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.     

Lack of growth of Listeria monocytogenes and Staphylococcus aureus in temperature abuse of E-beam treated ready-to-eat (RTE) cooked ham

The behaviour of Listeria monocytogenes and Staphylococcus aureus in vacuum-packed cooked ham slices treated with an electron beam and stored at 4, 7 and 10 °C was investigated. Cooked ham slices were inoculated with L. monocytogenes and S. aureus and electron beam treated at 2 and 3 kGy. After treatment, a long temperature-dependent death phase was observed, followed by growth at a slower rate than in untreated samples. Assuming a hypothetical load of 10 cells/g or cm² of L. monocytogenes and S. aureus as an original contamination in an industrial situation, an E-beam treatment of vacuum-packed cooked ham slices at 2 kGy guarantees the microbiological safety of the product along its shelf life, even if a noticeable temperature (10 °C) abuse occur during its storage period. Likewise, the E-beam treatment gave rise to a substantial increase of the RTE cooked ham shelf life off-sensory features associated to the spoilage only were detected in non-treated samples (controls) after 8 and 18 days of storage at 10 °C and 7 °C, respectively.     

Combined PEF,CO2 and HP application to chilled coho salmon and its effects on quality attributes under different rigor conditions

Effects of pulsed electric fields (PEF: 1–2 kV/cm, 20 μs) used alone and combined with carbon dioxide (CO₂: 70%) and high hydrostatic pressure (HP: 150 MPa, 5 min) on the physicochemical properties and microbiological shelf life of coho salmon under pre- and post-rigor conditions were studied during refrigerated storage (25 days). The PEF + CO₂ + HP treatments reduced color changes in pre-rigor more than in post-rigor salmon. Texture changes of pre- and post-rigor salmon differed between untreated and treated salmon. Combined treatments also effectively reduced the protease and lipase activity of pre-rigor salmon. Collagenase activity of post-rigor salmon remained low in all treatments. Principal component analysis showed a clear difference between pre- and post-rigor states in the evaluated parameters; however, microbiological shelf life increased with PEF + CO₂ regardless of the rigor condition. In conclusion, combined PEF, CO₂, and HP treatments can improve salmon quality during refrigerated storage and thus extend its microbial shelf life.Industrial relevanceThe current demand for processed seafood that is similar to fresh products has created a new area of development in non-thermal processing technologies. Refrigeration and freezing have been applied for many years to extend the shelf life of seafood products, but there is deterioration regardless of the preservation method. Therefore, the combination of non-thermal processing technologies (PEF + CO₂ + HP) could be applied to a large variety of seafood industries. Seafood products could be treated by PEF combined with CO₂ and HP to further evaluate quality attributes under different rigor conditions during chilled storage and estimate the shelf life of the processed product.     

Combined effect of active coating and modified atmosphere packaging on prolonging the shelf life of low-moisture Mozzarella cheese

In this work, the effect of active coating on the shelf life of low-moisture Mozzarella cheese packaged in air and modified atmosphere (MAP) was studied. The active coating was based on sodium alginate (2%, wt/vol) and potassium sorbate (1%, wt/vol). The MAP was made up of 75% CO₂ and 25% N₂ (MAP1), 25% CO₂ and 75% N₂ (MAP2), or 50% CO₂ and 50% N₂ (MAP3). The product quality decay was assessed by monitoring microbiological and sensory changes during storage at 4, 8, and 14°C. Results showed that the combination of active coating and MAP was able to improve the preservation of low-moisture Mozzarella cheese. Specifically, the shelf life increased up to 160 d for samples stored at 4°C, and 40 and 11 d for those at 8 and 14°C, respectively. A faster quality decay for untreated samples packaged in air was observed. In particular, the Pseudomonas spp. growth and the appearance of molds were responsible for product unacceptability. The combination of active coating and MAP represents a strategic solution to prolong the shelf life of low-moisture Mozzarella cheese and to ensure the safety of the product under thermal abuse conditions.     

