Chapter 4Biological Hazards

Biological Hazards

Acquired from disease-causing microorganisms and the poisonous toxins they may produce.

They are far the most dangerous foodborne hazard in the food service and food retail businesses.

• These include harmful microorganisms seen only under the microscope such as:

– Bacteria

– Viruses

– Parasites

– Molds

– Yeast

– And the biological substance prion, a protein molecule

– Other living organisms such as:• Insects• Rodents• Farm animals• Domestic pets• Birds• Fish and plants

Biological Hazards

Foodborne illnesses:

• Generally classified as:

– Infection

– Intoxication

– Toxin-mediated infection

Infection

• Occurs when a living microorganism is ingested as a part of food.

• After ingestion, the microorganisms attach themselves to the gastrointestinal tract and begins to grow.

• An example of a bacterial infection is Salmonella spp.

• This can lead to common foodborne illness symptoms like diarrhea.

• In some, instances, the microorganisms may be carried by the bloodstream from the gastrointestinal tract to the other parts of the body.

• Foodborne viruses and parasites are good examples of microorganisms that can cause infection.

Intoxication

• Arises when a living microorganisms that grows in food produces a toxin.

• The food is then ingested and the toxin itself causes the illness.

• Some examples of bacteria that cause food intoxication are Clostridium botulinum and Staphylococcus aureus.

• An intoxication may also occur due to consumption of a toxic chemical such as a cleaning chemical.

Toxin-mediated infection

• Takes place when a living microorganism is consumed and the ingested microorganisms produces a toxin in the body that leads to illness.

• An example of a microorganism that produces toxin in the body is the Clostridium perfringens.

Types of Microorganisms:

1. Beneficial Microorganisms – Are found in food production. Examples of these

microbes are those used in making bread, beer, yoghurt, and cheese.

2. Harmful Microorganisms– Spoil food and cause diseases.

Microbial Forms:

1. Bacteria

2. Viruses

3. Parasites

4. Fungi

5. Molds

6. Yeast

7. Prions

Bacteria

• Of all microorganisms, bacteria provide the most common threat to food safety.

• Bacteria are single-celled organisms and can cause illnesses in two ways:– Pathogenic (infectious; disease-causing) bacteria.– Toxigenic (poisonous) bacteria produce harmful

toxins

• Most bacteria exist in a vegetative state, the cells grow, reproduce , and produce waste just like any other living organism.

• However, some bacteria are able to produce protective, thick-walled structures called spores.

• Spores do not reproduce, but they enable the bacteria to survive some cooking and freezing temperatures and the destructive effects of cleaning and sanitizing solutions.

• They even survive when there is not enough food.

Classification of Bacteria:

• Spoilage bacteria – break down foods making them look, taste, and smell bad. They reduce the quality of food to unacceptable levels. When this happens, the food will have to be thrown away.

• Pathogenic bacteria – are disease-causing microorganisms that can make people ill if they or their toxins are consumed through food.

Bacterial Growth:

• Bacteria reproduce when bacterial cell divides to form two new cells.

• This process is called binary fission.

• The reproduction of bacteria and an increase in the number of organisms are referred to as bacterial growth.

• This means that during each growth generation, each cell gives rise to another cell.

• The generation time, or the time for cell numbers to double is typically 20-30 minutes but can also be as quick as 15 minutes.

• Under optimal conditions, this means that a single cell can generate over 1 million cells in just five hours.

• Proper storage and food handling help prevent bacterial growth.

Number of cells

1 2 4 16 > 1000 >1 million

Time 0 15 minutes

30 minutes

1 hour 3 hours 5 hours

Phases of Bacterial Growth:

• Lag Phase

• Log Phase

• Stationary Phase

• Death Phase

Lag Phase

• Growth is slow at first, while the microorganisms acclimate to the food and nutrients in their new habitat.

Log Phase

• Once the metabolic machinery is running, microbes start multiplying exponentially, doubling in number every few minutes.

Stationary Phase

• As more and more microbes are competing for dwelling food and nutrients, the booming growth stops and the number of bacteria stabilizes.

Death Phase

• Toxic waste products build up, food is depleted and the microorganisms begin to die.

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Bacterial Growth Requirements

• Remember the acronym FATTOM:

• Food

• Acidity

• Time

• Temperature

• Oxygen

• Moisture

Food

• Microorganisms like all living things need food to grow.• The presence of a suitable food supply is the most

important condition that affects bacterial growth.• The food must contain the appropriate nutrients needed

for growth.• Bacteria generally prefer foods that are high in protein

like meat and dairy items.

