Module 6

Question 1

What causes botulism?

This is a rare, but serious disease.

Answer 1

A toxin produced by a specific type of bacteria.

Clostridium botulinum and sometimes Clostridium butyricum and Clostridium baratii

Question 2

How is botulism spread?

Answer 2

• Not from person to person
• From:
  
  • Injection of illicit drugs
  • Eating food or drinking beverages contaminated with the toxin
  • Infants (children under 1) can get botulism from eating honey containing spores of the bacteria

Question 3

Food-borne botulism is caused by eating food or drinking beverages contaminated with the toxin. List some sources.

Answer 3

Improperly:
* Prepared home-canned foods (i.e., beets, peppers, etc.)
* Stored food products (i.e., oil, onions sautéed in butter, baked potatoes wrapped in aluminum foil and stored at room temperature)
* Traditionally prepared fish or marine mammal meat (i.e., seal, walrus, whale)

Question 4

What is wound botulism?

Answer 4

• Caused by bacteria getting into open wounds and producing toxin.
• This has never been reported in Canada, but has been increasingly reported in other countries among injection drug users when using contaminated needles or impure heroin.

Question 5

What is infant botulism?

Answer 5

• When children under 1 accidentally consume the spores of the bacteria, it can grow and produce toxin in their intestinal tract.
• Very rare in Canada, with fewer than 5-6 cases per year.
• In most cases, the source is not found.
• Honey is the only identified source (including pasteurized honey).

This is why there exists a recommendation to not feed honey to children under 1.

Question 6

Where is botulism found?

Answer 6

• The spores are widespread in nature and can be found in soil, dust, sediments at the bottom of lakes and oceans, and the intestines of animals, including fish and birds.
• These spores do not grow when exposed to oxygen.

Question 7

How do food and beverages become contaminated with botulism?

Answer 7

• When spores get into the products and grow and produce toxins.
• Canned foods and other sealed products provide ideal conditions for this bacteria to grow.
• Commercial processed foods are processed at high temperatures to kill bacteria. These foods have an exceptionally good safety record.
• Honey, the only known source of infant botulism, is contaminated with spores, not the toxin.

Question 8

How can botulism be prevented?

Answer 8

• Refrigerate leftovers promptly
• Use foods stored in oil within 10 days of opening
• Keep foods stored in oil in the fridge
• Prepare canned foods correctly if doing it at home
• Keep baked potatoes wrapped in aluminum foil hot until served, or refrigerated
• NEVER eat foods from cans that are dented, bulging, or leaking.

Question 9

What is blanching?

Answer 9

A form of thermal processing applied mainly to vegetables and some fruit by exposing them to heat or boiling water or even culinary steam for a short period of time.

Question 10

What is blanching designed to do? [3]

Answer 10

1. Inactivate enzymes so enzymatic degradation does not occur in the interval between packaging and thermal processing or during frozen storage or in the early stages of food dehydration and after reconstitution of dehydrated plant foods
2. Wilt vegetable products to enable packaging of products into containers so that proper fill weights can be achieved
3. Drive off inter- and intracellular oxygen and other gases from plant tissues so that containers are not deformed by excessively high internal pressures due to expanding gases within the container and to permit the formation of a vacuum in the container after thermal processing

Question 11

What is pasteurization?

Answer 11

A thermal process that involves using temperatures of at least 72°C for 15 seconds (high-temperature short time or HTST process), before packaging.

Question 12

What is the basis for preservation by pasteurization?

Answer 12

• Inactivate pathogens (disease-causing) bacteria and viruses in low acid food products like milk.

Question 13

Why are acid food products (pH < 4.6) pasteurized?

Answer 13

• To inactivate spoilage-causing bacteria
• Pathogenic microbes cannot grow and survive very well in acid foods like citrus juice (except for E. coli O157:H7).

Question 14

Spoilage-causing microorganisms can survive pasteurization.
True or False?

