HACCP-based determination of critical control points during frying by street deep-fried meat vendors and assessment of dietary exposure to malondialdehyde

In the bustling streets of many cities, the sizzle of frying oil is a familiar soundtrack, signaling the arrival of a quick, affordable, and often delicious meal. For millions of people, street vendors are a vital part of the food landscape, offering ready-to-eat meats that fit tight budgets and busy schedules. However, the very process that makes these foods appetizing—the repeated heating of oil and the open-air preparation—can also create invisible dangers. When fats are heated too long or too often, they break down chemically, producing compounds that can harm the body. One such compound is malondialdehyde, a substance formed when oils oxidize, which has been linked to damage in cells and DNA. Beyond chemical changes, the open nature of street food preparation also leaves food vulnerable to contamination by bacteria and other microbes. Understanding where these risks occur and how to stop them is a matter of public health, requiring a systematic look at the entire journey of the food from the pot to the plate.

Researchers in Bamenda, Cameroon, set out to examine this exact journey for street vendors selling deep-fried pork. They applied a structured safety framework known as Hazard Analysis and Critical Control Points, a method used to identify specific steps in a food process where risks can be prevented or controlled. Instead of just testing the final product, the team observed the vendors' daily routines, from how they displayed the meat to how they managed their frying oil. They collected samples of the fried meat to test for chemical degradation and microbial contamination, looking for signs that the food had become unsafe. Their goal was to pinpoint exactly where things went wrong and to calculate how much of the harmful chemical malondialdehyde a person might consume if they ate these foods regularly.

The investigation revealed a pattern of practices that put consumers at risk. The researchers found that the vast majority of vendors displayed their boiled meat on open wooden or metal stands, leaving it exposed to dust, insects, and traffic fumes. When it came to the oil, most vendors used bulk refined palm oil, but a significant portion never changed the oil, simply adding fresh oil to the old, degraded supply as it evaporated. Only a tiny fraction of vendors replaced their oil daily. The team also noted that while many vendors claimed to filter their oil, they used simple metal strainers that removed only visible food particles, leaving behind invisible chemical breakdown products. These observations suggested that the oil was being used far beyond its safe limit, accumulating toxic compounds over time.

When the researchers analyzed the fat extracted from the fried meat samples, the chemical data confirmed their suspicions. They found that 83 percent of the samples contained levels of malondialdehyde that exceeded safe thresholds, indicating that the oil had degraded significantly. The meat had absorbed these harmful compounds during the frying process. In addition to chemical risks, the microbial tests showed that the meat was often contaminated. More than half of the samples had high levels of general bacteria, and nearly half contained unsafe levels of Staphylococcus bacteria, which can cause food poisoning. A small but concerning number of samples also tested positive for Salmonella. The source of this contamination appeared to be the vendors' handling practices; many vendors handled money and then touched the food without washing their hands, and the water used for washing utensils was often of questionable quality.

Using the data they gathered, the researchers identified three critical moments where safety could be restored. The first was the display of the meat; keeping it in a closed glass or plastic case would shield it from the environment. The second was the frying process itself; using fresh oil and limiting the number of times it is used would prevent the buildup of toxic chemicals. The third was the service stage; separating the handling of money from the handling of food and using clean water for washing would stop bacteria from spreading. To understand the real-world impact, the team calculated how much malondialdehyde a person would ingest if they ate these meats every day. They found that 30 percent of the samples contained enough of the chemical to exceed the maximum safe daily limit for an adult. This means that for a significant portion of the street meat sold, the risk of consuming harmful levels of oxidation products is real and immediate.

The study concludes that while street-fried meat remains a crucial source of nutrition, the current practices in Bamenda pose a clear threat to consumer health. The dangers are not inevitable but are the result of specific, manageable choices regarding oil management, display methods, and hygiene. By implementing simple changes, such as using enclosed display cases, strictly limiting how often oil is reused, and separating money handling from food preparation, vendors could drastically reduce these risks. The findings serve as a call for better oversight and education, ensuring that the street food culture continues to feed the city without compromising the health of its people.