OSCILLATING MAGNETIC FIELD (OMF) AND PULSED ELECTRIC FIELD (PEF)-ASSISTED SUPERCOOLING FOR THE IMPROVED SHELF LIFE OF FRESH SALMON FILLETS

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2022

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In recent years, global fish and seafood markets have continued to expand, and seafood demand and transaction volumes have also increased yearly. Due to increasing demands for protein-rich fish products, countries such as China, India, and Indonesia have high consumption of fresh fish products. Meanwhile, salmon, a type of seafood with a broad market volume and potential, has significant shares in terms of revenue in the North American seafood market. As a result, consumers' inclination toward healthy lifestyles and changing dietary habits drive the demand for fish products.However, seafood is extremely perishable partly due to the presence of amino acids, which can decompose into biogenic amines and ammonia. Seafood is also rich in polyunsaturated fatty acids (PUFA), which is easily oxidized and leads to unpleasant odor, taste, nutrient loss, and color changes. Therefore, proper food processing techniques should be employed to maintain the quality of salmon and extend storage time. Freezing is the most common process for the long-term preservation of food. Immobilization of liquid water by lowering the storage temperature can reduce the quality deterioration rate. Freezing temperatures below 0°C also prevent the growth of microorganisms in the food that cause food spoilage and foodborne illness. However, during the freezing process, the initial freezing step forms ice crystals that damage food structures and reduce food quality. Therefore, there is a great need to preserve food without freezing damage. Supercooling is a new food processing technology that keeps food below the initial freezing temperature without forming ice crystals. It provides a longer shelf life for the food while maintaining the quality of the food. In the supercooling protocol developed by Dr. Jun’s lab, ice nucleation during freezing is prevented by the pulsed electric field (PEF) and oscillating magnetic field (OMF). The fundamental is that electric and magnetic fields have potential interference and rotation effects on water molecules present in the food, ultimately associated with the inhibited aggregation of water molecules. As a result of this, I investigated the effects of supercooling technology based on PEF and OMF on the preservation of salmon to extend salmon's storage time while maintain the freshness. Thiobarbituric acid reactive substances (TBARS) values represent quantitative oxidative changes in meat and meat products during storage. Malondialdehyde (MDA) is one of the most commonly used markers of lipid oxidation secondary products. The color index of frozen and refrigerated samples differed significantly (P<0.05) from the original state. Color differences of frozen, refrigerated, and supercooled samples were 4.2, 5.8 and 2.9, respectively. In addition, the TBARS value of the supercooled sample was about 0.96 MDA/kg, which was close to 1.06 MDA/kg of the frozen/thawed sample, but the value of the refrigerated sample was 2.13 MDA/kg. Meanwhile, the drip loss for the refrigerated samples reached as high as 4% and 2.5%, while the supercooled sample was as low as 0.9%, which was not frozen/thawed or damaged by ice, resulting in little change in drip loss. For the microbial enumeration experiments, after 10 days of experimentation, the microbial counts of all samples increased, the microbial counts of supercooled samples, refrigerated sample, and frozen/thawed samples were 5.4, 6.4, and 5.9 log CFU/ml, respectively. After the experiment of PEF and OMF-assisted supercooling treatment of salmon, our result showed that supercooling treatment could increase the storage time of salmon without quality degradation.

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Food science

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63 pages

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