Answer 14

True
In low-acid and acid foods, many spoilage-causing bacteria survive typical pasturization processes.
E.g., In milk, the proteolytic and lipolytic bacteria are more heat resistant and can survive, which explains why the spoilage pattern of milk reflects the proteolytic and lipolytic action of the psychrotrophic, spoilage-causing bacteria.

This is why milk must be refrigerated even after pasteurization to maintain shelf life quality.

Question 15

Spoilage-causing bacteria do not survive pasteurization.
True or False?

Answer 15

False.
In low-acid and acid foods, many spoilage-causing bacteria survive typical pasturization processes.
E.g., In milk, the proteolytic and lipolytic bacteria are more heat resistant and can survive, which explains why the spoilage pattern of milk reflects the proteolytic and lipolytic action of the psychrotrophic, spoilage-causing bacteria.

This is why milk must be refrigerated even after pasteurization to maintain shelf life quality.

Question 16

What is commercial sterilization?

Answer 16

• This thermal process involves heating the food with a minimum treatment of 121°C moist heat for 15 minutes.
• This process involves pre-sealing the food containers before heating (also known as ‘canning’).
• Other forms of commercial sterilization involve heating the food before it is aseptically packaged (UHT-aseptic packaging)

Question 17

What is the basis for preservation of commercial sterilization?

Answer 17

• To destroy both spoilage and disease-causing microorganisms in low-acid and acid foods, thus rendering the food ‘commercially sterile’.

Question 18

Define: Commercially sterile.

Answer 18

• Means the condition obtained in a food that has been processed by the application of heat, alone or in combination with other treatments, to render the food free from viable organisms, including spores, capable of growing in the food at temperatures at which the food is designed to normally be held during distribution and storage.
• Commercial sterilization involves the destruction of spoilage-causing and disease-causing microorganisms.

Commercially sterile foods may contain small numbers of extremely thermophilic bacterial spores; however, the spores cannot germinate and produce actively growing cells at room temperature, nor would they cause disease.

Question 19

Describe achieving sterility in cans.

Answer 19

• If a can of food is being sterilized, each food particle much receive the correct heat treatment.
• When food is placed in a can, the heat treatment will change since heat transfer to the food takes place at a slower rate.
• Depending on the size of the can, the time to achieve sterility could be several hours.

Question 20

Most commercially sterilized food products have a shelf life of […].

Answer 20

2 years or more

Question 21

What is the basis of ultra-high temperature (UHT) processing and aseptic packaging?

Answer 21

• Application of ultra-high temperature to food before packaging, then filling the food into pre-sterilized containers in a sterile atmosphere.
• This process will render the food shelf-stable without the need for refrigeration.

Question 22

Describe ultra-high temperature processing.

Answer 22

• Relatively new development in food processing
• Food is heated to 140-150°C very rapidly by direct injection of steam, held at that temperature for a short period of time (e.g. 4-6 seconds) and then cooled, in a vacuum chamber to flash off the water added in the form of condensed steam in a continuous flow operation.
• The decrease in production time due to the higher temperature, and minimal come-up time and cool-down time leads to a higher quality product.

Question 23

What is Tetra Pak technology?

Answer 23

• UHT processed foods are aseptically packaged into pre-sterilized containers (Tetra Pak aseptic technology), usually cartons made from laminated plastic, aluminum and paper, which are chemically sterilized with a combination of hydrogen peroxide and heat, and then filled in the same piece of equipment which is housed in a sterile environment.

Question 24

UHT-aseptically packaged products have a shelf-life of […].

Answer 24

6 months or more without refrigeration, depending on the type of product being packaged

Question 25

Give a few examples of UHT products.

Answer 25

* Liquid products like milk, juices, cream, yogurt, wine, salad dressings * Semi-liquid/solid products like baby foods, tomato products, fruits and vegetable juices, soups

Question 26

All UHT processed products are aseptically packaged. True or False?

Answer 26

False. Many products that are UHT treated are not necessarily aseptically packaged. This gives them the "advantage" of longer shelf life at refrigeration temperatures compared to conventional pasteurized (HTST) products. However, this does not produce a shelf-stable product at ambient temperatures due to the possibility of post-processing recontamination.

