Extending shelf life of desalted cod by high pressure processing

Salted fish need to be rehydrated before eaten, but rehydrated fish have a relatively short shelf life. To increase the shelf life the products can e.g. be frozen, packed in modified atmosphere or processed by high pressure (HPP). Here, rehydrated cod was packed with different packaging regimes; in vacuum, with CO₂ emitter or in modified atmosphere [MAP], either alone or in combination with HPP. A shelf life study was performed, and headspace gas composition, drip loss, pH, colour, texture and microbial counts were assessed in the packaged and processed portions. The results showed that a shelf life of minimum 49 days can be obtained by treating the rehydrated cod by HPP or by combining HPP with modified atmosphere or in combination with a CO₂ emitter. The results of this study have shown that different packaging and processing methods can increase the shelf life of desalted cod.Industrial relevanceThe growing trend and availability of “ready to cook” products are forcing the food industry to increase production of convenience products. Today desalted saltfish or clipfish need to be consumed immediately, stored chilled for a few days, stored frozen or being packed and/or processed to extend its shelf life. The use of high pressure processing represents a promising strategy to enhance the shelf-life of fish products. This study shows that HPP alone or combined with CO₂ can extend the shelf life of rehydrated cod. Hence, these results can open up for new products.     

Influence of different preservation treatments on the volatile fraction of desalted cod

In the present study, desalted cod underwent a water blanching treatment and the incorporation of additives (citric acid and potassium sorbate), combined with different types of packaging (air, vacuum and modified atmosphere), to achieve an improvement of the shelf life of ready-to-use desalted cod. The purpose of this work was to evaluate the effect of these combined methods of preservation on the volatile fraction of desalted cod during 42 days in cold storage. The volatile compounds identified in all samples were those mainly related to fresh odor in whitefish, although with some exceptions. Untreated desalted cod showed a high increase of 3-methyl-1-butanol (described as a microbial spoilage index) during the storage period; a higher increase in air packaging than in vacuum and modified atmosphere packaging. The slow increase of this compound, as well as the evolution of ketones and aldehydes observed for the rest of the samples submitted to treatment, demonstrated the effectiveness of the combined treatments applied. The most efficient treatment was the combination of additives together with modified atmosphere packaging.     

Using A New Measure To Define Shelf Life Of Fresh Whitefish

An acceptor set size measure was successfully employed to examine shelf life trade-offs when fresh lake whitefish fillets (Coregonus clupeaformis) were dipped in 0.0, 2.5 or 5.0% (w/v) potassium sorbate, packaged in low, intermediate, or higher barrier bags, placed in 100% CO₂ modified atmosphere packaging system and held under refrigeration at less than 3°C. When sorbate was varied, shifts in acceptor size indicated that fillets dipped in 5.0% sorbate had the longest shelf life, exceeding 14 days. No significant difference was found when film permeability was varied. For all barrier films, shelf life exceeded 15 days although the low barrier bag had smaller acceptor sizes.     

Microbial and sensory changes during refrigerated storage of desalted cod (Gadus morhua) preserved by combined methods

Water blanching and the use of additives (potassium sorbate and citric acid) combined with different types of packaging (air, vacuum "VP" and modified atmosphere packaging "MAP": 60% CO(2), 30% N(2) and 10% O(2)), were studied as new methods of preservation of chilled desalted cod. Microbial counts and total volatile basic nitrogen (TVB-N) analyses were carried out during a period of 42 days on all samples stored at 4 degrees C. No Aeromonas or sulphite-reducing Clostridium were isolated from any of the analysed samples. The lowest microbial counts of mesophilic, psychrotrophic, Pseudomonas, moulds and yeasts, were found in samples with additives in all kinds of packaging. These samples in VP or MAP maintained an excellent microbial quality throughout the 42 days of storage, with mesophilic and psychrotrophic counts always below 4 log CFU/g. Counts of the four microorganisms above-mentioned in blanched samples packaged with air, exceeded 5 log CFU/g on days 21-28, so it became necessary to use VP or MAP to maintain these microorganisms at an acceptable level for the entire storage period. TVB-N contents were low in samples with additives, regardless of the kind of packaging, as well as in blanched samples packaged in VP and MAP, never reaching 25 mg/100 g. Since there were no significant differences either in microbial growth or in TVB-N between samples in VP and MAP, a sensory analysis was performed only in desalted cod submitted to the two treatments (blanching and additives) combined with VP, both in raw and cooked samples. The results of this analysis showed that the addition of potassium sorbate and citric acid did not alter the typical organoleptic features of desalted cod. The sensory characteristics of both blanched samples and those with additives in VP showed no change during the period of the study.     

