Topic 4 Flashcards
Food processing
conversion of raw animal & plant tissue into forms that are convenient and practical to use
what is the purpose of food processing?
To make the food palatable
Make it more convenient
Improve taste (ex: strawberry jam vs. strawberries)
To increase shelf-life
food preservation
the use of specific thermal and non-thermal processing techniques to minimize the number of spoilage
increase the shelf-life of a food
spoiled
no longer palatable
physical appearance changes, moisture is lost
are all spoiled foods no longer edible or safe?
no
what are the 3 classes of food preservation?
physical
chemical
biological
physical food preservation techniques involved
asepsis
drying
heating
cooling
irradiation
blanching
heat
what type of preservation doesn’t include chemicals or microbes?
physical
what is goal of physical preservation?
to prevent the food from changing its physical properties (ex: moisture loss)
describe the affect cooling has on food
decreases growth rate of microbes
describe the affect freezing has on food
stops growth of microbes
frozen water is unavailable to microbes
blanching
heating followed by immediate freezing deactivates indigenous enzymes of the food that reduce the food’s quality (ex: enzymes that oxidize vit C)
enzymes can change colour of food
colour of blanched food is ____ than food that isn’t blanched
brighter
irridiation
methods of killing microbes
chemical food preservation
addition of sugar, salt or chemical preservatives
preventing oxidative rancidity is what type of food preservation?
chemical
preventing browning of apples is what type of food preservation?
chemical
what effect does salt have as a food preservative?
causes osmosis killing microbes, increases water holding capacity
what effect does sugar have as a food preservative?
hydroscorbicity making water unavailable to microbes
biological food preservation
fermentation
what effect do microbes have on food?
produce enzymes that produce compounds in foods- may or may not be harmful
can make the food unpalatable
what occurs when microbes break down food?
release ammonia
many foodborne illnesses are caused by what type of microbes?
aerobic
oxidative rancidity
rxn with oxygen & unsaturated FA
chemical oxidative rancidity
production of synthetic enzymes
biological oxidative rancidity
enzymes produced by microbes
aspesis
practice to keep micro-organisms out of food, protective coverings around food
what are the coverings used in aspesis?
Shells of nuts
Die skins of fruits & vegetables
Shells of eggs
Skin or fat on meat or fish
(also includes packaging - wraps, polythene covers, canning etc.)
what are the benefits of asepsis?
prevents moisture loss
prevents entrance of microbes
prevents oxidation
drying
removal of water from foods
inhibits growth of microbes
how was drying accomplished in ancient times?
sun drying
plate drying
puts the food in a single layer & puts it in the dehydrator
Dehydrator will have: Heat source & fans (push out moist air)
Moisture will leave food & remain in the air, when the moisture in the air is equal to the food, the food can longer be dried (no gradient is established). When this happens, new air is established by the fans pushing out the moist air
what is a negative & positive effect of plate drying?
Food that undergo this process lose most of their vit C
cheap
drum drying
dry liquids to make powders, drum is hot & rolls, as it rolls the liquid food is coated on it & the food dries out
spray drying
spray liquid food into a hot chamber, liquid droplets immediately dehydrate when introduced into the hot chamber. There is a vacuum pump that moves out the moist air
how is milk dehydrated?
spray drying
does drum or spray drying work better?
spray
is drum or spray drying cheaper?
drum
freeze drying
based on sublimation, put food in freeze drier that has vacuum pumps attached, moisture will escape as a vapour, the vacuum takes out the moist air causing the food to constantly lose its moisture & dry
what needs to occur to the food after freeze-drying & why?
When you remove the food product & place it into moist air, the food will regain moisture vacuum packed immediately after treating
what is a positive effect of freeze drying?
Doesn’t require heating - no vits or minerals destroyed, method of least nutrient loss
what drying method results in the least nutrient loss?
freeze drying
what is the problem with drying by heat?
loss of heat sensitive nutrients including vit C, riboflavin & niacin
drying by heat
Heat is applied to remove water to kill microbes, not to kill microbes directly
what envr factors are important in drying?
temp & moisture level
the longer the heating process =
the more vit & mineral loss
thermal processing
Food shelf life can be extended if sufficient heat is applied killing microorganisms & inactivating the present enzymes in food
pasteurization
• Heating foods to a specified high temp for a short time kills most disease-causing microbes
slightly extends shelf-life by killing most food spoilage & pathogenic organisms
Kill most microbes
sterilization
a more severe process which destroys all microorganisms & may change the organoleptic qualities of the product
Kill all microbes
canning
food is held at a high temp for several minutes
what is the closest form to sterilization in the industry ?
canning
Batch pasteurization (LTLT)
product is held in a specific temp range for a long time, low temperature, long time
Ex: 62-36C for 30-35 mins
High temp, short time (HTST) pasteurization
product is heated to a higher temp but for a shorter time
Ex: 72C for 15 secs for milk, using a plate heater
what method of pasteurization is more common?
HTST
ultra-high temp pasteurization
heats at very high temp under pressure
kills almost all microbes
what type of pasteurization do unrefrigerated milk products use?
ultra-high temp pasteurization
the longer the food is heated =
the more vits are lost
what form of pasteurization causes the most nutrient loss?
LTLT
sterilization
complete destruction of microbes
Food is exposed to wet heat (vapour) for 15 min at 121C
what type of microbes are killed in sterilization?
Pathogenic & toxin-producing organisms
Spoilage microorganisms
what temp is used in sterilization?
over 100 C
pressure cooking
atm pressure is increased to increase the BP of water (hotter), destroys spores & microbes
incres BP =
more destructive to microbes & spores
&
food cooks faster
how can pressure cooking result in food poisoning?
If correct temp isn’t reached, there is a possibility that the spores will germinate & could lead to poisoning
ultraheat treatment of ultrahigh temp (UHT)
Continuous process & product is packaged after sterilization into sterile containers
product is moving continuously rather then being stationary
how does sterilization & UHT differ?
UHT - shorter time & higher temp
canning
food is held for a number of mins at a high temp
above 110C & under pressure