Introduction to Food Safety
Have you ever had a foodborne illness? This question is often asked in food safety classes. Typically one or two hands are raised. Discussion of the ‘incident’ usually reveals stories of vomiting and diarrhea initiated several hours after eating and usually involves only the person telling the story. These characteristics make it very difficult to determine whether foodborne illness has really occurred. While actual statistics are impossible to verify, it is likely that approximately 10% of all Americans experience food poisoning each year. Probably, each person has experienced it at least once in their lives. Why are these reports so inconsistent?
Several factors are important. First, manifestations are often general: nausea, vomiting and diarrhea — which make it difficult to distinguish from common flu symptoms. As a victim reflects on their most recent meal, they remember sharing the same food with others who show no symptoms. Based on this simple observation, they conclude that their problems are not food related. Clarity comes when recognizing the second factor causing the confusion: incubation time.
Incubation time (also called ‘onset’ time) refers to the time required for symptoms of a foodborne illness to appear after ingestion of a food. Specific times may vary from two hours to several days or weeks. An individual experiencing these symptoms (commonly referred to as ‘hugging the toilet’) may be reacting to foods eaten several days prior. Often, no connection is made.
Contamination vs. Spoilage
Another area of common confusion is the difference between food contamination and food spoilage. Contamination occurs when food is exposed to a pathogen. (A pathogen is defined as a disease producing organism. This will be discussed in more detail later). Pathogens cannot be detected without laboratory examination. A person cannot see, smell or taste a pathogen or its toxin. If they could, food poisoning would be more rare. However, we are very capable of detecting food spoilage. The fact is that food does not last forever; it deteriorates. This may be due to enzymatic reactions within the food (such as apples browning) or due to the presence of bacteria.
Food spoilage can be defined as a disagreeable change in a food’s normal state. Such changes can be detected by smell, taste, touch, or sight. While consumption of this food may produce gastric distress and vomiting, it will not cause any long term distress. In fact, these bacteria usually act competitively with pathogens.
Conversely, food contamination, that is, consumption of food containing a pathogen causes disease. The disease process may be limited to the intestinal tract, or may also permeate the intestine and affect various organs and systems throughout the body.
Food Contamination
- occurs when food has been exposed to a pathogen
- not detectable by the senses of light, smell or taste
Food Spoilage
- damage to the edible quality of food
- often detectable by the senses of sight, smell or taste
Several factors may be contributing to this rise. First, people eat at home less often. As more hands are involved in food preparation, opportunity for the introduction of pathogens is greatly enhanced. According to those who gather statistics, people who eat out more than three times per week have increased from 3% to 7% of the population in the United States. In addition to eating in restaurants, this increased handling applies to any food partially or fully prepared prior to purchase, even though the food may be consumed at home. Frozen pizza, stuffed pork chops and lunches-to-go fit into this category.
Secondly, pathogens are evolving in manners that make them harder to predict and control. A good example of this is Shiga toxin-producing Escherichia coli (STEC). One of the most common pathogens worldwide, a new strain of this pathogen, E. coli (STEC) has continued to emerge in recent years. A far more deadly form, this pathogen was widely recognized after an outbreak in California and Washington state where several persons died after consuming hamburgers at a fast food restaurant (it was then identified by the name E. coli 0157:H7).
Further evidence of its survival ability has been seen in its presence in unpasteurized apple juice. Apparently the low pH of the apple cider was not enough to discourage the E. coli. The influence of pH and the growth of bacteria will be discussed later.
Most recently, STEC was responsible for the illness of 33 persons in several states due to the contamination of ready to eat salad. Salmonella enteritidis, mentioned earlier, has demonstrated the new capability of residing in a chicken’s ovaries, thus being implanted in the egg prior to being laid. No longer is visual examination of the outside integrity of an egg sufficient to determine its safety. This has had a great deal to do with the added emphasis on using pasteurized eggs in any uncooked or partially cooked egg products, including the banishment of eating uncooked cookie dough!
Several other evolving trends in the food industry impact the situation. We have moved into the era of “mega-food” production. No longer do we acquire foods predominately from the local area. We now have fewer food producers manufacturing food for millions of people.
A single mistake in production can affect hundreds of thousands of people. An outbreak of Salmonella originating in a single ice cream plant in 1995 affected over 200,000 people before being discovered and brought under control. In 1997, several thousand children required inoculation for hepatitis following its detection in strawberries packaged in a plant in San Diego and sold to school food services.
Additionally, our food has taken on a global nature, originating from many countries throughout the world. Two summers (1996 and 1997) witnessed outbreaks of Cyclospora traced to raspberries from Guatemala. Although opinions differ, there is no disputing the fact that sanitation practices and regulations vary in other countries. Global food is currently cited as a significant source of foodborne illness. A complex matrix exists which impacts the trends in foodborne illnesses.
Despite all of these factors, it should be remembered that most outbreaks occur as a result of food mishandling in food establishments or homes.
For example: It is interesting to note the personal food habits of individuals despite the level of awareness they may have. A survey of the Food and Drug Administration showed that 53% of adults surveyed ate raw eggs, 17% ate raw clams and oysters, 32% ate under cooked hamburger and 8% consumed raw sushi and ceviche.
This course will address those issues that we can control.
Foodborne Illness Increases are Due to:
- People eat out more: food is handled by more people prior to consumption.
- Pathogens are becoming more difficult to control.
- Greater amounts of food are being produced in fewer manufacturing plants.
- Food is being imported from many countries throughout the world.
