Why are foods processed? Making food safe

Food scientists are obsessed with the safety of foods. A fundamental difference between food scientists and everyone else in the world is that food scientists believe that food poisoning comes from natural sources that must be contained while most others believe that food processing is the cause of safety hazards. From the introductory course in their major, food-science students are warned about the danger of microbial contamination in the food supply. Later, a course in food microbiology scares them witless—a condition from which they never recover. Anyone who has ever lived with a food scientist will tell you about dealing with an overabundance of caution in the kitchen.

News stories tell us that we should be afraid of chemicals in our food (very afraid!), but food safety is all about the microbes. The fear of chemicals in our foods is overblown based on scare tactics. It seems that any substance with a chemical name is to be feared. I will tackle food chemicals in general and food additives specifically next month. What food scientists worry about, however, are food microbes—specifically food pathogens—the deadly kind of microbes in food. These are microbes with names such as Campylobacter, E. coli, Salmonella and Staphylococcus. Some of these pathogens cause infections—the microbe grows in the food, is consumed and grows in the body of the victim to produce an illness. Other pathogens produce toxins in the food. The pathogen may be killed by heat or some other means, but the toxin survives and poisons its victim. The most effective process to kill pathogens before they can do any damage is heat. Heat also induces many favorable chemical changes in a food including browning and new flavors.

It is easy to confuse spoilage with unsafe food. Spoilage of a food makes it look, smell, taste and/or feel (slimy for instance) bad. Spoiled foods are not necessarily unsafe foods and unsafe foods are not necessarily spoiled. It is obviously preferable to be served a spoiled food that is safe than an unsafe food that shows no signs of spoilage. Consumers are less likely to eat the spoiled food. Thus, processes are designed to promote spoilage of a food before it becomes unsafe. Federal regulators evaluate new processes from this perspective. Such principles are particularly important when evaluating processes for fresh and fresh-like products.


Safe or unsafe? Don’t confuse healthiness with safety.

When I was in my first food microbiology course in graduate school, each member of the class was assigned a pathogen to isolate and identify. We had a big class, so I did not get a mainline pathogen. Mine was an obscure one—Edwardsiella tarda. We learned that the easiest places to find these bad guys was in soil, water and animal waste. E. tarda loved water, and I lived next door to a swamp. What I thought would be the assignment from hell turned out to be a very rewarding one. I was able to isolate my assigned microbe with time and hard work. The point drilled home, however, was that most of the nasty organisms responsible for outbreaks that we hear about on the news come from contaminated water and soil.

Restaurants must take precautions to prevent outbreaks. There are several ways food poisoning can occur in restaurant foods:

  • food or water coming into the restaurant may be contaminated which is particularly problematic if food is to be served raw such as lettuce or fresh strawberries;
  • raw foods could be undercooked and thus sufficient pathogens could survive;
  • cross contamination such that a contaminated food like raw chicken touches directly or indirectly (say through a common utensil or cutting board) raw salad vegetables—the chicken is cooked thoroughly, but the vegetables are not;
  • a cooked food might have some residual pathogens that are not sufficient to cause illness, but if the food is then left out at room temperature for too long such that the harmful microbes can grow to the point that the item once again becomes a safety hazard; and
  • someone handling the food contaminates the food prior to it being served.

The above list is not complete, but note that the microbes are all part of nature. Most of these problems can be overcome by attention to detail and proper training of restaurant personnel. Small, ethnic restaurants and those that handle foods with bare hands are more likely to run into trouble than others. It is also more difficult to monitor numerous local farms and suppliers than fewer regional or national entities.

Safe or unsafe? Don’t confuse healthiness with safety.

A recent outbreak involved hot peppers contaminated with Salmonella. At least 32 victims were identified from nine states, but it was difficult to trace the offending source due to poor records. Customers of Mexican restaurants became sick, probably due to contaminated salsa prepared with the peppers as an ingredient. This outbreak highlights the danger of contaminated peppers that were purchased from a firm in Mexico who consolidated peppers from many small farms. The salsa was not cooked and apparently not acid enough to prevent the growth of Salmonella. The case also illustrates that peppers from a single farm can lead to food poisoning in restaurants across many states. It is probable that more than 32 people were sickened from the contaminated peppers, but the illnesses were either not reported or not directly linked to this specific outbreak.

Food processing plants make food safety Job One to borrow a slogan from a car company. Manufacturers have a quality department that checks incoming raw materials, monitors the process, and samples the finished product to ensure safety and quality of the product that leaves the manufacturing plant. The processed-food industry has a remarkable safety record considering how many products are manufactured and distributed each day. The recalls and outbreaks we hear about are those times where the quality system broke down. Although I consider processed foods and ingredients to be the safest foods I eat, a mistake by a food company is likely to affect more people because more people are likely to buy and eat that contaminated product.

A recent recall involved the mislabeling of a product that was supposed to contain chicken but contained tuna instead. The problem was not microbial but concerns about allergens. The biggest source of recalls of food products are related to allergens. The most recent recall I could find involving pathogens was for ground beef containing E. coli. Proper cooking of such ground beef and preventing cross contamination should render the product safe.

Food safety is the responsibility of everyone in the chain from the farm to the table. As we saw with hot peppers, safety starts on the farm. Organizations that collect food from farms must monitor the safety of such items. For any items that are not processed with heat or other lethal processes for microbes (known in the industry as a kill step), extra care must be taken to prevent growth of pathogens. The same principles apply whether in a processing plant or in a restaurant or home kitchen. Refrigeration and freezing are just two of such preventative steps. Last week I had a discussion with client at the food pantry about an expiration date on a package of deli ham. It is now July and the expiration date was in April, but the deli ham had been frozen before the expiration date. I tried to convince her that it was safe because it had been frozen, but I don’t think she believed me. She finally took the small package, which I suspect became food waste as soon as she returned home.

If food scientists are right that every raw food, particularly meat, can be considered to be a potential safety hazard, then the home-meal preparer must also take responsibility for food safety. Pundits who suggest that all purchased food should be safe, ignore the dangers of raw and minimally processed foods. The food supply could be much safer if every food was thoroughly processed to ensure a kill step. Our culture and our palates would suffer the consequences, however.

Next week: Why are foods processed? Extending shelf life

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