The effects of soluble gas stabilisation on the quality of packed sardine fillets (Sardina pilchardus) stored in air,VP and MAP

Sardine (Sardina pilchardus) is a species that for its abundance assumes great importance in the Portuguese fishing sector. In order to contribute for a better utilisation of this species, the aim of this study was to investigate the effect of the pre‐treatment with soluble gas stabilisation (SGS) (100% CO₂ at 2 bar, during 15 and 30 min) on the quality and shelf‐life of sardine fillets, packed in air (AP), vacuum (VP) and modified atmosphere (MAP: 5% O₂/35% CO₂/60% N₂). During the chilled storage, the quality changes were evaluated by sensory evaluation, chemical and microbiological analysis. The total volatile basic nitrogen content remained almost constant, between 16 and 19 mg N/100 g muscle, during the storage period, for all samples. The TBARs values increased with storage time, for all batches and storage conditions. The application of SGS treatment to sardine fillets, resulted in a bacteriostatic effect, contributing to the improvement of the microbiological quality of fillets. Considering a sensory criteria, the shelf‐life of SGS pre‐treated sardine fillets was found to be 5 days in AP and MAP while in VP‐treated fillets a shelf‐life of 8 days was reported. At sensory rejection, sardine fillets presented a K‐value of 30% in AP and MAP batches and 40% in VP batch.     

Comparison of the shelf lifes of map and vacuum packaged hot smoked rainbow trout (Onchoryncus mykiss)

The objective of this study was to determine the differences of microbiological and chemical quality in MAP and VP packages in refrigerated smoked trout fillets. Such information is important in evaluating the safety of these products. Three groups were constituted: group A – packed in 60%Co₂/40% N₂; group B – packed in 50%CO₂/50% N₂ and group C– vacuum packed. The ratio of fillet to package volume was 1/3 chemical analysis and microbiological analysis were done and also instrumental and sensory analysis were used to determined the shelf life. The observed shelf life of smoked trout was found at least 33 days in vacuum package, 47 days in 60% CO₂/40% N₂ gas mixture and 40 days in 50% CO₂/50% N₂ gas mixture according to results of microbiological analysis. The observed shelf life of smoked trout in MAP group A was determined as 14 days more than VP packs according to results of microbiological and sensory analysis in the study.     

Evaluation of Shelf Life of Superchilled Cod (Gadus morhua) Fillets and the Influence of Temperature Fluctuations During Storage on Microbial and Chemical Quality Indicators

Quality changes of aerobically packed cod fillets stored under superchilling and abusive temperature conditions were characterized by the growth of specific spoilage organisms (SSO) and the production of microbial metabolites measured by an electronic nose along with traditional sensory and chemical analysis (total volatile basic nitrogen [TVB‐N], pH). A new process based on quick contact freezing and cold air blasting was used to achieve superchilling of fillets before chilled (0.5 °C) or superchilled (‐1.5 °C) storage. Photobacterium phosphoreum dominated under temperature abusive conditions coinciding with high levels of TVB‐N and increased electronic nose responses indicating increased levels of alcohols and aldehydes at sensory rejection. Dominating growth of Pseudomonas spp. in 1 batch was associated with the origin, the catching method, and the cooling conditions during processing. The superchilling process followed by superchilled storage (‐1.5 °C) extended the sensory shelf life of the fillets for at least 3 d compared with traditional process, resulting in a total shelf life of 15 d. High content of TVB‐N was observed in superchilled fillets at sensory rejection. P. phosphoreum counts were lower under superchilling conditions (6.0 to 6.8 log colony‐forming units [CFU]/g), compared with the traditionally processed chilled fillets (7.2 log CFU/g). However, H₂S‐producing bacteria appeared to grow steadily under superchilling conditions reaching counts as high as 7.6 log CFU/g at sensory rejection.     

