Freshwater fish account for 42% of the world’s total aquaculture production, with an output value of 34%. At present, the processing rate of aquatic products in developed countries is more than 80%, while the processing rate of aquatic products in China is less than 30%, and the processing rate of freshwater fish is less than 10%, partly because the indigenous soil flavor of freshwater fish has brought about processing. Difficulty. Since freshwater fish products are relatively concentrated on the market, the meat is delicate, nutrient-rich, and high in water content. The enzymes in the fish are active and easy to corrupt. The corruption rate of freshwater fish caused by the limitations of storage and processing conditions is above 30%. The backwardness of China's freshwater fish processing technology has severely restricted the development of freshwater fisheries. In this paper, the status quo of the processing of low-value freshwater fish is studied and analyzed, and the possible approaches are proposed. The aim is to provide references for the research of freshwater fish production and comprehensive utilization in China.
1 Status of processing and utilization of low-value freshwater fishes China's freshwater fish processing industry started late, and its processing technology is relatively backward. It has a big gap with the developed countries, especially low-value fish that account for more than 60% of the freshwater fish production (such as fish and clams). Fish, etc.), also lacking stereotyped products, are basically sold in live form. The methods adopted for freshwater fish processing in China for many years are: (1) Fresh sales, but the economic benefits and social benefits of low-value freshwater fish as direct foods will become lower and lower; (2) “Three go†(visceral, go鳃 去 去 去 去 去 去 去 去 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 冷冻 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是 但是The cold chain must be perfect; (3) The traditional processing methods such as salting, drying, and smoking are adopted, but it is difficult to meet the needs of further improving the quality and modern production due to the limitations of natural climate and environmental conditions.
2 Ways of Processing and Utilizing Low Value Freshwater Fish
2.1 Fish meal Fish meal production has been the main means of developing and utilizing low-value fish protein. Today, fish meal has become the main source of animal protein in compound feeds. Although fishmeal was originally based on marine fish, freshwater fish can also be used through research and exploration. As a feed, fish meal protein is superior to vegetable protein because certain amino acids that make up the fish meal protein are absent from plant proteins such as lysine, methionine and cystine, which are essential for the growth of poultry, livestock and fish. It is even considered to be one of the most effective and inexpensive products to supplement animal protein needed by humans.
2.2 The basic principle of liquid fish protein is to add acid to inhibit the growth and reproduction of spoilage bacteria in raw materials, and use enzymes or microorganisms to decompose and digest proteins to degrade proteins into low molecular peptides and some amino acids. In China, the use of horse-faced waste for the production of acid-storage liquid feed has achieved good results in pigs, chickens, and fish farming.
2.3 The fish gills and their products are made of low-value fish as raw materials, and they are made into gills by removing viscera, collecting meat, rinsing, filtering water, fine filtration to remove connective tissue such as skin and tendons, and screw pressing to make fish gills. Raw fish meal products. It is characterized by unrestricted raw materials, and can be adapted to North and South flavors by adding different seasonings and spices. Fish gizzard products are characterized by high protein, low fat, convenient consumption, and portability. The existing surimi products mainly include fish balls, fish cakes, fish rolls, and fish sausages.
It has a large yield, white flesh, and good gel formation capacity. It is an ideal raw material for processing fish gills and their products. Recently, Northeast China Agricultural University has successfully developed a technology and formula for simulating shrimp cakes, simulating crab cakes and simulating crab legs using squid as a raw material. Hubei Agricultural Academy has developed freshwater fish sausages using squid and squid as raw materials.
2.4 Fish Bone Powder Currently calcium supplement products on the market, such as calcium citrate, calcium carbonate, and calcium gluconate, are mostly chemical preparations, and pure natural calcium products made only by physical methods are less. The fish bone meal is a natural calcium supplement product made by processing the remaining fish bones as a raw material and subjected to high temperature, saponification, degreasing, degumming, deodorization, drying and crushing. Shanghai Fisheries University took the herring vertebrae as the main raw material, developed a calcium-containing 10.93% freshwater fish bone meal, which is a white powder with no smell and no taste. The results of bio-utilization and clinical trials show that with good calcium absorption and retention rate, it is a high-quality natural calcium agent with high utilization rate.
2.5 Soft canned foods The characteristics of canned foods for aquatic products are storage-resistant and easy to carry and use. It is made from small freshwater miscellaneous fish as a raw material, impregnated with salt water, drained, fried, flavored, vacuum-packed and heat-sterilized to make a product. However, since the process of heating and sterilizing the canned fish can take some time, it will cause damage to the nutrition and flavor of the aquatic product. This is a topic to be studied.
3 Ways of using low-value freshwater fish waste Because of the low proportion of edible parts of freshwater fish, waste leftovers and other by-products after fish processing are not fully recycled, or sold as low-value feed, fertilizer, or discharged at will, causing waste of resources. Pollution of the environment, and high product costs, low profits and slow development. According to reports, the annual output of freshwater fish by-products in China is more than 2.5 million tons, and most of them have not been used. According to reports, Japan uses this type of waste to produce a special fertilizer that can control the growth of unwanted microorganisms and insects in the soil, and is particularly suitable for grassland fertilization on golf courses. At present, the by-products of fish processing in Japan and the United States can already reach the degree of classification and utilization based on their chemical composition and biochemical characteristics, and their processing output value can reach several to several tens times of that of fish.
4 Development Trend of Comprehensive Utilization of Low Value Freshwater Fish
4.1 The application of high-tech in modern food engineering The ultra-fine grinding technology in the food field, new food drying technology, new technology for sterilization of food packaging, supercritical extraction technology and food extrusion technology, etc., must be used in the process of comprehensive utilization of low-value freshwater fish. Will play an increasingly important role. Since the 1990s, there have been thousands of atmospheric pressure ultrahigh-pressure processed fish products, high-tech applications such as the separation of fish oil using supercritical technology. Japan uses fish, meat and carbohydrates as raw materials to produce sauces using Aspergillus spp. mixed fermentation. Using twin-screw extrusion technology and enzyme engineering technology, the arrowhead Chuanxiong meat as raw materials, developed a new type of aquatic food with good appearance and swelling characteristics.
4.2 Utilization of low-value freshwater fish wastes will become a research focus With the rapid development of China's freshwater fish aquaculture industry, the output of freshwater fish will continue to grow at a rapid rate, the proportion of deep processing of low-value freshwater fish will increase, and the waste generated will also More and more, how to effectively use these resources and turn waste into treasure will be a very important research topic. The use of waste can be solved well, and the value it creates will exceed the value of low-value freshwater fish processed products, thus promoting the processing of low-value freshwater fish and promoting the sustainable and healthy development of China's aquatic products business.
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