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University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

Historical Materials from University of Nebraska-Lincoln Extension Extension

1992

EC92-2307 Microbiology/Foodborne Illness

Julie A. Albrecht University of Nebraska - Lincoln, [email protected]

Susan S. Sumner University of Nebraska - Lincoln

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Albrecht, Julie A. and Sumner, Susan S., "EC92-2307 /Foodborne Illness" (1992). Historical Materials from University of Nebraska-Lincoln Extension. 1572. https://digitalcommons.unl.edu/extensionhist/1572

This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Nebraska Cooperative Extension EC92-2307-B

\., Food Microbiology/ Foodborne lllness

Julie.4. Albrecht, Ph.D., Extension Food Specialist Susan S. Sumner, PhJ)., Extension Food Microbiologist

Microorganisms in Food may be transferred from soil and water to plants and animals. Raw food stuffs , yeasts, and mold are microorganisms contain microorganisms which may be transferred to associatedwith . The individual processedfoods by carelesshandling. Food handlers cannot be seen without the aid of a microscope. The with poor practices may transfer microor- size of these microorganisms are measured in mi- ganisms to food. If suitable conditions exist, some of crons (1 micron is 1/1000of a millimeter or U25,40A these microorganisms may grow to create a public of an inch). More than a thousand microorganisms in health concern. Specific bacterial species are the a cluster are barely visible to the eye. main causesof foodborneillnesses in humans. Microorganisms may be classified into three groups according to their activity. Benefrcial mi- Bacteria croorganisms may be usedin the processof making new foods. Cheese is made with microorganisms Bacteria are single organisms which can be which convert the to an acid. Spoilage identified on the basis of their cell shape. There are microorganisms cause food to spoil and are not round bacteria called cocci, rod shaped cblls called harmful to humans. A spoilage microorganism is ba,cilli, curved bacteria (the uibrios), and corkscrew- responsible for souring milk. Pathogenic microor- shaped spirilla. Single bacterial cells grow and mul- \- ganisms are causing microorganisms. The tiply into chains, clumps or organized clusters. living microorganism or a (microbial waste Harmful bacteria may cause food . Useful product) must be consumedto causes5rmptoms asso- bacteria are used to make yogurt and several other ciated with specific pathogenic microorganisms. fermented foods. Microorganisms may exist as living cells; re- ferred to as vegetative cells. Vegetative microorgan- isms are actively growing. Some microorganisms have hairlike appendages called flagella. Flagella allow microorganisms to attach to surfaces. Some microorganisms can exist in a dormant state. These microorganisms produce a spore which may remain dormant for years. Under the proper conditions, sporesmay develop into vegetative micro- ooo Cocci organisms. Microorganisms can be found virtually every- where. Bacteria and molds are found in the soil and water. Yeasts are found mainly in the soil. Plant and animal food products support the growth of microor- ganisms. Bacteria have been detectedon plants and animals; molds are usually found on and veg- etables; yeasts are generally found on fruits. Many bacteria are part of the normal microflora of the Rods intestinal tracts of man and animals.

