Processing technology of large silverfish

Large silverfish, also known as noodle fish, was widely distributed in the middle and lower reaches of the Yangtze River and affiliated lakes. Its meat is delicious and nutritious, and it has a special fragrance of cucumber. The large silverfish is generally about 20cm in body length, no bone and no thorn. It is a kind of small and valuable fish with high economic value, which is very popular in domestic and foreign markets. From 1985 to the early 1990s, the reservoir transplanting and proliferation of large silverfish has been carried out in an all-round way in China and achieved success. Its distribution area is constantly expanding and its output is increasing day by day. How to do a good job in the preservation and processing of large silverfish is of great significance to the development of the economy of the reservoir area, increasing the income of the people in the reservoir area, enriching the vegetable baskets of urban and rural residents, and promoting the development of reservoir fishery in our country. This paper introduces the processing methods of two kinds of large silverfish.

1. Processing of quick-frozen large silverfish

Quick-frozen silverfish are exported to Japan, Southeast Asia and Europe, especially popular with Japanese consumers. With the continuous improvement of the output of large silverfish in the reservoir, quick-frozen big silverfish has become one of the export aquatic commodities with high exchange rate in China.

1. Preservation and transportation of raw fish

The big silverfish has a small body and thin skin, is prone to corruption and deterioration, and has strong seasonality in production. In order to ensure the quality of silverfish, when fishing, you can disembark with ice and keep it fresh at the first time. The specific method is to first select and classify the large silverfish caught on the ship, wash them, and slightly freeze them to keep the central temperature of the fish at about-3 ℃, and then ice the fish in layers.

Put it in an insulated fish box, you should do:

① with catch ice, ice layer ice, ice clean, small ice shape, the amount of ice depending on the climate, transportation distance and time, the proportion of ice fish 1:1-2:1.

② uses a larger plastic heat preservation fish box, each containing fish 10kg-15kg, covered and sealed, with a leakage hole in the bottom of the box to prevent the fish from being whitened by the accumulation of melting ice.

③ is connected to surface transportation to achieve fast loading, express transportation and quick unloading, and the requirements from production to processing plant do not exceed 10h-20h.

2. Processing process

Raw material treatment → cleaning → leachate → weighing → bagging → packing → Quick Frozen → Cold Storage

3. Operation essentials

(1) Raw material acceptance: raw material fish requires good freshness and fatness, complete strip shape.

Color and luster, clear eyes, elastic muscles, no dirt mucus, cucumber clear fragrance and no peculiar smell. Upon arrival, the raw fish is immediately unloaded to the processing workshop, box-by-box inspection and removal of defective products, pay attention to bare-handed grasp operation, do not use nail rakes, shovels and other hard tools, so as not to destroy the integrity of the fish.

(2) cleaning: use fish washing machine or manual rinsing, add large silverfish to evenly, avoid fish layer is too thick, affect rinsing quality. Clean with deep well water or tap water after cooling with ice, wash it several times and pick it up. Cleaning should be rapid, the front and back processes should be closely coordinated, and there should be no backlog.

(3) picking and draining water: while rinsing, remove the ice and weeds floating on the surface of the water, and pick out other fish and shrimp. Put the rinsed silverfish into a container with a leak at the bottom and drain 10min-20min.

(4) weighing: large silverfish that have been leached are weighed and bagged according to different specifications. When weighing, the net weight of each bag of silverfish must be 500g or 1000g after thawing, so it should be weighed by 10% depending on the size of the fish and the degree of filtration. Then put the silverfish bag into a carton, put it in a special frozen silver fish plate, each with 10 boxes, and send it to the quick-frozen warehouse in time.

(5) Quick freezing: the silverfish plates are arranged neatly on the pipe rack of the quick freezer. The temperature of quick-frozen storage should drop rapidly to below-25 ℃. After 15h-16h, the freezing process is completed when the central temperature of the fish reaches-15 ℃.

(6) packing and cold storage: immediately out of the warehouse after quick freezing, packed at low temperature, 20 boxes per box, net weight 10kg or 20kg. The bottom of the carton and the top cushion corrugated paper, the external bandage is firmly tied, and the product name, specification, weight, factory date, etc., are immediately sent to the freezer for storage. The cold storage temperature should be kept at-18 ±2 ℃, stacked according to production batches, specifications, and stored for no more than 12 months. When leaving the factory, the frozen silverfish center temperature does not exceed-15 ℃. When transporting and exporting, it must be transported by refrigerated truck at low temperature.

