Modified atmosphere packaging of seafood

Mild processing of seafood-A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.

Effects of Vacuum and Modified Atmosphere Packaging on the Quality and Shelf-Life of Gray Triggerfish (Balistes capriscus) Fillets

Seafood products are perceived as healthy foods. However, several species of seafood are still not fully utilized for different reasons or can be valued outside the original locale, if issues with the short shelf-life and/or the preparation/presentation form are overcome, e.g., gray triggerfish, Balistes capriscus. Consumed mostly fresh, its flesh is of excellent quality. We studied the effect of different types of packaging (in air (AIR), vacuum (VP), and modified atmosphere (MAP)) on physicochemical (color and texture, pH, and total volatile basic nitrogen), microbiological (total viable count, psychrotrophic, sulphide-reducing bacteria, and acid-lactic bacteria), and sensory qualities, and shelf-life of gray triggerfish fillets stored at refrigeration temperature for 15 days. The samples were analyzed on days 0 (fresh fish), 5, 10 (8 and 12 for sensory analysis), and 15 after filleting and packaging. During the trial, fillets became lighter (increased L*) and yellower (b* >> 0) with time of storage. Distinct patterns were observed for pH among treatments. Unexpectedly, the increasing trend observed in the texturometer-derived hardness of VP and MAP fillets, contrasted with the sensory assessment, wherein panelists perceived a clear softening of fillets. VP delayed and MAP inhibited the increase in TVB-N contents of fillets compared to fillets packed in AIR. Total viable count and psychrothropic bacteria of fillets in AIR exceeded the conventional limit of 7 log(CFU/g) on day 10, while in fillets packed in VP and MAP, their abundance remained below that limit during the trial. The organoleptic attributes of fillets perceived by a sensory panel changed significantly in all treatments during the storage trial. Willingness to consume the fillets decreased constantly in AIR and MAP, but not in VP fillets. Considering primarily sensory, but also biochemical and microbiological parameters, namely panelists’ rejection, total volatile basic nitrogen content, and total viable count and psychrotrophic bacteria abundance, the shelf-life of fillets packed in air was eight days. Vacuum and modified atmosphere packaging extended the shelf-life to 15 and 12 days, and thus can add value to this product. Future research regarding the VP and MAP of gray triggerfish fillets could involve the optimization of mixtures of gases use and/or the application of combined processes.

Modified Atmospheric Packaging (MAP) of Trichosanthes Dioica (Parwal) Sweet and Effect of Storage Temperature on the Physicochemical, Microbial and Sensory Characteristics

Trichosanthes dioica (Parwal) sweet was packed under air and modified atmospheric packaging (MAP) with a gas composition of 98% N2 (2% O2 impurity), and 70% N2 : 30% CO2, respectively. The samples were stored at 5, 10 and 25oC and evaluated for various microbial count, nutritional analysis (moisture, fat and protein), titratable acidity (TA), total carotenoids, vitamin C, DPPH inhibition activity, total phenolic content, hydroxymethylfurfuraldehyde (HMF), thiobarbituric acid (TBA), free fatty acid (FFA), Textural profile analysis and sensory attributes. Results showed that a combination of 70 %N2+30% CO2 had most significant effect to arrest the microbial growth followed by 100% N2 and fresh. Similarly this combination of N2 and CO2 retained the proximate and textural quality of the products concluded that the MAP conditions of 70% N2: 30% CO2 and storage at 5°C, were the most suitable conditions for preserving the Parwal sweet up to 50 day.

Technological options to control quality of fish burgers

This research was focused on preservation strategies applied to develop fish burgers enriched with tomato flour and extra-virgin olive oil. The effects of three different gas mixtures (5:95 O2/CO2; 10:60:30 O2/CO2/N2 and 5:50:45 O2/CO2/N2) on burger quality were analyzed by monitoring microbial cell load of main spoilage microorganisms, pH and sensory properties. As expected, modified atmosphere packaging significantly affected mesophilic bacteria with a reduction of about 2 log cycles for samples under 5% O2 and 95% CO2. Afterward, the best gas mixture was used in combination with various natural antimicrobial compounds (thymol, grape fruit seed extract and biocitrus). The biocitrus showed the strike balance between microbial and sensory quality, thus suggesting to be adopted for dipping treatment of the entire fish fillet before the mincing process. Later all the strategies tested individually were combined and samples were monitored for microbiological and sensory quality. Results obtained showed that dipping treatment of fillet in biocitrus solution (20,000 ppm) under modified conditions extended the shelf life by 8 days compared to the control sample, without affecting the sensory acceptability.

