Received Date: 29.11.2013 Accepted Date: 13.02.2014 Published Date: 30.06.2014
Seafood includes a number of high value food products with considerable economic importance. Fish freshness is the most important and fundamental single criterion for judging the quality of fish and fishery products. Fish is known to be a perishable product that requires effective preserving method to maintain quality and avoid food poisoning. Irradiation and high pressure treatment has been used to extend the shelf life of sea foods, especially fish and fish products, due to its microbial inhibition. Irradiation has been proposed as an alternative technique to thermal processing to destroy foodborne pathogens and spoilage organisms in order to enhance safety and shelf life of perishable foods. High hydrostatic pressure processing (HHP) is an alternative for pasteurization of food products as a non-thermal preservation method. HHP treatment can result in microbial destruction and product stabilization without affecting sensory qualities of foods. In this paper, the use of irradiation and high pressure treatments in seafood products preservation were reviewed.
Fish, Seafood, Irradiation, High pressure, Auality; Food safety
The role of fish in nutrition is being increas-ingly recognized as it supplies a good balance of protein, vitamins, and minerals (calcium, phos-phorus, and iron) associated with relatively low-calorie content. Apart from having a better pro-tein and calorie ratio than red meat, sea foods are also rich in unsaturated fatty acids (Sioen, 2007).
Seafood consumption varies greatly across in-dividuals, families, cultures and countries. As with any complex human behaviour, variation in seafood consumption will be influenced by many inter relating factors, such as properties of the food (quality and sensory attributes), characteris-tics of the individual (preferences, personality and knowledge), or characteristics of the envi-ronment such as availability, situation and sea-sons. Generally, consumers prefer fresh fish to frozen, canned, salted, pickled, smoked or dehy-drated products (Erkan and Çağıltay, 2011).
The high levels of moisture, nutrient content, weak connective tissue and neutral pH of fresh fish render itself as a perishable product. The quality of fish is composed of three separate components. These include (1) initial quality of the fish (intrinsic quality), that is, the quality at the time of the catch, depending on catch loca-tion, species, size, sex, composition, etc.; (2) quality, influenced by the handling conditions starting from harvest, on-board handling, icing, filleting, gutting etc.; and (3) the microbial quali-ty (initial microbiota, existance of pathogens). The spoilage of fish is usually caused by biologi-cal reactions such as oxidation of lipids, activities of the fish’s autolytic enzymes, as well as the loss of protein functionality, microbial growth and metabolic activities, resulting in a short shelf life of fish and other seafood products (Ababouch et al., 1996; Ashie et al., 1996; Erkan, 2003). Thus, maintenance methods to keep the quality of sea-food’s and delay the deterioration of fresh fish during storage have always had significant place to pursue for fisheries scientist.
Mostly used traditional preservation tech-niques such as chilling and super chilling gener-ally insufficient for the quality maintenance, long shelf life and safety of the product. In terms of inhibition or elimination of quality loss and path-ogen microorganisms in seafood, newly devel-oped technologies are coming into prominance. The most known of these technologies are radia-tion, high pressure processing (HPP). The effec-tiveness of these technologies have been proved by researchers (Jeevanandam et al., 2001; Sav-vaidis et al., 2002; Linton et al., 2003; Zare, 2004; Chéret et al., 2005; Ramirez-Suarez and Morrissey, 2006; Gómez-Estaca et al., 2007a; Özden et al., 2007a,b; Yağız et al., 2007; Arvan-itoyannis et al., 2009; Erkan et al., 2010; Erkan and Üretener, 2010; Günlü et al., 2014)
Since the global demand for fishery products is increasing (Erkan and Çağıltay, 2011), there is a need for efficient preservative methods. The major problem with respect to distribution of sea-food or fishery products is their susceptibility to spoilage, mainly due to the contamination of spoilage and pathogenic microorganisms (Erkan, 2003). Novel technologies (food irradiation and high pressure treatment) are process that have proven to be successful (Ashie et al., 1996), not only in ensuring the safety, but also in extending the shelf life of fresh meat, chicken, fish and fish products because of its high effectiveness in inac- tivating pathogens and spoilage organisms with-out deteriorating product quality.
