Hyperbaric cold storage versus conventional refrigeration for extending the shelf-life of hake loins

https://doi.org/10.1016/j.ifset.2017.01.003Get rights and content

Highlights

  • Hake loins were stored at 5 °C, both at atmospheric pressure and at 50 MPa, for 7 days.

  • Conventional refrigeration failed to extend the shelf-life of hake loins for 7 days.

  • Microbial counts and TVB-N content did not increase during hyperbaric cold storage.

  • Hyperbaric storage increased shear resistance and whiteness by 44% and 9%, respectively.

  • In cooked samples, sensorial differences before and after hyperbaric storage were moderate.

Abstract

Today, extending the shelf-life of fish, while retaining the organoleptic properties of the product, is still a challenge. To compare the effectiveness of conventional and hyperbaric cold storage in preserving fish quality, we stored Cape hake loins at 5 °C, both at atmospheric pressure and at 50 MPa. After 7 days of storage, microbial counts and total volatile basic-nitrogen content in conventionally refrigerated samples exceeded the limits recommended for consumption. By contrast, hyperbaric cold storage maintained these parameters unaltered, although it produced drip losses close to 5% and increased the shear resistance and whiteness of the raw samples by 44% and 9%, respectively. Nevertheless, after cooking, weight losses were less than half of those of the control loins and whiteness differences disappeared. Consequently, the sensorial analysis could only find moderate differences between the samples before and after hyperbaric storage. These results clearly prove that hyperbaric cold storage was more efficient than conventional refrigeration for the preservation of hake loins.

Industrial relevance

Hyperbaric cold storage opens interesting new doors for the fish-processing industry. Thus, it could be employed in different sections of the cold chain: on board, immediately after caught; at the food industry, during processing; on ship or trunk transport for long-distance markets; at school or hospital kitchens; at restaurants; or even at home. The increased cost resulting from hyperbaric storage should be overcome by an extended shelf life of a high-quality product.

Introduction

Fish is a very perishable product. Spoilage starts immediately after the caught and it is mainly produced by biochemical reactions and the activity of microorganisms (Ashie, Smith, & Simpson, 1996). To maintain high quality and safety in fish, preservation techniques must be applied continuously, from the point of harvest through storage, processing, and distribution, until the point of consumption.

Unfortunately, most preservation methods fail to simultaneously extend the shelf-life of marine products and keep their organoleptic properties intact. Thus, some traditional techniques, such as salting, smoking, or canning, among others, are able to prolong the shelf-life of fish considerably, but they produce substantial changes in the original characteristics of the product. Refrigeration is the method that better retains the sensorial properties of fish but, in return, it can only be used to store fish for a few days because biochemical and microbial reactions, even though slowed down, still occur at a significant rate (Rahman, 1999). For this reason, in the last years, many efforts have been made by the fish-processing industry to look for new preservation methods (Ashie et al., 1996, Sampels, 2015, Wilhelm, 1982).

Hyperbaric storage could be an innovative solution. It consists in storing food under relatively low pressure, usually lower than 200 MPa, for time periods of some days, weeks, or even months. The efficacy of hyperbaric storage in prolonging the shelf-life of food has been proved in several products, both at room and at low temperature, either above or below 0 °C (Fernandes et al., 2014). Hyperbaric storage at room temperature has been found to be more efficient than conventional refrigeration for the preservation of fruit juices (Pinto et al., 2016, Segovia-Bravo et al., 2012), raw bovine meat (Freitas et al., 2016), and ready-to-eat pre-cooked foods (Moreira et al., 2015b), among others. Depending on the level employed, pressure can not only inhibit microbial growth as refrigeration does but also produce some damage in the microorganisms, resulting in microbial inactivation (Bermejo-Prada et al., 2016, Freitas et al., 2016). Thus, Ko and Hsu (2001) observed that hyperbaric storage (50–300 MPa/25 °C) not only inhibited microbial growth in tilapia fillets but, at pressures between 200 and 300 MPa, it also produced certain microbial inactivation. Lamentably, these authors proved that fish freshness, even though better retained under pressure, was gradually lost over time (1  12 h), especially at pressures below 200 MPa. Furthermore, they observed considerable protein denaturation at pressures beyond 100 MPa (Hsu and Ko, 2001, Ko and Hsu, 2002, Ko et al., 2003, Ko et al., 2006). This is a well-known effect of pressure in myosystems and, thus, many authors in the literature have shown that pressure beyond 100 MPa can affect some quality properties of fish, such as texture, color, or water-holding capacity, among others (Chéret et al., 2005, Chevalier et al., 2001, Ko and Hsu, 2002, Ko et al., 2006, Matser et al., 2000, Montero and Gómez-Guillén, 2004). It follows from the above that hyperbaric storage alone is a strategy not enough powerful to effectively preserve the fish freshness. Therefore, if a significant extension of the shelf-life is aimed, pressure should be combined with some other hurdles to limit fish degradation.

