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Historicallyfood safety issues were the responsibility of each individual. As society became more industrialized the safety of food production,preparation and consumption became more of a concern. At the beginning of the twentieth century, lack of scientific knowledgeand food industry guidance led to outbreaks of foodborne illness all over theworld.
Withthe advent of more advanced scientific and medical knowledge as well astechnological advancement, foodborne pathogens were isolated and techniques forpreventing food contamination were developed. Understanding and communicating safe food practices is now known to beessential to the continued health of our entire society.
For the consumer, food safetyinvolves prudent food purchases, sanitary food preparation and safe foodpreservation. Old world traditionsand unsafe, unscientific practices need to be corrected before acceptance ofmodern methods can be assured. Knowing the populations at greatest risk forfoodborne illness can help target the message that food safety must be takenseriously.
RiskFactors
Theimportance of food safety in our modern world is ever increasing. The growth of the population of Americans over the age of 65 years meanshealth professionals need to be aware of loss of consumers natural defenses. As part of the aging process, diminished sight, smell and taste can failto warn seniors of spoiled, unsafe foods. Reduced stomach acid production oftenrelated to aging, reduces the defenses needed to protect the mature adult fromcontaminated food. Slower immuneresponse also may make seniors more vulnerable to the spread of infection.
Children are also at greater risk for foodborne illness due to theirimmature immune system. They mayrequire greater supervision due to their lack of education and their naturalinterest in exploring their environment, often involving unsafe food practices.Pregnant women also are at greater risk due to immaturity of defense system inthe developing fetus.
Persons that are immune compromised due to medical treatment or diseaseare at greater risk for foodborne illness. They may be unable to defend themselves from the spread of infection onceintroduced into their body.
Of concern for the general population is the threat of foodborne illnessdue to a changed environment. Withincreased workloads and less time devoted to food purchasing and preparation,many more people are turning to foods prepared outside the home. Due to increased demand, more of the food industry has become centralizedin its production, preparation and distribution leading to a greater chance ofwidespread contamination.
Pathogens are constantly changing to adapt to new environments and arebecoming more difficult to detect and treat. With the globalization of society, we now come into contact withpathogens that had remained localized in the past. Food trends also may increase the risk of foodborne illness.Recent interest in natural, organic, raw and untreated foods can lead to morerisky food consumption. For thesereasons, it is ever more important to prevent foodborne illness by followingsafe food practices, before the pathogens are allowed to multiply.
Organismsof Foodborne Illness
Bacteria, virus and fungi can cause foodborne illness. These organismscan cause health problems by either infection, where the organism enters theintestine of the host and begins multiplying, or by intoxication where theorganism begins to produce a toxin or poison in the food that is harmful to theconsumer.
Examplesof bacteria that infect their host through contact with food are Listeriamonocytogenes, Salmonella spp and Escherichia coli 0157:H7.Bacteria that are known to produce toxins in foods that can harm the consumerare Clostridium botulinum, Staphylococcus aureus and Bacilluscereus.
Listeria monocytogenes is most often associated with unpasteurizedmilk and cheese, ice cream, raw vegetables, poultry, meats and seafood. It canbe found also in chilled ready to eat foods made from these products. Symptoms in humans infected with this foodborne illness include nausea,vomiting, diarrhea, fever, and spontaneous abortion or stillbirth in pregnantwomen. Incubation period forillness is from three to seventy days, usually about three weeks. Preventative measures include using pasteurized milk and dairy products,cooking foods to proper temperature, clean surfaces and avoidance of crosscontamination.
Salmonella species are most often associated with poultry andpoultry salads, meat and meat products, fish, shrimp, milk, shell eggs, eggproducts, tofu, and fresh produce. Theincubation period for illness is from six to forty eight hours, usually betweentwelve and thirty six hours. Preventativemeasures include avoidance of cross contamination, refrigeration of foods,thorough cooking of poultry to 165°F for at least 15 seconds and good personalhygiene practices.
Salmonella enterica serotype Enteritidis commonly referred to asSE is the dominant organism of concern with regard to food safety from poultrysources. SE is of particularinterest to the egg industry because SE can infect the reproductive organs ofegg laying hens. Eggs can becontaminated if the hens are infected and SE may be deposited in or on the egg. The hen shows no sign of infection, and the egg appears to be normal. The rate of egg contamination with SE is sporadic, with estimates rangingfrom as little as one egg in twenty thousand eggs (0.005%) to one in tenthousand eggs (0.01%). Theprevalence of SE has been declining in the U.S. due to government and industryprograms that reduce the risk of spreading SE infection. These programs focus on producer actions that require thorough cleaningand disinfecting of layer houses between flocks, good rodent control techniques,and proper refrigeration of eggs.
Escherichia coli is most often associated with raw and undercookedground beef, imported cheese, unpasteurized milk and apple cider, dry salami,roast beef, lettuce and nonchlorinated (untreated) water. There are many typesof coliforms, most of which are found naturally in the gastrointestinal system. E. coli O157:H7 is the most dangerous form of the bacteriaand is infective in very small doses. Incubationperiod for illness is from three to eight days usually three to four days. Preventative measures include thorough cooking of ground beef to at least155°F for 15 seconds, avoidance of cross contamination and good personalhygiene.
Clostridium botulinum is most often associated with foods that areunderprocessed or temperature abused in storage, canned low acid foods, homecanned foods, leftover baked potatoes, stews, and meat or poultry loaves. C. botulinum grows in anaerobic environments. C. botulinum produces a neurological toxin that causes botulism inhumans. The incubation period isfour to eight days, usually twelve to thirty six hours. Preventative measuresinclude avoidance of home canned foods, rapidly cooling leftovers and usingcareful time and temperature control of food products. Commercially canned foods have been treated to inactivate Clostridiumbotulinum.
