NUFS 427 Lecture 8 Biological Hazards in Food IV

What is a biological hazard in food?

A microorganism, parasite, or toxin produced by organisms that poses a threat to human health.

How common is foodborne illness in Canada each year?

About 1 in 8 Canadians (4 million people) get sick each year, causing 11,500+ hospitalizations and ~240 deaths.

What are some major causes of foodborne illness in Canada?

Norovirus, Listeria, Salmonella, E. coli O157, and Campylobacter.

What are the main types of biological hazards in food?

Microorganisms, parasites, and biological toxins.

What is a parasite?

An organism that lives on or inside a host and depends on the host for food, shelter, or reproduction, usually causing harm.

What are the two major groups of foodborne parasites? Give examples.

Protozoan parasites: Cryptosporidium, Entamoeba histolytica, Toxoplasma gondii, Cyclospora cayetanensis

Parasitic worms: Taenia solium, Trichinella spiralis, Anisakid worms

What is Cryptosporidium and what disease does it cause?

An obligate protozoan parasite that causes the gastrointestinal infection cryptosporidiosis.

What is the difference between Cryptosporidium hominis and C. parvum?

C. hominis: primarily infects humans

C. parvum: infects humans + ruminants (e.g., cattle) and is zoonotic

How is Cryptosporidium transmitted and what are common sources?

Primarily fecal-oral, especially through contaminated water or human/animal feces. Less common food vehicles include raw milk and fresh produce.

What are Cryptosporidium oocysts and why are they a public health concern?

Oocysts are the infectious, environmentally resistant form. They are very small (~4-6 µm), resist routine chlorination, and can persist in water, soil, and on surfaces.

How can Cryptosporidium be controlled?

Heat, desiccation, and proper sanitation/hygiene.

How is Entamoeba histolytica transmitted, and what is its infective form?

Fecal-oral transmission through contaminated food or water. The infective form is the mature cyst, which is shed in human feces.

What symptoms can Entamoeba histolytica infection cause?

Symptoms range from mild diarrhea to severe colitis. Rarely, infection can spread outside the intestine and cause liver abscesses.

Why is Entamoeba histolytica a public health concern?

Extremely low infective dose

Prolonged cyst shedding

Cysts survive in moist environments

Relatively resistant to routine chlorination

How can Entamoeba histolytica be controlled?

Heat/pasteurization, desiccation, effective filtration, and good sanitation/hygiene.

What caused the 2026 iceberg lettuce outbreak, and what was the food vehicle?

Cyclospora cayetanensis (infective form = sporulated oocyst) linked to processed iceberg lettuce from central Mexico.

What was the impact of the 2026 Cyclospora iceberg lettuce outbreak?

Affected 21 U.S. states, with 12,883 cases, 570 hospitalizations, and 2 deaths.

What are the key food-safety lessons from the 2026 Cyclospora outbreak?

Fresh produce can transmit parasites, contamination can be difficult to control, and complex supply chains can amplify outbreaks.

What are the hosts of Taenia solium?

Pigs and humans.

How is Taenia solium taeniasis transmitted, and what symptoms does it cause?

Eating raw or undercooked pork containing larval cysts. Infection is often asymptomatic or causes mild gastrointestinal symptoms.

How is Taenia solium cysticercosis transmitted, and what can it cause?

Ingesting T. solium eggs through fecal-oral contamination. It can cause neurocysticercosis, a neurological disease commonly associated with seizures.

What is the key difference between taeniasis and cysticercosis transmission?

Taeniasis: ingest larval cysts in undercooked pork.

Cysticercosis: ingest eggs through fecal-oral contamination.

How can Taenia solium infection be controlled?

Thoroughly cook pork, good sanitation and hand hygiene, meat inspection, and prevention of fecal contamination of food and water.

What are prions and how do they cause brain damage?

Prions are misfolded proteins that cause normal brain prion proteins to misfold → prion accumulation/aggregation → formation of microscopic vacuoles in the brain.

Why are prion diseases sometimes called "slow virus diseases"?

They have a very long incubation period, although prions are proteins, not viruses.

What diseases are associated with prions in humans and cattle?

Humans: Creutzfeldt-Jakob disease (CJD)

Humans exposed to BSE agent: variant CJD (vCJD)

Cattle: Bovine spongiform encephalopathy (BSE)

Why are prions particularly difficult to control in food?