Acidity• Disease-causing bacteria grow best at acidity levels

equivalent to pH 4.6 to 7.5.• The term pH is used as a symbol to designate the food’s

degree of acidity.• The scale for measuring pH is from 0 to 14.• A pH of 7.0 is neither acidic nor basic and is considered

neutral food. • A pH less than 7.0 indicates that the food is acidic. A pH

range greater than 7.0 refers to basic food. (Examples of alkaline foods are olives, egg whites, or soda crackers).

• Very acidic food (pH below 4.6), like lemons, limes and tomatoes, cannot support the growth of disease-causing bacteria.

• Pickling fruits and vegetables by adding acids, such as vinegar, lowers the pH of the food and slows down the rate of bacterial growth.

• High alkaline foods are also unfavorable for the growth of microorganisms.

• Most bacterial growth is inhibited at an acidic environment or at a pH of below 4.6.

• The optimum growth pH for yeast is from 4.5 to 6.0 while molds require a pH from 3.5 to 4.0.

Time• Because bacteria grow rapidly,

it does not take long before many cells are produced.

• A rule of thumb in the food industry is that the bacteria need about four hours, inclusive of the time food is between 50C to 600C, to grow to numbers high enough to cause illness.

• Remember, a single bacterial cell can produce 1 million cells in just five hours under ideal conditions.

• It is very important not to give bacteria an opportunity to multiply.

• Proper storage and handling of foods help prevent bacteria from multiplying.

Temperature

• Temperature is probably the most important factor that affects growth of bacteria in food.

• Most disease-causing bacteria grow within a temperature range of 50C to 600C.

• This is the range where microbial growth and reproduction are at their peak.

• This is commonly referred to as the Temperature Danger Zone.

Classification of microorganisms according to temperature requirements:

• Psychrophiles

• Mesophiles

• Thermophiles

Psychrophiles

• These cold-temperature loving microorganisms thrive in a temperature range of 00C to 210C.

• They are especially troublesome because they are capable of multiplying at both refrigerated and room temperatures.

• Most psychophysics bacteria are spoilage organisms, but some can also cause diseases.

Mesophiles

• These middle-range bacteria grow at temperatures between 210C and 430C, with the most rapid growth at human body temperature.

Thermophiles

• Heat-loving microorganisms, they grow best at temperatures above 430C.

• All thermophilic bacteria are spoilage organisms

Oxygen

• Bacteria require different amounts of oxygen to grow.

• Some require a lot of oxygen (aerobic), while others cannot tolerate oxygen (anaerobic) at all.

• Those belonging to genus Clostridia require the complete absence of free oxygen to grow. Free oxygen is toxic for this group of microorganisms.

• Anaerobic bacteria grow well in vacuum package foods or canned foods where oxygen is not available.

• Anaerobic conditions also exist in the middle of cooked food masses such as stock pots and baked potatoes, or in the middle of a roast or ham.

• Some bacteria only grow within a narrow oxygen range (microaerophilic), usually three to six percent oxygen levels. While others can grow with or without oxygen (facultative anaerobes).

• Most foodborne-causing microorganisms are facultative anaerobes.

• Controlling oxygen conditions may be an effective way to prevent foodborne illnesses. However, even without any oxygen, some disease-causing bacteria can still find the conditions suitable for growth.

Moisture• Just like most forms of life, moisture is an

important factor affecting bacterial growth, which is why humans have been preserving food for thousands of years by drying them.

• Scientists have determined that bacterial growth is greatly influenced by the amount of available water which is designated with the symbol aw

• Aw is water not bound to the food and is

available for bacterial growth.

• It is measured on a scale from 1 – 1.0.

• Disease-causing bacteria can only grow in foods with an aw greater than .85

• In the Philippines, because of high relative humidity, the top layer of some exposed food can hydrate and make it moist enough for microorganisms to grow.

• Good packaging and the control of environmental relative humidity which can be achieved with air-conditioning, dehumidifier, or even adequate ventilation, can prevent this from happening.

• There are many preservation process that can be done to reduce the aw (below 0.85) of foods, including sun drying and freeze drying.

• The addition of salt or sugar can also be used to reduce available water. However, very high amounts of these substances need to be used, rendering this method impractical.

Bacterial, Viral, and Parasitic Foodborne Hazards

• Biological hazards are of the greatest concern to food service and food retail operators.