Food irradiation is a process for the treatment of food products to enhance their shelf life and to improve microbial safety. Generally, ionizing ra-diations emitted by radioisotopes, Cobalt-60, and Cesium-137 are used for food preservation. Ac-cording to many researchers food irradiation, sometimes called “cold pasteurization,” has been described as the most extensively studied food processing method in the history of humankind and is endorsed by virtually all medical and scientific organizations. Food irradiation is a process in which irradiation energy, which travels through space or matter in invisible waves, is ap-plied to kill microorganisms or insects in foods. The quantity of energy absorbed by the food dur-ing irradiation is called “absorbed dose.” The in-ternational unit for absorbed dose is the Gray (Gy). The dose used varies according to the type of food and the desired effect. Treatment levels can be grouped into three general categories: (1) “Low” dose, up to 1 kGy, (2) “Medium” dose, 1–10 kGy and (3) “High” dose, greater than 10 kGy. Medium dose is used to reduce spoilage and pathogenic microorganisms on various foods, to improve technological properties of food and to extend the shelf-life of sensitive foods (Mendes et al., 2005; Venugopal et al., 1999).
Positive information reported regarding the impact of irradiation dose on the shelf life and micro flora and sensory and physical properties of fish, shellfish, molluscs, and crustaceans. The first studies on this subject have been on the de-termination of the optimum dose (Arvanitoyannis et al., 2009; Snauwert et al., 1977; Reinacher and Ehlermann, 1978) (see Table 1). The optimum irradiation dose for Herring (Clupea herring) was found to be 1-2 kGy, which yields a shelf life of 10-14 days at 2°C (Snauwert et al., 1977). Ac-cording to Reinacher and Ehlermann, (1978) have been reported the optimum dose 1-2 kGy for Ocean perch (Sebastodes alutus) and this ap-plication which led to a shelf life 25-28 days at 0.6 °C.
Optimum irradiation dose for the different fishes have been reported and have been found suitable 1.5–3 kGy, for mackerel (Rastrellinger kanagurta) 1.5 kGy, for White pomfret (Sto-mateus cinereus), Black pomfret (Parastomatus niger) 1 kGy, for Sole (Parophyrs vetulus) 2–3 kGy (Arvanitoyannis et al., 2009). The shelf life of Bombay duck (Harpodon nehereus), under re-frigeration was shown to be about 5–7 days. Ra-diation doses of 1.5-2.5 kGy extended the shelf life to about 15–20 days (Kumta et al., 1970). According to Chuaqui-Offermanns et al. (1988), whitefish (Coregonus clupeaformis) were gamma irradiated at 0.82 and 1.22 kGy, and stored at 3°C for 17-21 days. The non-irradiated samples ex-hibited a sensory shelf life of 7-8 days, whereas those of the irradiated ones were extended by 10-13 days. Ahmed et al. (1997) studied irradiated Nagli fish (Sillago sihama) at a dose of 2-3 kGy gave a shelf life of 19 days stored at 1-2°C in comparison to a storage life of 8 days for the non-irradiated samples. According to Mendes et al. (2005), fresh Atlantic horse mackerel (Tra-churus trachurus) were gamma irradiated at 1 and 3 kGy, and stored in ice at 0 ± 1°C for 23 days. The non-irradiated samples exhibited a sen-sory shelf life of 8 days, whereas those of the ir-radiated ones were extended by 4 days. Özden et al. (2007a;b) determined the influence of gamma irradiation (2.5-5 kGy) and post-irradiation stor-age up to 15-17 days at 4°C on some chemical and microbiological criteria of sea bass and sea bream. The total volatile basic nitrogen for-mation, thiobarbituric acid values and total viable count was lower in irradiated fish than in the non-irradiated. The synergistic effect of irradiation in conjunction with other techniques such as salting, smoking, freezing, and vacuum packaging has also reported (Savvaidis et al., 2002; Özden et al., 2007 a, b; O’bryan et