Shellfish hygiene and purification technology research

Shellfish hygiene and purification technology research

According to statistics, the total area of ​​shallow beach coatings in China is about 93,000 square kilometers, with more than 700 kinds of marine shellfish, and the output of shellfish is ranked first in the world. In 1999, the total output of shellfish in China was about 10 million tons, which is about the whole country. One-fourth of the total fishery production is an important part of China's aquatic products, of which marine shellfish accounts for more than 95% of the total output of shellfish. Shellfish is not only nutritious and delicious, but also rich in taurine. It has nutrition and health functions for people of all ages and is well received by domestic and foreign sellers. It is one of the important varieties of export earnings in China.
However, shellfish are different from swimming fish. Its growth position is relatively stable. Once water pollution is encountered, it is difficult to avoid it. In addition, bivalve molluscs belong to filter-feeding organisms. When they feed on food organisms, they also inhale the harmful substances in the water, which can cause human consumption poisoning. In 1989, 300,000 people in Shanghai suffered from hepatitis A virus-contaminated frizzles. This is an obvious example.
In view of the above situation, countries all over the world attach great importance to the protection of shellfish culture environment, specifically demarcate shellfish aquaculture waters, and strengthen the treatment of industrial wastewater and domestic sewage, especially manure, including livestock manure. Regularly monitor the water quality of the aquaculture waters and shellfish sanitation, and set up a purification plant in the shellfish culture area to purify the shellfish that does not meet the hygienic requirements and reach the hygienic standard before it can be listed. At present, the developed countries in the world economy have built A large number of shellfish purification plants and a national-level shellfish sanitation and purification research center are responsible for the monitoring of shellfish aquaculture water quality and shellfish sanitation in various countries, the research of various shellfish purification technologies and equipment, and the production of shellfish. Households and purification plants conduct guidance. After more than 20 years of practice, the cost of shellfish purification is much lower than the cost of medical expenses incurred by consumers because of consumption of shellfish poisoning. Therefore, all governments encourage the establishment of shellfish purification plants.
Therefore, in order to enable Chinese consumers to eat hygienic and safe shellfish, import the shellfish of our country into the international market, and create more foreign exchange for the country, it is imperative to conduct studies on the shellfish purification technology for the purification of shellfish in China. Industrialization laid the foundation.
First, the current status of foreign shellfish purification Many countries in the world have built shellfish purification plants, such as the United States, Australia, New Zealand, the Philippines, Thailand, Malaysia, the United Kingdom, Spain, France, Denmark, and Canada and Turkey and other countries. Some countries are mandatory, while others are voluntary. Now we briefly introduce the situation in these countries.
Australia uses UV to purify shellfish, but ozone is also used, but less. Sydney Rock Oysters is Australia's main shellfish, with NSW alone estimating that its production value exceeds A$300 million, and Australia’s shellfish production value totals A$2 billion. Shellfish entering the market must be forced to purify but harvested from Tasmania and Victoria. Pacific oysters that meet the microbiological criteria set by the National Institute of Health and Medical Research can be marketed without purification. New Zealand harvests and exports a wide range of shellfish, such as mussels, oysters, scallops, cormorants and cockles, with a total export volume of 7,775 tons and an output value of more than 360 million New Zealand dollars.
The Southeast Asian Union’s production of shellfish in Malaysia, Singapore, Thailand, the Philippines, and Indonesia totals more than 2.8 million tons, and the purification system uses mainly UV systems. Europe, such as the United Kingdom, Italy, Spain, France, Denmark and other countries require the mandatory purification of all mollusks. The United Kingdom has been engaged in shellfish purification for 86 years. The first purification plant used chlorine to disinfect seawater and started work in North Wales in 1914. Currently, it mainly uses ultraviolet systems. Spain is the country with the largest consumption of shellfish in EU countries. It produces 225-500,000 tons of shellfish per year. The main economic shellfish are oysters, mussels and beaks. There are 63 official purification plants in Spain. Chlorine disinfects seawater, and a small number of small factories use ultraviolet systems. Like Spain, Italy also uses chlorine as the main disinfectant. There are currently more than 50 purification plants. Although not all of them are open all year round, these factories are mobile and open to the outside world. In contrast to Spain, France uses ozone as the main means to purify shellfish. Chlorine, bromide and ultraviolet light are also used for the purification of shellfish, but it is relatively rare. Each year, 200,000 tons of shellfish are farmed, harvested and sold, and the income is 23 million francs. France is Europe's largest producer of oysters, and its main farmed species are oysters, mussels, and mussels. Denmark uses an ultraviolet system and its main species is oysters. Turkey only produces about 30,000 tons of shellfish per year. Its main varieties are mussels, oysters, mussels, Kidonya and Lipina. At present, there is only one qualified purification plant. Many factories still need to be converted to comply with European market requirements. Shellfish purification plants have emerged much later in Canada than in Europe. Currently only two registered purification plants are in operation, all located on the Atlantic coast, producing only 363 to 69 kl per year. In the early and mid-1980s, the United States built more than 20 shellfish purification plants using UV systems, and has since successively designed and built many shellfish purification plants.