The Most at Risk
Who are the most susceptible populations? As expected, the weakest individuals such as the very young or very old. In addition, persons with suppressed immune systems such as those who have just sustained a significant illness, have undergone chemotherapy or are battling AIDS. The degree to which a person suffers the symptoms of foodborne illness depends of how strong they are and the actual number of pathogens they ingest. In other words, how badly contaminated was the food? The Food Code refers to these persons as “highly susceptible populations” or HSP.
Forms of Contamination
Biological Contamination
The above mentioned types of contamination, chemical and physical have a common element: they do not grow. If we put bleach in the soup or a fingernail in the salad, at least we don’t end up with twice as much bleach or two fingernails! However, if a worker sneezes on a burrito, the pathogen present might reproduce and ultimately produce a dangerously high number of pathogens.
Herein lies the problem: biological contamination is alive. (Note the prefix bio, which means “life.”). What can the food handler do to prevent the continued and harmful growth of living, reproducing pathogens?
First, let’s explore further the meaning of “pathogen.” As stated earlier, a pathogen is a disease-producing organism. For the purposes of this course, we will address bacteria and viruses. While both viruses and bacteria are considered pathogens, they differ greatly in their natures and characteristics.
Pathogenic Bacteria
Do all bacteria make a person sick? No, in fact we often pay extra money for bacteria in the food we buy — when purchasing yogurt, many people look for the term “live cultures.” This simply means the presence of live Lactobacillus bacteria. After a round of antibiotics, a physician may suggest yogurt or acidophilus milk to replace the bacteria in the gut. These organisms add to our health and actually manufacture vitamins during digestion!
Some bacteria, however, may sicken or kill a victim and are referred to as pathogens. (Notice the prefix patho which means “disease” or “suffering”). Some pathogens are limited to the digestive tract, while others penetrate the intestinal wall and circulate throughout the body, attacking various organs. For example, STEC may cause renal failure.
As we outline the process of bacterial growth, it may be helpful to remember that food which has already been contaminated may enter a food establishment. Hamburger rarely becomes contaminated with STEC at a restaurant; more likely, the pathogen comes from the packaging facility. Therefore, all food must be treated as if it were contaminated, because it is impossible to detect pathogens with the senses. Controlling the growth of bacteria is key in any food operation.
Chemical Contamination
The usual chemicals identified in a food system are insecticides and cleaning agents such as glass cleaners, soaps, sanitizer and oven cleaners. (1)The danger of these being added to the food is obvious. How could this happen? The usual response suggests that they may spill or be airborne or left as residues on work surfaces. While all of these are possibilities, there is a much greater threat to overall food safety.
Often, chemicals are purchased in large quantities and subsequently transferred to smaller, more easily handled containers. These may be unlabeled, mislabeled or labeled in a language that some persons cannot read. If the chemical is placed near a food preparation area, it may be added to the food intentionally but in error. A couple of examples may prove useful.
A chemical that is nearly identical in appearance to powdered sugar is filter powder. Filter powder is no more than finely ground glass — it is used to clean equipment. In a food establishment with limited storage space, it may be stored in close proximity to food. Hurried or careless workers, or those with limited English capabilities, have on occasion mistaken it for its look-alike and filled the powdered sugar container with ground up glass! No one realized the error until customers mentioned the “funny” taste of the French toast.
Another example is the pretzel display case. Often, a spray bottle of water for spraying the pretzels to keep them crisp is kept beside the case. Next to that may be an identical bottle of window cleaner for cleaning the glass case.
The stories are endless. The bottom line is that all chemicals must be clearly labeled and stored away from food — preferably out of sight. As good as it is to keep surfaces clean, it should not be too convenient.
A third type of chemical contamination can occur when certain types of metals come into contact with high acid foods. Galvanized metal, copper and lead are good examples.
An unfortunate incident involved a wedding reception. Lemonade was prepared in a galvanized pot, causing zinc to leach out of the container. Zinc is a powerful emetic — within a short time, most of the wedding guests were vomiting profusely!
Finally, a fourth type of chemical contamination occurs when chemicals naturally present in foods cause poisoning. Examples of these are certain kinds of mushrooms, moldy grains or nuts. Also included are ciguatoxin poisoning, scomtoxin poisoning (both of these are associated with fish) and shellfish toxins. Quite a cumbersome list, isn’t it? Thankfully, these poisonings are not common but are considered a foodborne illness resulting from ingestion of a chemical.
Important Points Regarding Chemical Poisoning
- All chemicals must be stored away from food.
- All chemicals must be clearly labeled with the common name and in all language limitations of persons using the food.
- Chemical poisoning can also be caused by certain metals, such as galvanized metals coming into contact with food.
- Some naturally occurring chemicals may result in contamination.
Physical Contamination
Physical contaminants are easy to identify. These are foreign objects that accidentally enter the food. Their presence causes the customer to call a wait person to their table to exclaim, “I want to see the manager; look what I just found in my food!” Items such as staples, nails (metal or finger), hair, glass, shells and bones fit into this category. After finishing my third glass of iced tea at lunch recently, I felt an article in my mouth that was clearly not ice. It was a piece of glass, small enough to go through the straw. I inquired of the manager, “What does your staff use to scoop the ice for tea?” His answer of an ice scoop was not convincing. The glass chip had come from using a glass to scoop the ice.
A dull or dirty can opener may cause physical contamination as bits of metal shavings or dirt enter the can as the lid is removed. Food prepared by a food handler wearing acrylic nails may have one of the nails as an unintended ingredient.
Foreign objects in food that can cause injury:
- fingernails
- stones
- toothpicks
- broken glass
- pieces of bones
- shards of metal from cans opened with a dull can opener