• The have been classified as:• Spore-forming bacteria• Nonspore-forming bacteria• Viruses, and;• Parasites

Foodborne Illnesses Caused by Bacteria:

Spore-Forming Foodborne Bacteria

• The following group of bacteria can produce a spore structure that allows a cell to withstand environmental stress such as cooking, freezing, salting, drying, and pickling.

• Generally, bacterial spores are not harmful if ingested. However, if conditions of the food are changed, permitting the spore to turn into a vegetative cell, the vegetative cell can grow in the food and cause illness if eaten.

• Spore-forming bacteria are generally found in ingredients grown near the soil like vegetables and spices.

• They can be particularly troublesome in food retail-type environments because they can survive on foods.

• When conditions are improved, for instance, adding dried spices to a beef stew mixture, spores can become vegetative state.

• Spores are mostly likely to turn vegetative when:– Heat-shocked (heating causes spores to

change)– Optimum conditions exist for growth (high

protein and high moisture)– Temperatures are in the food temperature

danger zone or between 50C to 600C and– The amount of time the food is in the danger

zone is four hours or more.

• To keep spore-forming bacteria from changing to the dangerous vegetative state, it is critical that hot foods be maintained at 600C or higher and cold foods be kept at less than 50C.

• Cooking, reheating, and cooling of foods should also be done as quickly as possible to limit bacterial growth.

• Important spore-forming pathogens in the food retail industry include: Bacillus cereus, Clostridium perfringens, and Clostridium botulinum.

Nonspore-Forming Foodborne Bacteria

• The following groups of bacteria are not capable of producing a spore structure; they are always in the vegetative state.

• Compared to spore-forming bacteria that are in the spore state, vegetative cells are easily destroyed by proper cooking.

• There are numerous examples of nonspore-forming foodborne bacteria that are important in the food retail industry.

Foodborne Illnesses Caused by Viruses:

• Foodborne viruses differ from foodborne bacteria. Viruses require a living host (animal, plant, or human) to grow and reproduce.

• Unlike bacteria, they do not reproduce or grow in foods. However, the consumption of even a few particles is enough for a person to experience an infection.

• Viruses are usually transferred from one food to another, e.g. from a food handler to a food, or from a water supply to a food.

• A PHF is not needed by a virus to survive.• There are viruses common in food retail preparation:

Hepatitis A, Norwalk virus, and rotavirus

Foodborne Illnesses Caused by Parasites:

• Foodborne parasites are among the common foodborne biological hazards.

• Parasites are microscopic creatures that need to live on or inside a host to survive.

• Parasites can be found in irrigation water, animal feces, muscle tissues of improperly fed cattle and swine, and fish muscles.

• Human can become infected when undercooked meat and fish are consumed.

• There are several examples of parasites that can come in contact with food and cause foodborne illnesses.

• Parasitic infection is far less common than bacterial or viral foodborne illnesses.

Foodborne Illnesses Caused by Fungi:

• A fungus is a eukaryotic organism that is a member of the kingdom Fungi.

• Fungi are heterotropic organisms that possess a chitinous cell wall.

• The majority of its species grow as multicellular filaments called hyphae forming mycelium; some fungal species also grow as single cells.

• Sexual and asexual reproduction occur commonly through spores which are often produced on specialized structures or in fruiting bodies.

• Yeasts, molds, and mushrooms are all examples of fungi.

• Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi.

• They perform as essential role in all ecosystems in decomposing organic matters and indispensable in nutrient cycling and exchange.

• Some fungi become noticeable when fruiting, either as mushrooms or molds.

• Many fungal species have long been used as a direct source of food, such as mushrooms and truffles, and in the fermentation of various food products, such as wine, beer, and soy sauce.

• More recently, fungi are being used as sources of antibiotics used in medicine and various enzymes, including cellulases, pectinases, and proteases, which are important for industrial use or as active ingredients of detergents.

• However, many fungi produce bioactive compounds called mycotoxins that are toxic to animals and humans.

• Several species of fungi are significant pathogens of human and other animals.

• They are also the causes of diseases of crops (e.g. rice blast disease) and food spoilage, thereby proving that they have a large impact on human food supply and local economies.

Foodborne Illnesses Caused by Prions:

• Prions refer to proteinaceous infectious particles (PrP).

• They are small glycosylated protein molecules found in brain cell membranes.

• Prion disease, also called transmissible spongiform encephalopathies (TSEs), create spongiform pathological changes in the brain, resulting in encephalopathy or brain damage.

• Prion diseases are fatal neuro-degenerative disorders in humans and other animals.

• Mad Cow Disease is the best known bovine spongiform encephalopathy (BSE).