al., 2008; Arvanitoyannis et al., 2009). Jeevanandam et al. (2001) reported shelf life of non-irradiated and irradiated (1 and 2 kGy) Threadfin bream (Nemipterus japonicus) packaged in polyethylene pouches and dipped in 10% (w/w) sodium chloride was 9 day and 14-28 day. Total mesophilic counts for salted vacuum-packed, refrigerated control and irradiated sea bream reached an average value of 7 log cfu/g after 14 days (0 kGy), 23 days (1 kGy) and 40 days (3 kGy) (Jeevanandam et al., 2001). Sav-vaidis et al. (2002) reported counts of 7 log cfu/g for vacuum packed trout after 9, 14 and 24 days for non-irradiated and irradiated samples at 0, 0.5 and 2 kGy, respectively. Kasımoglu et al. (2003) studied irradiated sardines (Sardina pichardus) at a dose of 2-3 kGy and vacuum packaged in poly-ethylene bags gave a shelf life of 21 days stored at 4°C in comparison to a storage life of 10 days for the non-irradiated samples. Chouliara et al., (2005) reported that initial total volatile basic nitrogen (TVB-N) levels of vacuum packed-irradiated (1–3 kGy) sample stored under refrigeration sea bream were 27.5 mg/100 g, 27.3 mg/100 g and 25.1 mg/100 g, reaching the acceptable limit at day 10 in control, at day 21 and 28 for 1 and 3 kGy irradiated sea bream.
The positive effects of irradiation in quality of sea are as follows:
• Microbial load decreased,
• Lower total volatile basic nitrogen value,
The negative effects of irradiation in quality of sea are as follows:
• Based on species, irradiation may cause in-crease in Tiobarbituric acid (TBA) values as a result of radiolytic products formation. However, in most of the studies it has been claimed that mentioned values have lower compared to non - treated samples.
• Some fatty acids decreased by irradiation treatments at all doses.
• Thiamin loss was more severe at higher dos-es (≥4.5 kGy), whereas riboflavin was not affected.
• L* value decreased, whereas a* and b* val-ues increased throughout storage.
• pH values decreased gradually (Chouliara et al., 2005; Genç and Diler, 2013; Jeevanan-dam et al., 2001).
High-pressure treatment is effective in reduc-ing microorganisms, and is known as a good method for inactivating pathogens in food materials. Pressure treatment causes changes in morphology, cell wall and membrane, biochemical reactions, and genetic mechanisms of microor-ganisms. High-pressure processing offers a num-ber of advantages over conventional thermal processing. For instance, high pressure inactivates spoilage and pathogenic bacteria, without effect-ing the vitamin content, colour and flavour. This allows the production of wholesome foods, with little loss in nutritional and sensory qualities (Amanatidou et al., 2000; Yuste et al., 2001; Bal-asubramaniam and Farkas, 2008). High hydro-static pressure (HHP) treatment, in combination with good refrigeration and handling practices, provides a means to increase fish product shelf-life (Linton et al., 2003; Zare, 2004; Chéret et al., 2005; Ramirez-Suarez and Morrissey, 2006; Yağız et al., 2007; Erkan et al., 2010; Erkan and Üretener, 2010; Günlü et al., 2014). Although there is a increasing interest in the application of HHP technology to fish-based products, limited research has been performed regarding the use of HHP in the development of high-quality fresh seafood products (Linton et al., 2003). Zare (2004) determined the effects of HHP (at 200 MPa for 30 min and 220 MPa 30 min) on micro-biological, chemical, and sensory properties of tuna stored in a refrigerator (4ºC). Results of this study indicate that the shelf life of HHP treated and untreated tuna stored in refrigerator as de-termined by the overall acceptability sensory scores was 18 and 6 days, respectively. Ramirez-Suarez and Morrissey (2006) found that high pressure (275 MPa and 310 MPa for 2, 4 and 6 min) increased the shelf-life of albacore tuna to >22 days at 4ºC based on