Module 6 Flashcards
What causes botulism?
This is a rare, but serious disease.
A toxin produced by a specific type of bacteria.
Clostridium botulinum and sometimes Clostridium butyricum and Clostridium baratii
How is botulism spread?
- 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
Food-borne botulism is caused by eating food or drinking beverages contaminated with the toxin. List some sources.
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)
What is wound botulism?
- 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.
What is infant botulism?
- 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.
Where is botulism found?
- 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.
How do food and beverages become contaminated with botulism?
- 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.
How can botulism be prevented?
- 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.
What is blanching?
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.
What is blanching designed to do? [3]
- 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
- Wilt vegetable products to enable packaging of products into containers so that proper fill weights can be achieved
- 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
What is pasteurization?
A thermal process that involves using temperatures of at least 72°C for 15 seconds (high-temperature short time or HTST process), before packaging.
What is the basis for preservation by pasteurization?
- Inactivate pathogens (disease-causing) bacteria and viruses in low acid food products like milk.
Why are acid food products (pH < 4.6) pasteurized?
- 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).
Spoilage-causing microorganisms can survive pasteurization.
True or False?
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.
Spoilage-causing bacteria do not survive pasteurization.
True or False?
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.
What is commercial sterilization?
- 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)
What is the basis for preservation of commercial sterilization?
- To destroy both spoilage and disease-causing microorganisms in low-acid and acid foods, thus rendering the food ‘commercially sterile’.
Define: Commercially sterile.
- 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.
Describe achieving sterility in cans.
- 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.
Most commercially sterilized food products have a shelf life of […].
2 years or more
What is the basis of ultra-high temperature (UHT) processing and aseptic packaging?
- 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.
Describe ultra-high temperature processing.
- 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.
What is Tetra Pak technology?
- 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.
UHT-aseptically packaged products have a shelf-life of […].
6 months or more without refrigeration, depending on the type of product being packaged
Give a few examples of UHT products.
- Liquid products like milk, juices, cream, yogurt, wine, salad dressings
- Semi-liquid/solid products like baby foods, tomato products, fruits and vegetable juices, soups
All UHT processed products are aseptically packaged.
True or False?
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.
Not all UHT processed products are aseptically packaged.
True or False?
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.
When comparing salted and unsalted butter, why does the latter have to be kept in the freezer?
To prevent rancidity and microbial spoilage.
Salted butter is less prone to this type of degradation due to the preservative effects of salt.
What is clarification?
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).
What is homogenization?
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.
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?
- 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.
How are heat treatments selected?
- What is the objective or purpose?
- Are there additional preservation steps?
- What are the physical and chemical properties of the food?
- What is the heat resistance of the microorganisms in the food?
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.
What is the microorganism of greatest concern in low acid foods that are to be thermally processed and vacuum-sealed within gas-tight containers?
Clostridium botulinum
How can we determine if C. botulinum spores have been destroyed?
- 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.
What is a survivor curve?
a.k.a. thermal death rate
- 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)
What is D-value?
- The time required to kill 90% of the microbial population at a specific temperature and in specific conditions (e.g., type of food).
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’).
What is a thermal death time curve?
- 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
What is a z-value?
- 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
What is an F-value?
- 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
What is a retort?
- 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.
A processing temperature of 250°F (121°C) is achieved by establishing a steam pressure of 15 pounds per square inch within the retort.
Compare conduction and convection heating.
- 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.
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?
200 minutes
