The specific types of pathogens responsible for food- borne illnesses are FUNGI, VIRUSES, PARASITES, & BACTERIA.
FUNGI, which include molds and yeast, are more adaptable than other microorganisms and have a high tolerance for acidic conditions. They are more often responsible for food spoilage than for food-borne illness. Beneficial fungi are important to the food industry in the production of cheese, bread, wine, and beer.
VIRUSES do not actually multiply in food, but if through poor sanitation practice a virus contaminates food, consumption of that food may result in illness. Infectious hepatitis A, caused by eating shellfish harvested from polluted waters (an illegal practice) or poor hand-washing practices after using the restroom, is an example.
Once in the body, a virus invades a cell (called the host cell) and essentially reprograms it to produce more copies of the virus. The copies leave the dead host cell behind and invade still more cells. The best defenses against food-borne viruses are good personal hygiene and obtaining shellfish from certified waters.
PARASITES are pathogens that feed on and take shelter in another organism, called a host. The host receives no benefit from the parasite and, in fact, suffers harm or even death as a result. Amebas and various worms such as Trichinella spiralis, which is associated with pork, are among the parasites that contaminate foods.
Different parasites reproduce in different ways. One example is the parasitic worm that exists in larval stage in muscle meats. Once consumed, its life cycle and reproductive cycle continue. When the larvae reach adult stage, the fertilized females release more eggs, which hatch and travel to the muscle tissue of the host, and the cycle continues.
BACTERIA are responsible for a significant percentage of biologically caused food-borne illnesses. In order to better protect food during storage, preparation, and service, it is important to understand the classifications and patterns of bacterial growth.
Among the different conventions for the classification of bacteria, the most relevant to chefs are their requirement for oxygen (aerobic/anaerobic/facultative), their effects on people. (pathogenic/undesirable/beneficial/benign), and their spore-forming abilities. Aerobic bacteria require presence of oxygen in order to grow.
In other hand Anaerobic bacteria doesn’t require oxygen & may even die when exposed to it.
Facultative bacteria have the ability to function with or without oxygen. It is also important to know at which temperature bacteria grow best. Some bacterias are able to form endospores, which serve as a means of protection against adverse circumstances such as high temperature or dehydration. Endospores allow an individual bacterium to resume its life cycle if favorable conditions should recur.
Bacteria require three basic conditions for growth and reproduction: a protein source, readily available moisture, and time. The higher the amount of protein in a food, the greater its potential as a carrier of a food- borne illness.
The amount of moisture available in a food is measured on the water activity (Aw) scale. This scale runs from 0 to 1, with 1 representing the Aw of water. Foods with a water activity above 0.85 support bacterial growth. A food’s relative acidity or alkalinity is measured on a scale known as pH. A moderate pH—a value between 4.6 and 10 on a scale that ranges from 1 to 14—is best for bacterial growth, and most foods fall within that range. Adding highly acidic ingredients, such as vinegar or citrus juice, to a food can lower its pH and extend its shelf life.
Many foods provide the three conditions necessary for bacterial growth and are therefore considered to be potentially hazardous. Meats, poultry, seafood, tofu, and dairy products (with the exception of some hard cheeses) are all categorized as potentially hazardous foods.
Foods do not necessarily have to be animal based to contain protein, however; vegetables and grains also contain protein. Cooked rice, beans, pasta, and potatoes are therefore also potentially hazardous foods. There are also other unlikely candidates that are ripe for bacterial growth such as sliced melons, sprouts, and garlic- and-oil mixtures.
Food that contains pathogens in an amount that is enough to cause illness may still look & smell normal. Disease-causing microorganisms are too small to be seen with the naked eye, so it is usually impossible to ascertain visually that food is adulterated. Because the microorganisms—particularly the bacteria—that cause food-borne illness are different from the ones that cause food to spoil, food may be adulterated and still have no “off” odor.
Although cooking food will destroy many of the microorganisms present, careless food handling after cooking can reintroduce pathogens that will grow even more quickly without competition for food and space from the microorganisms that cause spoilage. Although shortcuts and carelessness do not always result in food- borne illness, inattention to detail increases the risk of creating an outbreak that may cause serious illness or even death.
The various kinds of expenses related to an outbreak of food-borne illness, such as negative publicity and loss of prestige, are blows from which many restaurants can never recover.
LINKS: Photo by Michael Schiffer on Unsplash