The use of sodium metabisulfite as a food preservative requires attention. This white crystalline powder (chemical formula Na₂S₂O₅) is widely used in seafood preservation and fruit processing due to its sulfur dioxide release properties, offering significant cost advantages; the cost of preserving each kilogram of seafood is only a few cents.
The national standard GB 2760-2014 clearly stipulates usage limits: ≤0.1g/kg for frozen shrimp and other aquatic products, and ≤0.05-0.1g/kg for candied fruits and biscuits. Excessive use may cause respiratory irritation, digestive discomfort, and allergic individuals are more prone to rashes and asthma. In 2023, a test on Ecuadorian white shrimp on an e-commerce platform showed sulfur dioxide residue reaching 0.155g/kg, far exceeding the safety threshold.
Consumers can mitigate risks in three ways: First, check the ingredient list and be wary of products containing ingredients not explicitly listed, such as a company in Zhanjiang, Guangdong, that used excessive phosphates to increase the weight of shrimp. Second, observe the product's appearance; normal shrimp is bluish-gray and slightly translucent, while problematic products are often pale, swollen, and abnormally elastic. Third, use a sulfur dioxide rapid test card; products exceeding the limit will show a red line.
At the industry regulatory level, South Korea relaxed its sulfite residue standard for fruit wine to 0.2g/kg this year, while my country is tightening its controls. Although the new national standard for 2025 does not directly address this additive, the trend of banning chemical preservatives in canned foods is clear. In reality, a food factory in Jiangxi was involved in a case exceeding 20 million yuan for illegal use, and the local regulations in Golmud, Qinghai, became invalid due to illegal additives; merchants frankly stated that "not adding them means losses."
The "cleanliness" of food labels should not only be about the quantity of ingredients, but also about ensuring that every additive can withstand scrutiny. From shrimp fishing to dried fruit processing, from national standards to testing methods, consumers can only truly safeguard food safety by paying close attention to the details of the ingredient list.
