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FOOD QUALITY & CULTURE > Food Preservation Methods > Flashcards

Food Preservation Methods Flashcards

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1
Q

what is food preservation

A

the science of extending the shelflife of food to maintain its nutritional quality and avoid the growth of unwarned microorganisms

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2
Q

how is shelf-life labeled

A
  1. date of minimum durability (best before)

2. expiration date (use by)

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3
Q

what is food spoilage

A

undesirable changes occurign in food due to airt, heat, light or moisture that motivates microorganism growth

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4
Q

how is food mainly spoilt

A
  1. microorganisms
  2. enzymes
  3. insects
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5
Q

two ways bacterial infections are caused

A

infections

intodications

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6
Q

carrier issues

A

healthy subjects hosting pathogens working in food industry might contaminate/transmit pathogens

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7
Q

main cause of food posioning?

A

cross contamination

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8
Q

how can one avoid cross contamination

A

avoid letting raw meats/animal products/raw veggies touch other food

always clean utensils/board

clean worktops with detergent

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9
Q

types of bacteria

A

cause spoilage
can be useful (health, fermentation)
dangerous (toxins/pathogens)

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10
Q

3 main sources of food contamination

A
  1. raw matieral I.e. meat, egg shells, fresh milk
  2. environment: storage of food, breeding, cultivation
  3. manufacturting practice: failure of HAACP
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11
Q

types of preserved foods

A
  1. stored products [frozen/dried/canned]
  2. semi preserved products [pasteurized, chilled]
  3. processed [fermented, salted, seasoned, smoked]
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12
Q

methods of preservation

A

phsyical
chemical
biological (fermentation)

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13
Q

physical preservation methods

A 
refridgeration 
freezing 
modified atmosphere packing 9MAP)
high  temperature 
pasteurization 
sterilization 
packaging (tetrapak/aspeptic)
dehydration 
concentraiton
lyophillization (free drying)
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14
Q

chemical prservation methods

A 
salting
sugaring
vegetabale oils
vingegar
ethyl alcohol
food smoking/liquid smoke
use of preservatives
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15
Q

explain the process of refrigeration

A
  • 1 to 8.C
    1. food is refrigerated during transport/storage and sold at room temp (fruit/veggies)
    2. food fully sold/distributed in fridge
    i. e. meat, milk, fish, salads, etc.
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16
Q

explain the process of: CA (controlled atmosphere)

A

oxygen kept at 5%
carbon dioixe at 1-3$
temperature dependign on food

used to extend post-harvest life of fruits

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17
Q

how does CA extend the harvest life of fruits

A
  1. reducing oxygen= reduces microbial contamination
  2. hydrating in water and creating acidic environment by carbnon dioxide= kills them
  3. inhibits enzymes/tissue metablism
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18
Q

where is oxygen icnreased in CA

A

for red meat storage to increase myoglidoin red pigment meat colour

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19
Q

why is adding oxygen bad to food

A

promotes enzymatic/chemical oxidation
activates beta-carotene degradation
substrate of respiration of plant/microbial cells

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20
Q

explain the process of: MAP (modified atmosphere packaging)

A

extends shelf life by creating barrier using packaging (to gas/contaminants) or vacuum packaging

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21
Q

example of MP matieral

A

polyvinyl chloride
polypropylene
polyethylene
vacuum packaging

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22
Q

where/which foods is MAP used

A

fresh apsta
baked goods
meats
frest cut fruts coffee

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23
Q

proces of vaccum packaging

A

pressure put below atmopshreic value

  1. stored in CRYOVAC (waterpoof vaccum)
  2. bags sealted under vaccum
  3. pacakge immersed in water at 90C
  4. hearable film adheres to film
24
Q

types of freezing methods

A

flash freezing
industrial flash freezing
deep freezing

25
Q

explain flash freezing

A

food quickly frozen at extreme cold temperature between -0.5/4 degrees which stops enzymatic reactions when water is solidifed

is fast to create smaller icecrystals that don’t damange the food

26
Q

what is industrial flash freezing

A

forms smaller chrystals at fast temprature

27
Q

how does flash freezing occur

A

sample placed in sample with liquid nitrogen/dry ice + ethanol

or

product pressed between 2 plates at -40/50 c (spinach cubes)

or

bulk subjected to jet of air in tunnel/freezing cells (peas, carrots)

or

product sealed in wterpoof packaged in placed in non freezable liquids (poultry)

or direct use of freezing product

28
Q

what is the cold chain?