Quantifying Variability in Growth and Thermal Inactivation Kinetics of Lactobacillus plantarum

The presence and growth of spoilage organisms in food might affect the shelf life. In this study, the effects of experimental, reproduction, and strain variabilities were quantified with respect to growth and thermal inactivation using 20 Lactobacillus plantarum strains. Also, the effect of growth history on thermal resistance was quantified. The strain variability in μmax was similar (P > 0.05) to reproduction variability as a function of pH, aw, and temperature, while being around half of the reproduction variability (P < 0.05) as a function of undissociated lactic acid concentration [HLa]. The cardinal growth parameters were estimated for the L. plantarum strains, and the pHmin was between 3.2 and 3.5, the aw,min was between 0.936 and 0.953, the [HLamax], at pH 4.5, was between 29 and 38 mM, and the Tmin was between 3.4 and 8.3°C. The average D values ranged from 0.80 min to 19 min at 55°C, 0.22 to 3.9 min at 58°C, 3.1 to 45 s at 60°C, and 1.8 to 19 s at 63°C. In contrast to growth, the strain variability in thermal resistance was on average six times higher than the reproduction variability and more than ten times higher than the experimental variability. The strain variability was also 1.8 times higher (P < 0.05) than the effect of growth history. The combined effects of strain variability and growth history on D value explained all of the variability as found in the literature, although with bias. Based on an illustrative milk-processing chain, strain variability caused ∼2-log10 differences in growth between the most and least robust strains and >10-log10 differences after thermal treatment.

IMPORTANCE

Accurate control and realistic prediction of shelf life is complicated by the natural diversity among microbial strains, and limited information on microbiological variability is available for spoilage microorganisms. Therefore, the objectives of the present study were to quantify strain variability, reproduction (biological) variability, and experimental variability with respect to the growth and thermal inactivation kinetics of Lactobacillus plantarum and to quantify the variability in thermal resistance attributed to growth history. The quantitative knowledge obtained on experimental, reproduction, and strain variabilities can be used to improve experimental designs and to adequately select strains for challenge growth and inactivation tests. Moreover, the integration of strain variability in prediction of microbial growth and inactivation kinetics will result in more realistic predictions of L. plantarum dynamics along the food production chain.

Modified Atmosphere Systems and Shelf Life Extension of Fish and Fishery Products

This review aims at summarizing the findings of studies published over the past 15 years on the application of modified atmosphere (MA) systems for shelf life extension of fish and fishery products. This review highlights the importance of CO₂ in the preservation of seafood products, and underscores the benefits of combining MA technology with product storage in the superchilled temperature range. It is generally accepted that MA technology cannot improve product quality and should not be utilized as a substitute for good sanitation and strict temperature control. Benefits derived from application of MA, however, can significantly impact preservation of product quality and it subsequent shelf-life. For this reason, this review is the first of its kind to propose detailed handling and quality guidelines for fresh fish to realize the maximum benefit of MA technology.

Clostridium botulinum Toxin Production in Relation to Spoilage of Atlantic Salmon (Salmo salar) Packaged in Films of Varying Oxygen Permeabilities and with Different Atmospheres

Shelf life of fish packaged under modified atmosphere (MA) is extended, but within the United States, commercial application of MA with impermeable packaging films is restricted due to concerns that botulinum toxin production would precede spoilage when contaminated fish are held at abusive storage temperatures. Use of semipermeable packaging films has been advocated; however, previous studies are inconclusive in determining the oxygen transmission rate (OTR) of a film that is needed to achieve an acceptable margin of safety (i.e., toxin production occurs only after spoilage). This study was conducted to determine the influence of OTR (target OTRs of 3 to 15,000) on the development of spoilage volatiles and toxin in salmon inoculated with type E Clostridium botulinum and subjected to air, vacuum, or 75:25 CO2:N2 MA and storage temperatures of 4, 8, 12, or 16°C. The most dominant headspace volatile peak that was produced during spoilage of samples at 4, 8 or 12°C was a peak, having a Kovats retention index (KI) of 753, and at which external standards of 2- or 3-methyl 1-butanol also eluted. Under anaerobic conditions, both the aerobic microbial populations and the size of the KI 753 spoilage peak were less in inoculated samples compared with uninoculated samples. C. botulinum-inoculated samples that were stored at 12 or 16°C under conditions favorable for anaerobic growth were also characterized by a KI 688 peak. Using a previously developed model that related the percentage of elderly consumers who would prepare a sample having the KI 753 spoilage peak of a specific size, it was determined that for salmon packaged with 3 or 3,000 OTR films under any atmosphere and stored at 12 or 16°C, 2 to 61% of the consumers could potentially prepare toxin-contaminated samples. Hence, when abusive storage conditions are suspected, the fish should not be consumed.

Antimicrobial effect of bayberry leaf extract for the preservation of large yellow croaker (Pseudosciaena crocea)

BACKGROUND

Chemical preservatives have been widely used to keep large yellow croaker fresh. However, the potential harm to human health cannot be ignored. This study was undertaken to investigate the antimicrobial effect of bayberry leaf extract and to evaluate the efficacy of this natural product on the preservation of large yellow croaker.

