The packaging of aquatic products in China has changed little over the years. Most of the fresh aquatic products are packed in plastic boxes and transported to the market for sale; frozen fish is a dozen catties and simply packaged with PE film and corrugated boxes on the market. Thawing retail, many aquatic products are no longer fresh at the time of sale, which greatly reduces their value. Aquatic products are advantageous products in the coastal areas, and they attach importance to their packaging to take full advantage of this geographical advantage, creating brand-name products in the region and transforming their advantages into benefits.
Aquatic products are characterized by liveliness and deliciousness, but are prone to corruption. Rational packaging should be based on the characteristics of different types of aquatic products.
Large-scale fish for aquatic products
There are many bacteria in and out of the fish, but there are fewer naturally occurring immunoglobulins in it. The enzymes in the fish have the effect of breaking down the protein, resulting in softening of the muscle tissue and a decrease in freshness. When the decomposition products reach a certain degree, the fish will also emit odors and provide favorable conditions for the further breeding and reproduction of bacteria. In addition, the fish is easily oxidized and the meat deteriorates, fades or discolors. The freezing and refrigerating methods alone are not ideal for the preservation of fish products. To obtain better preservation results, the following packaging measures can be used.
(1) The packaging of fish should use rigid containers. Fish tissue is inherently fragile. After freezing, the tissues in the fish will be subject to certain damage. Excessive compression during packing will cause the fish to be broken and further damage to the fish tissue. This not only affects the appearance, but also the injury site. The meat's odor affects the consumption. At the same time, when the damaged part is thawed, bacteria can breed easily. Obviously, the use of a rigid packaging container that is not easily broken or easily collapsed helps to prevent various mechanical damages in the transportation and handling of fish products, thereby maintaining the original form and quality.
(2) Minimize water loss in fish products. Fish not only loses moisture during the freezing process, but also loses moisture from the fish due to the sublimation of fine ice crystals on the surface of the fish during cold storage, which will result in constant weight loss and reduced freshness. At the same time, due to the continuous deepening of water evaporation on the surface of the fish body, a certain thickness of sponge layer will be formed on the surface and inside, so that the fish loses its original taste and nutrient content. Therefore, the use of a packaging material having a water vapor barrier property for sealed packaging can prevent the loss of water in the frozen, frozen, and sold fish meat, thereby maintaining its original freshness. It should be noted that there are extra gaps between the frozen fish products in the package, the water in the fish body evaporates easily, the dehydration of the fish meat takes place, and frost builds inside the package. Therefore, the void inside the packaging container should be minimized. If it is packaged in plastic film bags, the film should be tightly attached to fish products.
(3) Using vacuum packaging and other anti-oxidation means. Fish products contain unsaturated fatty acids, and some fish are high in content. When it is oxidized, it will turn the fish meat brown and taste bad. Although the method of adding antioxidants in the packaging process has a certain effect, it will also have certain side effects on the meat quality. The use of vacuum packaging can achieve better preservation results. The vacuum packaging of the fish must draw out the air inside the packaging container, so that the plastic film bag can tightly adhere to the fish product, which is extremely advantageous for reducing the packaging volume and the internal space. In order to prevent oxidation, vacuum packaging must use low oxygen permeability packaging materials, and tightly seal the packaging container to isolate the oxygen outside the packaging.
(4) Manufacturing "artificial air" to prevent the oxidation of fish products and inhibit the growth and reproduction of bacteria. The so-called artificial air refers to the air that increases the content of carbon dioxide or nitrogen. If the fish product is placed in the air with a carbon dioxide concentration of 10%, because of its relatively low oxygen content, not only can the effect of low-temperature refrigeration be improved, but also there is good preservation effect under normal temperature conditions. In the cold store, to achieve an artificial air environment, large-scale gas-conditioning equipment is needed, and its operating cost is high; and achieving air-conditioning in the packaging container is much simpler. Only the air-packing machine is required, and part of the air in the package can be extracted. Refill with one or more protective gases. In this way, the quality of fish products can be effectively protected both in cold storage and in the sales process.
(5) Avoid ultraviolet radiation. Ultraviolet light can promote the oxidation of fish products (such as sunlight, light, etc. contain ultraviolet light) and warm the fish meat. These adverse effects are particularly evident when fish products are placed on refrigerated displays. In this regard, the packaging of fish products can use opaque materials to prevent the intrusion of UV rays. In addition, printing inks can prevent the passage of 90% of ultraviolet rays. Therefore, the use of ink on the surface of transparent materials to print more graphics and the like can also play a role in shading.
Small batch of fish packaging
For small-lot, low-volume high-end aquatic products, it is more valuable to develop fresh-keeping packaging. At present, international attention has been paid to fresh-keeping packaging of aquatic products, and there are many new fresh-keeping packaging methods. The following are introduced:
(1) Methods for keeping fish fresh. The United States invented a fish preservation method: the newly caught fish was put into a plastic bag and mixed gas was injected into the bag (60% of carbon dioxide, 21% of oxygen, and 19% of nitrogen), sealed and wrapped, and then packaged. Fresh fish is placed in an ordinary warehouse. After 4 weeks, the appearance and taste of the fish did not change, just as it had just been caught.
(2) Canned live fish. There is a new type of live canned fish on the Japanese market. The practice is to soak the live fish in a coma and put them into a can, which will not die within two days. Before cooking, just remove the fish in the can and put it into clean water. After 10 minutes, the fish will wake up. This live fish canned is easy to carry, clean and delicious.
(3) Ship live shrimp packaging. Japan developed a special packaging container for the delivery of live shrimp. The packaging container used polyethylene as the inner layer, foamed polystyrene as the outer layer, and crushed ice between the two layers. The inner layer should prevent water leakage and the outer layer should prevent damage. In the polyethylene tank where the live shrimp is moving, the sterilized seawater is filled with a certain amount of oxygen, and then sealed with a lid and transported. With this method, the survival rate of live shrimp can be maintained at more than 90% within 24 hours even at an external temperature of up to 40°C.
(4) Oyster preservation. Oyster is a world-famous delicious seafood food, but died shortly after the water was out, and it was easily contaminated by Listeria and spoiled. Researchers at the New Zealand Institute of Marine Fisheries have invented a new process that can transform raw oysters into a long-term storage that preserves their umami taste. The process is to immediately pasteurize the live oysters that have just been harvested from the sea, and pasteurize them at a temperature of 100°C and a pressure of 1.3 kg/m2. This will kill the bacteria attached to the oyster shells. The sterilized oysters were vacuum-foiled and blister-packed. Since the oyster shells did not open during the autoclave sterilization, the fresh juices remained in the shells. After the consumer purchases, it can be heated in a microwave oven for 2 to 3 minutes to taste delicious grilled oysters.