A

how products are frozen from raw matieral to consumers to fridege/freezer in the supply chain in :
procurement, trasnport, storage and customer retail

29
Q

cons of just deep freezing

A

creates larger chrystals that when thawing, might damage the nutritional properties of food

30
Q

high temperature methods

A

blanching

pasteurization

31
Q

what is blanching

A

slighly cooking food (veggies) to inactivate enzymes/slow them down and:
clean surface from dirt and mold
brighten colour
make it easier to cook/pack

32
Q

what is pasterurization

A

heat prevents bacterial flora to ferment

other proesses often used with it (chemicals, vaccuum packaging, freezing)

33
Q

types of pasteuriziation

A

high temperature (70-75 c for few minutes)
low (60-65 for 30 minutes)
HTST: high temperature and fast time (liquid for few seconds)

34
Q

how is milk pasteruized

A

HTST applied isuing steel plates

kills lactophillus bacteria which need sto be added in after pasteurization for lactose fermentation

35
Q

two types of milk

A

extended shelf-life milk (extremment HTST)
raw unpasteruzied milk (special outlets and filtering rules)
pasteurized

36
Q

what is sterilization

A

kills all microboial forms to can them/jar them

37
Q

how does commercial sterilization occur

A

temperature related to acidity of the food for canning
(if pH lower than 4.5 100 c used, if higher: 115-120)
especially for meat products

38
Q

compromise in sterliziation

A

high temperature: microbio safety

moderate temp: product quality

39
Q

method of sterilization

A
  1. pressure cookers used (autoclaves)
  2. steam injected at high temperature
  3. indirect UHT (ultra high tempt), direct UHT
  4. cooling
  5. aspeptive pacakging in sterile containers
40
Q

packaing methods

A

tetrapak

aspeptic packaing

41
Q

tetrapak composition

A

paper (75), plastic (20), aluminum (5)

42
Q

aspeptic packaging process

A

sterilized food placed into sterile containers
superior nutritional quality but shorter duraiton and prevents additive use
must be santiized by hydrogen perodixe vapour (which is ecological as split into oxygen and water)

43
Q

dehydration method

A

water encourages micro/enzyme activity: hence:
total dehydration for milks/cereal
partial dehydraiton for tomato juice/fruitjuise

often combined by other tech

44
Q

methods of dehydration

A
  1. cold
  2. hot (special evaporater machines or industrial ovens)
  3. concentration
  4. lyiphillization
45
Q

pros of dehydration

A

long shelf life
reducton of volume and weight
lower tranpsort costs

46
Q

concentration method aim

A

reduce foods weight to make less expensive, easier to store and easier to transport

47
Q

dehydration types

A 
evaporation
cyroconcentraion (lowers coneglation point)
membrane technology (filtration and reverse osmosis)
48
Q

lyophillization method

A

freeze drying method; preserves biomatierals for extended perio to be used at room temperature using the process of sublimation (solid to vapour state)

49
Q

proces of lyophilliziation

A

rapid freezing of food at -30/40 and then dehydraiton by sublimiation in vaccum

50
Q

common food types lyophilized

A 
coffee
fruit and juice
veggies
meat
fish
eggs
dairy
51
Q

salting process

A 
dry salting (fish, sausages)
wet salting (for smoking, fridge, saline solutions, etc. )

salting= kills pathogens due to NaCl dehyrating them

52
Q

sugaring

A

use of sucrose to dehydrate microrganisms

53
Q

vegetable oils

A

protect food from air (like olive oil)

54
Q

issue with oils

A

clostridium bacteria can still develop anaerobically so contamination still possible

55
Q

food smoking process

A

exposesd cured meats, fish and dairty to aromatic wood to:

  1. increase palatabiltiy
  2. presreve food
56
Q

types of chemical preservatives

A 
sulphates
sorbic acid
ntirates
benzoic acid
salts
ascorbic acid

FOOD QUALITY & CULTURE (17 decks)

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