They are extremely stable and resistant to denaturation by typical food-processing methods, including normal cooking temperatures.

How can exposure to BSE (mad cow disease) lead to variant Creutzfeldt-Jakob disease (vCJD)?

Humans can develop vCJD after consuming food contaminated with the BSE prion agent, particularly tissues containing infectious prions.

Which cattle tissues are most important for preventing transmission of BSE prions through food?

High-risk tissues include the brain, spinal cord, and certain intestinal tissues, which are kept out of the human food supply.

What are the early symptoms of variant Creutzfeldt-Jakob disease (vCJD)?

Psychiatric/behavioral changes and painful, unusual sensory symptoms.

What neurological symptoms occur later in vCJD?

Poor coordination/unsteadiness, involuntary movements, progressive cognitive decline, and loss of mobility.

Is there a curative treatment for vCJD?

No. There is currently no curative treatment available.

What are the two main approaches to controlling biological hazards in food?

Safe product formulation

Safe process design

Why is safe product formulation important for controlling biological hazards? (Formulation)

It is the most important first step and should be researched and validated using appropriate control measures based on the product's intrinsic factors.

What is water activity (aᵥ), and how can it be reduced to improve microbial stability? (Formulation)

Water activity measures available water in food: aᵥ = P/P₀. It can be reduced by removing water (dehydration), adding solutes (salt/sugar), or otherwise making water unavailable.

How do pH and acidulants affect microbial growth in food? (Formulation)

pH, total acidity, and type of acidulant determine which microorganisms can grow. Short-chain organic acids can strongly inhibit microbial growth.

What is the important food-safety pH threshold? (Formulation)

pH ≤ 4.6 is an important food-safety threshold because growth of many important bacterial pathogens is restricted.

How can chemical food preservatives help control biological hazards? (Formulation)

They act as antimicrobial agents that inhibit or prevent microbial growth. Examples include organic acids, sulphur compounds, sodium nitrite, and nisin.

What is the antimicrobial role of short-chain organic acids? (Formulation)

They inhibit the growth of certain microorganisms and can therefore be used as food preservatives.

What are sulphur compounds used to control in foods? (Formulation)

Sulphur compounds can help control yeast spoilage in dried fruits and wine and bacterial spore growth in dehydrated foods.

What is sodium nitrite used for in foods? (Formulation)

It is a key antimicrobial in curing salts for meat, poultry, and seafood and helps reduce the risk of botulism in cured products.

What is nisin and how is it used as a food preservative? (Formulation)

Nisin is an antimicrobial produced by lactic acid bacteria that inhibits bacterial spores. It can be used in products such as pasteurized cheese spreads and liquid pasteurized eggs.

What are the three main areas to consider when designing a safe food process? (Design)

Destroy/eliminate microorganisms (kill step)

Prevent microbial growth and multiplication

Prevent contamination

What are the two main categories of kill steps used to destroy microorganisms? (Design)

Thermal: pasteurization, sterilization

Non-thermal: filtration, chemical disinfectants, UV light, ionizing irradiation, pulsed electric fields, cold plasma, high-pressure processing.

What is pasteurization? (Design-Thermal)

A thermal process at atmospheric pressure designed to destroy vegetative pathogenic microbial cells and viruses while minimizing nutritional and palatability changes.

Does pasteurization sterilize food? (Design-Thermal)

No. It reduces microbial numbers but does not destroy all microorganisms or spores, so other hurdles may be needed.

What additional hurdles can be combined with pasteurization? (Design-Thermal)

Refrigeration, reduced water activity (aᵥ), or pH reduction.

What microorganisms are generally destroyed by pasteurization? (Design-Thermal)

Vegetative pathogens such as Salmonella, Listeria monocytogenes, E. coli O157:H7, Mycobacterium bovis, and Coxiella burnetii, plus most spoilage microorganisms.

What biological hazards can survive pasteurization? (Design-Thermal)

Bacterial spores (B. cereus, C. botulinum, C. perfringens), some heat-resistant viruses, and heat-stable toxins.

Which toxins are heat-sensitive vs. heat-stable during pasteurization? (Design-Thermal)

Heat-sensitive: B. cereus diarrhoeal enterotoxin

Heat-stable: S. aureus enterotoxin and B. cereus emetic toxin.