RESULTS

The minimum inhibitory concentration (MIC) values of bayberry leaf extract against bacteria were 1.0 mg mL⁻¹ for Micrococcus luteus, 0.5 mg mL⁻¹ for Staphylococcus aureus, 0.25 mg mL⁻¹ for Escherichia coli, 0.5 mg mL⁻¹ for Pseudomonas aeruginosa, 0.0625 mg mL⁻¹ for Vibrio parahaemolyticus, and 0.03125 mg mL⁻¹ for Listeria monocytogenes, respectively. This result was confirmed by the diameters of inhibition zone (DIZ) assay. Further studies showed that the bacterial growth was significantly retarded when large yellow croaker was pretreated with bayberry leaf extract (2 g L⁻¹) compared to that in the control group. Moreover, the generation of total volatile basic nitrogenous compounds (TVB-N), ATP degradation products (K-value) and thiobarbituric acid-reactive substances (TBARS) were significantly reduced compared to that in the control group.

CONCLUSION

Our results demonstrated that the shelf life of large yellow croaker can be extended when supplemented with bayberry leaf extract, which might have implications for natural preservatives.

Shelf life extension of whole Norway lobster Nephrops norvegicus using modified atmosphere packaging

Once a nuisance by-catch, today the Norway lobster (Nephrops norvegicus) is a valuable UK fisheries commodity. Unfortunately, the species is very susceptible to quality deterioration post harvest as it quickly develops black spots and also spoils rapidly due to bacterial growth. Treatment with chemicals can stop the blackening and carefully monitored cold storage can result in a sensory shelf life of up to 6.5 days. The high susceptibility to spoilage greatly restricts the extent to which N. norvegicus can be distributed to retailers and displayed for sale. The application of modified atmosphere (MA) could be extremely beneficial, allowing the chilled product to stay fresh for a long period of time, thus ensuring higher sales. In the present study, we identified a gas mix for the MA packaging (MAP) of whole N. norvegicus lobster into 200 g retail packs. Our results show that a shelf life extension to 13 days can be achieved when retail packs are stored in MAP at 1 °C. Effectiveness of the MAP was evaluated by using a newly developed QIM for MA-packaged whole N. norvegicus and also by analyzing bacterial plate counts. Changes in the microflora and effects of different storage temperatures on the quality of the MA packs are also presented. The main specific spoilage organism (SSO) of modified atmosphere packaged Norway lobster is Photobacterium phosphoreum.

Effect of selected plant essential oils or their constituents and modified atmosphere packaging on the radiosensitivity of Escherichia coli O157:H7 and Salmonella typhi in ground beef

Twenty-six different essential oils were tested for their efficiency to increase the relative radiosensitivity of Escherichia coli and Salmonella Typhi in medium-fat ground beef (23% fat). Ground beef was inoculated with E. coli O157:H7 or Salmonella (10(6) CFU/g), and each essential oil or one of their main constituents was added separately at a concentration of 0.5% (wt/wt). Meat samples (10 g) were packed under air or under modified atmosphere and irradiated at doses from 0 to 1 kGy for the determination of the D10-value of E. coli O157:H7, and from 0 to 1.75 kGy for the determination of the D10-value of Salmonella Typhi. Depending on the compound tested, the relative radiation sensitivity increased from 1 to 3.57 for E. coli O157:H7 and from 1 to 3.26 for Salmonella Typhi. Addition of essential oils or their constituents before irradiation also reduced the irradiation dose needed to eliminate both pathogens. In the presence of Chinese cinnamon or Spanish oregano essential oils, the minimum doses required to eliminate the bacteria were reduced from 1.2 to 0.35 and from 1.4 to 0.5 for E. coli O157:H7 and Salmonella Typhi, respectively. Cinnamon, oregano, and mustard essential oils were the most effective radiosensitizers.

Microflora assessments using PCR-denaturing gradient gel electrophoresis of ozone-treated and modified-atmosphere-packaged farmed cod fillets

Denaturing gradient gel electrophoresis (DGGE) of a PCR-amplified 16S rDNA sequence was used to characterize changes in the microbial flora caused by ozone (O3) treatment of farmed cod (Gadus morhua). Portions of cod were produced under controlled conditions, bathed in fresh water supplemented with 2 ppm of O3 for 30 min, and packaged in modified atmosphere (MA: 60% CO2 and 40% N2) before 4 degrees C storage. Control samples were packaged in MA or air, without prior O3 treatment. Samples were analyzed by PCR-DGGE to determine the predominant bacterial flora and to examine possible differences in the microbial community due to O3 treatment. The DGGE analysis during the storage period showed that the O3 treatment produced no significant difference in the microbial flora compared with the controls. Sequencing of 16S rDNA detected the specific spoilage bacteria Photobacterium phosphoreum, Pseudomonas spp., Shewanella baltica, and Shewanella putrefaciens as the predominant bacteria in all samples. PCR-DGGE results were supported by culture and sensory analyses used in predicting product shelf life. Aerobic plate count, H2S-producing bacteria, and psychrotrophic bacterial counts demonstrated no significant extension of the shelf life of MA-packaged, O3-treated cod fillets.

