Lecture 3: Thermal Processing Flashcards
what did Nicolas Appert invent?
canning or appertisation
what did louis pasteur establish?
microbiologcal basis for food spoilage
what four scientists worked together to discover pH classification of foods?
what was the importance of pH classification?
bigelow, esty, prescott and underwood
importance:
- clostridium botulium only grew in certain pH levels
- established general method for process calculation
what is the ball formula method?
mathematical basis for process calculation
who revised the ball method?
what is this important for?
stumbo
integrated lethality
what did teixeira and manson discover?
computer applications for process calculations and optimization
who discovered retorting? what is it?
chevalier-appert
pressure cooking
what happens when you add salt to water?
increases the boiling point. Allows cooking in water to occur at higher temperatures
what is canning
- method of food preservation that renders a food and its container commercially sterile by the application of heat, alone or in combination with pH and/or water activity and/or chemicals
- the hermetically sealed container maintains sterility of food (prevents entry of microorganisms)
only kills pathogens
what is commercial/shelf sterility
rendering the product free of viable microorganisms of public health significance as well as those capable of reproducing the food under normal non-refrigerated conditions of storage and distribution
describe the steps of commercial canning operations
- harvest
- receiving raw product
- soaking and washing
- sorting and grading
- blanching
- peeling and coring
- filling
- exhausting
- sealing
- processing
- cooling
- labeling
- warehousing and packing
What is the exhausting step in canning?
when the lid of the can is heated with steam, which results in the air space of the can to be replaced by steam to create a vacuum
what is blanching?
mild heat treatment given to fruits and veg prior to freezing, drying and canning
what is the primary purpose of blanching in freezing and drying?
what are other purposes of blanching used in canning?
in freezing and drying: enzyme inactivation
in canning:
- expels intercellular gases (protects can integrity, better vacuum and heat transfer)
- softens tissues for more compact packing
- reduces product microbial load
what are examples of oxidative enzymes?
peroxidase catalse polyphenol oxidase lipase lipoxygenase pectin esterase
what oxidative enzyme is used as the index of blanching adequacy?
peroxidase
which oxidative enzyme is very heat resistant and has a wide occurrence?
peroxidase
what are some common blanching mediums?
water
stea
hot gas
microwave
blanching is….
energy intensive
what are examples of efficient steam blanching systems?
- ABO blanchers
- heat - hold - cool approach
- steam heating and recycling
- forced air cooling (fog get humidified)
what are methods of peeling?
- by hand
- high pressure and steam (for tomatoes and potatoes)
- mechanical (knives)
- chemical: lye peeling (using cuastic soda, dip/spray, acid drip)
what is the important of head space in cans?
- allows for expansion of products to occur when heated
- allows for space for mixing (since mixing can’t occur if the can is completely full)
- allows for high vacuum
what are the types of agitation?
- end over end: rotating up and down
- axial: rotating circularly
- shaken: side to side (most efficient)
what is exhausting?
- process of removing headspace from cans
- reduces strain on cans and jars during retorting
- provides O2 free environment vacuum)
what are 3 methods of exhausting?
- thermal exhausting
- steam closing
- mechanical vacuum sealing
describe the process of thermal exhausting
- hot filled cans are conveyed through a steam chamber (exhaust box)
- steam replaces air and can is sealed while hot
- on condensation, steam leaves a avacuum
how is steam closing different than thermal exhausting?
what is the benefit of steam closing compared to thermal exhausting?
steam closing is the same as thermal exhausting, except it uses high pressure steam injected into cans before closing
benefit
- more efficient
- less energy intensive
describe mechanical vacuum sealing
- clinched cans are subjected to vacuum
- remove headspace air
- high speed vacuum treatment
what are the dimensions of a 401 x 411 can?
4 and 1/16th inch diameter
4 and 11/16th inch height
what are can lacquers used for
for protecting cans that contain:
- high acid products (AR)
- containing pigments (R)
- sulfur resistence (SR)
what are the goal of thermal processing?
what is the goal from a safety and stability point of vieW?
main goal: to make the product safe and shelf stable
safety POV: reduce number of microorganisms of public health concern to a statistically small level
stability POV: kill all bacterial spores which can grow at storage conditions. Create an environment around food to suppress the growth and activity of other spoilage microorganisms
what is the most serious and heat resistant (low acid) microorganism?
clostridium botulinum
what is the survivor probability of clostridium botulinum?
1 in 10^12
the success of thermal processing depends on what factors?
- removing O2 from package
- controlling the pH
- giving adequate heat treatment
- controlling the storage temp
foods are packaged in ___ to prevent recontamination
hermetically sealed containers
what are the 3 types of oxygen requirements?
obligate aerobes
facultative anaerobes
obligate anaerobes
what is considered a low acid food?
pH equal or above 4.5
what is considered a medium acidic food?
pH = 3.7 - 4.5
what is considered a high acid food?
pH < 3.7
describe an obligatory aerobe
requires o2 for growth
describe an obligatory anaerobe
requires absence of O2 for growth
describe a facultative anaerobe
can grow in the complete absence or presence of only small amounts of O2
what is an example of an obligatory aerobe?
most molds
what is an example of an obligatory anaerobe?
clostridium botulinum
what is an example of a facultative anaerobe?
staphylococcus aureas
what type of organism grows best at:
35-55degC?
10-40degC?
0-35degC?
thermophyllic
mesophylic
psychrophylic
what is pasteurization?
- mild heat treatment that destroys pathogenic vegetative microorganisms
- temporary shelf life extension
- associated with hermetically sealed packaging
- heat treatment (55-100degC)
in pasteurization, how is spoilage controlled in low acid products?
they are refrigerated (below 4degC within 2h after pasteurization)
describe sterilization or appertisation
- application of heat for the purpose of shelf life extension and promotion of safety
- most severe heat treatment
- long term preservation
- commercially sterile
- heat treatment (100-150degC)
- associated with strong hermetically sealed packaging
what heat treatment is applied in pasteurization?
55 to 100degC
is sterilization or pasteurization for long term preservation?
sterilization
what is another name for sterilization
appertisation
what is the reference T value to kill pathogens and mesophilic spore formers in sterilization?
T= 121degC
what is killed in sterilization?
pathogens and mesophilic spore formers
vacuum sealed cans prevents the growth of _____
obligate aerobes
how should a high acid food be treated?
what does this do?
pasteurization
- this controls vegetative bacteria, yeasts, molds and enzymes.
- inactivates pathogens and spores
- makes shelf stable products for fruits and acidified foods
how can low acid foods be mildly and severely? (2)
- pasteurization: mild treatment (<100degC)
2. sterilization: severe treatment (>110degC)
in pasteurization of low acid foods, what remains active? what is controlled?
- pathogens are controlled
- bacterial spores are active
what is the minimum D-value process for clostridium botulinum during sterilization?
12D
what are the spoilage concerns of sterilization of low acid foods?
what is not a spoilage concern if stored below 30degC?
- mesophilic obligate anaerobes, which are more resistant than facultative types
- heat resistant thermophiles are not of concern if stored below 30degC