Which viruses are more vs. less susceptible to pasteurization? (Design-Thermal)

Heat-sensitive: rotavirus, influenza

More heat-resistant: hepatitis A virus and norovirus.

Why must both time and temperature be considered during pasteurization? (Design-Thermal)

Microbial destruction depends on the combination of heating temperature and exposure time; higher temperatures generally allow shorter treatment times.

What are the LTLT and HTST pasteurization conditions for milk? (Design-Thermal)

LTLT: 63°C for 30 min

HTST: 72°C for 15 sec

What are the LTLT and HTST pasteurization conditions for ice cream mix? (Design-Thermal)

LTLT: 69°C for 30 min

HTST: 80°C for 25 sec

What is sterilization in food processing? (Design-thermal)

A high-temperature thermal process used to destroy microorganisms, including highly heat-resistant forms such as bacterial spores.

How does commercial sterilization differ from complete sterilization? (Design-thermal)

Commercial sterility means destroying microorganisms capable of growing in the food under normal storage conditions; it does not necessarily mean every microorganism is destroyed.

How are foods commonly processed during retort sterilization? (Design-thermal)

Foods are sealed in metal cans, glass containers, or retortable pouches and processed under pressure with steam at about 110-121°C or higher.

What is the 12-D "botulinum cook" used for? (Design-thermal)

It is used for low-acid canned foods to provide a 12-log reduction of Clostridium botulinum, e.g. about 2.4 min at 121°C.

What is a D-value? (Design-thermal)

The time at a specific temperature required to reduce a microbial population by 90% (1-log or 10-fold reduction).

Why may retort sterilization use longer heating times than the minimum required for C. botulinum? (Design-thermal)

To provide a margin of safety and destroy spoilage microorganisms that may be more heat-resistant than C. botulinum.

What is UHT processing? (Design-thermal)

Ultra-High Temperature (UHT) processing sterilizes food at a very high temperature for a very short time, e.g. 140-150°C for several seconds.

How are UHT products packaged to prevent recontamination? (Design-thermal)

They are aseptically packed in an enclosed system into separately sterilized packages.

What methods can be used to sterilize packaging for UHT foods? (Design-thermal)

Flame sterilization, superheated steam, H₂O₂ (hydrogen peroxide), or high-intensity UV irradiation.

Why are non-thermal processes used instead of thermal processing for some foods? (Design-Non thermal)

They are used to minimize undesirable changes/damage caused by heat, although they are generally more costly and less effective at reducing microbial populations than thermal processes.

How does filtration control microorganisms in foods? (Design-Non thermal)

It physically removes microbes from liquids using filters, commonly around 0.22-0.45 μm; it is used in dairy, fruit juice, and wine production and can also filter incoming air.

How are chemical disinfectants used as a non-thermal microbial control? (Design-Non thermal)

They reduce microbial loads in liquids or food materials; disinfectants such as chlorine and ozone can sanitize water used for washing/dipping fruits and vegetables.

What is the most effective type of UV light for food-safety applications? (Design-Non thermal)

UV-C (200-280 nm).

What can reduce the antimicrobial effectiveness of UV light? (Design-Non thermal)

Absorption and scattering of UV light by particles in air or liquid can reduce its effectiveness.

How is UV light used for water treatment? (Design-Non thermal)

Large UV bulb arrays: municipal water supplies

Smaller arrays: water in food-processing plants

What types of ionizing radiation can be used in food processing? (Design-Non thermal)

Gamma rays, X-rays, and high energy electron beams.

Why is food irradiation sometimes called "cold pasteurization"? (Design-Non thermal)

It can reduce or destroy microorganisms without the high temperatures used in conventional thermal pasteurization.

What other preservation effect can irradiation have on fruits and vegetables? (Design-Non thermal)

It can slow ripening and inhibit sprouting, extending storage life.

Does irradiation make food radioactive? (Design-Non thermal)

No. Approved food irradiation exposes food to ionizing energy but does not make the food radioactive.

What determines how easily organisms are inactivated by irradiation? (Design-Non thermal)

Larger biological targets are generally easier to inactivate than smaller targets. Smaller organisms/targets tend to be more radiation resistant.

What foods are permitted to be irradiated in Canada according to the lecture? (Design-Non thermal)

Potatoes, onions, wheat/wheat flour/whole-wheat flour, whole or ground spices, dehydrated seasoning preparations, and ground beef.