At present, many countries classify the shellfish aquaculture waters into three categories. One type of waters is clean seas. The cultured shellfish can be listed without purification. The second type of waters are polluted waters. The cultured shellfish must be purified or shellfish before they are listed. Classes are stocked for more than 15 to 60 days in a category of waters, and are listed after reaching health requirements. This method is used less frequently because of high labor intensity and loss, and is rarely used. Type III waters are heavily polluted waters and shellfish farming is prohibited.
Shellfish cleansing is suitable for the removal of bacteria from live shells harvested from the two types of waters in lightly polluted areas. It is not suitable for shellfish harvested from heavier polluted areas and shellfish contaminated with petroleum hydrocarbons, heavy metals, pesticides and marine toxins.
The hygienic standards for the purification of shellfish are mostly based on the indicators in the 91/492/EEC directive promulgated by the European Union in 1991:
Before purification, 90% of the samples of bivalve molluscs cannot have coliforms exceeding 6000/100 g of shellfish, or E. coli cannot exceed 4600/100 g of shellfish, otherwise purification is not allowed and must take 2 months. The above holdings until the standard requirements are met. After purification, there are less than 300 coliform bacteria per 100 grams of shellfish or less than 230 E. coli bacteria, and no salmonella is present in 25 grams of shellfish.
Second, the progress of research in China In the East China Sea Fisheries Research Institute in 1997 to undertake the China Agricultural Science and Education Fund project - shellfish purification technology research, based on extensive collection of foreign data and inspection, based on the first domestic shellfish purification technology research, In 1997 and 1998, it conducted a two-year laboratory basic research at the Mariculture Laboratory in the East China Sea Fisheries Research Institute. From 1999 to 2000, it designed and built a 2T/time shellfish purification pilot base at Qingdao Haifeng Group. Pilot trials were conducted on shellfish such as Philippine oysters, clams, oysters and oysters, and a large number of experimental data and practical experiences were obtained.
1. Main results obtained in the study (1) The sterilization effect test of ultraviolet, ozone, and chlorine-containing disinfectants on E. coli, and the determination method of ozone concentration in seawater were completed.
(2) Completed the design and manufacture of purification equipment for small experiments and research on the purification process of shellfish, barley, clams, oysters, oysters, and oysters; according to international experience in the purification of shellfish, we will purify with shellfish. The effects of temperature, water flow, salinity, dissolved oxygen, and other factors, using orthogonal test methods, conducted more than one hundred tests, and obtained the best purification process conditions for shellfish, clams, quails and other mussels. When shellfish contain 105 strains of E. coli, the shellfish can be purified within 24 to 48 hours and meet the requirements of the European Community.
(3) Design mode of shellfish purification plants At present, international shellfish purification plants have the following modes: 1 Shallow flume system 2 Multi-layer system 3 Vertical multi-layer system 4 Large box system Due to the low construction cost of the shallow flume system, operation It is easy to use this model to design the vast majority of shellfish purification plants in various countries of the world. The only disadvantage of this system is that it covers more land, while the other three models are just the opposite, with a small footprint but high construction costs. Operation is not easy.
2? Pilot demonstration site construction (1) Completed the design and manufacture of the treatment device (2) Designed the trial shellfish purification shallow water double layer system 2T/times (3) Conducted three shellfish purification pilot tests in During the trial period, we conducted pilot-scale studies on 11 batches of oyster shells such as Philippine oysters, clams and oysters. The test used nearly 12 tons of shellfish. Through the pilot test, it was further confirmed that the process obtained by the small test was feasible. The system and device designed by us were operating normally with good performance and achieved satisfactory results. All pilot shellfish are monitored by national statutory authorities and can meet the European Community's purifying standards within 24 hours.
The coliform bacteria in the water at the outlet of the purification tank during the small-scale test and the pilot-purification process were detected to be less than 30/l after multiple tests.
(4) Completed the research on preservation of shellfish preservation and packaging technology. The pilot product was distributed by the sales team organized by Haifeng Group Co., Ltd. Currently, it has contacted supermarkets such as Qingdao, Shanghai and Jinan, and some shellfish have entered. Supermarket test marketing is welcomed by consumers.
(5) Decontamination cost calculation: Calculated at one metric ton of Philippine 1 Electricity fee: 116.56 yuan 2 Water fee: 4.05 yuan 3 Labor cost: 600.00 yuan Due to impurities and dead shellfish in the Philippine cockroach, picking is very labor-intensive. Other shellfish can save a lot of artificial 4 consumables and other: 40.00 yuan 5 equipment depreciation: 32.47 yuan Total: 793.08 yuan Third, strengthen the promotion of results and health management The State Development Planning Commission and the Ministry of Agriculture decided in Qingdao and Dalian established two shellfish purification plants. In addition, Xiamen, Zhejiang, Jiangsu, Shenzhen and other places also contacted us and requested the establishment of a shellfish purification plant. At present, two purification plants in Qingdao and Xiamen are under construction and it is expected to start production in 2001.
On June 19, 2000, the Bureau of Fisheries of the Ministry of Agriculture held a national shellfish purification technology promotion conference at our Qingdao pilot base to promote our research results nationwide.

Next Article
Prev Article