1.What are the risks of zinc coating?
Reaction with Acid: Many foods (such as fruits, meats, and vegetables) release acid or moisture during heating. Zinc reacts chemically in an acidic environment, forming zinc salts. These salts may dislodge and enter the food.
Risk of Zinc Poisoning: Excessive zinc intake can cause acute symptoms such as nausea, vomiting, abdominal pain, and diarrhea. Long-term excessive intake can also have adverse health effects.
Zinc has a low melting point: At higher drying temperatures (well above its melting point of 419°C, which is uncommon, but localized overheating can be a problem), the zinc layer may become unstable, accelerating its release.
2.What do food safety regulations stipulate?
Food safety regulations worldwide (such as China's GB standards, the US FDA standards, and the EU's EC1935/2004) clearly stipulate that surface materials in direct contact with food must be non-toxic, non-adsorbent, corrosion-resistant, and non-reactive with food.
Ordinary galvanized steel sheets (whether electro-galvanized or hot-dip galvanized) are not food-grade certified, and their zinc coating and any trace amounts of impurities such as lead that they may contain do not meet these regulatory requirements.
3.In what situations might you "likely" see the use of galvanized sheet metal?
For cost reasons, some non-standard or low-end equipment may use galvanized sheet metal on certain parts that do not come into direct contact with food. Examples include:
Equipment housing and frame
Hot air circulation system duct housing (although stainless steel is preferred for the interior duct walls)
Equipment support structures
However, please note that even these areas present risks: If the galvanized coating dislodges due to high temperature, high humidity, or mechanical wear, the resulting dust or oxides could enter the food area through air circulation, causing contamination.
4.What are the recommended materials for food drying equipment?
Food-grade stainless steel - This is the most commonly used and recommended material.
304 stainless steel: The most common choice, offering excellent corrosion resistance and mechanical properties, and easy to clean and disinfect.
316 stainless steel: Offers better resistance to chloride corrosion than 304 and is recommended for use in environments with high salt content or humidity.
These stainless steels have a smooth surface, are non-toxic, heat-resistant, and non-reactive with food, fully complying with food safety standards.
Food-grade aluminum alloys
Anodic oxidation treatment is typically required to form a hard, stable, non-toxic oxide film that effectively protects the aluminum from direct food contact. Ensure that it is "food-grade anodizing."
Food-grade coatings
Apply a certified food-grade, high-temperature-resistant coating to the carbon steel substrate. This coating must be stable to ensure it does not decompose or release harmful substances at the operating temperatures of the equipment.
5.What are the core principles?
Do not use ordinary galvanized coils in any part that may come into direct or indirect contact with food.