Several fresh-keeping techniques for prawns

2021-02-08 14:20:36

     Prawns belong to the phylum Arthropods, Crustacea, Decapoda, Swim, Penaeidae, Penaeus. Because of its high protein content and low fat content, it has been called an indispensable part of a reasonable diet. In international trade, shrimp is a highly competitive product, and its trade volume accounts for 10% of the global aquatic product trade. While the current development of the shrimp industry is facing severe challenges, there are also huge opportunities. From the perspective of demand for shrimp products in the domestic and foreign markets, shrimp with good freshness is not only easy to sell, but also at a high price; shrimp with poor freshness is just the opposite.

Prawn Quick Freezer

    At present, there are many preservation technologies applied to shrimps, such as low-temperature preservation, modified atmosphere preservation, chemical preservation, and biological preservation. Among these preservation methods, low-temperature preservation is widely used.

    Low temperature preservation

    Low-temperature preservation is divided into refrigeration preservation, micro-freezing preservation and frozen preservation. Refrigeration preservation is a method of storing shrimps at 0-4°C. There are usually two types: ice storage and refrigerator storage. Under this temperature condition, the activities of endogenous enzymes and microorganisms in the shrimp are inhibited, the original properties of the shrimp are maintained to a large extent, the freshness changes little, and its unique flavor is guaranteed. However, when shrimps are stored at 0℃, the action of endogenous enzymes and microorganisms is still going on slowly, and deterioration problems will still occur in long-term storage. Therefore, this method is limited to short-distance offshore operations.

    Micro-frozen fresh-keeping is a kind of light-freezing or partial freezing fresh-keeping method that reduces the temperature of shrimps slightly below its freezing point (about -3°C), also known as super-cooling or partial freezing. Since the temperature of micro-freezing preservation is just in the large ice crystal formation zone -1℃--5℃, when shrimps are frozen, in order to make the freezing process have great reversibility, it is necessary to pass this temperature zone as fast as possible, so in actual During the operation, the super-cooled salt water is often sprayed on the surface of the shrimp that has just been caught, so that the surface of the shrimp is quickly frozen, and the temperature inside the shrimp is quickly cooled, and then stored in a refrigerator at about -2~-3°C. The method can significantly inhibit the effects of enzymes and microorganisms, and can significantly reduce dry consumption, and there is little juice loss during thawing. It has been widely used in the preservation of offshore fisheries.

    Frozen storage and preservation is to quickly freeze shrimp products to about -30°C, and store them at -18°C after being coated with ice. At this temperature, the microorganisms in the shrimp are inhibited, and various enzyme reactions in the shrimp are affected. The chemical reaction is at a standstill, so the spoilage of shrimp meat can be inhibited. However, under freezing conditions, the protein of the shrimp itself is deformed, and the moisture of the shrimp is easily lost during the freezing process, which has an adverse effect on the appearance and taste of the shrimp after thawing, and a large amount of juice is lost during thawing, which is not suitable for people. Pursue the requirements of natural foods.

    Modified atmosphere preservation

    Modified atmosphere preservation is a preservation technology developed in the early 1950s. It replaces the air in the package with mixed gases (CO2, N2, O2) of different concentrations to inhibit the growth of microorganisms and the oxidative deterioration of nutrients. At present, this technology has been widely used in the preservation of food such as meat, fish, fruits and vegetables. Someone studied shrimp. The shelf life of shelled shrimp and others under the controlled atmosphere state, it was found that the modified atmosphere packaging can effectively inhibit the growth of spoilage bacteria and achieve the purpose of extending the shelf life. There have been a lot of reports that it can improve the quality of various products such as meat products, aquatic products, fruits and vegetables, extend shelf life and reduce the number of microorganisms. Therefore, the application of modified atmosphere preservation technology to the preservation of prawns has attracted people's attention. However, the quality and physiological changes of marine shrimp in a modified atmosphere environment are still unclear in China, so further research is needed.

    Chemical preservation

    Chemical preservation is a method of adding bacteriostatic and harmless chemical substances to shrimps to improve the storage performance of shrimps. In the 1950s, vegetarian shrimp was used at home and abroad for preservation, and certain research results have been obtained. For the browning phenomenon that shrimps are prone to, sodium acetate, sodium sulfite and other reagents are often used to treat them.

    Biological preservation

    Biological preservation is a preservation technology developed based on biological science and integrated with multidisciplinary technologies. Although its definition has not yet been accurately formulated, with the wide application of biologically active substances, enzyme preparations and some microorganisms capable of producing bacteriocins in food, biological preservation technology has attracted great attention.

    Food stored in the ice temperature area has advantages that other storage methods cannot match, such as preventing the formation of ice crystals, inhibiting the activity of harmful microorganisms and the activity of various enzymes, reducing the speed of metabolism, and improving the flavor and taste of food. At present, some progress has been made in the research of ice temperature preservation agent, ice temperature vacuum preservation, and ice temperature and atmosphere control.


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