- Heat stable, boiling for 30 mins does NOT kill - It's TOXIN is heat sensitive, boil for 10 mins to kill ~ Commercially, foods are retorted to kill this bacteria
Explain why C. botulinum bothers us
It is not the bacteria that bothers us, it is the toxin that it produces that bothers us
List the 2 heat treatments of foods
1. Blanching 2. Pasteurization
What is blanching used on and at what temp/time?
Used on veggies that are to be frozen to inactivate the natural food enzymes - it will kill a few bacteria. ~ 180-212°F for 1/2 - 3 minutes
Sufficient heat is used to destroy the most heat resistant pathogen that has been found in the food
Why do we pasteurize milk?
To kill ALL the pathogens and 90-99% of the bacteria (Does NOT kill all the bacteria)
List the variations of the temps/times in pasteurization
130 - 212°F 1/10th - 30 minutes
At what temperature do we start killing bacteria?
Since pasteurization does not sterilize food, so where does it have to be kept?
***The most severe heat treatment -sufficient heat is used to ensure the destruction of C. botulinum - pressure is used so food can be heated up to 240-260
What are 2 important roles in retorting?
1. Sufficient heat is used to ensure the destruction of C. botulinum 2. Pressure
List the temp/time/lbs of pressure used in retorting
240-260°F for 10-20 minutes at 10-20 lbs. of pressure
What is the most heat resistant bacteria found in milk?
no bacteria are present and it will usually keep on the shelf for at least 2 years
Give and example of conduction heating. Where is the cold point?
- Solid particles (chunks of meat) of food in a can, heat moves from one particle to the next in straight lines - center of the can
What is an example of convection heating? Where is the cold point?
- Canned liquids - center of the can diameter wise but 1/3 up from the way height wise
What instrument is used to determine the cold point when retorting canned foods?
List the 4 factors that determine heat treatments
1. Food consistency 2. Food pH 3. Food composition 4. Size of the can
What is the most heat resistant pathogen found in canned foods?
What are the 2 Test bacteria's?
1. Putrifactive Small Anaerobe 3679 2. Bacillus Stereomophilus
List the 3 characteristics of the test bacterias
1. Both non-pathogenic 2. both more heat resistant than C. botulinum 3. Used to determine heat treatments for food sterilization
The lower the pH, the ___ the temp needed to kill the bacteria. Give and example.
Lower ~ Acid
The ___ the salt/acid, the ___ the temperature required to kill bacteria
More ; lower
What are the 2 Heating Curves?
1. Survivor Curve 2. Thermal Death Time Curve
- The temp. is constant for each run/experiment
What is the formula for survivor curve?
What is the formula for the Thermal Death Time Curve?
What is the standard temperature for Survivor curve?
total heating time in minutes
initial number of bacteria per gram or per cc PRIOR to the heating process
number of bacteria per gram or per cc AFTER the heating process
time in minutes at 250°F required to transverse one log cycle on a survivor curve or to kill 90% of the bacteria
The food industry commonly uses __D's in retorting foods to make sure that it is safe for human consumption
Time in minutes at 250°F required to kill all the bacteria
temp (°F) used other than 250°F
time in minutes at the temp used other than 250°F required to kill all bacteria
°F required to transverse 1 log cycle on a thermal death time curve
Acid foods have a pH of...
pH of 4.6 or less
Why are acid foods normally not retorted?
Because C. botulinum can't grow and produce its toxin at pH levels less than 4.7
Low Acid Foods
pH with or above 4.7 ~ normally retorted if C. botulinum is not a problem
List the 4 food constituents that slow heat penetration
1. Sugar 2. Starch 3. Protein 4. Fat/Oil
Use the shortest heat treatment time that produces cans with no evidence of bacterial survival (non-bulging cans)
___ moreso than temp is usually the factor that damages food flavor, color, and texture
List the 2 forms of pasteurization of milk
1. Vat or Batched 2. HTST - High Temp Short Time
High Temp Short time ~ milk is heated to at least 161°F and held at least 15 seconds and cooled to at least 45°F
What label goes on the X-axis of semi log paper for the Thermal Death Time Curve? The Y-axis?
X-axis: "Temperature in °F" Y-axis: "Time in minutes"
What label goes on the X-axis of semi log paper for the Survivor Curve? The Y-axis?
