First, some stalls lack access to clean water, so vendors reuse a basin of water to wash raw meat. Some even put the meat directly into the meat grinder. As a result, dust adhering to the meat's surface, as well as unclean substances and pathogenic bacteria from knives and cutting boards, are mixed into the meat filling.
Second, after each grinding, some meat residue remains in the grinder and is mixed in with the new meat during the next grinding. Since the time intervals between grinding sessions are not fixed, the residue remains in the grinder for varying lengths of time. If the residue stays for a long period, certain microorganisms like pathogenic bacteria can easily grow and multiply in suitable temperatures, and may even produce toxins. If the operators fail to thoroughly clean the grinder daily after work, the meat filling is more likely to be contaminated.
Furthermore, operators need to periodically add a small amount of lubricant to the grinder, but in most cases, they use inedible mechanical oil. If added improperly or if the grinder is old, a small amount of lubricant might mix into the meat filling.
The situations mentioned above all expose the meat filling to varying degrees of biological hazards (pathogenic bacteria) and chemical hazards (pathogenic bacterial toxins or lubricant). If not heated thoroughly, pathogenic bacteria can remain in the food, causing consumers to experience gastrointestinal discomfort or even food poisoning.
Therefore, vendors should use clean water to wash meat before processing, follow standardized procedures during processing to avoid cross-contamination, promptly clear any meat residue from the grinder after use, and regularly clean and disinfect the grinder. Additionally, it is recommended that consumers choose stalls with good hygiene conditions for grinding meat, or grind it at home themselves to ensure food safety.