Quality of superchilled vacuum packed Atlantic salmon (Salmo salar) fillets stored at −1.4 and −3.6 °C

The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6 °C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were investigated during storage and compared to ice chilled and frozen references. Drip loss was not a major problem in superchilled salmon. Textural hardness was significantly higher in superchilled salmon fillets stored at −3.6 °C compared to those stored at −1.4 °C, ice chilled and frozen references. Cathepsins B and B + L were not deactivated at the selected storage temperatures. The storage time of vacuum packed salmon fillets can be doubled by superchilled storage at −1.4 °C and −3.6 °C compared to ice chilled storage.     

Effect of modified atmosphere and temperature abuse on the growth from spores and cereulide production of Bacillus weihenstephanensis in a cooked chilled meat sausage

The effect of modified atmosphere packaging (MAP) on the germination and growth of toxin producing psychrotolerant Bacillus spp is not well described. A model agar system mimicking a cooked meat product was used in initial experiments. Incubation at refrigeration temperature of 8 °C for 5 weeks of 26 Bacillus weihenstephanensis including two emetic toxin (cereulide) producing strains showed that B. weihenstephanensis is sensitive to MAP containing CO₂. The sensitivity to 20% CO₂ was dependent on strain and oxygen level, being increased when oxygen was excluded from the MAP. Growth from spores was observed at the earliest within 2 weeks when 20% CO₂ was combined with 2% O₂ and in 3 weeks when combined with “0”% O₂ (the remaining atmosphere was made up from N₂). Results were validated in a cooked meat sausage model for two non-emetic and one emetic B. weihenstephanensis strain. The packaging film oxygen transfer rates (OTR) were 1.3 and 40 ml/m²/24 h and the atmospheres were 2% O₂/20% CO₂ and “0”% O₂/20% CO₂. Oxygen availability had a large impact on the growth from spores in the MAP meat sausage, only the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h and “0”% O₂/20 % CO₂) inhibited growth of the three strains during 4 weeks storage at 8 °C. Cereulide production was undetectable during storage at 8 °C irrespective of choice of the MAP (quantified by liquid chromatography mass spectrometry/mass spectrometry). MAP storage at 8 °C for 1 and 3 weeks followed by opening of packages and temperature abuse for 1.5 h daily at 20 °C during 1 week resulted in increased cell counts and variable cereulide production in the meat sausage. A pre-history at 8 °C for 1 week in MAP with OTR of 1.3 or 40 ml/m²/24 h and 2% O₂ resulted in cereulide concentrations of 0.816 – 1.353 µg/g meat sausage, while a pre-history under the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h, “0”% O₂/20 % CO₂) resulted in minimal cereulide production (0.004 µg/g meat sausage) at abuse condition. Extension of MAP storage at 8 °C for 3 weeks followed by abuse resulted in a substantially reduced cereulide production.Data demonstrates that MAP can be used to inhibit growth of a psychrotolerant toxin producing Bacillus spp. during chill storage at 8 °C, and substantially reduce the risk of emetic food poisoning at abuse condition. Results are of relevance for improving safety of ready to eat processed chilled foods of extended durability.     

The effects of high oxygen modified atmosphere packaging on protein oxidation of bovine M. longissimus dorsi muscle during chilled storage

Modified atmosphere packaging (MAP) extends the shelf life of beef, especially in the context of visual colour. High O₂ MAP (70-80%) may cause quality deterioration through lipid and protein oxidation, the latter linked to a reduction in meat tenderness. The objective of this study was to investigate the effects of MAP in comparison to vacuum packaging (VP) on protein oxidation and subsequent tenderness of LD (M. longissimus dorsi) beef steaks during chilled storage (4 °C) of periods up to 14 days. Steaks were analysed for carbonyl content, free thiol groups, drip loss, Warner-Bratzler shear force (WBSF) and SDS-PAGE of extracted myofibrillar proteins. Free thiol groups were lower in high O₂ MAP (80% O₂/20% CO₂) steaks, after 14 days of storage, indicating protein oxidation compared to VP steaks. SDS-PAGE (non reducing conditions) showed the presence of high molecular weight cross linked myosin heavy chain aggregates in the high O₂ atmosphere packaged steaks, which were absent in VP steaks.     