Sensory, physical, chemical and microbiological changes in European sea bass (Dicentrarchus labrax) fillets packed under modified atmosphere/air or prepared from whole fish stored in ice

Quality changes and shelf‐life in European sea bass fillets packed under 40% CO₂: 60% N₂ (MAP) and air (AIR) or prepared from the whole ungutted fish stored in ice (ROUND) were compared. Raw and cooked sensory scores, pH, colour, expressible water, malonaldehyde, total viable count, Pseudomonas spp., H₂S‐producing bacteria, Lactobacillus spp., Streptococcus spp., Staphylococcus spp., coliforms and proteolytic counts, were determined until AIR and MAP raw fillet spoilage. Raw ROUND fillets had the best quality and shelf‐life (10 vs. 8 vs. 7 days after slaughtering in ROUND, MAP and AIR, respectively), while the MAP fillets had better sensorial scores, lower pH values and better microbiological counts, but greater lightness values than the corresponding AIR fillets. MAP fillets also had the highest malonaldehyde levels. The higher correlation between Streptococcus spp. and odour scores (r = ?0.971, P < 0.01) compared to the other species could suggest that it is a specific spoilage organism in the MAP condition used.     

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors,and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready‐to‐eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O₂, 5% CO₂, 90% N₂ (MAPC—commercial control), 21% O₂, 5% CO₂, 74% N₂ (MAP 1), 45% O₂, 5% CO₂, 50% N₂ (MAP 2), and 60% O₂, 5% CO₂, 35% N₂ (MAP 3)) and 4 °C for up to 10 d. The quality and shelf‐life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf‐life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf‐life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.     

Improvement in the Microbiological Quality of Ready-To-Use Desalted Cod

ABSTRACT: To reduce the microbial load of ready-to-use desalted cod, 2 different concentrations of sodium chloride (3.13% and 5.78% in water phase), potassium sorbate (0.14% and 0.20% in water phase), and citric acid (pH 6.10 and 5.77), with 2 kinds of packaging procedures (air or vacuum), have been used. The vacuum packaging was effective only in the samples with 3.13% salt after 28 d of storage, whereas no important differences between both packaging procedures were observed in samples with 5.78% salt. This last salt level only limited the Pseudomonas growth, however it was necessary to combine this salt concentration with potassium sorbate plus citric acid to inhibit mesophilic, psychrotrophic, and molds and yeasts.     

Original article: Effect of modified atmosphere packaging using different CO2 and N2 combinations on physical,chemical, microbiological and sensory changes of fresh sea bass (Dicentrarchus labrax) fillets

The effect of different modified atmosphere packaging (MAPs) on physical, chemical, microbiological and sensory changes of sea bass fillets when stored at 4 °C and standard light conditions was investigated for up to 21 days and compared to a control batch stored in overwrap. Sea bass fillets were packed using different CO₂ and N₂ combinations (40% CO₂–60% N₂; 50% CO₂–50% N₂; 60% CO₂–40% N₂), and quality assessment was based on instrumental, chemical, microbiological and sensory analysis. The results showed that MAP extended shelf‐life of sea bass fillets from 7 days (overwrap packaging) to 14 days. Drip loss, pH values and thiobarbituric acid reactive substances (TBARS) measurements were higher in overwrap samples but no differences (P ≤ 0.05) were found between MAP samples. Bacteria grew most quickly and showed higher counts in overwrap samples followed by 40% CO₂–60% N₂; 50% CO₂–50% N₂ and finally 60% CO₂–40% N₂. Sensory analyses were in good relation with chemical and microbiological results establishing best scores and an extended shelf‐life for MAP samples especially in MAPs with high CO₂ levels.     

Predictive modelling and selection of Time Temperature Integrators for monitoring the shelf life of modified atmosphere packed gilthead seabream fillets

The objective of the present study was to validate a kinetic model for growth of spoilage bacteria in modified atmosphere packed (MAP) gilthead seabream fillets and to select a Time Temperature Integrator (TTI). The temperature and CO₂ dependence of the growth of lactic acid bacteria in MAP gilthead seabream fillets was expressed by an Arrhenius-type model for the range of 0-15 °C and 20-80% CO₂, which was validated at isothermal, variable and chill chain conditions. A new UV activatable photochemical TTI, was kinetically studied and the influence of the level of activation on the response of the TTI was modelled. Applying the developed models, the required charging levels were estimated so that the TTI response was tailored to monitor the shelf life of fish fillets at selected MAP conditions, during the chill chain storage. A simulation experiment of the product distribution and storage in various chill chain conditions showed the applicability of the TTIs as shelf life monitors.     

