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HDSO Food Science > Lecture 4 > Flashcards

Lecture 4 Flashcards

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1
Q

When did canning start?

A

1795, the idea for food preservation started

1874 Retort for pressure canning was developed in the U.S.

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2
Q

What is the purpose of canning?

A

Canning involves heat treatment of foods to destroy enzyme actions and spoilage microorganisms

Food is sealed in sterile, airtight containers to prevent it from contamination by new sources

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3
Q

What is an acid food, what could contaminate it and how do we process those cans?

A

Acid Foods (pH < 4.5)

Fruits, tomatoes, pickles, sauerkraut, jams, jellies

Yeast and Molds : Heat Sensitive

Process in boiling water bath

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4
Q

What is a low acid food, what could contaminate it and how do we process those cans?

A

Low Acid Foods (pH> 4.5)

Meat, seafood, chicken, milk, fresh vegetables

Bacteria grow well

C. botulinum (spore former): Heat Resistant

Pressure Canner (120C)

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5
Q

What is the purpose of heat processing?

A

Safety
Preservation (increase shelf life)
Increase sensory and nutritional quality

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6
Q

Why is safety important in heat processing?

A

Micro-Organisms ↓
Natural Toxic Factors ↓

Trypsin Inhibitor (Raw Soy Beans)
-Protein inhibits action of trypsin that helps with the digestin of protien

Avidin (Raw Eggs bind with Biotin)
-Biotin B vitamin, whn cook eggs avidin is inactiavted and no loner available for binding

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7
Q

How can heat processing preserve milk?

A

Fresh Milk – 3 days

Past. Milk – 10- 14 days

Sterilized Milk – 1 year

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8
Q

Which is more effective in killing microorganisms dry or wet heat processing?

A

Wet Heat

  • Moisture is a good conductor of heat
  • Water penetrate into microbial cells and spores
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9
Q

What are the Effects of Fats and Oils on Heat Processing of Foods?

A

Mocroorganism overed by a layer of fat

High fat food dry heat is more effective

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10
Q

What is conduction?

A

Heat is directly transmitted through a substance when there is a difference of temperature between adjoining region

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11
Q

What is convection?

A

The movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under which consequently results in transfer of heat.

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12
Q

What are the Effects of Starch on Heat Processing of Foods?

A

When starch is heated in presence of water= geletanization (liquid to semi liquid)

When starch is in the system, and presense of water, becomes more viscous, moree dense and would slow down the heat transfer because the heat condiction is by conduction and not convextion (convection is faster but it turns to conduction bwhich is slower)

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13
Q

What is blanching?

A

Heating food in steam or hot water

Until the temperature of food reaches
82-87 0C

Then lowering temp. by adding cold water

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14
Q

What is the purpose of blanching?

A

Shrinks the product and provides a better fill of the container

Removes gases and provides a better vacuum after sealing

Destroys enzymes in foods

Fixes the natural colour of vegetables (Chlorophyll)

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15
Q

What does blanching inactivate?

A

Lipoxygenase: Off-Flavour

Polyphenol Oxidase: Browning Rxn

Ascorbic Acid Oxidase

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16
Q

What are the 2 kids fo heat processing?

A

Pasteurization (↑ shelf-life)

Sterilization

  • In-Container
  • Continuous (Aseptic Packaging)
17
Q

What is aseptic packaging?

A

Food is sterilized outside of the cans and then aseptically placed in sterilized containers and sealed in an aseptic environment

Processed outside of the can and packaged into container and sealed

18
Q

What is absolute sterilization?

A

Complete destruction of microorganisms

not achievable in food processing

19
Q

What is commercial sterilization?

A

There might be a few bacterial spores left in the food after heat processing, but they are inactivated and cannot grow or produce any toxins.

20
Q

What is the D value?

A

Time needed at a given temp to decrease the microbial population by one log cycle or 90%

21
Q

What is the Z value?

A

Temp. change required to change D-value by factor of 10

22
Q

What is the F value?

A

Time at specific temp. to destroy a specific number of M.O.

23
Q

What is the sterilization value?

A

F = (Sv) (D)

24
Q

What is still retort?

A

Pressure cooker

Simplest Method
Temp. must be less than 1210C
Longer Time
Best for Solid Foods

25
Q

What is agitating retort?

A

Less Time
Best for Liquids or
Semi-Liquid Foods

26
Q

What temps to still and agitated reports get too?

A

0.78 min at 1270C
5.27 min at 1180C
36 min at 1100C
330 min at 1000C

Give same results in terms of MOs presesnt at the end but all impact snespry protperties differently

27
Q

What are heat sensitive foods?

A

Milk
Meat
Juice

28
Q

What is the difference between batch and continuous heating?

A

Batch:

  • older
  • Longer Time
  • Lower Quality

Continous:

  • Faster
  • More Efficient
  • Less Damage
  • Higher Quality
29
Q

What temp is always better to use?

A

Always better to use high temp with shorter time to give the best results , especially for heat sensitive foods

30
Q

What is the most common temp for juice processing?

A

100 oC 12 Sec (Commonly Used)

121 oC 2 Sec (Commonly Used)

31
Q

What is the most common temp for milk processing?

A

62 oC 30 Min (Batch Past.)

72 oC 16 Sec (HTST)

135-150 oC 3-4 Sec (UHT)

HTST = High Temp. Short Time
UHT = Ultra Heat Treatment
32
Q

What does heat penetration depend on?

A

Type of product

Size and Shape of the container (small, tall)

Agitation promote convection

Type of Container (Aluminum, Copper)

33
Q

Where is the cold point when using conduction with more solid foods and convection with liquid/particulate foods?

A

Conduction comes from all directions if solid filling
Cold point center

When there is a different cin temp, the hot
Cold point at the bottom (colder and denser at bottom)

34
Q

What are inoculated pack studies?

A

When there is a different cin temp, the hot
Cold point at the bottom (colder and denser at bottom)

Use time and temp

35
Q

What are the most heat resistant bacteria?

A

Putrefactive anaerobe [PA 3679]

  • Bacillus stearothermophilus [FS 1518]
36
Q

How do they test to see if they’ve processed it enough to kill the MOs?

A

Do formula for when is the optimal time for cooking/foor processing

The process cans at all other times with the bacteria then store cans to grow the bacteria

Cans are checked for:
Bulging
Bacterial Count

Lower time higher preservation os sensory qualities. So if there are ano signs of spoilage they woll go with the lower one

37
Q

How can you tell a canned food is spoiled?

A
  1. Colour change, darker on top of the can
    Caused by air left in the jar (oxidation)
  2. Gas bubbles, bulging caps
    Caused by gas – forming bacteria
    **Discard
  3. Acid
    Caused by putrefactive bacteria
    **Discard
  4. Bad odour, softening of food
    Caused by putrefactive bacteria
    **Discard
  5. Toxin production
    Caused by C. botulinum
    **Discard
38
Q

What is the only way to determine food spoilage?

A

Only sight and smell

HDSO Food Science (17 decks)

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