Different postharvest strategies to preserve broccoli quality during storage and shelf life: Controlled atmosphere and 1-MCP

Broccoli (Brassica oleracea var. italica) is a vegetable that requires the application of postharvest techniques to extend its marketability. Controlled atmosphere and 1-MCP treatments are most used to extend the shelf life of broccoli and reduce post-harvest deterioration. The aim of this study was to evaluate the visual, physicochemical and functional changes of broccoli head samples stored at 1–2 °C and 85–90% relative humidity (RH) in air (Control samples), under controlled atmospheres (10% O₂ and 5% CO₂) (CA samples) and treated with 1-MCP (0.6 μL/L). After storage all samples were maintained at 20 °C for 2 and 4 days, in order to assess their shelf life. The most suitable postharvest treatment to extend broccoli quality during storage and shelf life, in terms of maintaining the visual quality and reducing loss of health-promoting compounds, was achieved by storage under controlled atmosphere conditions. The use of 1-MCP reduced the loss of green colour and chlorophyll pigments, but only during cold storage not during shelf life at 20 °C.     

Evaluation of CO2 absorption and desorption rate in oysters (Cassostrea gigas) using the soluble gas stabilisation method

Soluble gas stabilisation (SGS) is a recently proposed method to extend the shelf life of food. However, no studies have determined the amount of carbon dioxide absorbed in food and particularly in oysters. Thus, the aim of this study was to determine CO₂ absorption and desorption rates in oysters during the solubilisation process. Cooked oysters were placed in the apparatus's chamber, CO₂ was injected into the chamber, and the SGS process started at different pressures, temperatures and gas/product (g/p) ratios. CO₂ absorption and desorption rates were obtained from data of CO₂ concentration in the chamber headspace and calculated by mathematical models. The results showed higher absorption rates under higher pressure, higher g/p ratio and lower temperature (0 °C). The concentration of CO₂ dissolved in the oysters was 21008.45 mg CO₂ kg product^?1. On the other hand, lower desorption rates occurred for the lowest pressure (200 kPa) and lowest gas/product ratio (1:1). For CO₂ desorption from oysters, it was observed that 10 min was enough to desorb a large amount of CO₂ under normal atmosphere.     

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.     

Modified Atmosphere Storage of Dungeness Crab (Cancer magister)

A modified atmosphere (MA) of 80% CO₂ and 20% air coupled with refrigerated storage was effective in extending shelf life of cooked whole Dungeness crab. Aerobic plate counts were lower over the storage period tested (25 days) for samples held in MA compared to controls held in air. Tissue pH decreased in MA samples, but increased in samples held as air controls (AC). There were significant differences in redox potential between groups, but these did not appear large enough to affect bacterial growth. Trimethylamine and ammonia values were similar for 14 days, then became higher in controls. There were no differences between treatment groups in thiobarbituric acid values, in textural properties as determined by Instron or in reflectance measurements. After removal from MA storage, the crab had a microbial shelf life that mimicked that of a fresh product.     

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     

Effect of high carbon dioxide atmosphere packaging and soluble gas stabilization pre-treatment on the shelf-life and quality of chicken drumsticks

The effects of an aerobic modified atmosphere packaging (MAP) (70% CO₂, 15% O₂ and 15% N₂) with and without a CO₂ 3-h soluble gas stabilization (SGS) pre-treatment of chicken drumsticks were determined for various package and product quality characteristics. The CO₂ dissolved into drumsticks was determined. The equilibrium between CO₂ dissolved in drumsticks and CO₂ in head space was reached within 48 h after packaging, showing highest values of CO₂ in SGS pre-treated samples. This greater availability of CO₂ resulted in lower counts of TAB and Pseudomonas in SGS than in MAP drumsticks. Package collapse was significantly reduced in SGS samples. The average of CO₂ dissolved in the MAP treatment was 567 mg CO₂ kg^− 1 of chicken and, 361 mg CO₂ kg^− 1 of chicken during the MAP treatment, in SGS pre-treated samples. This difference could be the quantity of CO₂ dissolved during SGS pre-treatment.     

