Analysis of Alternative Shelf Life-Extending Protocols and Their Effect on the Preservation of Seafood Products

Seafood is essential to a healthy and varied diet due to its highly nutritious characteristics. However, seafood products are highly perishable, which results in financial losses and quality concerns for consumers and the industry. Due to changes in consumer concerns, demand for healthy products has increased. New trends focusing on reducing synthetic preservatives require innovation and the application of additional or alternative strategies to extend the shelf life of this type of product. Currently, refrigeration and freezing storage are the most common methods for fish preservation. However, refrigeration alone cannot provide long shelf-life periods for fish, and freezing worsens sensorial characteristics and consumer interest. Therefore, the need to preserve seafood for long periods without exposing it to freezing temperatures exists. This review focuses on the application of other approaches to seafood products, such as biodegradable films and coating technology; superchilling; irradiation; high-pressure processing; hyperbaric storage; and biopreservation with lactic acid bacteria, bacteriocins, or bacteriophages. The efficiency of these techniques is discussed based on their impact on microbiological quality, sensorial degradation, and overall preservation of the product’s nutritional properties. Although these techniques are already known, their use in the industrial processing of seafood is not widespread. Thus, the novelty of this review is the aggregation of recent studies on shelf life extension approaches, which provide useful information for the selection of the most appropriate technology and procedures and industrial innovation. Despite the fact that all techniques inhibit or delay bacterial proliferation and product decay, an undesirable sensory impact may occur depending on the treatment conditions. Although no technique appears to replace refrigeration, the implementation of additional treatments in the seafood processing operation could reduce the need for freezing, extending the shelf life of fresh unfrozen products.

Innovative Seafood Preservation Technologies: Recent Developments

Fish and fishery products are among the food commodities of high commercial value, high-quality protein content, vitamins, minerals and unsaturated fatty acids, which are beneficial to health. However, seafood products are highly perishable and thus require proper processing to maintain their quality and safety. On the other hand, consumers, nowadays, demand fresh or fresh-like, minimally processed fishery products that do not alter their natural quality attributes. The present article reviews the results of studies published over the last 15 years in the literature on: (i) the main spoilage mechanisms of seafood including contamination with pathogens and (ii) innovative processing technologies applied for the preservation and shelf life extension of seafood products. These primarily include: high hydrostatic pressure, natural preservatives, ozonation, irradiation, pulse light technology and retort pouch processing.

Dielectric Barrier Discharge High Voltage Cold Atmospheric Plasma: An Innovative Nonthermal Technology for Extending the Shelf-Life of Asian Sea Bass Slices

Impact of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) generated with the mixture of oxygen and argon (10:90) for various treatment times (2.5 to 10 min) on the qualities of Asian sea bass slices during 4 °C storage was investigated. Microbial load of slices treated with DBD-HVCAP were lower than the control. The efficacy of bacteria reduction by DBD-HVCAP was dependent on the treatment times (P < 0.05). Total viable bacteria count (TVBC) was more than 6.0 Log CFU/g at day 6 for the control kept in air. Slices treated with DBD-HVCAP for all treatment times used had TVBC lower than the limit at day 12. Total volatile nitrogen base content (TVNB) as well as trimethylamine (TMA) content in slices treated with DBD-HVCAP were lower than that of the control throughout the storage. TVNB as well as TMA contents were lower in HVCAP treated slices in a treatment time-dependent manner. Nevertheless, lipid oxidation in samples treated with DBD-HVCAP was higher than that of the control. Polyunsaturated fatty acids were decreased in slices treated with DBD-HVCAP for more than 5 min after 12 days of storage. Therefore DBD-HVCAP treatment for 5 min was demonstrated to be potential means for increasing the shelf-life of Asian sea bass slices with minimal negative effect on chemical and sensory properties, in which they could be stored longer than 12 days at 4 °C. PRACTICAL APPLICATION: Microbial inactivation capacity of dielectric barrier discharge high-voltage cold atmospheric plasma (DBD-HVCAP) has been documented with limited information on its application in extending the shelf-life of foods. DBD-HVCAP was demonstrated as an innovative technology for extending the shelf-life of Asian sea bass slices, which could be implemented in seafood industries for assuring safety and extending shelf-life of products. The shelf-life of the slices treated with DBD-HVCAP was extended to 12 days of storage at 4 °C as compared to the 6 days of the untreated counterpart.

