Module 11: High Temperature Preservation Flashcards
True or False: The kind of heat for high temperature processing cannot vary.
FALSE; heat can vary
What are the characteristics of MILD HEAT?
- Kills pathogens
- Reduce bacterial count
- Inactivates enzymes
- Minimal damage to flavor, texture, and nutritional quality
- Short shelf life
- Another preservation must be used
What are the characteristics of SEVERE HEAT?
- Kills all bacteria
- Food will be commercially sterile
- Major changes in texture, flavor, and nutritional quality
- Long shelf life
- No other preservation is necessary
- Food is overcooked
True or False: There is such a thing as ‘sterile food’.
False; There is no such thing as sterile food but there is such a thing as commercially sterile food.
What are the six kinds of cooking methods?
- Baking
- Broiling
- Roasting
- Boiling
- Stewing
- Frying
Cooking is a form of what kind of treatment?
Mild Heat Treatment
Why do we cook our food?
- To make food more palatable, improve taste
- Alteration of color
- Improved digestibility
True or False: Cooking is a form of preservation technique.
False: Cooking is not a preservation technique but it destroys or reduces MOs, inactivates enzymes, and destroys toxins.
True or False: Cooking does not give food a long shelf life.
True
What kind of MILD HEAT TREATMENT is applied to tissue systems prior to freezing, drying, or canning?
Blanching
Explain the process of blanching.
- Let the water boil
- Immerse vegetables for a few minutes
- Remove the vegetables
- Immerse in cold water
What does blanching do prior to freezing or dehydration?
- Inactivates enzymes such as (peroxidase and catalase)
What are the four benefits of blanching prior to canning?
- Remove tissue gases
- Increase temperature of the tissue
- Cleanse the tissue
- Activate or inactivate enzymes
What process kills part but not all of the vegetative MOs present in the food?
Pasteurization
What are five examples of supplementing pasteurization?
- Refrigeration
- Packaging
- Anaerobic conditions
- Drying
- Chemical Preservatives
Why is supplementing pasteurization important?
Because after pasteurizing we can add on these techniques to increase shelf life.
What is the process of inactivating microorganisms?
Sterilization
True or False: In sterilization, there is generally no need to remove thermophilic organisms which have no public health significance.
True
What do you call hot loving microorganisms?
Thermophilic
What is Commercial Sterility?
The condition achieved by the application of heat, sufficient alone or in combination with other ingredients and or other treatments to render the product free of MOs capable of growing in the product at non-refrigerated conditions.
What is the requirement for products in terms of storage conditions in Commercial Sterility?
Products should not be stored at a temperature of 32ºC when the MOs will germinate causing product spoilage.
What is the primary objective of commercially sterile foods?
Destroy the most heat resistant pathogenic spore-forming organisms (e.g., C. botulinum in products which > pH 4.6).
Botulinum is a _____________?
Pathogen
What are characteristics of botulinum?
- heat resistant and spore forming
What happens to botulinum when exposed to adverse conditions?
It becomes a heat-resistant spore.
What is the secondary objective of commercially sterile foods?
Destroys vegetative and spore-forming microorganisms that cause spoilage.
Where is C. botulinum spp. found?
Soil and water.
Which bacterium has the ability to produce heat-resistant spores?
Botulism
The spores of C. botulinum causes __________?
Botulism
From the 7 known types of botulism, how many are able to cause illness in humans?
4
To germinate, the spores need the following conditions: a. __________ environment, b. __________ food, c. __________, d. __________.
a. Anaerobic
b. Low-acid
c. 4ºC to 50ºC
d. Relatively high moisture
Explain: If a product is not properly canned, can spores form?
Yes, because if not properly canned, then O2 may still be present in the can, which can lead to spore formation.
How many mice can 1 mg of botulism toxin kill?
655
True or False: Food can contain the botulism toxin without showing any signs.
True
True or False: Antitoxin is available; and recovery is fast.
False; Recovery is slow, and permanent nerve damage may result.
True or False: Spores do not grow in high-acid foods.
True
True or False: Spores are not killed when low acid foods are heated long enough at a specific temp.