Microbiological and biochemical changes in pearl spot (Etroplus suratensis Bloch) stored under modified atmospheres

AIMS

This study aimed to determine the effect of packaging [air, modified atmosphere (MA)] on microbial growth, sensory and chemical parameters and also on shelf life of fresh pearl spot (Etroplus suratensis Bloch) and on the selection of microbial association.

METHODS AND RESULTS

Fresh pearl spot (whole, gutted) were packaged under both 100% air and MAs (40%CO(2)/60% O(2), 50%CO(2)/50%O(2), 60% CO(2)/40%O(2), 70% CO(2)/30% O(2) and 40% CO(2)/30% O(2)/30% N(2)) and stored at 0 degrees C. Microbial growth (counts of total aerobic bacteria, H(2)S-producing bacteria, Lactic acid bacteria, Brochothrix thermosphacta, yeast and mould), chemical spoilage indicators (pH, total volatile basic nitrogen) and sensory characteristics were monitored. Microbial changes in Pearl spot packed under 100% air and 40% CO(2)/30%O(2)/30% N(2) were similar. The total volatile basic nitrogen values increased, but the values never exceeded the acceptability limit of 25 mg 100 g(-1).

CONCLUSIONS

MA 60% CO(2) : 40%O(2) was found to be better with a shelf life of 21 days whereas air stored samples had a shelf-life of 12-14 days only.

SIGNIFICANCE AND IMPACT OF THE STUDY

Storage of pearl spot under MAs 60% CO(2) : 40%O(2) is a promising method to extend shelf-life. Longer shelf life expands the market potential of pearl spot and reduces waste during distribution and retail display.

Role of sulfites and 4-hexylresorcinol in microbial growth and melanosis prevention of deepwater pink shrimp (Parapenaeus longirostris) using a controlled atmosphere

A controlled atmosphere containing 48% CO2 and 7% O2 was used in association with refrigeration for storage of deepwater pink shrimp (Parapenaeus longirostris). Shrimp were treated with two different concentrations of sodium metabisulfite or 4-hexylresorcinol and subjected to the controlled atmosphere immediately after capture onboard ship or on arrival in port. Total volatile basic nitrogen, total viable counts, enterobacteria, lactic acid bacteria, and luminescent bacteria were determined, and black spot progression was evaluated. The combined effect of controlled atmosphere and melanosis inhibitors was used to delay black spot development as compared to the shrimp stored in ice alone. Storage under the controlled atmosphere without ice limited microbiological quality, namely, total viable counts, but enterobacterial growth was lower.

Explorative multivariate analyses of 16S rRNA gene data from microbial communities in modified-atmosphere-packed salmon and coalfish

Modified-atmosphere packaging (MAP) of foods in combination with low-temperature storage extends product shelf life by limiting microbial growth. We investigated the microbial biodiversity of MAP salmon and coalfish by using an explorative approach and analyzing both the total amounts of bacteria and the microbial group composition (both aerobic and anaerobic bacteria). Real-time PCR analyses revealed a surprisingly large difference in the microbial loads for the different fish samples. The microbial composition was determined by examining partial 16S rRNA gene sequences from 180 bacterial isolates, as well as by performing terminal restriction fragment length polymorphism analysis and cloning 92 sequences from PCR products of DNA directly retrieved from the fish matrix. Twenty different bacterial groups were identified. Partial least-squares (PLS) regression was used to relate the major groups of bacteria identified to the fish matrix and storage time. A strong association of coalfish with Photobacterium phosphoreum was observed. Brochothrix spp. and Carnobacterium spp., on the other hand, were associated with salmon. These bacteria dominated the fish matrixes after a storage period. Twelve Carnobacterium isolates were identified as either Carnobacterium piscicola (five isolates) or Carnobacterium divergens (seven isolates), while the eight Brochothrix isolates were identified as Brochothrix thermosphacta by full-length 16S rRNA gene sequencing. Principal-component analyses and PLS analysis of the growth characteristics (with 49 different substrates) showed that C. piscicola had distinct substrate requirements, while the requirements of B. thermosphacta and C. piscicola were quite divergent. In conclusion, our explorative multivariate approach gave a picture of the total microbial biodiversity in MAP fish that was more comprehensive than the picture that could be obtained previously. Such information is crucial in controlled food production when, for example, the hazard analysis of critical control points principle is used.