Question 27

Not all UHT processed products are aseptically packaged. True or False?

Answer 27

True. Many products that are UHT treated are not necessarily aseptically packaged. This gives them the "advantage" of longer shelf life at refrigeration temperatures compared to conventional pasteurized (HTST) products. However, this does not produce a shelf-stable product at ambient temperatures due to the possibility of post-processing recontamination.

Question 28

When comparing salted and unsalted butter, why does the latter have to be kept in the freezer?

Answer 28

To prevent rancidity and microbial spoilage. ## Footnote Salted butter is less prone to this type of degradation due to the preservative effects of salt.

Question 29

What is clarification?

Answer 29

Whereby pre-heated milk is centrifuged at 6000 rpm to obtain a predetermined butter fat content (e.g., 0% for skim; 2% for 2% milk; and so on).

Question 30

What is homogenization?

Answer 30

Whereby milk is forced through fine nozzles at pressures of 17,000 kPa, which breaks up the fat globules to a size that will keep them in suspension.

Question 31

Will canned food and aseptically packaged UHT food products require a durable life date stamped on the label? What about products that have been UHT processed but not packaged under aseptic conditions?

Answer 31

* Most prepackaged foods with a shelf-life of 90 days or less are required to have a 'durable shelf life date' on the label. * This is not mandatory for foods with a shelf life greater than 90 days. * Products with a shelf life of 90 days or less require a durable life date; longer shelf life products are evaluated on a case-by-case basis.

Question 32

How are heat treatments selected?

Answer 32

1. What is the **objective** or purpose? 2. Are there additional preservation steps? 3. What are the physical and chemical properties of the food? 4. What is the heat resistance of the microorganisms in the food? ## Footnote It is imperative that thermal preservation processes be designed so that the slowest heating portion of the food commodity receives the specified time-temperature thermal treatment to minimize risks of illness and/or post-processing spoilage.

Question 33

What is the microorganism of greatest concern in low acid foods that are to be thermally processed and vacuum-sealed within gas-tight containers?

Answer 33

*Clostridium botulinum*

Question 34

How can we determine if *C. botulinum* spores have been destroyed?

Answer 34

* To determine the thermal resistance of heat-resistant spores in foods, 'incoulated pack studies' are carried out using a non-pathogenic spore-forming bacterium, *Clostridium sporogenes* PA3679 (a putrefactive anaerobe). * Since PA3679 spores are *more* heat resistant than those of *Clostridium botulinum* spores, a process designed to kill PA3679 spores will definitely kill *Clostridium botulinum* spores with a wide margin of safety.

Question 35

What is a survivor curve? ## Footnote a.k.a. thermal death rate

Answer 35

* Depicts the logarithmic order of death. * The time taken to traverse one log cycle represents the time, at a constant temperature, required to kill 90% of a microbial population (a.k.a. the decimal reduction time or D-value)

Question 36

What is D-value?

Answer 36

* The time required to kill 90% of the microbial population at a specific temperature and in specific conditions (e.g., type of food). ## Footnote If we were to start with a population of 10^5 (=100,000) bacterial cells in a unit volume or mass of food at time 'A', only 10^4 (=10,000) cells would survive after one logarithmic cycle on the graph was traversed (time 'B').

Question 37

How does temperature affect D-value?

Answer 37

* As temperature increases, D-value decreases because the rate of microbial death increases.

Question 38

What is a thermal death time curve?

Answer 38

* Can be constructed from several thermal death rate curves by exposing the microorganism to a variety of temperatures and determining the decimal reduction time (D-value) at each temperature * Provides information about the *time* required to kill a particular microorganism in a particular food at a variety of temperatures * All of the time-temperature combinations represent the same killing power * Any point above the line will ensure the microbe is killed * Any point below the line will not kill all of the microbes present

Question 39

What is a z-value?

