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Food Fundamentals 2 > Food Preservation > Flashcards

Food Preservation Flashcards

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1
Q

What % of the worlds food supply is lost by spoilage?

A

25%

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2
Q

What % of landfills in the US are food?

A

20%

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3
Q

What is food spoilage? what are the most perishable foods?

A

-decomposition an loss of nutritive value
-consumption by microorganisms
-obvious and detectable
Most perishable foods = high protein and or water

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4
Q

What are the 3 changes that lead to food spoilage?

A

1) Biological
2) Chemical
3) Physical

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5
Q

What are some biological changes ?

A

Yeasts, bacteria and molds

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6
Q

What are some chemical changes ?

A

Enzymes that are naturally present, increase or decrease

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7
Q

What are some physical changes ?

A

Water loss and separation

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8
Q

In biological food spoilages, what is yeast? what does it do?

A
  • A fungus (plant that lacks chlorophyll)
  • Ferments sugars
  • Used for producing foods such as bread and alcohol
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9
Q

In biological food spoilages, what is bacteria & mold? what does it do?

A
  • Can produce toxins
  • mold is visible, bacteria is not
  • BACTERIA can ferment sugars
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10
Q

How can we destroy or inhibit the growth of bacteria and molds?

A
  • boiling
  • refrigeration
  • drying
  • curing (high sugar and salt)
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11
Q

In chemical food spoilages, what are enzymes? what does it do?

A

-catalyze relations and are categorized by their substrate and mode of action

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12
Q

What do proteases do? lipase? carbohydrates?

A

Protease (proteins -> AA)
Lipase (TG -> FA + glycerol)
Carbohydrase (CHO -> glucose)

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13
Q

In chemical food spoilages, what are non enzymatic reactions? what does it do?

A

-oxidation of fat, maillard rxn.

May occur with long storage of non-fat dry milk (lactose + protein = non enzymatic browning)

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14
Q

What are some physical changes in food spoilage?

A
  • evaporation/dehydration
  • separation
  • damage/mechanical bruising, tearing of tissues
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15
Q

What happens during separation?

A
  • drip loss
  • emulsion breakdown
  • syneresis (gel)
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16
Q

What are the methods of food preservation? ((6)

A

1) High temperature
2) Low temperature
3) Removal/tying up of moisture to control microbial growth
4) Keeping out Microorganism
5) Chemical preservatives
6) ionizing radiations

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17
Q

What does growing do?

A

Removes water in food and inhibits growth of microorganisms

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18
Q

What are the types of commercial drying?

A
  • conventional
  • vacuum
  • osmotic
  • freeze-drying
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19
Q

What is conventional drying?

A

Uses heat, such as drying room, tunnel drying, spray drying and drum drying.

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20
Q

What s vacuum drying?

A

Uses low pressure

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21
Q

What is osmotic drying?

A

Uses strong syrup

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22
Q

What is freeze drying?

A

Vaporization of ice crystals

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23
Q

What is curing? What is added

A

Preservation with use of salt & drying

Sugars, spices and nitrates may be added

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24
Q

What is fermentation?What does it do?

A

Microorganisms (bacteria, yeast and holds) while convert CHO -? CO2 and ethanol
-Preserves food and creates changes in flavour, colour and texture

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25
Q

What do the chemical changes in fermentation depend on?

A
  • Raw material
  • Selected microorganisms
  • Processing steps
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26
Q

what are some fermented products of milk?

A

cheese, yogurts, buttermilk, sour cream

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27
Q

What are some fermented products of meats?

A

Sausages

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28
Q

what are some fermented products of grains?

A

Yeast breads
Beer and Sake (japanese wine)
Whiskey

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29
Q

what are some fermented products of vegetables?

A 
Pickles
Green olives
Sauerkraut
Kimchi
Miso
Soy Saue
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30
Q

what are some fermented products of fruit?

A

Wine

31
Q

What are some example of fermented foods?

A
  • Hakari
  • Kefir
  • Netetou
  • Natto
  • Kimchi
32
Q

What is pickling?

A

Preservation of acidification y adding acid/vinegar OR fermentation

33
Q

What is an edible coating?

A

A the layer of edible material (CHO, protein or fat) used on fruits, vegetables, cheese, nuts, dried fruits and processed meats

34
Q

What are some advantages of an edible coating ?

A
  • Increases shelf life
  • Improves handling
  • Improves appearance
  • Vehicle for added ingredients
35
Q

What is the 2 step process of canning?

A

1) Food packed into sterilized containers and sealed

2) Containers :”canned” (heated) to destroy microorganism and enzymes

36
Q

How are containers “canned”?

A

Extended boiling/heating to temperatures much higher than the regular boiling point

37
Q

What are the two methods of canning?

A

1) Boiling water process

2) Pressure canning

38
Q

When is the boiling water method ideal?

A

When items have a lower pH

39
Q

When is the pressure canning method is ideal? What happens? What does it destroy?

A

Ideal for high pH items.

Water is boiled at high temperature under pressure, and will destroy C. Botulinum

40
Q

Whats an example of a high acid food?

A

Fruits + tomatoes (pH 4.5 or below)

41
Q

How do we can high acid foods? How are microbes reduced? What happens to surviving organisms?

A

High acid foods are safely canned in a boiling water bath. The heat resistance of microbes is decreased by the acidic pH and can be destroyed in reasonable processing times.
The surviving organism will not grow in an acidic diet.

