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food processing > Thermal Processing > Flashcards

Thermal Processing Flashcards

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1
Q

Who invented canning? When?

A

Nicolas Appert; early 1800s

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2
Q

What is “retort” processing, and when did it first become used?

A

Pressure cooking; 1850 (Appert-Chevalier)

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3
Q

When did computerized applications for thermal processing begin?

A

1960s

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4
Q

What is Louis Pasteur known for?

A

Discovery of microbiological basis of spoilage

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5
Q

What was the original method of sterilizing?

A

Boiling water, corked glass bottles

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6
Q

True/False: the Ball formula is still used as an industry standard today.

A

True

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7
Q

In the 1920s, Bigelow, Etsy, Prescott and Underwood made important developments in…(3)

A
  • classifying acid/low acid foods
  • importance of C botulinum
  • *created GENERAL METHOD for process calculation
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8
Q

Further improvements on the general method were made by ____ and ____.

A

Ball

Stumbo

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9
Q

Which is more accurate, Ball or Stumbo method?

A

Stumbo

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10
Q

What developments were made in the 2000s? (3)

A

high pressure pasteurization
High pressure + high temperature for sterilization
pulsed electric field (non thermal)

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11
Q

True/False: commercially sterile means there are NO viable microbes in the product.

A

False; refers to shelf stability
No viable microbes of significance to public health/spoilage concerns
(certain thermophiles may still be present)

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12
Q

Name the key developments in sterilizing equipment in the 1950s (5)

A
  • Continuous Agitating cookers
  • Flame sterilization
  • HTST or UHT or ASEPTIC processing
  • Bulk processing in 55gallon drums
  • Storage of sterilized liquid in large steel tanks
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13
Q

When did thermal processing sterilization equipment become fully automated/computerized?

A

1980s

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14
Q

What factors in canning act to make it commercially sterile? (5)

A 
Heating (or alternative)
lowering pH
Adding chemicals (preservatives)
Lowering Aw
Sealing to keep sterile
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15
Q

What are tetra paks, and when did they come into use?

A

Cartons made from waxed cardboard/plastic material, filled under aseptic conditions (sterile containers and contents) - for dairy or fruit beverages
1960s/70s

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16
Q

The key developments in 1960/70s were: (3)

A

Tetra-paks
Crateless retorts
Hydrostatic sterilizers

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17
Q

For what types of products would a scraped surface heat exchanger be useful?

A

Viscous products; scraped to prevent from burning

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18
Q

Why would an agitating system be advantageous over a stationary system?

A

Faster rate of heat transfer, more even heat distribution

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19
Q

What are the alternative processing treatments established in the 1990s? (3)

A

Microwave/Radiofrequency heating
Ohmic heating
Acidification + Pasteurization

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20
Q

What are the key developments in sterilizing equipment in the 1980s? (3)

A

computerized/automated systems
scraped surface heat exchangers
agitating vs stationary systems

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21
Q

Acidic products are notable because they prevent ___ growth.

A

spore

also prevents most microbes/fungi

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22
Q

What is the “blanching” step? When does it happen, for what products, and what is the purpose?

A

Mild heat treatment (1-5 min of boiling)

  • prior to adding to cans
  • usually vegetables, some fruits
  • stop enzyme activity, expel gases, soften tissue (packing purposes), reduce microbial load
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23
Q

What enzymes are of main concern in plants, and which one is used as an index for measuring inactivation by blanching?

A

Oxidative enzymes: PO, PPO, catalase, lipase, LOX, pectin esterase
PEROXIDASE used as index; most heat stable and widely present

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24
Q

How might acidification be beneficial to a product in terms of processing?

A

lowering pH allows for lower processing temperature (100C) for pasteurization, which can help retain quality.

25
Q

What is the ABCO blancher? Why makes it more efficient?

A

More efficient blanching equipment
Uses recycled steam
Heat-hold-cool approach: Steam to heat surface, hold to allow heat penetration, cool with humid air

26
Q

List the methods for peeling (5)

A 
By hand
Mechanical (knives)
Chemical (Lye, caustic soda NaOH)
Abrasive
High Pressure steam/water
27
Q

Blanching (IS/IS NOT) a highly energy intensive process, and requires about ___% of the total energy for processing.