microbiological num-bers. Erkan et al., (2010) found that a pressure treatment of 220 MPa for 5 min at 3ºC increased the microbiological shelf-life of red mullet, based on a psychrotrophic count of 106, from 11 days at 4ºC to 15 days. Treatment at 330 MPa for 5 min at 25ºC increased it further to 17 days. Erkan and Üretener (2010) also reported that a pressure treatment of 250 MPa for 5 min at 3ºC and 15ºC increased the microbiological shelf-life of gilt-head bream from 10 days to 16 and 13 days re-spectively. It is apparent that for all microorgan-isms examined, obtained populations were higher for unpressurized fish than those for pressurized fish species stored in a refrigerator throughout the entire storage period. Günlü et al., (2014) deter-mined the effect of HHP on the shelf life of vac-uum packed rainbow trout fillets. In accordance with chemical and microbiological results 4 days shelf life extension was determined for the chilled stored (4±1 °C) fillets after HPP applica-tion. Lower microbiological counts have been re-ported for pressurized tuna (Zare, 2004), sea bass (Chéret et al., 2005), albacore tuna (Ramirez-Suarez and Morrissey, 2006), mahi mahi-rainbow trout (Yağız et al., 2007) and rainbow trout (Günlü et al., 2014). Practices in this regard are presented in Table 3. Pressures between 200 and 600 MPa are commonly applied to extend the shelf-life of products decreasing the counts of spoilage microbiota. After HP treatments at 200 MPa for 30 and 60 min, fresh salmon resulted in a product with total viable counts lower than 100 cfu/g (Amanatidou et al., 2000). HP processing of cold-smoked dolphin fish at 300 MPa for 15 min reduced the counts of aerobic and lactic acid bacteria to levels below the detection threshold for three weeks (Gómez-Estaca et al., 2007b). HP technologies can have detrimental effects on the quality of smoked fish. Colour changes following treatments include higher L* values associated with higher opacity. Harder textures and lipid oxidation are also alterations reported in pressurized smoked fish products. Of particular relevance is smoked salmon, one of the most sensitive fish products to this processing technology, which intense red colour lightened after pressurization. The effect of HP on sensory quality varies within various seafood products and different pressurization conditions. Proteins can be denatured by the process, especially above 300 MPa. This may result in raw high protein products such as beef and fish taking on a “cooked” appearance, depending on processing conditions used (Lakshmanan et al., 2005; Karim et al., 2011). Matser et al. (2000) observed that pressure at 100 MPa did not affect the hardness of frozen cod while treatments at 200 and 400 MPa increased this characteristic. Increased rates of lipid oxidation during the storage of pressur-ized fish (Cheah and Ledward, 1996) were relat-ed with high concentration of polyunsaturated fats and oxidative changes induced by pressure (Angsupanich and Ledward, 1998). According to the results of this study, advantages of HHP in seafood were reported as lower microbial count and higher shelf life. Disadvantage of HHP in sea food are colour changes, lipid oxidation, and tex-ture changes (Medina-Meza et al., 2014).
High pressure processing and irradiation tech-nology significantly decrease the rate of microbial and chemical spoilage developed in packed and unpackaged raw fish stored on ice and refrigerator. As a result of this reduction, the shelf-life of perishable products (i.e. sea foods) are pro-longed from 50 % to 75 % compared to control groups. By taking into account the category of seafood which is perishable, shelf-life extension is much higher when novel technologies are used compared to applied traditional methods. Additionally, higher rate of food borne pathogen elim-ination could be achieved with these mentioned technologies.