Answer 39

* Z-value is the number of degrees required for a specific thermal death time curve to pass one log cycle * Different microorganisms in a given food will have different z-values * Similarly, a given microorganism will have different z-values in different foods * The z-value indicates the resistance of a microbial population to changing temperature

Question 40

What is an F-value?

Answer 40

* A mathematically calculated number that describes the total lethal effects of the process at the slowest heating point in a food container * The standard reference temperature is generally selected as 121.1°C (250 °F), and the relative time (in minutes) required to sterilize any selected organism at 121°C is known as the F-value of that organism * The F-value is the equivalent of all heat considered with respect to its capacity to destroy spores or vegetative cells of a particular microorganism * It is a measure of lethality, or the capacity of heat to sterilize

Question 41

What is the concept of 'margin of safety'?

Answer 41

* Refers to the probability that a container of food would still contain a viable spore of *Clostridium botulinum* after the completion of thermal processing. * As the spore population in a food system is increased, the total time required at a particular temperature to kill ALL spores increases (inherent in the log order of death of microbial cells and spores)

Question 42

What margin of safety is used for low acid foods?

Answer 42

* 12D process * This means that the foods are subjected to a thermal process such that the slowest heating portion of the food is exposed to an amount of thermal energy which will reduce the microbial spores by 12 successive decimal reduction times. * This has the capacity to destroy one trillion spores per container. * The D value is temperature dependent, so at a higher temperature, the lower D-value means less time is required to achieve a 12D process (i.e., 'botulinum cook')

Question 43

What margin of safety is used in acid foods?

Answer 43

* *C. botulinum* is very sensitive to acid, so a lower margin of safety is required to process these foods * Therefore, a 12D process would be excessive and unncessary . * Typically, a 5D process is used for acid foods

Question 44

If the spore population in a container of food were increased from 100 spores to 10,000 spores, would the margin of safety of a 12D thermal process increase or decrease? What is the effect of a higher initial microbial load on the margin of safety?

Answer 44

* **Increased Initial Spore Load:** If the spore population increases from 100 to 10,000, the margin of safety of a 12D thermal process decreases. * **Effect on Margin of Safety:** A higher initial microbial load means the margin of safety is reduced, as there is a greater chance that some spores may survive the thermal process. Therefore, while a 12D process is highly effective, the initial microbial load plays a critical role in determining the final safety level of the processed food. Reducing the initial microbial load through proper handling and preparation can significantly enhance the overall margin of safety.

Question 45

What is the cold point in foods?

Answer 45

* The slowest heating portion of the food

Question 46

What factors affect the heat transfer characteristics of a food? [3]

Answer 46

* The **consistency** of the food (liquid -viscous or non-viscous- or solid) * The chemical **composition** of the food * The **container** size, shape and composition

Question 47

What is a retort?

Answer 47

* An environment of pressurized steam within a vessel * Foods that are thermally processed after being packed in containers (e.g., metal cans, glass bottles, plastic pouches), are processed in retorts. ## Footnote A processing temperature of 250°F (121°C) is achieved by establishing a steam pressure of 15 pounds per square inch within the retort.

Question 48

Compare conduction and convection heating.

Answer 48

* If the food is solid (salmon, for example), heat energy is transferred by conduction. This is a slow process. * If the foods are non-viscous liquids (canned evaporated milk, for example), heat energy is transferred by convection. * Combination foods are heated by a combination of convection and conduction heating.

Question 49

Where is the cold point and how is it found?

Answer 49

* The location of the cold points in relation to conduction heating (in the geometric centre of a cylindrical container) and convection heating (one-third of the way up the centre axis measured from the bottom of the cylindrical container). * The actual cold point needs to be determined by extensive heat penetration studies using the insertion of thermocouples inside the can and collecting the heating data throughout the process. * The cold point of a container of food must receive the required amount of thermal energy to ensure the killing of *Clostridium botulinum* spores that may be present and to ensure a sufficient margin of safety. ## Footnote If a food formulation is changed such that the mechanism of heat transfer is altered from convection heating to conduction heating, the processing times should be altered to accommodate the change in the mechanism of heat transfer, otherwise the food could be under processed and could pose a potential health hazard with respect to botulism. In the past, outbreaks of botulism have occurred due to such changes in heat transfer resulting from changes in product formulation or in the changes in product piece size which can affect the rate of heat transfer.