Staphylococcus aureus is most often associated with reheatedfoods, ham and other meats, poultry and other protein foods, milk and dairyproducts and potato salad, custards, cream filled pastries and salad dressing. Incubation period is from one to seven hours usually two to four hours. Preventative measures include good personal hygiene including avoidanceof contact with unwashed hands, avoidance of food contact by persons with skininfection, proper refrigeration and cooking of prepared foods. Many people are carriers of Staphyloccus aureus and are unaware. The bacteria is harmless until it has contact with food and has thenutrients to multiply and a toxin is produced. Good hygiene, including hand washing, is the most important preventativefactor.
Bacillus cereus is most often associated with rice products andstarchy foods, sauces, pudding, soups, casseroles, pastries, salads, meats,milk, vegetables and fish. Incubation period is thirty minutes to sixhours or six to fifteen hours depending on route of symptom. Preventative measures include careful time and temperature control aswell as quick chilling and adequate cooking of food.
Nearly all the foodborne illnesses cited above first appear as similarsymptoms. Common symptoms include nausea, vomiting, diarrhea, headaches andfever. Generally, the duration of foodborne illness is less than a week. Some may progress to more severe symptoms such as Clostrium botulinumthat can cause eventual paralysis and death.
NaturalDesign Protective Qualities in Egg
Itis important to remember that an egg has many natural barriers to preventbacterial growth. These barriersinclude the shell, the membranes within the shell and the egg white itself.
Eggs are laid with a natural protective coating on the shell that isremoved when the eggs are washed and replaced with a coating of mineral oilbefore the eggs are packed. Theinner shell membrane is made of nonporous protein fibers that contain lysozyme,a substance that naturally protects against bacterial invasion. The outer white layer is alkaline and therefore an unfavorable medium forbacterial growth. In addition,nutrients required to support bacterial growth are absent from the outer whitelayer.
The thick white surrounding the yolk is also alkaline, and in addition tolysozyme it contains conalbumin and ovatransferrin that bind iron and othermetals. Also found in the egg white is avidin that binds biotin and flavoproteinwhich binds riboflavin, making these nutrients unavailable to bacteria or humansuntil the egg white is cooked. The viscosity of the egg white can contribute tothe immobilization of bacteria and anaerobic conditions that discouragebacterial growth.
The chalaziferous layer of the white, just before the yolk, is verydense. It contains little of the water which bacteria need, but a highconcentration of all the thick whites protective materials. The thick, ropey egg white strands, called chalazae, hold the yolkcentered in the egg where it receives maximum protection from all the otherlayers. A prominent chalazae is asign of a fresh egg.
As the egg ages and the white thins, the yolk membrane becomes morepermeable and bacteria can, if given the right time and temperatures, reach thenutrient dense yolk and begin to grow. To ensure that eggs remain safe toconsume, proper handling, cooking and storage procedures are of utmostimportance.
The vast majority of reported cases of foodborne illness associated witheggs or foods containing eggs have involved improper handling procedures,inadequate refrigeration and undercooking.
FoodSafety Regulation of Shell Eggs
Eggs are regulated by both theFood and Drug Administration (FDA) www.fda.gov and the US Department of Agriculture(USDA) www.usda.gov . The USDA administers a voluntary grading program for shell eggsthrough the Agricultural Marketing Service (AMS) www.ams.usda.gov/
Shell eggs are regulated by theFDA. In December 2000, the FDAissued two new rules for shell eggs, one for refrigeration and one for labelingeggs with safe handling instructions. Bothagencies are expected to publish proposed rules to address the Egg Safety ActionPlan. This will be a comprehensivefarm to table plan to reduce human illness from Salmonella Enteritidis ineggs 50% by 2005 and 100% by 2010. Thegovernment agencies and the egg industry will work together to implement the newregulations when introduced.
In shell pasteurization of eggshas been approved by the Food and Drug Administration and is available for useby consumers, hospitals and nursing homes where consumers of highest riskreside. The FDA has most recentlyapproved the use of irradiation in shell eggs. Eggs now join a growing list of foods permitted to utilize irradiation toreduce the risk of foodborne illness. Irradiationhas previously been approved for use on raw meat and meat products, poultry,fruits, vegetables, flour and spices. Irradiationusing the maximum of three kilgrays of ionizing radiation has been found tocause only minimal changes in protein, lipid and carbohydrate levels of fresheggs and has been determined by FDA to not differ in any significant manner fromnon-irradiated eggs.
FoodSafety Regulation of Egg Products
Egg products areregulated under the Egg Products Inspection Act of 1970 (EPIA). The EPIAassures that all egg products undergo continuous inspection and are pasteurized. Examples of egg products are whole liquid eggs, liquid whites, yolks, andall frozen and dried egg products. Basically, once an egg is broken by an egg processor, it falls under the EPIAand must be pasteurized. The USDA’s Food Safety and Inspection Service www.fsis.usda.gov/ isresponsible for inspecting egg products.
Most egg products are used by food manufacturers and food serviceinstitutions. Some companies are starting to offer different egg productsto consumers at retail stores, such as dried egg whites, and whole liquid egg.
Since egg products are pasteurized based on temperature and time requirements todestroy Salmonella in eggs, they are safe to consume raw or undercooked. However, once the original package is open, the shelf life of liquid and frozenproducts is very short. Egg products should be refrigerated properly andhandled with the same care as shell eggs.
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