozen (SFC), regardless of the canning storage time, were characterized by a mushy texture and appearance, which can negatively impact consumer acceptance. Therefore, freezing prior to hot-smoking may represent a better choice if the fillets are intended for canning.
Tag: Quality
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Cecile Dargentolle
Project Manager
cecile@matis.is
The purpose of the study was to investigate the possibility of slow-aging "dry-ageing" of different types of fish: lean and fatty. Since the dry-ager was homemade, it was not possible to work with a lower temperature than 4°c. We worked with that temperature and saw how the fish reacted to it. By trying to put both fillets and whole fish in a dry-ager, it was found that it took less time for fillets to reach a similar point of action as whole fish. Shrinkage had to be at least 15% in order to achieve the correct effect: improved texture and taste. These studies also showed that a specially designed and constructed dry-ager would give more accurate answers, as both temperature and humidity can be controlled much better, resulting in a much better final product. pH value, color, water content and shrinkage together with sensory evaluation are promising in the use of slow-aging (dry-ageing) of fish to increase shelf life and more valuable sensory evaluation effects.
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Those trials were aiming at evaluating the feasibility of dry-aging different types of fish: lean and fatty. As the dry-ager was homemade, the temperature could not be lowered lower than 4°C, allowing the trials to see if the fish would support those temperatures. By trying both fillets and full fish to be dry-aged, the project showed that the time in the dry-age would be shorter for fillet to get to a similar stage than full fish. The weight loss of both should at least be 15% to get a desirable stage: improved texture and taste. Those trials also showed us that commercial dry-ager would present more benefits, as with more stability of both temperature and humidity, the quality of the final product will be better. pH, colour, water content and weight loss as well as sensory showed promising results to use dry-aged fish as a preserving technique to improve both shelf life and sensory characteristics of seafood.
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Cecile Dargentolle
Project Manager
cecile@matis.is
The second part of the research on dry-aging fish focused on increasing the understanding of the parameters that work best (temperature, humidity and time) to achieve the desired characteristics of dry-aged fish. Dry-ageing is a process in which the water content of fish is reduced and the fish deteriorates, until the decomposition of the fish slows down enough to ensure low microbial growth (similar to smoked fish). These studies revealed that it is necessary to work with a lower humidity than 82% and a temperature of 2°c is suitable. The shelf life of fish can be extended by dry-ageing, and a whole fish was kept in the dry-ager for 2 weeks and kept for another 2 weeks without spoiling. Experiments with freezing and storage showed that dry-aged fish is suitable for both. These studies make it possible to make the first statements regarding dry-ageing of fish, as these are the first scientific studies that have been carried out.
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The second batch of trials from the project dry-aged fish, aimed at understanding which parameters would be best (temperature, humidity, and time) to reach satisfactory dry-aged characteristics to the fish. Dry-ageing is a process where the water content in the fish reduces and the fish loses some weight, to reach a stage where the degradation will be slow enough to ensure low bacterial growth (similar to smoked fish). Those trials showed that humidity should be lower than 82% and that 2°C is working. Shelf life of fish can be extended thanks to dry-aging as whole fish could stay in the dry-ager for at least 2 weeks and then stored for 2 more weeks without having any bad attribute developing. Freezing tests and storage tests allowed to show that dry-aged fish supports both processes. Those trials allowed to set the first statements regarding dry-aging fish, with the first scientific data collected.
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
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Kolbrún Sveinsdóttir
Project Manager
kolbrun.sveinsdottir@matis.is
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Aðalheiður Ólafsdóttir
Sensory evaluation manager
adalheiduro@matis.is
In the Norwegian oceanic fleet, whitefish onboard processing creates a great amount of rest raw materials. Cod heads are nutritious and a good source for the production of high-quality marine peptides. Frozen cod heads, captured by trawl or longline, were evaluated based on the lightness and redness in the neck cut to compare the quality in heads from the different fishing gears. The heads were subjected to enzymatic hydrolysis. The hydrolysates have been chemically and sensory characterized. There was no significant difference in quality or chemical and sensory characteristics based on type of fishing gear. The resulting hydrolysates were of high quality, although moderately bitter. The study demonstrates that frozen cod heads from the oceanic fleet can be an excellent source of high-quality proteins for human consumption.
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Sigurjón Arason
Chief Engineer
sigurjon.arason@matis.is
Maximizing the quality of frozen redfish products / Quality optimization of frozen redfish products
The aim of the study was twofold. Firstly, to explore the influence of time and temperature during frozen storage on lipid deterioration of red fish. That was done by comparing the effect of temperature fluctuation and abuse during frozen storage, as can be expected during transportation, on the physicochemical characteristics and lipid stability of redfish fillets. Secondly, to investigate the effect of 4 days postcatch and 9 days postcatch, and seasonal variation on the quality and storage stability of frozen red fish.
Storage temperature and storage time affected the physical- and chemical properties in redfish, eg free fatty acids, TBARS and TVB-N. Season of capture affected both the nutritional value and stability of golden redfish. The light muscle of fish caught in November was richer in EPA and DHA than in the fish caught in June. The fish caught in November was also more unstable through frozen storage, due to a more unsaturated nature of the fatty acids present, indicating that special care needs to be applied during handling and treatment of golden redfish caught at this time. The light muscle had a higher nutritional value than the dark muscle and is a good nutritional source for human consumption. However, the dark muscle was prone to lipid oxidation which may have a negative influence on the more valuable light muscle. So there seems to be a need to separate them.