Host range and in vitro lysis of Listeria monocytogenes seafood isolates by bacteriophages

Listeria-infecting bacteriophages (listeriaphages) can be used to control Listeria monocytogenes in the food industry. However, the sensitivity of many of seafood-borne Listeria strains to phages has not been reported. This research investigated the host ranges of three listeriaphages (FWLLm1, FWLLm3 and FWLLm5) by the formation of lytic zones and plaques on host lawns and in vitro lysis kinetics of listeriaphage FWLLm3. The study also predicted the phage titres required to lyse host cells. The host ranges of the phages were determined using 50 L. monocytogenes strains, of which 48 were isolated from the seafood industry and two from clinical cases. Of the 50 strains, 36 were tested at 25 and 30 ℃ and the remainder (14) at 15 and 25 ℃. Based on the formation of either discrete plaques or lytic zones (host kill zones), the host ranges of FWLLm1, FWLLm3 and FWLLm5 were about 87%, 81% and 87%, respectively, at 25 ℃. Six L. monocytogenes strains from the seafood environment were insensitive to all three phages, while the other seafood strains (42) were phage-sensitive. The adsorption rate constant ( k value) of listeriaphage FWLLm3 was between 1.2 × 10−9 and 1.6 × 10−9 ml/min across four host strains in tryptic soy broth at 25 ℃. The cultures (at 3–4 log colony-forming unit (CFU/ml) were completely lysed (<1 log CFU/ml) when cultures were infected with FWLLm3 at > 8.7 log phage-forming units (PFU/ml) for 30 min. Re-growth of phage-infected cultures was not detected after 24 h. The effective empirical phage titre was similar to the calculated titre using a kinetic model. Results indicate the potential use of the three phages for controlling L. monocytogenes strains in seafood processing environments.

Quality assessment of commercially processed carbon monoxide-treated tilapia fillets

Carbon monoxide (CO) has been used to stabilize the color of fish muscle during frozen storage and distribution. This study compared changes in the quality profiles of CO-treated and untreated (UT) tilapia fillets stored at 21 to 22 °C (room temperature), 4 to 5 °C (refrigerated), and 0 °C (iced). Samples (n = 3) were analyzed at different time intervals for chemical, lipid oxidation, microbiological, color, and expert sensory profiles. CO samples contained greater (P < 0.05) apparent ammonia and total volatile base nitrogen (TVB-N) at day 0, with greater (P < 0.05) TVB-N throughout refrigerated and iced storage. At time 0, peroxide values (POV) and thiobarbituric-acid-reactive substances were lower (P < 0.05) for CO samples and continued to have lower trends throughout all storage temperatures. Microbiological analysis at time 0 did not show any differences between UT and CO samples. Redness (a*) color values were greater (P < 0.05) in CO tilapia at time 0; however, treated product showed a more rapid decline in a* throughout all storage temperatures. While expert sensory evaluation showed no statistical differences between UT and CO tilapia at time 0, CO product failed sensory assessment sooner than UT product when stored refrigerated and in ice.

Bacteriophage significantly reduces Listeria monocytogenes on raw salmon fillet tissue

We have demonstrated the antilisterial activity of generally recognized as safe (GRAS) bacteriophage LISTEX P100 (phage P100) on the surface of raw salmon fillet tissue against Listeria monocytogenes serotypes 1/2a and 4b. In a broth model system, phage P100 completely inhibited L. monocytogenes growth at 4 degrees Celsius for 12 days, at 10 degrees Celsius for 8 days, and at 30 degrees Celsius for 4 days, at all three phage concentrations of 10(4), 10(6), and 10(8) PFU/ml. On raw salmon fillet tissue, a higher phage concentration of 10(8) PFU/g was required to yield 1.8-, 2.5-, and 3.5-log CFU/g reductions of L. monocytogenes from its initial loads of 2, 3, and 4.5 log CFU/g at 4 or 22 degrees Celsius. Over the 10 days of storage at 4 degrees Celsius, L. monocytogenes growth was inhibited by phage P100 on the raw salmon fillet tissue to as low as 0.3 log CFU/g versus normal growth of 2.6 log CFU/g in the absence of phage. Phage P100 remained stable on the raw salmon fillet tissue over a 10-day storage period, with only a marginal loss of 0.6 log PFU/g from an initial phage treatment of 8 log PFU/g. These findings illustrate that the GRAS bacteriophage LISTEX P100 is listericidal on raw salmon fillets and is useful in quantitatively reducing L. monocytogenes.

The use of water and ice with bactericide to prevent onboard and onshore spoilage of refrigerated megrim (Lepidorhombus whiffiagonis)

This study investigates the effectiveness of ozonated water and flake ice (combined Petfrost system) to increase the quality and stability of fresh megrim on fishing boats. The captured fish were washed, placed in plastic boxes, covered with flake ice and refrigerated at 2°C for up to 2-weeks onboard and, thereafter, for 11 days onshore. The experiments employed sterile, filtered and ozonated water at a concentration of 2ppm for washing the fish and making the flake ice. The results are compared with samples from a traditional treatment consisting of water and flake ice of marine origin. Fish were caught in four different hauls, which took 14, 12, 8 and 3 days in being landed. Subsequently, fish were stored for 1, 5, 7 and 11 days at 3°C. The different treatments were evaluated using sensory, microbiological and chemical techniques. Fish treated with ozone always showed the best quality. Megrim treated with ozone was still suitable for consumption after 14 days on board, and megrim stored for 12, 8 and 3 days on board could be stored for a further five days in the ice state once landed with an acceptable quality. In contrast, control fish were not suitable for consumption if stored for longer than three days on board.The results indicate that treatment with water and ice flakes made from sterile and ozonated water maintains the quality of fresh megrim onboard fishing boats and upon arrival onshore.

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.