\. Issuedinturtheranceffi#"ffirff:?"H*t1ff:y3,:fr1iru".:Lf,l*;.ffiT:onwirhtrre L4n3l. University of Nebraska, Institute of Agriqrlture and Natural Resources. h is the policy of the Univcrsity of Nebraska-LincolnImtiturc of Agricultw md Natural Reorcs not to disdiminate on the basisof sex, age,hmdicap, ne, colc, rcligion, marital status,yeteru's status,national d cthnic cigin r sxual riaution. Yeast (\) describes the degree of water available infood. Water activityinfoods ranges Yeasts are single cell fungi (plants without ehlo- from 0 to 1.0. Water activity for various foods is listed rophyll) with various shapeswhen viewed under a in Table 1. microscope.Yeasts are undesirable when they cause Table l. pH values, A* vdues of common foode. spoilage in foods such as jams, jellies, , sauerkraut, and beverages.However, gas produced pHrange A* range by yeast causesbread to rise and the production of Fmits, fresh (most) 2.8-4.6 0.97-l-.0 beer. Melons 5.2-6.7 Juices 2.2-3.5 0.9? Vegetables, fresh, canned (D (low-acid) 4.8-7.0 0.93-1.0 Tomatoes 4.1-4.6 0.93-1.0 Meats-fresh 5.3-6.4 0.9&1.0 5.5-6.4 0.95-1.0 (D Fish 6.2-7.L 0.95-1.0 Processed neatsy'fish Ham 5.9-7.0 0.85-0.90 Lunch meat 6.2 0.93-0.97 Canned meat 4.6-5.2 0.9$0.9? T\lna 5.9-6.1 0.93-0.97 U- 6.0-9.5 0.90 Yeast Egg" I 0.98-0.99 Milk 6.5-7.O Cheese 4.5-5.4 0.6&0.98 Mold Butter 6.1-6.4 9.75-0.84 Yogurt 9.7-4.4 0.9&0.98 Flour 0.67-0.84 Mold growth on foods appears fazzy or cottony Pasta <{.60 and may be colored.Molds are multicell microorgan- Cake 0.90-0.94 isms which consist of frlaments called hyphae. The Breads 5.0-6.0 0.94-0.96 whole mass ofhyphae is called the mycelium. Hyphae CereaVCrackers 0.10-0.20 \- may be growing below the surface of the food. Some Snack chips <{.60 molds doproduce toxic substances(mycotoxins). Use- Jams, jellies 3.0-5.0 0.60-0.85 ful molds allow production of blue cheese. Honey 3.0-5.0 0.60-0.85 Mayonnaise 3.0-3.8 Salad dressings 3.7 Vinegar 2.9 are ultramicroscopic particles which re- quire a to replicate. is a virus which Most bacteria cannot grow at a water activity of can be transmitted to humans via food and cause less than 0.91,.Yeasts can grow at water activities as foodborneillness. low as 0.87. Molds do not grow at water activities of less than 0.80. Water activity ranges are given for Growth Factors of Microorganisms bacteria in Table 2. "tie" Sugar and added to foods up water and All microorganisms require moisture, a food lower the water activity. When enough sugar or salt source,enough time, and suitable temperatures to is added to a food, the water activity will be lowered grow and multiply. to a level that will prevent microorganisms from growing. In general, bacterial glowth is inhibited by Moisture. Microorganisms are composedof about the addition of 5-L5Vosalt. Yeasts and molds can 80Vowatnr which is an essential requirement for tolerate up to ISVosalt. To inhibit mold growth, 65- microorganismsto grow. Moisture requirementsvary TAVosugar must be added. The addition of up t'o 50Vo for each speciesof microorganism. In general bacte- sugar will inhibit bacteria and yeast growth. rianeed more waterthanyeasts. Yeastsrequire more Somemicroorganisms are tolerant of certain con- water than molds to grow. ditions. Halophilic (salt-liking) microorganisms re- If water is not available for microorganisms in a quire salt to be present for the organism to grow. food product, the microorganisms may remain but Osmiop hilic ( sugar-liking) microorganism s, usually will not grow and multiply. Certain components in yeasts, grow best at high concentrations of sugar. v foods will make water unavailable for microorgan- Xerophilic (dry-liking) microorganisms can grow with isms. limited moisture. Table 2. pH and A* ofbacteria. MICROBIAL GROWTII CI'RVE

Bacteria pHrange Minimum A*

Staphylocecus dureus 4.3 - 9.0 0.83 3.8 - 9.0 0.95 5.0 - 8.9 0.96 C lostridium perfr i ngens E - + botulinwn 4.8 8.5 0.95 ' cereus 4.4 -9.3 0.93 tr rR Listerio monocytog enes 4.5 - 8.0 unknown Y er sinia enterocolitica 4.4 - 9.6 o.97 Canrpylobacter jejuni 4.9 - 9.0 unknown cholerac 6.0 - 11.0 0.97 E s ch er ia hi.a col i 0757 :H7 unknown unknown firne