Combining hyperbaric storage with low temperature seems to be particularly promising. Thus, Charm, Longmaid, and Carver (1977) stored cod and pollock, at pressures close to 25 MPa and temperatures between 1 °C and − 3 °C, for periods of up to 36 days. They proved that, unlike in conventional refrigeration, total bacterial counts in cod fillets did not increase during storage under pressure. Moreover, the organoleptic studies on raw and cooked samples showed that hyperbaric storage retained fish freshness better than conventional refrigeration. Thus, dressed whole cod and pollock were acceptable for consumption after 12 and 21 days of storage at 24 MPa and 1 °C, respectively. By contrast, they were considered unacceptable when stored at atmospheric pressure for the same period. Unfortunately, after these encouraging results, no more investigations on hyperbaric cold storage were performed in fish.

All the facts set out above suggest that hyperbaric cold storage, at pressures below 100 MPa, could be effective in both extending the shelf-life of fish and preserving the organoleptic properties of the product. Obviously, this novel technology would be more expensive than conventional refrigeration. Thus, the total cost of hyperbaric cold storage not only includes the costs of high-pressure equipment, maintenance, and energy but also the costs associated to refrigeration. Even though the energy cost for compression is almost negligible, the price of high-pressure equipment is high. Consequently, the amortization can increase the cost of hyperbaric storage substantially (Bermejo-Prada, Colmant, Otero, & Guignon, 2017). Nevertheless, it is important to note that this barrier has not stopped the implantation of other high-pressure technologies in the food industry when real advantages over the conventional techniques have been identified.

Therefore, the main objective of this paper was to assess whether hyperbaric cold storage could offer any advantage over conventional refrigeration for fish preservation. To test this hypothesis, we stored hake loins at 5 °C for 7 days, both at atmospheric pressure (conventional refrigeration) and at 50 MPa (hyperbaric cold storage). After storage, we compared the quality of the hake loins, both before and after cooking, by using microbial, chemical, and physical quality indicators. Moreover, we also evaluated the effect of hyperbaric storage on the sensorial quality of the product. To do so, we compared hake loins before and after 7 days of hyperbaric cold storage to check if storage under pressure caused an overall difference in the product.

The current study provides valuable new data for evaluating the effectivity of hyperbaric storage in extending the shelf-life of fish and, thus, it increases the knowledge on this innovative technology for food preservation.

Section snippets

Sample

Three frozen batches of Cape hake loins (Merluccius spp.: M. capensis, Cast/M. paradoxus, Franca), commercialized by three different Spanish manufacturers, were acquired in a local market and stored at − 20 °C until utilization. According to the product label, hakes were captured at the Southeast Atlantic Ocean, cut in portions, packed, and frozen on board. Loin portions were 11.2 ± 0.8 cm in length, 4.3 ± 0.3 cm in width, and 2.5 ± 0.3 cm in height and they weighed 84.8 ± 10.6 g. Before each experiment, a

Effects of cold storage on the hake quality: conventional versus hyperbaric cold storage

Hake loins were stored at 5 °C, either at atmospheric pressure or at 50 MPa, for 7 days. Before storage, the samples presented a pinky-white flesh and a wet and bright appearance. The skin had a metallic grey color and it was firmly attached to the flesh. After 7 days of storage, some modifications could be easily detected by the naked eye in all the samples. C_CS loins become sticky and off odors were detected in these samples. By contrast, HP_CS samples did not show perceptible changes to the

Conclusions

The results obtained in this paper clearly show that hyperbaric storage, at 50 MPa and 5 °C, is a method more effective than conventional refrigeration for limiting hake degradation. Thus, conventional refrigeration failed to extend the shelf-life of the samples for 7 days, both if 6 log10 CFU/g or if 35 mg/100 g are considered as TAM and TVB-N limits of acceptability. By contrast, hyperbaric cold storage allowed to maintain microbial counts and TVB-N content unaltered for, at least, 7 days. Storage

Acknowledgments

This work was supported by the State Plan for Scientific and Technical Research and Innovation 2013–2016 of the Spanish Ministry of Economy and Competitiveness (MINECO) through the CONSOLIDER-Network MAT2015-71070-REDC and the project AGL2014-52825. The authors thank Laura Barrios, head of the Statistical and Operational Research Service of CSIC (Spain), for her advice in the statistical analysis of the data; María José Jiménez, head of the Sensory Analysis Unit of ICTAN-CSIC, for her help in

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