• An infected cow is observed to be disoriented, irritable and unable to stand or walk properly.

• Most cases in Great Britain occur in dairy cow’s between three to six years of age. Milk production decreases and the animals show nervousness, aggression, abnormal posture, poor coordination, and difficulty in rising.

• BSE is a chronic, degenerative disease that affects the central nervous system of cattle.

• It also affects sheep, the disease being called scrapie.

• The incubation period takes months or years and the illness is progressively debilitating.

• There is no treatment and the infected animal dies.

• BSE is believed to affect goats as well. This is of no interest to consumers in the Philippines who relish calderetang kambing and other indigenous cooking of goat meat.

• The first case of BSE in humans was observed in 1989 and was believed to have been transmitted from beef to humans when contaminated bovine offal was used as animal feed.

• Offal is made from the remains of butchered animals. This practice is now banned.

• Creutzfeldt-jacob Disease (CJD) is a rare and fatal neurodegenerative disease in humans.

• People affected are usually between 50 to 75 years old. The etiology is unknown.

• Typical clinical signs and symptoms include a rapidly progressive dementia.

• A neuropathlogical examination reveals cortical spongiform changes giving CJD another name – spongiform encephalopathy.

• Majority of cases are sporadic (about 85%) while 10 – 15% are familial.

• An inherited abnormal gene causes the latter.

• In the United Kingdom, with a population of about 58 million, there are only a few death a year caused by genetic CJD.

• The sporadic type occurs all over the world at a rate of about one case per million per year.

• The cause of sporadic CJD remains uncertain.

• However, the most favored theory suggests that the normal prion protein in the brain undergoes a spontaneous change to an abnormal form that results in disease.

How to Control Microbial Growth?

• Any method to slow down the pathogenic organism, or totally kill them, based on the application of the principles of FATTOM will prevent/reduce the incidence of foodborne illnesses.

• Food preservation techniques, whatever traditional or newer ones, are effective means of prolonging the shelf life of foods, and improving palatability qualities in some cases because of their effects on microbial life and growth.

Methods on How to Control Microbial Growth

• Application of Heat• Application of Low Temperatures• Controlling pH Conditions• Reduction of Free Oxygen• Reduction of Available Water• Role of other Chemicals• Safe and Sanitary Food Handling

Application of Heat• Adequate heat (proper temperature and period of exposure) kills

microorganisms by changing the physical and chemical properties of their proteins.

• As structural proteins and enzymes are altered, the organisms will die.

• Blanching and canning are examples of applying heat.

• Modern commercial canning processes are complex and include a sterilization process designed to eliminate the most resistant bacterial spores, especially those of the genera Clostridium and Bacillus.

• Boiling destroys nonspore-forming microorganisms rapidly.

• To ensure safe drinking water, bring the water to a boil and continue boiling it for a few minutes.

• In cooking meat, fish, poultry, eggs and other foods, follow their suggested time and temperature for cooking and use a reliable thermometer to measure recommended internal temperatures.

Application of Low Temperatures

• This category includes refrigerating and freezing.

• Modern refrigeration at 400F will stop or slow down the growth of most microorganisms, although they can still survive at refrigeration temperatures.

• Storage periods in refrigerated conditions for specific kinds of foods have to be monitored to prevent food spoilage.

• It is best to use refrigerated foods as soon as possible and not to wait for the maximum storage time.

• Keep foods covered to avoid cross-contamination and drying.

• Label and date foods, especially leftovers.

• Defrost regularly and do not crowd the food containers to allow air to circulate.

• Check the temperature with a refrigerator thermometer.

• Freezing halts the growth of all microorganisms. Frozen foods should be kept solidly frozen.

• Check your freezer with an accurate thermometer.

• One way to detect if your home freezer is working well is to check the ice cubes and a brick of ice cream. These should be completely frozen, attaining a temperature of - 180C or 00F throughout the product.

• Avoid temperatures higher that 50F or – 150C.

• Be sure to date food packages and use moisture and vapor-proof packaging materials.

Controlling of pH Conditions

• Lowering the pH of a food to a level where most microorganisms cannot survive (<4.6) can be accomplished by fermentation or acidification with ingredients like vinegar, lemon juice or citric acid.

• Fermentation refers to the anaerobic and aerobic metabolism of carbohydrates by microorganisms.

Reduction of Free Oxygen

• Some pathogenic microorganisms require free oxygen for growth.

• Particle or complete removal of available oxygen will therefore retard their growth and their metabolic activities which are harmful to humans.