Shelf Life Determination of Sliced Portuguese Traditional Blood Sausage—Morcela de Arroz de Monchique through Microbiological Challenge and Consumer Test

Morcela de Arroz (MA) is a ready‐to‐eat blood and rice cooked sausage produced with pork, blood, rice, and seasonings, stuffed in natural casing and cooked above 90 °C/30 min. It is commercialized whole, not packed, with a restricted shelf life (1 wk/0 to 5 °C). The objective of this work was to establish sliced MA shelf life considering both the behavior of L. monocytogenes through a microbiological challenge test (MCT) and the consumer acceptability of MA stored: vacuum packed (VP), modified atmosphere packed (MAP: 80% CO₂/20% N₂), and aerobic packed (AP). The MCT was conducted inoculating ±3 log CFU/g of L. monocytogenes cell suspension on the MA slices. Packaged samples were stored at 3 ± 1 °C and 7 ± 1 °C until 20 d. At 3 ± 1 °C, L. monocytogenes behavior was not affected by packaging or storage time. At 7 ± 1 °C, the pathogen increased nearly 1 log CFU/g in the first 4 d. L. monocytogenes populations in AP were higher (P < 0.05) than in MAP. The pathogen may grow to hazardous levels in the 1st days if a temperature abuse occurs. Considering the acceptability by the consumers, the shelf life of MA stored at 3 ± 1 °C was 4.4 d for AP, 8.1 d for VP, and 10.4 d for MAP. The sensory shelf life established based on sensory spoilage is shorter than the shelf life to maintain the population of L. monocytogenes in safe levels.     

Biochemical,microbiological and sensory changes in shrimp (Panaeus aztecus) dipped in different solutions using face‐centred central composite design

Biochemical, microbiological and sensory changes during shelf‐life at ?1 °C were determined in shrimp (Panaeus aztecus) previously dipped in ascorbic acid, citric acid, potassium sorbate and 4‐hexyl resorcinol solutions using face‐centred central composite design. Microbiological count, trimethylamine and hypoxantine production were measured. The lowest level of the total psychrotrophic bacteria, hypoxantine and trimethylamine were found in samples dipped in all containing chemicals solutions comparing to control treatment. Sensory studies showed that treatment A (ascorbic acid 4.50, citric acid 0.12, potassium sorbate 18.60 and 4‐hexyl resorcinol 0.25, all g L^?1) and B (ascorbic acid 4.37, citric acid 1.26, potassium sorbate 7.03 and 4‐hexyl resorcinol 0.25, all g L^?1) did not alter the typical sensory features of shrimp and were effective at delaying the bitter off‐flavour formation for 26 days. This study constitutes a promising alternative to extent shelf‐life of shrimp kept at ?1 °C without freezing.     

The combined effect of superchilling and modified atmosphere packaging using CO2 emitter on quality during chilled storage of pre‐rigor salmon fillets (Salmo salar)

BACKGROUND: Pre‐rigor fillets of Atlantic salmon were either superchilled or chilled prior to packaging in air or in modified atmosphere (MAP, 60% CO₂/40% N₂) with a CO₂ emitter, in 5.3 L high‐density polyethylene trays with three to four layers of fillets (3.0–3.7 kg). All samples were stored at 0.1 °C for 28 days. RESULTS: Fillets stored in MAP had significantly lower bacterial growth compared to fillets stored in air, and MAP superchilled bottom fillets had lower bacterial counts compared to the corresponding chilled fillets. Samples superchilled prior to refrigerated storage in air had similar bacterial growth to ordinary chilled samples. Faster fillet softening during storage and higher liquid loss were observed in superchilled MAP samples. CONCLUSION: Combining short‐term superchilling and MAP with a CO₂ emitter prolonged the shelf‐life of pre‐rigor salmon fillets, which can improve sustainability throughout the value chain. The superchilling method needs to be optimized to avoid negative effects on texture and liquid loss. Copyright © 2009 Society of Chemical Industry     

