Written by Dr. Fred Genthner, Microbiologist, U.S. Environmental Protection Agency
Microbial food-borne illnesses pose a significant health problem in Japan.
In 1996 the world's largest outbreak of Escherichia coli food illness occurred in Japan. Since then, new regulatory measures were
established, including strict hygiene practices in meat and food processing
plants, as well as facilities serving food to large numbers of people.
As most food in Japan is consumed in the home, an informational leaflet
was also prepared in March 1997 by the government of Japan to provide instructions
for safe handling of food in private residences. As in most countries food-borne
disease remains a persistent public health problem in Japan. In 2005, there
were 1545 incidents of food poisoning in Japan, in which 27,019 people
were affected and seven died 1. To help reduce this public health problem
this article presents a brief discussion and review of food borne illnesses
and safe food handling practices for the home.
It is normal and natural for most foods to contain microorganisms. In fact, sometimes we intentionally introduce microorganisms into food to initiate fermentation. Not only are foods such as miso, natto, and tempe produced by the use of microorganisms, their nutritional value and resistance to spoilage is enhanced by this process. Most microorganisms in foods, however, are unwanted. Major sources of unwanted microbial contamination are through soil, water, air, insects and rodents. Microorganisms causing disease are referred to as pathogens. Only a small fraction of all microorganisms in food are pathogens, but all unwanted microbial growth in food results in spoilage. In addition, the more unwanted microorganisms present in food the greater the risk for the presence of food-borne pathogens. Although unwanted microorganisms may be introduced into food by producers or manufacturers during slaughter, handling and processing - many food-borne illnesses are caused through improper food storage, preparation and handling by the consumer after purchase.
Food-borne diseases caused by microorganisms follow a course of either infection or intoxication. Infection requires the ingestion of living microorganisms, while food intoxication is caused by ingesting toxins produced by microorganisms growing in or on foods. Many toxins causing food illness are not destroyed at temperatures which kill most microorganisms. Often the length of time between ingesting a contaminated food and onset of symptoms is shorter with a food intoxication than a with food infection. Recognizing these differences is important for implementing strategies and approaches for preventing food-borne diseases.
Some foods are more likely to pose a risk of food-borne illnesses than others. These potentially hazardous foods can be divided into several categories. Under-cooked or raw foods are often more dangerous than cooked foods. This is because heat is effective in killing most microbial pathogens. To reduce your risk of food-borne illness, whenever possible, either cook or wash raw foods before eating them. Bland foods, or foods that contain low amounts of salt and/or acid, provide more favorable conditions for microbial growth. Foods containing multiple ingredients present a greater risk of food-borne illness as each ingredient carries with it microorganisms, so the chance of introducing a food-borne pathogen is increased. Foods that have to be extensively handled during their preparation also present a greater risk because each processing step has the potential to introduce microorganisms. Contamination can come from the cook or from the cooking utensils used in preparation. Finally, foods intentionally prepared in advance or served as left-overs have a greater potential to contain harmful microorganisms and/or their toxins as these foods may have been exposed to extended periods of time at temperatures which promote rapid bacterial growth and production of toxins
A report published in 2000 on risk factors causing outbreaks of food-borne
illness originating in school lunch facilities in Japan exemplifies common
unsafe food handling practices. In this report contaminated food items
were involved in 29 incidents (46.8%); storage of foods for an extended
period before serving in 29 incidents (46.8%), inadequate cooking and cross
contamination in 21 incidents (33.9%); and infected employees in nine incidents
(14.5%). The most common causative bacterial agents in the 269 outbreaks
studied were Salmonella spp., Campylobacter jejuni, E. coli and Staphylococcus aureus. The first three bacterial species listed cause food infections. The last
species S. aureus, causes food intoxication. With this in mind it is not
surprising that the foods causing the most outbreaks included uncooked
or partially cooked items, salad or egg products. Cooking or proper food
storage temperatures would have prevented most of these illnesses. Cooking
to a sufficiently high enough temperature would have killed the pathogens
causing food infections, and proper storage temperatures would have prevented
bacterial growth and, thus, the formation of microbial toxins in the food.
You can't see, smell, or taste harmful microorganisms or their toxins that cause illness. However, if food smells spoiled – don’t eat it! The United States Department of Agriculture recommends the consumer follow four Fight BAC!™ guidelines to keep food safe. The following guidelines should be followed in every step of food preparation;
• Clean — Wash hands and surfaces often.
• Separate — Don't cross-contaminate.
• Cook — Cook to proper temperatures.
• Chill — Refrigerate promptly.
Wash your hands frequently, a minimum of 20 seconds in warm soapy water, to prevent contamination of foods. Never handle foods if you have an open sore or infected cut on your hands. It is important to separate raw meats and poultry from other foods during preparation as they often contain food-borne, bacterial pathogens such as Salmonella spp. in poultry and eggs, E. coli in red meats and Listeria monocytogenes in seafood. Heat kills most microbial pathogens. Thus, you can prevent
food-borne infections by cooking your food to a temperature which will
kill these pathogens. Some recommended cooking temperatures include 71
°C for foods containing eggs, pork or ground beef, 82°C for chicken
and a minimum temperature of 63°C for beef. Most food-borne bacterial
pathogens cannot grow below 4°C. Therefore, store and serve cold foods
at or below 4°C. Thaw frozen foods in the refrigerator or in cold water.
Change the water frequently while thawing. Perishable foods should not
be left out more than 2 hours at room temperature (1 hour when the temperature
is above 32°C).
An important concept to remember is that temperatures between 4 and 63°C
are within the “danger zone”. This term comes from the fact that most food-borne
bacterial pathogens grow in this temperature range. Thus, keeping the length
of time that food is in the danger zone to a minimum prevents numbers of
food-borne bacterial pathogens from multiplying and prevents the production
of bacterial toxins in foods. These are basic guidelines to assist in reducing
risk of food-borne illness in your home.
(1) MHLW – Food Poisoning and Monitoring Report (in Japanese) 2006. http://www.mhlw.go.jp/topics/syokuchu/index.html
Dr. Fred Genthner is a microbiologist with the U.S. Environmental Protection Agency. He was serving as an Embassy Science Fellow at the U.S. Embassy in Tokyo.