• Examples of processes that reduce free oxygen include vacuum-packaging, modern canning with hermetic seals, and modified atmospheric packaging (MAP).

• Another method to reduce the amount of available oxygen for bacterial growth is to coat the foods with wax or other edible coatings, as done with fresh fruits and vegetables in the US.

• Consumers should be aware that some of these coatings are regarded as food additives.

Reduction of Available Water

• Drying is one of the oldest methods of food preservation.

• Modern techniques of dehydration still apply the same principle of depriving the microorganisms of free or available water for growth.

• The amount of free water or water activity needed by molds, yeasts, and bacteria varies.

• Molds require the least water, which is why they can still grow on dried fruit, jam, and jelly whereas bacteria cannot.

• Most dry foods are relatively stable. However, they should still contain over 20% water so kitchen shelves should not be close to a stove or any source of heat.

Role of Other Chemicals

• Besides the chemical additives mentioned in lowering the pH of food, other agents that may retard microbial growth are nitrates, nitrites, salt, and sugar.

• Antioxidants and antibiotics also affect microorganisms or reduce microbial growth.

Safe and Sanitary Food Handling

• Bacteria and other microorganisms cannot move by themselves.

• They need carriers to be transmitted to other places, which could be living and nonliving habitats.

• The most common carriers of foodborne illnesses are food handlers.

• Kitchen personnel are given an orientation that includes personal hygiene, grooming, physical safety, etc.

• The food handler must likewise undergo an extensive training on food safety and sanitation which includes food preparation, storage, service, and other job-related sanitary practices.

• Animals and insect-borne diseases are transmitted to humans by exposure to the infected animal or insect.

• These include farm animals, domestic pets, marine organisms, and household pests.

• How each group transmits pathogenic organisms and how their transfer and conditions for growth should be controlled.

Prevention of Foodborne Illnesses:

• Most cases of foodborne illnesses can be prevented through proper cooking or processing of the food.

• In addition, because bacteria multiply rapidly between 400F and 1400F, food must be kept out of this temperature range.

Follow these tips to prevent harmful bacteria from growing in food:

• Food Preparation Stage

– Refrigerate food promptly. If prepared food stands at room temperature for more than two hours, it may not be safe to eat anymore. Set your refrigerator at 400F or lower and your freezer at 00F.

– Prevent cross-contamination. Bacteria can spread from one food product to another throughout the kitchen and can get onto cutting boards, knives, sponges, and counter tops. Keep raw meat, poultry, seafood, and their juices away from ready-to-eat foods.

– Handle food properly. Always wash your hands for ate least 20 seconds with warm, soapy water before and after handling raw meat, poultry, fish, shellfish, or eggs. Wash your hands after using the bathroom, changing diapers, or touching animals.

– Wash utensils and surfaces before and after use with hot, soapy water. Better still, sanitize them with diluted bleach – one teaspoon of bleach to one quart of hot water.

– Wash sponges and dish towels weekly in hot water in the washing machine.

• Food Processing Stage (Cooking)

– Cook food with the appropriate internal temperature: 1450F for roasts, steaks, and chops of beef, veal, and lamb. 1600F for pork, ground veal, and ground beef; 1650F for ground poultry; and 1800F for whole poultry. Use a heat thermometer to be sure. Foods are properly cooked only when they are heated long enough and at a high enough temperature to kill the harmful bacteria that causes illnesses.

• Food Storage Stage

– Keep cold food cold and hot food hot.– Maintain hot, cooked food at 1400F or higher.– Reheat cooked food to at least 1650F.– Refrigerate or freeze perishables, produce,

prepared food, and leftovers within two hours.– Never defrost food on the counter. Use the

refrigerator; cold running water; or the microwave oven.

– Never let food marinate at room temperature, refrigerate it.

– Divide large amount of leftovers to small, shallow containers for quick cooling in the refrigerator.

– Remove the stuffing from poultry and other meat immediately and refrigerate it in a separate container.

– Wash all unpackaged, and packaged and not marked “pre-washed,” fruits and vegetables, under running water just before eating, cutting, or cooking. Scrub firm produce, such as melons and cucumber, with a clean produce brush. Dry all produce with a paper towel to further reduce any possible bacterial growth.

– Do not overcrowd the refrigerator. Cool air must circulate to keep food safe.

Acknowledgment:

Textbook:

Food Safety and Sanitation

By:

Mary Jean C. Ang

And

Hannah A. Balanon

C & E Publishing, inc., 2010 edition

End of Presentation