THE SHELF-LIFE EXTENSION OF HADDOCK IN CARBON DIOXIDE-OXYGEN ATMOSPHERES WITH AND WITHOUT POTASSIUM SORBATE

Fresh haddock, whole fish or fillets, treated or not with various potassium sorbate dips, were sealed in gas impermeable bags containing gas atmospheres of 60% CO₂, 20% O₂ and 20% N₂, air or vacuum, stored on ice in insulated AIRBOX containers at 0°C and subsequently assessed using the Torry freshness scale after 11 to 18 days storage. The trends in the data suggested higher freshness scores for gas and gas plus dip compared with the air and vacuum packs. The dip alone was not effective. It was important to maintain the fish at 0° C.     

Thawed Chilled Barents Sea Cod Fillets in Modified Atmosphere Packaging-Application of Multivariate Data Analysis to Select Key Parameters in Good Manufacturing Practice

The purpose of the present study was to select key parameters in good manufacturing practice for production of thawed chilled modified atmosphere packed (MAP) cod (Gadus morhua) fillets. The effect of frozen storage temperature (−20 and −30 °C), frozen storage period (3, 6, 9 and 12 mo) and chill storage periods up to 21 d at 2 °C were evaluated for thawed MAP Barents Sea cod fillets. Sensory, chemical, microbiological and physical quality attributes were evaluated and multivariate data analysis (principal component analysis and partial least-squares regression) applied for identification of key parameters in good manufacturing practice for this product. Frozen storage of up to 12 mo had no significant effect on quality attributes and shelf-life at 2 °C was above 14 d irrespective of the time of frozen storage. As compared to a previous study with Baltic Sea, cod drip losses during chill storage was low for thawed MAP Barents Sea cod and this fish raw material seemed the more appropriate for production of thawed chilled MAP products. Frozen storage inactivation of the spoilage bacteria of Photobacterium phosphoreum was modest in Barents Sea cod, possibly due to high trimethylamine oxide (TMAO) and NaCl contents.     

Effect of O2 scavenger on the shelf‐life of catfish (Pangasius sutchi) steaks during chilled storage

BACKGROUND: Active packaging for preserving meat products, including seafoods, has been gaining importance in recent times. The present study was undertaken to assess the effectiveness of O₂ scavenger, the most widely used active packaging technology, on the shelf‐life of catfish steaks in chilled storage conditions. RESULTS: O₂ scavenger was effective in reducing the oxygen concentration inside the packaging to as low as 0.42% within 24 h. This reduction in oxygen in O₂ scavenger packages showed positive effects on quality parameters compared to control air packs. Total volatile base nitrogen (TVB‐N), thiobarbituric acid value and peroxide value of catfish steaks packed in O₂ scavenger was significantly different (P < 0.05) compared to air‐packed samples. Based on the sensory, microbiological and TVB‐N values, the control samples were acceptable only up to 10 days, compared to 20 days in O₂ scavenger‐packed samples, extending the shelf‐life by 10 days. CONCLUSION: O₂ scavenger reduced the oxygen concentration inside the package significantly within 24 h compared to control air packs. By using this technique, the use of a vacuum packing machine can be avoided. Further, O₂ scavenger extended the product's shelf‐life up to 20 days, compared to 10 days in control packs. Copyright © 2007 Society of Chemical Industry     

The determination of the shelf-life of pasteurized and non-pasteurized sardine (Sardina pilchardus) marinades stored at 4 °C

In this study the shelf‐life of sardine marinades was investigated. After the marination process, sardine fillets were packed into glass jars with 2% citric acid, 4% sodium chloride and spices. The effect of pasteurization at 70 °C for 20 min on the shelf‐life of the sardine marinades was determined. At the end of 6 months storage the differences between thiobarbituric acid, free formaldehyde (FA(ex)), free and bound formaldehyde (FA(dest)) and peroxide value of pasteurized and non‐pasteurizated marinades were not significantly (P > 0.05) different, while the difference between total volatile basic nitrogen, trimethylamine, pH, total plate count and lactic acid bacteria count of pasteurized and non‐pasteurized marinades were. The shelf‐life of both pasteurized and non‐pasteurized sardine marinades was found to be 5 months at 4 °C.