Detailed Explanation of Silverfish Processing Technology and Key Operational Points

Through processing, silverfish can be turned into high-quality fish products that sell well in domestic and international markets, increasing the value of silverfish and thereby enabling the fishery to achieve high economic returns. Therefore, processing is an important component of silverfish and the fishery industry. Because silverfish have a relatively high protein content, the catch spoils easily, requiring that ice be used to keep it fresh during the purchasing and processing stages. At present, silverfish products in China are mainly processed according to export standards into packaging units of 1000 grams, and there are also domestic-sale products processed into 500-gram, 250-gram, and 150-gram packages according to customer needs.

Processing techniques and technical requirements for export silverfish products:

1. Rinsing: Transport the collected silverfish catch to the processing workshop and rinse it first. That is, place an appropriate amount of the catch into a large basin, barrel, or other container, then place the container under a tap so that running water rinses the catch. While washing, use a small dip net to remove floating impurities such as leaves and water weeds, then place the washed silverfish into another container for later use.

2. Screening: Grade and screen the rinsed silverfish according to size specifications. Generally, large silverfish are sorted into 3 specifications: 8-10 cm, 10-12 cm, and over 12 cm. Small silverfish such as Taihu Lake icefish are generally sorted into 4 specifications: 3-5 cm, 4-6 cm, 5-7 cm, and 6-8 cm. For each specification of silverfish, the proportion of large, medium, and small individuals is generally 20:60:20. For example, for the 5-7 cm specification, the minimum required ratio is 5 cm : 6 cm : 7 cm = 20:60:20. There is no upper limit on an increased proportion of large individuals, but if the proportion of small individuals increases, the price will decrease proportionally because the product does not meet the specification grade.

3. Bagging: Weigh the screened silverfish as needed, put them into plastic food bags, flatten and seal them, then place them in small paper packaging boxes and put them into transfer trays. Because silverfish lose water and therefore weight during processing, an appropriate excess of raw fish should be added when bagging, so that the processed silverfish product does not fail to meet standard requirements due to insufficient weight. For example, for 1000-gram packaging, generally about 1050 grams of raw fish should be used. Other packaging specifications follow the same principle.

4. Quick freezing: Immediately place the silverfish collected in the transfer trays into the quick-freezing workshop for quick freezing. The room temperature of the quick-freezing room should be kept below -38°C; continuous freezing for 24 hours is sufficient. If the quick-freezing temperature is too high, the freezing time will be too long, causing excessive water loss from the silverfish and reducing the quality and quantity of the silverfish product.

5. Cold storage: Place the quick-frozen silverfish separately into previously prepared cardboard boxes (generally 24 boxes per carton) and move them into the cold storage room for storage. The room temperature of the cold storage room should be kept below -18°C.