Question 50

What is the heat transfer mechanism for canned tomato juice, tomatoes packed in brine, and tomato paste? Other things being equal (e.g size of the can, net quantity), which would you expect to reach uniform complete heating first? last?

Answer 50

* Canned tomato juice, a non-viscous liquid: convection * Tomatoes in brine, a combination food: convection and conduction * Tomato paste, a highly viscous product: conduction * Order of reaching uniform heating: convection; convection and conduction; conduction ## Footnote This order is determined by the nature of heat transfer mechanisms and the physical characteristics of each product, which affect how quickly they can be heated uniformly throughout the container.

Question 51

Describe the protective effects of food constituents.

Answer 51

* Sugars, oils, fats and salt can have the effect of protecting spores and vegetative cells from the killing effects of heat, thus requiring the use of longer exposure times or higher temperatures for processing those foods exhibiting these protective effects. * Certain spices may have antimicrobial activity and change the resistance of microorganisms and spores to the killing effects of high temperatures (D and z values are decreased). * Food processing companies must be very careful in re-evaluating the lethality of the thermal processes they used after they reformulate foods that are preserved by thermal processing (commercial sterilization, pasteurization).

Question 52

Describe concerns with home-canning.

Answer 52

When canning foods at home, be sure to process all low-acid products in a pressure canner following the manufacturer's instructions closely. Any deviation from those instructions could substantially decrease the margin of safety of the process being used.

Question 53

What are the most common packaging materials used for thermally processed foods? [5]

Answer 53

* Steel body cans 'tin cans' * Glass jars * Sterile cartons (Tetra Pak) * Retortable pouch * Plastic cans/bottles

Question 54

Give some observations about 'tin cans'.

Answer 54

* Steel body cans with a thin layer of tin are the most widely used containers * Can withstand high temperatures and pressure differentials * Not readily breakable * The can lids provide a good indication of the presence of a vacuum and thus hermetic seal (a seal that is impervious to the transmission of gases, water, and microorganisms) * The steel, and very often the tin plating, must be protected with lacquers to minimize the reaction of the metals with the food constituents

Question 55

Give some observations about glass jars.

Answer 55

* More resistant to corrosion and reaction with food constituents * Allows the consumer to see the contents * Glass is heavy and bulky and must be packaged with extra protection to prevent breakage during transport * Glass filled containers must also be processed in the retort with extra care to prevent breakage due to thermal shock

Question 56

Give some observations about Tetra Pak.

Answer 56

* Made from laminated plastic, aluminum and paper.

Question 57

Give some observations about the retortable pouch.

Answer 57

* Relatively new packaging made from a laminate of plastic films and aluminum. * Heat penetrates these pouches faster due to their thinner profile, allowing the 12D process at the cold point to take place in a shorter time period as compared to metal or glass. * Nutrient retention is superior in foods processed in these pouches * The pouch itself must be packaged in an outer protective carton to minimize physical damage to the food due to handling by the consumer

Question 58

Give some observations about plastic cans/bottles.

Answer 58

* New types of plastic packaging can be produced in the shape of a can/bottle * Can be hermetically sealed and thermally processed in a steam retort to acheive the 12D process for low acid foods * Newer plastic bottles can even be used with UHT-aseptic packaging technologies * Some of these containers are used for foods that are ready to eat. These containers, unlike metal cans and glass bottles can be placed in the microwave

Question 59

Applied mainly to vegetables and some fruits, involves the application of boiling water or steam for a short period of time.

Answer 59

Blanching

Question 60

The process requires temperatures of at least 72C for at least 15 seconds.

Answer 60

Pasteurization

Question 61

The process requires temperatures of at least 121C using moist heat for at least 15 minutes.