4. Quality of finished products

Require smooth frozen block, uniform ice coat, clean, air-free dry oxidation and ice blackening caused by slow freezing; silverfish fresh, complete and clear, with translucent shape, no belly breaking or abdominal expansion, no dirty mucus, solid muscle tissue, good elasticity; no peculiar smell; basically no yellow stripes; general body length 18cm-22cm, no lower than the prescribed weight after thawing.

Second, the processing of light and dry products of large silverfish

The processing technology of light dry crystal silverfish is simple and convenient for storage, and this processing is more popular among consumers than dried salt products because it can preserve the inherent flavor of silverfish.

1. Processing process

Raw material → cleaning → alum water soaking → secondary drying → stacking cooling → packaging → preservation

2. Operation essentials

(1) Raw material treatment: first of all, remove miscellaneous fish, shrimp and other impurities, pour the silverfish into a wooden bucket filled with half a bucket of water in advance, add a few drops of useful oil, stir 2min-3min by hand to remove foam mucus.

In cloudy and rainy weather, fresh silver fish must be soaked in different concentrations of alum to prevent decay and accelerate drying. However, the treatment with alum ice will affect its quality and reduce the rate of products. Therefore, the following three points must be mastered when washing with alum water:

① weather is good, the sun is strong, evaporation, alum should be little or no alum. The standard of alum water is that it can wash off the silverfish mucus, and the fish tail can not be alum white. The ratio of alum to water is 1:60, alum can be used three times, the first soaking time can not exceed 1min, the second time can be extended to 2min, the third time can be extended to 5min, after washing and drying.

When ② is overcast, the water evaporates slowly, and the amount of alum can be more. The standard of alum is that you can whiten the fish tail, but not the fish body, the ratio of alum to water is 415 / 60; alum can also be used three times, the length of time is mainly based on the alum of the fishtail.

③ rainy days when the air is moist, easy to mildew, alum to water ratio at 12:60, soak the silverfish in alum until the whole body is white, rinse and dry with water after sunny days. It is usually used when it rains for one or two consecutive days in the thunderstorm season.

(2) drying for the first time: spread the processed raw materials on the fish rack on the ship, gently flatten it and dry it in the sun. When drying the fish, it should be laid thin and evenly, in order to shorten the drying time and accelerate the drying. After drying, put it into the cabin for temporary storage.

(3) the second drying: after 3-5 days, it will be exposed to the sun on the cement site, and the thickness of the shop depends on the degree of the first drying. The first time drying in 7-80%, thickening 6cm-10cm, more than 90%, thickening 10cm-15cm. After drying for 1 hour, in order to make the finished product dry evenly, turn every other lOmin-15min and 5min once in the hot sun until it is completely dry.

(4) drying standard: to identify the standard of drying, in addition to holding the hand without wet feeling, you can take a silverfish, place it flat on the separate middle finger and index finger, press the middle part of the fish body with your thumb, and if it has become brittle and can be broken, or if there are broken white marks, it will be completely dry. Special attention should be paid to not drying too much in the sun, otherwise it is easy to break after packing.

(5) Packaging: dry and complete silverfish, moved into the warehouse and stacked on the board, after one day and night, waiting for the heat to diverge and complete cooling for packaging, if with hot packaging, it is easy to crush or deteriorate. Can be packed in gunny bags, each bag of 50kg or 100kg should be packed tightly, otherwise not only the volume is large, it is difficult to carry, but also the gap in the middle is large, which is easy to absorb moisture and cause deterioration, and can also be sealed with plastic bags of different specifications. The finished product can be preserved for more than half a year and can be preserved for one year under cold storage.

3. Finished product rate and finished product classification

The finished products of light dried large silverfish are graded and identified by experience. First-grade products: dried strips of the same size, no alum or light alum, fresh in the sun, no impurities, white in color at the time of purchase, and then turned to flesh color. Second-grade products: dry, the same size, heavy alum, fresh in the sun, dry round and slightly curved, yellowish at the time of purchase, and then turn yellow. Third-grade goods: dry, the same size, produced in rainy days, heavy alum, dry koji, impurities, yellow at the time of purchase, and then turned red and yellow.