Effects of high O2 levels on post-harvest quality and shelf life of table grapes during long-term storage

Freshly harvested Kyoho table grapes (Vitis vinifera × V. labrusca) were stored in controlled atmospheric chambers, either in air, 80% O₂, or 40% O₂ + 30% CO_2, for up to 60 days at 0 °C in 95% relative humidity followed by 5 days in air at 20 °C. Physical and chemical properties were recorded initially and at 15-day intervals during storage. Storage in 80% O₂ or 40% O₂ + 30% CO₂ improved berry hardness, springiness, chewiness, flavors and membrane integrity over control stored in air. In addition, these high O₂ storage conditions significantly reduced fruit decay, berry drop, rachis browning and weight loss, delayed the decrease of soluble solids, titratable acidity and ascorbic acid of table grapes, compared with storage in air. Treatment in 80% O₂ resulted in a significantly firmer berry, better texture, berry adherence strength, and sensory scores than those treated with 40% O₂ + 30% CO₂, but did not significantly affect cohesiveness, springiness, aroma and membrane integrity. Data obtained in this study suggest that high oxygen treatment improve the quality of table grapes and extend its shelf life.     

Lysozyme/EDTA disodium salt and modified-atmosphere packaging to prolong the shelf life of burrata cheese

To prolong the shelf life of burrata cheese, we evaluated the effects of lysozyme and EDTA disodium salt (Na₂-EDTA) with or without modified-atmosphere packaging (MAP) conditions. In particular, 3 concentrations of enzyme were combined with packaging in air and under MAP (95:5 CO₂:N₂). The decline in quality of burrata cheese stored at 8°C was assessed by monitoring microbiological and sensory quality, in addition to pH and headspace composition. The combination of lysozyme/Na₂-EDTA and MAP prolonged cheese shelf life, especially at the highest lysozyme concentration. In particular, the tested strategy was effective against microbial spoilage phenomena that appeared to be the quality factor that determine product unacceptability.     

Quality changes during superchilled storage of cod (Gadus morhua) fillets

Superchilling is a method with potential for extending the shelf life of food products by partial freezing. For centuries, Atlantic cod (Gadus morhua) has been the most important commercial species in the North Atlantic fisheries and is now regarded as a very promising species in cold water fish farming. In the present work, superchilled storage at −2.2 °C of fillet portions of farmed cod was investigated. Superchilled cod showed increased shelf life with respect to reduced growth of sulphide producing bacteria compared to ice chilled. Drip loss was lower in superchilled cod. However, liquid loss by low-speed centrifugation was higher in superchilled cod fillets compared to ice chilled. This can be explained by freeze denaturation of muscle proteins, which is supported by the lower extractability of salt soluble proteins. There is a need for process optimization to minimize protein denaturation.     

Shelf life of powdered Campomanesia adamantium pulp in controlled environments

The objective of this study was to evaluate the shelf life of powdered guavira pulp obtained by a foam mat drying process. The dehydrated guavira pulp was packed into low density polyethylene (LDPE) bags and stored under two controlled conditions: environmental (25 °C, RH 75%) and accelerated (35 °C, RH 90%) for 90 days. The shelf life was accompanied by carrying out the following analyses every 10 days: moisture content, water activity, vitamin C content, pH and titratable acidity. Vitamin C was the quality attribute used to determine the shelf life of the product, by determining its degradation kinetics as a function of storage time. The linear regression data showed that the vitamin C degradation reaction fitted the zero and first order kinetic models. The shelf life of the powdered guavira pulp under environmental conditions was approximately 49 days, and under accelerated conditions (35 °C) 45 days. The Q10 was equal to 1.09, predicting a shelf life similar to that found under environmental conditions. The moisture content for these conditions was 10.0% e 5.4% for 35 °C and 25 °C, respectively. The above demonstrate the efficiency of the accelerated test in predicting the shelf life of the product.     

