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NUFS 100 > Lecture 5: Food storage > Flashcards

Lecture 5: Food storage Flashcards

1
Q

What is the most common form of food preservation?

A

Cold temperature food preservation.

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2
Q

What are the two main ways someone uses cold storage of foods?

A
  • Refrigeration

- Freezing

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3
Q

What dose low temperature actually do?

A

The use of low temperature can extend the shelf life of food.

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4
Q

What is “Refrigeration”

A

anything from 0 to 5 C

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5
Q

What is “Freezing”

A

anything from 0 to -18C

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6
Q

When was the first mechanical ammonia based refrigeration system invented?

A

in 1875

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7
Q

How dose a refrigerator work?

A

You have a box with a contained system that has a Refrigerant within it.

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8
Q

What is a refrigerant?

A

Liquid that evaporates inside the refrigerator to create cold temperatures

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9
Q

What are the two things that you need to know about chemistry to understand refrigerators?

A

When liquid evaporates it absorbs heat

When vapor condenses it releases heat.

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10
Q

What is one of the most common refrigerants?

A

Hydrofluorocarbons (HFCs)

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11
Q

What is the goal of food preservation?

A
  • minimize food spoilage
  • Maximize safety and stability
  • Maintain nutritional value and acceptability
  • goals may be short or long term.
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12
Q

What is the purpose of Refrigeration?

A
  • A means of gently reducing the temperature of a food item to slow down food deterioration due to microbes, chemicals, and enzymes.
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13
Q

True or false:
Refrigeration is often combined with other
preservation methods

A

True

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14
Q

Why is ammonia bad as a refrigerant?

A

Super toxic.

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15
Q

What is the best way to predict the length of time a food product will last in a fridge?

A

Through looking at the temperature of the fridge

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16
Q

What is the temp of the average of the household fridge?

A

4.5-7C

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17
Q

PHF means what?

A

Potentially hazardous foods

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18
Q

What type of microbes may grow in the fridge?

A

Psychrophilic microbes

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19
Q

True or false:

Refrigeration destroys all microbes?

A

false:

Other microbes are not destroyed by refrigeration temperatures.

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20
Q

When dose refrigeration work best?

A

When foods are cooled right after slaughter/harvest.

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21
Q

What do we do to employ rapid heat removal?

A

Hydrocooling, vacuum cooling

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22
Q

Refrigerated storage requires control of T, air circulation, and ______

A

humidity

80% to 95%

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23
Q

What are the effects of refrigeration storage on foods?

A
  • minimal effects on taste, texture, and nutritional value.
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24
Q

What are some adverse effects of refrigeration on foods?

A
  • Chill injury to fruits
  • Flavor/odour absorption
  • Changes in firmness, color, and flavor
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25
Q

True or false:

Refrigeration is not a good preservation method for every food.

A

true

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26
Q

Why don’t we put potatoes in the fridge?

A

it absorbed proteins and undergoes the miard reaction (browning)

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27
Q

What technology has ushered in the age of convenience foods?

A

Freezing

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28
Q

Who is the father of frozen foods?

A

Clarence Birdseye (1920’s)

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29
Q

What is the growth rate of frozen fruits and vegetables?

A

Sales are growing at a rate of 4% per year.

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30
Q

Why are sales of frozen foods increasing so much?

A
  • Increased consumption of plant-based foods
  • Convenience
  • New product offerings
  • Suited for small households.
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31
Q

Dose freezing destroy microbes and enzymes?

A

No, although it will greatly reduce the rate of food deterioration.

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32
Q

What happens to microbes when they are frozen?

A

They decrease in activity due to water being unabaibile (in solid form)

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33
Q

What happens to enzymes when they are frozen?

A

They maintain level of activity, which is why it is important to blanch foods before freezing.

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34
Q

Is there a set shelf life within frozen foods?

A

It is dependent upon the temperature.

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35
Q

What is the average temp frozen food is stored at?

A

-18 C or around it.

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36
Q

What is freezing point depression?

A

reduces freezing point below 0C

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37
Q

What depresses freezing point?

A

Dissolved substances in the aqueous phase will depress the freezing point.

38
Q

Method process analysis is

A

Macroscopic

39
Q

What is most important when attempting to maintain quality within frozen foods?

A

A fast freeze

The faster the freeze, the smaller the crystals

40
Q

How much more voluminous is ice than water

A

Water = x

ice = 1.09x

41
Q

What is the benefit of small ice crystals?

A

it results in better quality products

42
Q

Why are large ice crystals bad?

A

large ice crystals will damage the cell structure of fruits & vegetables and meats

43
Q

What is the result of inconsistent freezing rate in foods?

A

Inconsistent size of ice crystals

44
Q

What do you do when you want to maintain quality (texture) of froze foods.

A

Rapid freezing

45
Q

How do you promote the production of small ice crystals

A

modify the food product to increase surface area of he food product.

46
Q

What effect will large ice crystals have on foods?

A
  • damage plant and animal cells
  • Juice are released upon thawing
  • loss of moisture, water, soluble nutrients, firmness
  • poor quality products (soft texture)
47
Q

What effect do fluctuating temperatures have on food quality?

A
  • shorter shelf life

- thaw - refreezing cycle will make large crystals.