X-axis: "Number of bacteria per gram or cc" Y-axis: "Time in minutes"
List 3 forms of heating foods prior to consumption
Cooking, frying, boiling
makes foods more palatable, tender, and destroys a large portion of microorganisms and natural enzymes in foods
List the 3 commercial forms of heat preservation of food
1. Blanching 2. Pasteurization 3. Canning
What is sterilization?
The complete destruction of microorganisms
Because of the resistance of certain bacterial spores to heat, sterilization frequently requires a treatment of...?
At least 21°C of wet heat for 15 minutes and every particle of the food must receive this treatment
Degree of sterilization at which all pathogenic and toxin-forming organisms have been destroyed ; may contain a small number of heat resistant bacterial spores
Most canned and bottle foods are ______ sterile.
Heat treatments of choice
The mildest heat treatments that guarantee freedom from pathogens and toxins and produce the desired storage life - ensures the highest food quality and conserves energy
What 2 things must be known to select a safe heat-preservation treatment?
1. Time-temp combination required to inactivate the most heat-resistant pathogens and spoilage organisms in a particular food 2. Heat-penetration characteristics in a particular food
Heat energy is transferred by what 3 things?
1. Convection 2. Conduction 3. Radiation
Why is wet heat more lethal than dry heat?
because moisture is an effective conductor of heat and penetrates into microbial cells and spores
List some constituents of foods that protect microorganisms against heat
Sugar, starch, protein, fat/oil
Describe the process of Inoculated Pack studies
organism (PA 3679) is inoculated into cans of food, then processed in a retort, then stored at a temp that would be favorable for growth of any surviving spores. They're periodically examined for evidence of growth/spoilage
What is the greatest practical importance in modern heat processing?
Different temperature-time combinations that are equally effective in microbial destruction and differ greatly in their damaging effects on foods
We separate heat preservation practices into what 2 broad categories?
1. Heating foods in their final containers 2. Heat prior to packing
List the 5 methods used in heating food in containers
1. Still retort 2. Agitating retorts 3. Hydrostatic cooker and cooler 4. Direct flame sterilization 5. In-package sterilization
List the 5 methods used in heating foods prior to packaging
1. Batch pasteurization 2. High-temp - short-time pasteurization 3. Aseptic packaging 4. Hot pack or hot fill 5. Microwave heating
- cans remain still while being heated - temperatures DONT exceed 121 degrees C ; heating time is relatively long
shaking/spinning the cans during heating to reduce processing time and improve food quality
Hydrostatic cooker and cooler
"U" shaped tube continuous retort and cooler
Direct flame sterilization
- sterilizing temps above 100 degrees C are needed - direct flame to contact cans as the cans are rotated as they are being conveyed pas gas jets
hot water sprays or steam jets in varying temp zones → cooling zones (must be gradual to prevent shock)
Batch pasteurization "holding method of pasteurization"
Earliest method of pasteurizing liquid foods to heat the food in a vat with mild agitation; destroys pathogens & inactivates the enzyme lipase (lipase = rancid milk)
Describe the process of Batch pasteurization
raw milk is pumped into a steam heated jacket vat, brought to temp, held for a prescribed time, and then pumped over a plate-type cooler prior to bottling
In HTST, it must be a temperature of at least __°F for at least __seconds
171°F ; 15 seconds
Food is sterilized outside of a can and then aseptically placed in previously sterilized containers and sealed in an aseptic environment
Hot Pack or Hot Fill
- packing of previously pasteurized or sterilized foods, while still hot, into clean containers under clean conditions
__ ___ is the most effective with acid foods.
heats foods in a unique fashion that largely eliminates temperature gradients between the surface and the center of food masses - produces heat in materials that absorb it
GMPs (Good Manufacturing Practices) ~ Why do we have them?
The FDA requires thermal processing to be carried out under GMPs to assure food safety and wholesomeness
Hot Pack Canning ~ What foods?
Jam, acid juices, sauerkraut
In-Package Pasteurization ~ What foods?
food and beverages in cans, bottles, and jars ex: beer containers
What are the pros and cons of Aseptic packaging?
Good: Rapid/fast Bad: must be very careful of contaminmation
What is the mildest heat treatment? The most severe heat treatment?
The mildest heat treatment = Blanching The most severe heat treatment = Retorting
Chapter 8- Heat Preservation and Processing21 terms