42
Q

How an we can low acid foods? What does it require?

A

Requires a high processing temp to destroy the all-spore-forming microorganisms, particularly C. Botulinum.
Also requires a pressure canner where temp > boiling pt of water can be achieved.

43
Q

What are some examples of low acid foods?

A

Vegetables, meat, fish, poultry and milk

44
Q

What are 3 methods of heat preservation?

A

1) boiling
2) Pasteurization
3) Ohmic Heating

45
Q

what is boiling?

A

The simplest method, for 10 minutes at boiling water

46
Q

What is pasteurization?

What does it kill?

A

Liquids are heated to a certain temp for a certain period of time.
Kills bacteria, yeasts and molds

47
Q

What is the temperature range and time for pasteurization?

A

71C for 15 seconds, OR 138C for 2 sec

48
Q

What is ohmic heating? What uses ohmic heating?

A

Electrical current passed through food, generating heat that destroys microorganisms.
Liquids eggs, fruit juices.

49
Q

What are the two types of cold preservation?

A

refrigeration and freezing

50
Q

What does refrigeration do? What is the temperature?

A

Slows down the biological, chemical and physical reactions that shorten shelf life of food.
Just above freezing or less than 4C

51
Q

what kinds of foods are best refrigerated?

A

Mostly high water content foods

52
Q

What is freezing? At what temperature?

A

H2O is unavailable to microorganism, slows chemical and physical reactions (enzymes)
Temperatures is -18C or 0F or less

53
Q

What are some problems with freezing?

A
  • reactions still continue (O2), so shorter life than canned goods
  • Recrystallization
  • Cell rupturing
  • Fluid loss
  • Freezer burn
54
Q

What are 2 changes that occur during freezing and the frozen stage? why does this occur?

A

1) Formation and growth of ice crystals
2)Freezer Burn
Since dispersion medium in most frozen foods is water

55
Q

What happens when ice crystals are RAPIDLY frozen?

A

Ice crystals are small and numerous, are mostly intracellular and gives superior food quality.

56
Q

What happens when ice crystals are SLOWLY frozen?

A

Ice crystals are large and fewer in number, form in extracellular spaces, upon thawing, loss of juices occur.

57
Q

What happens during freezer burn? Why does it happen?

A

Dehydration on the surface of frozen food, creates white or greyish patches.
Mostly caused by inadequate packaging, where water evaporates and may recrystallize on surface of food.

58
Q

What may occur during the frozen stage?

A
  • Oxidation of polyphenolic substances by polyphenolases in plant tissues .
  • Oxidation of fat
  • oxidation of ascorbic acid
59
Q

What does oxidation of polyphenolic substances result in?How can it be fixed ?

A

-Undesirable bronwing

Blanching vegetabes will destroy these enzymes which cause browning.

60
Q

What happens during oxidation of ascorbic acid? How can it be minimized? Where else is ascorbic acid lost?

A

Lost with long periods of frozen storage.
Can be minimized by blanching vegetables which inactivates ascorbate oxidase.
Some additional loss of ascorbic acid will occur during the blanching process.

61
Q

what is ascorbic acid?

A

Vitamin C

62
Q

What changes of colloidal substances occur during frozen storage?

A

-Retrogradation of starch + syneresis
-Toughening of cellulose
Breaking of emulsion
-Changes in nutritive value

63
Q

What nutritive losses occur in colloidal substances during the frozen storage?

A

Not much effect on macronutrients but 4% loss of vitamins in drip. (Vitamin C and Vitamin B, especially folate)

64
Q

What are some changes during freezing and frozen stage? Where does it come from?

A

Development of odours, from the accumulation of volatile carbonyl compounds in unbalanced or under blanched frozen vegetables

65
Q

How can these odours be minimized?

A

By blanching before freezing, using boiling water or steam

66
Q

By blanching before freezing, using boiling water or steam, how does this reduce odours of vegetables in the fridge? (4)

A
  • destroys enzymes responsible for development of off: flavours
  • Controls undesirable changes in colour and texture
  • Inhibits conversion of bright green chlorophyll to olive green pheophytin
67
Q

What is the disadvantage of blanching vegetables?

A

Loss of some vitamin C and folate

68
Q

What is irradiation?

A

Cold pasteurization

69
Q

How does irradiation occur? How does it destroy bacteria, holds and yeasts?

A

Treatment of food with ionizing radiation (Gamma rays, X-rays or electrons)- reduced microbial load on spices and dehydrates seasonings.

70
Q

What else does irradiation control?

A
  • Controls insects on wheat, flour and whole wheat flour.

- increases shelf life by preventing sprouting or germination in potatoes and onions

71
Q

What is Aseptic packaging?

A
  • Sterilized, packed and sealed own sterilized container under sterilized conditions.
  • Can sit at room temperature
  • Juice boxes, puddings, baby foods and UHT milk
72
Q

What is MAP packaging?

A
  • Composition of surrounding air is changed (usually a deer is O2, incr. in CO2)
  • Occurs in fruits and veg, meats/poultry and baked goods.
73
Q

What is hermetically sealed?

A

Foods that have been packaged airtight by a commercial sealing process.

74
Q

What does MAP stand for?

A

Modified-Atmosphere Packaging

Food Fundamentals 2 (26 decks)

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