48
Q

How will moisture loss change the texture of frozen foods?

A

Freezer burn may be caused.

49
Q

What is freezer burn?

A

Frozen food damaged by dehydration and oxidation due to air reaching the foods surface.

50
Q

How do you prevent freezer burn?

A

Moisture resistant, airtight packaging.

51
Q

Why do vegetables need blanching prior to freezing?

A

Blanching inactivate enzymes in the vegetables. Helping to maintain original quality.

52
Q

What are the effect of over blanching vegies?

A

Loss of color

53
Q

What are the effects of under blanching vegies?

A

Stimulates enzyme activity

54
Q

What is blanching?

A

Treating vegetables with steam or boiling water for a short period of time and then shocked with ice water to halt the cooking process.

55
Q

What are the three main purposes of blanching vegetables?

A
  1. Denature (inactivate) naturally occurring enzymes to prevent spoilage.
  2. reduces microbial load (mild effect)
  3. aid in the removal of skins from nuts and fruits,
56
Q

What is a flum?

A

A common method of moving things around.

57
Q

When is blanching used?

A

before fruits/vegetables are frozen, caned, or dried.

58
Q

What is one of the chemical changes of enzymes within foods when frozen.

A

They can cause browning

59
Q

What Vitamin is lost in fruits when frozen?

A

Vit C is lost when frozen.

60
Q

Are fruits blanched?

A

Not normally, this is in order to maintain freshness.

61
Q

What is another method to control enzyme activity within frozen foods?

A

Use of chemical compounds can control enzyme activity

62
Q

What are methods of preventing browning

A

Addition of ascorbic acid to reduce browning

63
Q

What is it called when you try to make more money from your product?

A

Value added

64
Q

What are some compounds used as a “Prevention” of browning of frozen foods?

A

Citric acid, lemon juice and sugar syrup used but not as effective.

65
Q

What happens to fats when frozen?

A

They can undergo rancidity.

Undergoing oxidation of the fats, resulting in off-falvours and odors.

66
Q

What food products are most likely to see fat based rancidity?

A

Foods with high fat content.

Fish and meats.

67
Q

How do you prevent Fat rancidity when they are frozen?

A

Wrapping/packing material, vacuum packing them.

68
Q

What are three results of unintentional freeze concentration?

A
  • water would like to freeze as pure ice crystals
  • water “moves” and leaves concentrated solutes behind.
  • The solutes undergo deleterious reactions
69
Q

What are some desired outcomes of freeze concentration.

A

An alternative to evaporation processes

used for aroma reduction for higher quality products (Fruit juice, coffee, extracts)

70
Q

Freezing point decreases by 1.88 C for each increasing of how many moles of solute?

A

1 mole of solute decreases freezing temp by 1.885 C

71
Q

What are the three main categories of industrial freezing techniques?

A

Air

Contact pate

Immersion

72
Q

What are the three different types of freezing within the “Air” category?

A

Sharp freezing

Blast freezer

Liquidized bed freezer

73
Q

What is still freezing?

A

Placing the product in still cold air, allowing them to freeze.

74
Q

What is Blast freezing?

A

Pushing cold air at high velocity across a food product in order to freeze it as quickly as possible.

75
Q

What is Batch Blast Freezing?

A

Food stacked on trays in rooms or cabinets to be frozen.

76
Q

What is continuous blast freezing?

A

Product is frozen as it moves through a tunnel on a conveyer belt.

77
Q

What is the primary goal of blast freezing?

A

Fast freezing.

78
Q

What is a Fluidized bed freezer?

A

Refrigerated air is forced under a perforated tray and “products behave like liquid”

79
Q

What are the benefits of a Fluidized bed freezer?

A

Superior product quality, through quick freeze and minimal dehydration.

80
Q

What is the main use of Fluidized bed freezer?

A

Creates IQF food products for consumers and as ingredients in food industry formulations

81
Q

What is the process of Contact plat freezers?

A
  1. After loading the food products, the plates are pressed

2. refrigerant circulates through plates, freezing the product by contact.

82
Q

What is contact plat freezing used for?

A

Used for flat food products or “brick shaped packaged products’

83
Q

Where is one place the contact plate freezer used?

A

on fishing trawlers.

84
Q

What is the main freezing method around immersion?

A

Cryogenic freezing

85
Q

What is cryogenic freezing?

A

Food is exposed to -60C through direct contact with liquefied gases (LN2, or CO2)

86
Q

What foods are commonly frozen through cryogenic freezing?

A 
High value products such as:
Fish fillets 
Seafoods 
fruits 
Berries
87
Q

What is an example of a cryogenic food product?

A

Dippin’Dots are a cryogenically frozen ice cream.

88
Q

True or false:

Frozen foods can be more nutritious than fresh.

A

Sometimes true.

89
Q

How long dose it take between harvest of vegetable and consumption?

A

generally 2 weeks, meaning there is 2 weeks of deterioration.

90
Q

What is the % loss of nutrients in Green beans from harvest to plate?

A

45% (11-15 days from field to plate)

91
Q

Why are frozen vegetables better for your than fresh?

A

Because they are processes (frozen) the same day they are picked. limiting the amount of nutrient loss

NUFS 100 (10 decks)

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