False; spores are killed when low acid foods are heated long enough.
What kind of products usually do not contain C. bot?
Fruits
What is the ideal temperature of processing low-acid foods to prevent botulism?
115ºC and above
What instrument is used for all low-acid foods?
Pressure canner
Cite examples of ways to prevent botulism.
- Properly prepare and process food
- Check canner for accuracy and operate it correctly
What did the ancient people believe was the enemy of food and wine?
Air
When did the Greeks seal their wine in air tight vessels using pine resin?
3000 years ago
What are the two other ways how food was protected?
- Hot oil
- Coating with melted fat
What way of preservation caused loss of nutrients and taste?
Salt
Who started the can revolution?
Napoleon Bonaparte
When did Bonaparte urge the French Government to give a prize for someone who is able to figure out how to deliver fresh food to the army?
1795
When did Nicolas Appert come up with the idea of canning?
1809
When did Durand adapt Appert’s idea by replacing glass bottles with tin?
1810
What was canning called before?
Appertizing
When did Peter Durand receive a patent for the tin-plated can?
1810
What do you call the sealing for the preservation of food using various containers such as metal cans and glass canisters?
Hermetic sealing
What does heat in canning do?
- Cooks the food
- Destroys or inactivates enzymes
- Destroys or inactivates microorganisms
- Creates a vacuum
What kind of environment should canning produce?
Anaerobic Environment (absence of O2)
What are the pH ranges for the three pH groups?
- High-acid foods: pH < 3.7
- Acid foods: 3.7 < pH < 4.6
- Low-acid foods: pH > 4.6
True or False: For low-acid foods, if the water activity (Aw) is <0.85 then it can still be classified as an acid though pH >4.6.
False
True or False: Spore-forming bacteria do not grow at pH values less than 3.7.
True (high-acid foods)
What are heat processes generally based on?
Inactivation of yeasts or molds
Which bacterium is the most heat-resistant, anaerobic, spore-forming pathogen, which can grow in low-acid canned foods?
Clostridium botulinum
What is the process of Conventional Canning?
- Product is filled in the container
- Container is hermetically sealed
- Container and product are thermally processed at a specified time and temperature to achieve commercial sterility.
what do you call the airtight seal in canning
Hermetic seal
how to determine if hermetic sealing is good
% of overlap is measured
general flow of canning line
- prepare materials
- bring container
- fill seal
- packaging
- storage
- distribute
- consume
what is headspace
distance at the top of the product and bottom of the lid
what happens if headspace is too little or too much
- too little = bulge during heating
- too much = underweight cans
how is the most sterile environment created in canning
food is cooked inside the can
Stages of canning
stage 1: select suitable foods in prime condition followed by preparation of food (cut, blanch, remove damage) as cleanly, rapidly and perfectly possible
stage 2: pack product in hermetically sealable containers followed by removing air and sealing the containers
stage 3: stabilize food by heat, at the same time achieving correct degree of sterilization, followed by cooling below 38 C
stage 4: store at suitable temp below 35 C to prevent growth of food spoilage microorganisms
stage 5: labeling, secondary packaging, distribution, marketing and consumption
difference of raw and hot pack
RAW PACK: add very hot canning liquid to cover raw food, but leave head space
HOT PACK: raw foods are boiled 3-5 minutes in saucepan or blancher then poured into jars
disadvantages of raw and hot pack
RAW PACK: floating food, air bubbles, discoloration over time
HOT PACK: texture loss
what is added as suspending medium
brine/syrup
purpose of brine/syrup
- add flavor
- conservation of natural flavor
- mask metallic flavor
- strengthen fruit tissue and prevent disintegration
- fix color
what is exhaustion
removal of air from containers before sealing
steps in sealing
- remove air bubbles
- wipe rim
- preheat lid (soften sealing compound)
- attach lid
- after processing, hear seal “pop” remove screw band
difference in sealing at home and industrial sealing
at home = use spoon
industrial = exhaustion
methods of exhaustion
- hot filling food into container
- cold filling food then heating container with contents (80-95C) with lid partially sealed
- mechanical removal of air
why are foods immediately cooled after sterilization
to induce thermal shock
two methods of canning