Answer 61

Commercial sterilization

Question 62

The process requires temperatures of 140-160C using directly injected steam for about 4-6 minutes.

Answer 62

UHT processing

Question 63

The time required to kill 90% of a microbial population. Expressed in minutes.

Answer 63

D-value

Question 64

The number of degrees required for a change of D-values by a factor of 10. Expressed in degrees.

Answer 64

Z-value

Question 65

The final lethality at 121C. Expressed in minutes.

Answer 65

F-value

Question 66

The number of surviving cells plotted against time.

Answer 66

Thermal death rate curve

Question 67

D values plotted against temperature

Answer 67

Thermal death time curve

Question 68

If the D-value of a species of bacteria is 2 minutes at 70˚C and there are 10,000 of these bacteria in a given food, then how many bacterial cells would be left in that food if it was heated at 70˚C for 6 minutes?

Answer 68

10

Question 69

The D-value of a species of bacteria is 2 minutes at 70˚C, it has a Z-value of 5˚C. How many minutes would it take to kill 90% of the bacteria if the temperature was at 60˚C?

Answer 69

200 minutes

Question 70

What is an advantage of using a retortable pouch over a tin can?

Answer 70

The pouch allows better heat penetration reducing the amount of time spent exposed to thermal stress.

Question 71

What is a public misconception about UHT processing?

Answer 71

Something is added to the food to provide the longer shelf life.

Question 72

When heating food, what is the difference between convection and conduction?

Answer 72

Convection is the heat transfer mechanism in liquid food through the flow of fluid; conduction heats solid food through the transfer of heat from molecule to molecule.

Question 73

If the amount of microorganisms increases in a food the D-value does NOT change, but the margin of safety decreases. True or False?

Answer 73

True.

Question 74

If the amount of microorganisms increases in a food the D-value does NOT change, but the margin of safety increases. True or False?

Answer 74

False. If the amount of microorganisms increases in a food the D-value does NOT change, but the margin of safety decreases.

Question 75

Spores are more heat resistant than vegetative cells. This means that spores have higher D-values than vegetative cells. True or False?

Answer 75

True.

Question 76

Spores are more heat resistant than vegetative cells. This means that spores have lower D-values than vegetative cells. True or False?

Answer 76

False. Spores are more heat resistant than vegetative cells. This means that spores have higher D-value than vegetative cells.

Question 77

The goal of blanching is to kill spoilage and disease-causing microbes along with inactivating the enzymes. True or False?

Answer 77

False. The goal of blanching is to inactivate the enzymes.

Question 78

The goal of blanching is to inactivate the enzymes. True or False?

Answer 78

True.

Question 79

A can heated by convection and conduction have cold spots in the same location. True or False?

Answer 79

False.

Question 80

A can heated by convection and conduction have cold spots in different locations. True or False?

Answer 80

True.

Question 81

Altering a recipe by adding spices does NOT alter the resistance of microbes to killing by heat. True or False?

Answer 81

False.

Question 82

Altering a recipe by adding spices does alter the resistance of microbes to killing by heat. True or False?

Answer 82

True.

Question 83

Products that are pasteurized require additional methods of preservation because spoilage causing microbes have not been destroyed. True or False?

Answer 83

True.

Question 84

Products that are pasteurized do not require additional methods of preservation because spoilage causing microbes have been destroyed. True or False?

Answer 84

False. Products that are pasteurized require additional methods of preservation because spoilage causing microbes have not been destroyed.

Question 85

High pH foods (pH>4.6) require a cook time of 5D, while low pH foods (pH≤4.6) require a safe processing time of 12D. True or False?

Answer 85

False. High pH foods (pH>4.6) require a cook time of 12D, while low pH foods (pH≤4.6) require a safe processing time of 5D.

Question 86

High pH foods (pH>4.6) require a cook time of 12D, while low pH foods (pH≤4.6) require a safe processing time of 5D. True or False?

Answer 86

True

Question 87

What is the full name of the microorganism that is of particular concern in low –acid foods that are processed through canning?

Answer 87

*Clostridium botulinum*