How is food irradiation regulated in Canada? (Design-Non thermal)

Food irradiation is regulated under Division 26, Part B of the Food and Drug Regulations (FDR), with labelling requirements under Division 1, Part B.

What are some foods approved for irradiation in the United States? (Design-Non thermal)

Examples include milled cereal grains, fruits, vegetables, spices, meat, and poultry products.

What are three additional non-thermal preservation technologies? (Design-Non thermal)

Pulsed electric fields (PEF), cold plasma, and high-pressure processing (HPP).

What are the three main areas considered when designing a safe food process? (Design-Prevent)

1) Destroy microorganisms (kill step),

2) prevent microbial growth/multiplication, and

3) prevent contamination.

How does refrigeration help control microbial growth? (Design-Prevent)

Refrigeration at ≤4-5°C slows microbial growth, but does not necessarily stop or kill microorganisms.

Why can refrigerated foods still spoil? (Design-Prevent)

Some spoilage and pathogenic microorganisms can still grow slowly at refrigeration temperatures, so shelf life is limited.

How does freezing at −18°C affect microorganisms? (Design-Prevent)

It prevents microbial growth, but does not necessarily kill the microorganisms.

Why can microbial growth increase after frozen food is thawed? (Design-Prevent)

Freezing damages food cells, and thawing releases intracellular nutrients that microbes can use, allowing faster growth.

Why are vegetables blanched at ~90°C before freezing? (Design-Prevent)

To inactivate enzymes that could cause quality deterioration during frozen storage.

What temperatures should cold and hot foods be held at? (Design-Prevent)

Cold foods ≤4°C; hot foods ≥60°C.

What is the food temperature danger zone? (Design-Prevent)

4-60°C, where foodborne pathogens can grow. Food should not remain in this range for >2 hours without refrigeration or reheating.

How do modified-atmosphere packaging (MAP) and vacuum packaging inhibit microbes? (Design-Prevent)

MAP adds inhibitory gases, while vacuum packaging removes oxygen, inhibiting mainly aerobic microorganisms.

What packaging properties are needed for MAP/vacuum packaging to remain effective? (Design-Prevent)

The package must be hermetically sealed and gas-impermeable to the relevant gases.

What food-safety risk can modified-atmosphere or vacuum packaging create? (Design-Prevent)

Reduced oxygen can promote anaerobic or facultative anaerobic pathogens, so additional safeguards such as refrigeration are required.

How can oxygen scavengers or fats/oils affect microbial growth? (Design-Prevent)

They can further reduce available oxygen and inhibit aerobic microbial growth.

What is the third main area when designing a safe food process? (Design-contamination)

Prevent contamination, including preventing cross-contamination.

What is cross-contamination? (Design-contamination)

The unintentional transfer of microorganisms, chemical contaminants (including allergens), or foreign substances from a food, person, or object to another food product.

What are the four major sources of biological hazard contamination in a food manufacturing facility? (Design-contamination)

1. Environment

2. Machinery and food-contact surfaces

3. People

4. Food

What is zoning and segregation used for in food-processing facilities? (Design-contamination)

To separate areas with different contamination risks, helping prevent contaminants from moving from one area or product to another.

How does controlled traffic flow help prevent cross-contamination? (Design-contamination)

It controls the movement of people, equipment, and materials between areas, reducing the transfer of contaminants.

Why are color-coded tools used in food-processing facilities? (Design-contamination)

To keep tools designated for specific areas or tasks, reducing accidental cross-contamination.

Who was "Typhoid Mary" and why is her case important?

Mary Mallon (1869-1938) was a New York City cook who carried Salmonella Typhi and transmitted typhoid fever through food. Her case became significant in public health and food safety history.

What made Mary Mallon especially dangerous as a source of typhoid fever?

She was an asymptomatic carrier of Salmonella Typhi — she carried and transmitted the pathogen without showing symptoms herself.

What was the impact of Mary Mallon working as a cook?

Between 1900-1907, nearly two dozen people developed typhoid fever in households where she worked, demonstrating how an infected food handler can cause cross-contamination and outbreaks.

How was Mary Mallon identified as the source of the typhoid outbreaks?

Sanitary engineer Dr. George Soper investigated the outbreaks, and Salmonella Typhi was eventually detected in Mallon's stool samples.