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who invented canning or "appertisation"?
Nicolas Appert
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who established the microbiological basis for food spoilage?
Louis Pasteur
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what is blanching?
mild heat treatment given to fruits and vegetables prior to freezing, drying and canning
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when is blanching a primary method?
- before freezing and drying
- before canning
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why is blanching done before freezing and drying?
for enzyme inactivation
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why is blanching done before canning?
- expels intercellular gases (protects can integrity, better vacuum, better heat transfer)
- softens tissue for more compact packing)
- reduces product microbial load
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which oxidative enzymes does blanching protect against?
peroxidase, catalase, polyphenol oxidase, lipase, lipoxygenase, pectin esterase
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what is known as the index of blanching?
- peroxidase inactivation
- because it is very heat resistant
- wide occurrence in foods
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what is blanching time?
- most vegetables (1-5min) boiling water or steam
- corn-on-cob (7-10min)
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what is the blanching medium?
water, steam, hot gas, microwave
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why is blanching energy intensive?
- 35% of total energy in processing
- 2/3 generally lost
- energy use: steam-water-MW-air
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which types of blanching have more pollution?
- water and steam
- (air and microwave have less)
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how can you make blanching more efficient?
- use an ABCO blancher (made by AAFC)
- use the heat-hold-cool approach
- steam heating and recycling
- forced air cooling (fog-jet humidified)
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how are most products peeled?
by hand
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which products are peeled with high pressure steam/water?
potato, tomato
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which products are peeled abrasively?
potato, carrot (roots)
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which products are peeled mechanically (knives)?
apples, pears, pineapple
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how are products are peeled chemically?
- lye peeling
- caustic soda (NaOH) dissolve product skin
- dip or spray product (concentration, temperature, time, agitation)
- washing in acid dip
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how is a can declared "full"?
by declared fill weight
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when is headspace not important?
in hot-fill process
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when is headspace a must for containers?
- at high temperature
- under agitation (end-over-end and axial)
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what is exhausting?
- the process of removing headspace as from cans
- reduces strain on cans and jars during retorting
- provides oxygen free environment (vacuum)
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what are the three methods of exhausting?
- thermal exhausting
- steam closing
- mechanical vacuum sealing
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what is thermal exhausting?
- hot filled cans conveyed through a steam chamber (exhaust box)
- steam replaces air and can is sealed while hot
- on condensation, steam leaves a vacuum energy intensive
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what is steam closing?
- same principle as thermal exhausting
- instead of slow exhausting, high pressure steam injected into cans prior to closing
- more efficient
- less energy intensive
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what is mechanical vacuum sealing?
- clinched cans are subjected to vacuum
- removes headspace air
- high speed vacuum treatment (may not remove dissolved air from product)
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how are can dimensions expressed?
give an example?
- using 2 numbers (3 digits each) either in tin, steal, aluminum
- ex: 401x411 (means 4 and 1/16" diameter from outside edge of both double seams, by 4 and 11/16" in height (outside edge of both terminal seams)
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what is the purpose of thermal processing?
- to make the product safe and shelf-stable
- reduce the number of microorganisms of public health concern to a statistically small level
- create an environment around food to suppress the growth and activity of spoilage microorganisms
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what does the success of thermal processing depend on?
- removing oxygen from package
- controlling pH
- giving adequate heat treatment
- controlling the storage temperature
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how can recontamination be prevented once foods have been thermally processed?
package the foods in hermetically sealed containers
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what are obligate aerobes?
- microorganisms requiring oxygen to grow
- ex: most molds
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what are facultative anaerobes?
- microorganisms that can either make ATP using oxygen, but if no oxygen is available, they can use fermentation instead
- ex: s.aureus
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what are obligate anaerobes?
- microorganisms that grow without oxygen, some can even be killed by oxygen
- ex: c. botulinum
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what is a low acid food?
- pH ≥ 4.5
- ex: all meats, fish, vegetables, most soups
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what is a medium acidic food?
- pH 3.7-4.5
- ex: fruit jams, fruit cocktails, grapes, tomato, peach, pimiento, pineapple, potato salad, prune juice, vegetable juice
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what are thermophylic bacteria?
grow in 35-55°C
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what are mesophylic bacteria?
grow in 10-40°C
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what are psychrophylic bacteria?
grow in 0-35°C
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what is a high acid food?
- pH < 3.7
- ex: fruit juice, apple, berries, cherries,plum, sour pickles, sauerkraut, vinegar
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what is pasteurization?
- mild heat treatment
- destruction of pathogenic microorganisms
- temporary shelf-life extension
- product refrigerated to control spoilage
- temperature applied (55-100°C)
- lower the product temperature to below 4°C within 2 hrs after pasteurization
- associated also with hermetically sealed packaging
- for low acid product with refrigeration, added acids, added sugar or added salt
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what is sterilization?
- also known as appertisation
- application of heat for the purpose of shelf life extension and promotion of safety
- more severe heat treatment
- long term preservation
- "misnomer" because product not sterile
- "commercially sterile"
- temperature applied of 100-150°C, reference T-121°C
- associated with strong hermetically sealed packaging and storage at below 30°C (usually at room temp)
- environment will prevent the growth of microorganisms of public health concern and spoilage type
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if a can is vacuum sealed (no obligate aerobes), what does pasteurization do to a high acid food?
- control of vegetative bacteria, yeasts, molds, and enzymes
- pathogens and spore formers inactive
- shelf stable products for fruits and acidified foods
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if a can is vacuum sealed (no obligate aerobes), what does pasteurization do to a low acid food?
- only pathogens controlled
- bacterial spores active
- only short term storage at refrigerated conditions
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if a can is vacuum sealed (no obligate aerobes), what does steriliization do to a high acid food?
- public health concern: c. botulinum
- bot cook - 12D process is required
- spoilage concern (non-pathogenic)
- mesophylic obligate anaerobes (more resistant than facultative types)
- heat resistant thermophiles are of no concern if stored below 30°C
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