Figure 1. Bactcrial growth surve. Food. Microorganisms need a source of nutri- ents to gtow and multiply. Individual microorgan- isms have specific requirements. AII microorganisms rather than number. T'his is called the lag phase. need an energy source. Carbohydrates provide the The next phase is the log phase where growth is main source of energy. Protein is also required by rapid. The third phase is called the stationary microorganisms for growth. Other nutrients vary phase. During this phase the number of microbial accordingto the species.Food from plants and ani- cells produced equal the number of microbial cells mals provide these nutrients for microorganisms to that are dying; the total number of microorganisms grow. remain the same. When the nutrients are depleted, the growth rate decreases.This is the phase. Time. When microorganisms have suitable con- Microorganisms grow be st within ditions, reproductive growth will occur. Microorgan- Ternperatune. ranges. Bacteria are classified isms reproduce by dividing into two parts. Under certain temperature groups, on the temperature at favorable conditions (enoughmoisture andfood avail- into three depending gtows best. able with the desired temperature), this division may which the bacteria * (coldliking) bacteria occur every 20 to 30 minutes. The time for a microbial Psychrophilic - range 32-77"F cell to double is called the generation time. Table 3 Growth - 68-77"F illustrates the large numbers which can result from Optimum temperature * (middle-liking) bacteria one microbial cell under ideal conditions multiplying Mesophilic - range 68-110'F ever 20 minutes. Growth - Optimum temperature 68-113'F x Thermophilic (heatliking) bacteria Table 3. Bacterial multlplication. - Growth range 113-158"F Time Number - Optimum temperature 122-131"F lnminutee mlcroorganisms The bacteria which cause foodborne illness in humans grow best at body temperature (98.6"F - 0 1 mesophilic bacteria). Psychropbilic bacteria are re- 20 2 sponsible for in the refrigerator. 40 4 Psychrotrophic bacteia can grow at refrigerated (l 60 hour) I temperatures and grow rapidly at room tempera- 80 16 tures. Another type of bacteria is thermoduric (heat 100 32 These bacteria can survive but do 120(2 hours) u tolerant) bacteria. r.40 123 not grow and multiply at high temperatures. 160 2rc Yeasts thrive best at room temperatures, but are 180(3 hours) 512 capable of survival for many weeks at temperatures 2W 102/4, well below freezing. Moderate heat (140'F) for a few 2n zo4a minutes will destroy yeast. 420(7 hours) 2,097,L52 Molds will flourish at room temperatures, but can grow from 32-L08"F. Microorganisms do not grow at a constant rate. Many microorganisms can survive freezing tem- Figure l illustrates the growth curve for a microor- peratures but cannot grow or rnultiply at low tem- ganism. Initially the microbial cells gtow in size peratures. Oxygen. Microorganisms differ in their require- food containing live bacteria which grow and estab- ments for oxygen.Aerobic bacteria require oxygen lish themselves in the human intestinal tract. to survive. Anaerobic bacteria grow in the absence Foodborne intoxication is caused by ingesting ofoxygen. Oxygen is toxic to these types ofbacteria. food containing formed by bacteria which Facultative anaerobes grow in the presenceor the resulted from the bacterial growth in the food item. absenceofoxygen, preferring oxygenbut capable of The live microorganism does not have to be con- growth without oxygen. sumed. Yeasts grow in the absenceof oxygen,but multi- For a foodborne illness to occur, the following ply faster in the presence of oxygen. Molds are eonditionsmust be present: aerobicand require an abundant sourceofoxygen to . The microorganismor its toxin mustbe present grow. in food. o The food must be suitable for the microorgan- pH. The acidity or alkalinity of a food affects the ism to grow. ability of a microorganism to survive and grow. pH is o The temperature must be suitable for the mi- a measure of the acidity or alkalinity of a food. Most croorganism to grow. microorganismsprefer a pH near neutral (pH = 7.0). . Enough time must be given for the microor- A list offoods with their pH range is given in Table 1. ganism to grow (and to produce a toxin). The general pH range of microorganisms is given in o The food must be eaten. Table 2. The most common symptom associated with foodborneillnesses is . Each pathogenicmi- Light. Microorganisms usually grow best in the croorganismhas its set of characteristic symptoms. dark, although it is not a requirement. Ultraviolet Table 4lists most of the pathogenicmicroorganisms light is lethal to microorganismsand may be used in with their growth ranges, nature of the illness each some sterilization processes. causes,and the time required for the symptoms to occur (). The table also lists the Foodborne Illnesses foods commonly associated with each pathogenic microorganism and control measures to prevent or "I must have the flu bug," is a common explana- eliminate growth of that microorganism in food. tion for gastrointestinal upset. Flu-like symptoms The severity ofthe foodborneillness dependson are characteristic of many foodborne illnesses. In- the pathogenicmicroorganism or toxin ingested,the stead of the flu, food contaminated with pathogenic amount of food consumed (dose), and the health microorganisms may have been the cause of many status of the individual. For individuals who have stomachupsets. immunocompromised health conditions, or for the It is estimated that more than Sl million casesof aged, children, or pregnant women, any foodborne foodborne illnesses occur each year in the United illness may be life-threatening. States. Many of these illnesses are misdiagnosedas the flu and are not reported. Pathogenic (disease References causing)microorganisms in food are the prime cause of foodborneillnesses. Frazier, W.C. and Westhoff, D.C. 1988. Food Microorganisms that cause disease are found Microbiolory 4th Edition. McGraw-Hill Inc., New naturally in the environment. Foods contaminated York, N.Y. with pathogenicmicroorganisms usually do not look IAMFES. 1991. Procedures to Implement the bad, taste bad, or smell bad. It is impossible to Hazard Analysis System. In- determine whether a food is contaminated with patho- ternational Association of Milk, Food and Environ- genic microorganisms without microbiological test- mental Sanitarians, Inc. Ames, Iowa. ing. To avoid potential problems in foods, it is very important to control or eliminate these microorgan- IF'I Scientifrc Status Summary. 1988. Bacteria isms in food products. Associatedwith FoodborneDiseases. Food Technol. Pathogenic microorganisms can be transmitted 42:181-200. to humans by a number of routes. These routes "New'food- include air, water, direct person-to-personcontact, Ryser,E.T. and Marth, E.H. 1989. and food. Some pathogenic microorganisms can be borne pathogensof signifrcance.Am. J. transmitted to foodby animals, or by contactwith the Diet. Assoc.89:948-956. soil, or by contact with contaminated surfaces and equipment. USDA-FSIS. 1989. FSIS Facts, Preventable Diseaseswhich result from pathogenic microor- Foodbornelllness. Bulletin # FSIS-34.United States ganisms are of two types: and intoxieation. Department of Agriculture, Inspection Foodborne infection is causedby the ingestion of Service.Washington, DC. Table 4. Pathogenic Microorgo-isns and Foodborne lllness

