There are two disease pathways with food borne illness. One is the fecal-oral route the other is allowing bacteria to reproduce to levels high enough in food for illness to occur. The second one is significant for most food borne illness bacteria require large numbers to result in disease. Cross-contamination like moving from handling raw meat to making ready-to-eat food without washing hands or putting on gloves can also come in to play with number two.

Without knowing detailed knowledge of the bacteria and viruses associated with disease relating to food there are four factors that go a long way to preventing illness caused by these organisms.

1. Proper Handwashing. This means keeping hands lathered for at least 20 seconds before rinsing.

2. Keeping hot food hot (1350F or more) and cold food cold (410F or lower). This includes a cool-down time from 1350F to 700F in two hours or less and from 700F to 410F in four hours or less for a total cool-down time of six hours or less. The reason for this is most food borne illness bacteria requires large numbers for illness to occur and most reach their highest numbers in the shortest time between 1200F and 700F.

3. Preventing bare-hand contact with ready-to-eat-food.

4. Using sanitizer solution at the concentration for use on food-contact surfaces. With unscented bleach this is 50 – 100 parts per million free available chlorine. Quaternary ammonia sanitizers have a maximum concentration of 200 parts per million. Iodine as a sanitizer has a range of 12.5 to 25 parts per million. Bleach (chlorine) is the most common and mixing ˝ capful or ˝ teaspoon of bleach in one gallon of water gives approximately 100 parts per million.

The sanitize step is the last in the 3-step wash, rinse and sanitize process for dishes, utensils, etc. – anything that is used in the cooking process and/or that comes in contact with food. These steps can be done in a three-vat sink, a two-vat sink with a portable tub for sanitizing or three portable tubs. Either way the three-step process is one of the ways to break the food borne illness cycle.

Now that we have general knowledge of disease pathways associated with food and some of the preventive measures that can be effective to stop illness then we can begin to apply this to lessen the risk for illness associated with food. One of the first steps is to identify potentially hazardous foods that can support the growth of pathogenic organisms. These provide a suitable climate for bacteria to reproduce and thrive.

There is a rather lengthy definition in the 1999 Missouri Food Code but it does provide insight for foods most likely to contribute to illness. Potentially hazardous food is one that is natural or synthetic and that requires temperature control because it is in a form capable of supporting:

(1.) The rapid and progressive growth of infectious or toxigenic microorganisms;

(2.) In raw shell eggs, the growth of Salmonella Enteritidis which is one of the Big 4 in the ’99 Food Code.

Potentially hazardous food also includes animal foods that are raw or heat-treated (cooked) and plant foods that are cooked or consists of raw seed sprouts, cut melons or garlic-in-oil mixtures that are not modified (such as acidified) so they no longer support bacterial growth.

It is also insightful to remember what is not a potentially hazardous food. Three factors can be used to identify potentially and non-potentially hazardous foods. These are water activity, pH (specifically a pH of 4.6 or below) and a temperature range allowing for rapid growth of bacteria. Laboratory instruments are not always necessary to identify foods with one or both or all for once you know what to look for identification is much simplified.

This definition for potentially and non-potentially hazardous is not all inclusive as documented in the ‘99 Missouri Food Code but it does provide a basis upon which to identify foods that are likely to support bacterial growth.

Water Activity is measured on a scale from 0 to 1.0 with distilled water having a water activity of 1.0. Aw refers to the availability of water and bacteria need water, suitable temperature and food to grow and reproduce. Potentially hazardous foods have water activity values of above 0.85. From this we know that ‘wet’ foods have the potential for supporting bacterial growth. So how can we apply this? Food buffets, salad bars and other hot and cold holding areas provide numerous examples. Shredded cheese is not considered potentially hazardous because the water activity is too low to support microbial growth. On the other hand, cottage cheese has sufficient water activity to support microbial growth. As a general rule, raw meats, cooked meats and cooked potentially hazardous foods have sufficient water to support growth whereas dried meats like jerky do not.

pH is measured on a scale from 0 to 14.0 with 7.0 being neutral. Our interest in limiting bacterial growth stems from the fact that foods with a pH of 4.6 and below are seldom implicated in food borne illness because most bacteria cannot grow well in foods within this pH range. Meats and poultry products generally have a pH above 4.6 and thus can support bacterial growth. Tomatoes, citrus fruits and commercially prepared mayonnaise all have a pH below 4.6. Even though commercially prepared mayonnaise contains eggs it is not considered potentially hazardous due to the pH below 4.6 does not support microbial growth well.

Reheated cooked foods have more potential for bacterial growth than raw foods. In addition, the longer a potentially hazardous food is within the ideal bacterial incubation temperatures of 1200F - 700F the greater the likelihood that growth will occur to levels sufficient for illness to occur. Therefore, cooling temperature requirements are based on growth parameters of bacteria that multiply rapidly under temperature and time abuse.

The great thing about cooking is that it kills bacteria and viruses. Once you go above 1300F you are killing both and the higher the temperature the more you kill in a shorter period of time and we are talking about thousands or millions. This is where keeping hot food hot and cold food cold and cooling potentially hazardous foods down to certain temperatures within certain time frames comes in to play. With potentially hazardous foods often times the trick is to not contaminate it after cooking for cooking results in a sterile product if heated long enough at a high enough temperature.

Now that we know the two disease pathways with food borne illness, have some idea of measures to prevent illness, have some idea on how to identify a potentially hazardous food and we know a little about the microbiology of the organisms we are dealing with then we are ready to apply this knowledge to a menu or food. Microbiology along with the other parameters is important for ultimately preventing illness is what you want and prevention is the key. It’s a lot easier and cheaper to prevent something from happening than to deal with it after the fact. Remember the adage ‘an ounce of prevention is worth a pound of cure’ - this applies to illness associated with food as well.

Applying the four factors from page one on a regular basis along with identifying potentially hazardous foods on your menu and taking steps to stop the growth of bacteria to large numbers greatly reduces the risk for illness to occur.