- boiling water canning = used for high acid foods
- pressure canning = used for low acid foods
Why are there 2 methods of canning
- yeast, mold and most bacteria are destroyed at boiling temperature (100 C at sea level)
- C. botulinum forms spores that require higher temperatures for destruction in a reasonable period of time - usually 115C or above sea level
T or F: To ensure that all microorganisms do not grow, high acid is combined with sterilization
False. There is no need for high acid if high heat is applied since it can damage the product
Characteristics of high acid foods and how they are canned
- pH 4.5 or lower
- use boiling water canner
- temperature reaches 93-100C
- tomatoes, jams, fruits, BBQ sauce
Characteristics of low acid foods and how they are canned
- pH is above 4.6
- use pressure canner
- temperature reaches 115-121C
- vegetables, meat, soups
Process of boiling water canning
- Fill canner halfway with water
- Preheat to 140 F for raw pack and 180 F for hot packed foods
- Load filled jars with lids into rack and then lower into the water
- Add more boiling water to cover at least 1 inch (jars should be fully submerged)
- Turn heat to highest setting until water boils vigorously
- Start timer once water boils vigorously
- Cover and turn down heat until gently boiling
- Add more boiling water as needed
- When time is up turn off heat and remove lid
- Remove from canner and set on a towel at least 1 inch apart to cool
- After lids seal (pop) remove screw bands
Characterisitcs of a pressure canner
- aluminum or steel
- lid with gasket
- flat or concave bottom
- weighted or dial gauge (check annually)
- pressure safety valve
- jar rack
- cans are not submerged in water (only a little water is needed)
Process of Pressure Canning
- Put 2-3 inches of water in canner, lower rack of filled and lidded jars into canner and fasten cover securely
- heat until steam escapes from vent port
- Let steam vent for 10 minutes then place weight on vent port or close petcock. Allow to pressurize
- Begin to time when recommended pressure is reached
- Adjust heat to regulate a steady pressure on gauge
- If pressure drops below required amount, reset timer to 0
- When time is completed, turn off heat and let the canner depressurize. DO NOT force-cool the canner-may result in food spoilage
- After canner is depressurized, remove the weight from the vent. Wait 2 minutes, remove lid and avoid steam
- Remove jars and place on towel or rack to cool
Cooling in Canning Process
- using cold running water
- prevent stack burning, softening of food item/further cooking, kill flat sour organisms and conserve color
- do not retighten lids
- cool at room temp 12-24 hrs on rack or a towel
How are canned foods stored
- remove screw band
- label and date jar
- do not allow to freeze or overheat
- shelf life: 12-18 mos. boiling water canner & 18-24 mos for pressure canned
- optimal environment = clean, cool, dark, dry
Coding and Labeling in Canning Process
- to check for improper fill
- for grading
- for easy location in case of error
what are retorted foods
- products processed in the package-can, flexible pouch or glass
- Processing time depends on heating the most slowly heating part of the product
where are retorted foods named after
biggest pressure canner is called retort
Types of retorted foods
- still = containers do not move inside
- rotary = containers rotate inside
- hydrostatic cooker = additional feature using water
A can that is bulged on both ends but not so tightly that the ends cant be pushed in somewhat with a thumb press
soft swell
when can is pushed, it returns to normal
soft swell
A can that is so tightly bulged on both ends that the ends can’t be pressed in.
hard swell
A can with a hard swell will generally “____” before it bursts
buckle
how does hard swell form
from an error in sealing/processing
A can whose end normally look flat, but “flips out” when struck sharply on one end
flipper
A can with one end bulged out. With sufficient pressure, this end will flip in, but the other end will flip out (bulge transfers to one end)
springer
A can with a crack or hole in the container that has caused leakage
Leaker
What to do if can is dented after purchasing
should consume immediately since integrity of can is compromised
Characteristics of pull tabs
- should not move
- should be flat
- should be stable
What does it mean if pull tab moves
force is applied and oxygen has entered
T or F: You can eat contents of can immediately after opening
True since contents are overcooked
What to do if contents of can are not fully consumed
transfer contents to a different container