Reduction of spoilage of chilled vacuum-packed lamb by psychrotolerant clostridia

Methods for the reduction of spoilage, of lamb, by psychrotolerant clostridia were investigated including exposure to air, hot and cold water spray washing and tyndallisation. Initially vegetative cells of psychrotolerant clostridia associated with spoilage of chilled vacuum-packed meat were exposed to aerobic cooked meat medium at room temperature (21 °C) to determine how long they remained viable. Survival of strains varied from 2 h to 3 days. Vegetative cells of Clostridium estertheticum subsp. estertheticum survived 7 days at 10 °C with little reduction in viable numbers. This ruled out exposure to air as a practical method for reducing spoilage. Trials were also carried out on chilled vacuum-packed lamb inoculated with spores of Cl. estertheticum subsp. estertheticum. The time until inoculated packs reached the loss of vacuum stage varied from 38 to 53 days. Hot and cold water washing extended the shelf life by 12 to 13 days in comparison to untreated packs.     

Shelf stable intermediate moisture pineapple (Ananas comosus) slices using hurdle technology

A process has been developed to prepare shelf stable ready-to-eat (RTE) intermediate moisture pineapple (Ananas comosus) slices using hurdle technology. The combination of hurdles including osmotic dehydration, infrared drying, and gamma radiation dose of 1 kGy successfully reduced the microbial load to below detectable limit. The shelf life of the intermediate moisture pineapple slices was found to be 40 days at ambient temperature (26 ± 2 °C). The untreated control samples spoiled within 6 days. The RTE intermediate moisture pineapple slices were found to have good texture, colour and sensory acceptability during this 40 days storage.     

Efficacy of bacteriophage LISTEXP100 combined with chemical antimicrobials in reducing Listeria monocytogenes in cooked turkey and roast beef

The aim of this study was to verify the effectiveness of the commercially available anti-Listeria phage preparation LISTEX^™P100 in reducing Listeria monocytogenes on ready-to-eat (RTE) roast beef and cooked turkey in the presence or absence of the chemical antimicrobials potassium lactate (PL) and sodium diacetate (SD). Sliced RTE meat cores at 4 and 10 °C were inoculated with cold-adapted L. monocytogenes to result in a surface contamination level of 10³ CFU/cm². LISTEX^TMP100 was applied at 10⁷ PFU/cm² and samples taken at regular time intervals during the RTE product's shelf life to enumerate viable L. monocytogenes. LISTEX^™P100 was effective during incubation at 4 °C with initial reductions of L. monocytogenes of 2.1 log₁₀ CFU/cm² and 1.7 log₁₀ CFU/cm², respectively, for cooked turkey and roast beef without chemical antimicrobials (there was no significant difference to the initial L. monocytogenes reductions in the presence of LISTEX^TMP100 for cooked turkey containing PL and roast beef containing SD-PL). In the samples containing no chemical antimicrobials, the presence of phage resulted in lower L. monocytogenes numbers, relative to the untreated control, of about 2 log CFU/cm² over a 28-day storage period at 4 °C. An initial L. monocytogenes cell reduction of 1.5 log₁₀ CFU/cm² and 1.7 log₁₀ CFU/cm², respectively, for cooked turkey and roast beef containing no chemical antimicrobials was achieved by the phage at 10 °C (abusive temperature). At this temperature, the L. monocytogenes cell numbers of samples treated with LISTEX™ P100 remained below those of the untreated control only during the first 14 days of the experiment for roast beef samples with and without antimicrobials. On day 28, the L. monocytogenes numbers on samples containing chemical antimicrobials and treated with LISTEX^TMP100 stored at 4 and 10 °C were 4.5 log₁₀ CFU/cm² and 7.5 log₁₀ CFU/cm², respectively, for cooked turkey, and 1.2 log₁₀ CFU/cm² and 7.2 log₁₀ CFU/cm², respectively, for roast beef. In both cooked turkey samples with and without chemical antimicrobials stored at 10 °C, the phage-treated samples had significantly lower numbers of L. monocytogenes when compared to the untreated controls throughout the 28-day storage period (P < 0.0001). For roast beef and cooked turkey containing chemical antimicrobials treated with LISTEX^TMP100 and stored at 4 °C, no more than a 2 log CFU/cm² increase of L. monocytogenes was observed throughout the stated shelf life of the product. This study shows that LISTEX^™P100 causes an initial reduction of L. monocytogenes numbers and can serve as an additional hurdle to enhance the safety of RTE meats when used in combination with chemical antimicrobials.