Orgonisla Growth Foodbome S5rmptoms of Incubation lmplicated foods Control neasures range illness illness period Staphyluoccus 45 - 118"F Staphylo- abdominal pain, 1-6hs salads, cream filled 1 Properhand washing \-. dureus coccal , voniting, pastry 2. Prompt refiigeration (Staph) (7 - 48.c) Intoxication diarrhea in shallow containers

Salmonella 43 - 115"F SaLnonellosis abdominal paia, 6-48 hrs raw or undercooked 1. Thomughly cooked Infection diarrhea, nausea, meats and poultry, meat, poultry, eggs (6 - 46"C) chills, fever eggs, unpasteurized 2. Pasteurize milk milk 3. Prevent cross- contnmination

Clostridiwn ffi -722ry Clostridium diarrhea, sldeminal 8-22 brs meat, meat products 1. Keep hot foods above perfringens Perfringens pain & poultry 140"F (15- 5o"C) Infection/ 2. Keep cold fmds below Intoxication 4()"F 3. Properly cook meat and poultry products 4. Reheat to 165"F thoroughly

Clostridium 50 - 122"F double vision, 12-48 hrg canaed foods 1. Properly processed botulinum Intoxication diffrculty in speaking, canned foods types A & B (10- 50"c) swallowing, and breathing type E 38 - 113"F (can be fatal) fish 1. Properly processedfrsh (3.3- 45"C)

Bacillus cereus 42- 122dF Bacillus diarrhea, sldeminal &L6 hrs rice & rice dishes; 1. Cook fmd properly cereus pqin, nausea, meat & meat 2. Cool foods quickly (5 - 50"C) Intoxication pmducts; seasonings, 3, Prevent cross- spices contamination

Listeria 34" - 113"F meningitis, 2days-3 vegetables, milk, 1. Pasteurize milk naonocytogenes abortion, fever, weeks cheeses, fermented 2. Prevent cross- \- (1" - 45"C) headache, nausea, meats contamination vorriting 3. Cook fmds propedy

Yersinia 32"- 113"F Yersiniosis enterocolitis; 1-3 days raw milk, chocolate 1. Pasteurize milk enterocolitica may mimic acute milk, water, pork 2. Prevent cmss- (0"- 45"C) appendicitis and other raw meats contamination with raw products 3. Cook foods properly

Campylobacter 86" - 117"F f,smFylo- diarrhea, 1-7 days 1srf,milk, cake icing, 1. Pasteurize milk jejuni bacteriosis abdoninal eggs, poultry, raw 2. Prevent cmss- (30"- 4?"c) cramping, fever beef, water contamination 3. Cmk fmds properly

Vibrio cholerae 59" - 108"F Vibrio watery diarrhea, 12hrs-5 water, crab, shrimp, 1. Prevent cross- Infection vomiting, chills, duys oysters contamination with raw (15. - 42.C) fever pmducts 2. Thoroughlycook shell- fish, including oysters

Escherichia unknown* 113"F severe abdominal 2-4 days gmund beef, raw 1 Pasteurize milk coli cramps, bloody milk, chicken 2. Thomughly cook meat 0157:H7 (unknown - 45'C diarrhea. 3. Prevent cross- *No growth vomiting, naus€a "ontcmination with raw when incubated products at 50"F (lo'C) for 48 hrs

Trichinello Tridrinosis fever, muscular &15 days pork, wild game l. Thoroughly cmk to spiralis pqin, weakness, 160"F swelling amund eyes

\, Hepatitis A Hepatitis letharry, loss of 2-6 weeks any fmd 1. Proper hand washing appetite, nausea, 2. Personal hygiene vomiting fever, practices

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