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64 Cards in this Set

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why is 28 F considered refrigeration if water freezes at 32F
thats the freezing point of water but there are solutes, fats etc
bacteriostatic
mesophile
keep chilled, prevent growth (freezing, fridge temp)
bacteriocidal
can kill organisms
soda holds more gas as??
it cools, increased CO2 solubility
cooling
removing heat vs. putting in refer
when should cooling begin
immediately at harvest or slaughter
what happens with corn that loses sweetness?
doesnt change nutrition, just sweetness bc enzymes are making sugars into starch
heat removal of leafy vegetables
spray with cold water
heat removal of produce
cold air from evaporating liquid nitrogen can be used
heat removal of bulk liquids
heat exchangers: use cold water, glycol or brine
heat removal with carcasses
cold air in refrigerated area
-convection
ice bath: conduction
gentlest form of food processing
refrigeration/cold storage
is wet or dry heat more effective for killing pathogens, why?
wet because heat moves through water faster than dry air
starches thickening later etc
can keep them in convection mode longer now because they can thicken upon cooling
freezing methods
1. freeze in air
2. freeze by indirect contact with refrigerant
3. freeze by direct contact immersion in refrigeratn
explain same product but different cultivars
company supplies seeds, not as many choices bc of quality
-commercialization of agriculture and loss of farmers choice
freezing process
1. area closest to cold source freezes firt
2. water first
3. concentration of solutes...harder to freeze the rest
what happens when water super cools?
< 32 F
-disturbance leads to crystallization
-can be liquid below freezing
changes due to freezing
1. textural
2. break emulsions
3. denature proteins
4. colloidal suspensions
5. dehydration
6. ice crystals
explain freezing change in texture
rupturing of cells, loss of turgor
-leads to precipiation of solutes, conc effect
explain denaturing of proteins during freezing
solutes that concentrate but don't ppt, salt out
-acidic solutes become conc, drop pH, isoelectric pt issue
isoelectric point
pH of minimum solubility...coagulate
explain colloidal suspensions with freezing
concentration of anions and cations leads to loss of suspension. ppt out
explain dehydration with freezing
water freezes
concentrates solutes
water gradient
water moves and dehydrates
explain ice crystals and freezing
cells can be ruptured by crystals
ice cream slow freeze =
loss of volume
BTU
british thermal unit
calorie
amt of energy it takes to inrease 1 g of water 1C
specific heat
amt of atp it takes to increase a pound of water by 1F
specific heat with calories and BTUs
BTU: 1 lb food 1F
cal: 1 g food 1C
tons of refrigeration
number of BTU's it takes to convert 1 ton of water at 32F to 1 ton of ice at 32 F
144 BTU = ??
1 lb/1F
how can you decrease spoilage enzymes even more than just doing the -18C
blanch them before freezing
heat removal needed to maintain room
1. door openings
2. personnel
3. respiration: minimal
determining amt of refrig needed in freezing
1. heat removal before freezing
2. heat related to freezing process (latent heat of crystallization)
3. heat related to heat removal to get to desired temp
issues with freezing in air
1. if unwrapped...
-lose moisture during freezing and
-lose moisture during frozen storage
2. freezer burn
freezing in air issues are accelerated by
blast freezer
sublimation
frozen water changing to gas w/o going to water state
still air freezing, conduction or convection
conduction
two things you have to do for freeze in air
1. change temp of air
2. change velocity of air
most efficient heating or cooling method
countercurrent flow
how do you choose still or agitated retort
based on the type of food being processed
-size matters
how does a tubular heat exchanger work
1. scrapers will most of internal area
2. forces food to outer region so its in contact with cold surface
3. scrapers keep cold surface free of layer of frozen product
4. scrapers remove any ice crystals which form
5. scrapers keep product moving through the tube, no freezing tube solid
what happens when teh scrapers remove the ice crystals
they go into the food and act as seeds for further freezing of the product
why are meat/fish cooled more efficiently than vegetables and shrimp?
larger surface area
-vegs and shrimp might have air pockets in between that serve as insulation
pasteurization
requires that every particle reaches the required temp for the required length of time
pasteurization is a heat treatment that will...
kill human pathogens present in a product but not all orgs or spore formers
how is z value determined
1. plot D value v temp
2. draw best fit line
3. determine change in temp to get 1 log drop
what is the practical value of the z-value
allows us to determine how long it would take at a temp we never tested
-make determinations on preocessing based on theoretical kill b product degradation that would occur at a given temp
why frozen foods
1. save money, get more food
2. allows for long distance travel of foods
3. convenient
4. eliminate prep time
5. thawing/cooking only thing left and you can do them at the same time
how do you determine amt of refrigeration required?
1. heat from produce/food to reduce it to desired temp
2. heat of respiration during storage
3. heat loss due to door opening/ppl 2F
4. loss due to insulation properties of the cooler, efficiency
functions of heating
1. change sensory props, more palatable
2. change flavor/chemical make up
3. decrease mic load
-sterilization: veg cells killed easily but not spores
Spores: 121 C wet heat 15 mins, retort
-can take a long time, degrades, every part treated to proper time temp
4. inactivate nat enzymes
5. inactivate heat labile toxins
refrigeration v freezing
Refrigeration
-spoilage issue, psychrotrophs
-some pathogens, list mono
-slows enzymatic degradation
-short term storage, days to few weeks

Freezing:
-greatly decreases microbial spoilage
-prevents GROWTH of pathogens
-storage time greatly increased, months to years: FIFO
must release P in retort slowly to prevent?
1. cans imploding
2. jars bursting
3. flexible pouches from bursting
continuous retorts you must
regulate the rate at which the product moves from pressurized situation to atmospheric pressure
still/batch retorts you must
regulate teh rate the steam is dissipated
retort loaded...pressure applied =?
steam
what happens when moisture in the food starts to vaporize
builds up pressure equal to the pressure in the applied steam
when is after pkging in package pasteurization used
beer...140F...will get killing of spilage microorgs but not overly affect the flavor
how is direct flame used with after pkging in pkg pasteur
pass cans directly over gas jets
-not used much
after pkg in pkg pasteurization typically runs at ?? P??
atmospheric pressure
does after pkg in pkg pasteurization result in sterile or commercially sterile food
no
after pkg in pkg pasteurization is gentle on>>?
glass containers
after pkg in pkg pasteurization typically uses?
steam or hot water jets to heat the product