A

is; 35

28
Q

Describe the process of chemical peeling:

A

Lye or NaOH is applied to dissolve the skin
Application done with dip/spray
product then neutralized by ACID dip

29
Q

Potatoes may be peeled using: (2)

A

abrasive; high pressure steam

30
Q

What % of energy is lost during blanching?

A

66%

31
Q

What heat transfer media can be used for blanching?

A

Steam, Water, Microwaves, Air

32
Q

What is headspace and why is it important (3)?

A

Unfilled portion of can
gives room for expanding contents during heating (maintain can shape/integrity)
better vacuum
better agitation

33
Q

The _____ in canned foods is important and must be declared.

A

Fill Weight

34
Q

What are the benefits/negatives of peeling?

A

Good: better texture, hygiene
Bad: removing nutrients/minerals, extra step in process

35
Q

True/False: high acid foods treated at low temperatures (<100C) can still be shelf stable.

A

True: if pH is below 4.5

36
Q

True/False: if a pasteurized product is sealed, it will be shelf stable.

A

False; bacteria spores still active, and pathogens are only reduced in number. These products require refrigeration and have a shorter shelf life.

37
Q

The main goals of thermal processing is to? (2)

A

Prevent growth of:
spoilage bacteria
pathogens

38
Q

What pasteurized products will still require refrigeration? Why?

A

Low acid foods (>4.5)

only pathogens are CONTROLLED (reduced number); spores still active, so refrigeration needed to prevent fast growth

39
Q

What considerations should be made when calculating processing time in order to prevent overcooking? (5)

A

Integrate thermal destruction effect over entire process
Consider pH of food
Consider final storage temperature/storage life
Heating behaviour of food
Microbial destruction kinetics

40
Q

The simple act of vacuum sealing a can will prevent growth of _____.

A

Obligate aerobes

41
Q

What is the temperature range for sterilization?

A

100-150C (121 is reference)

42
Q

The main pathogen of concern in canned low acid food is _____. The process needed to ensure safety from this pathogen is ____.

A 
Clostridium botulinum
Bot cook (12D reduction)
43
Q

What process removes most of the air in headspace from cans?

A

Exhausting

44
Q

why should cans be stored at cool temperatures (<30C)?

A

To prevent thermophilic bacteria from growing (may not have been as affected by thermal processing)

45
Q

Why would air in the headspace be an issue? (2)

A

Growth of aerobic bacteria

expanding air will cause can swelling

46
Q

How are dimensions of cans described?

A

2 three digit numbers, representing diameter and height respectively
1st digit is INCHES, 2nd is sixteenths of inch
ex: 401x411

47
Q

What are the 3 exhausting methods?

A

thermal exhausting
steam closing
mechanical vacuum sealing

48
Q

Most molds require ____ for growth. This makes them ____ _____.

A

oxygen; obligate aerobes

49
Q

What strains are there of C. botulinum, and what conditions do they grow in?

A

Anaerobic, low acid
Mesophilic (strains A and B)
Psychrophilic (E)

50
Q

What step must take place after pasteurization?

A

Cool to below 4C within 2 hours

51
Q

What are the different temperature classes of bacteria?

A

psychrophiles (<5 to 35C)
mesophiles (10 to 40)
thermophiles (35 to 55C)

52
Q

The temperature range for pasteurization is:

A

55-100C

53
Q

What are the pH classifications of food?

A

low acid >4.5
medium acid 3.7-4.5
high acid <3.7

54
Q

What does the success of thermal processing depend on? (5)

A 
Removal of oxygen
Proper heat treatment
pH control
Sealed in sterile container
Proper storage
55
Q

What are can lacquers used for?

A

To prevent chemical reactions that may erode the can

56
Q

The classes of microbes based on oxygen requirements are:

A

Obligate aerobes
Obligate anaerobes
Facultative anaerobes

57
Q

What types of products may need can laquers? (3)

A
  • high acid (AR)
  • Sulfur resistant (SR)
  • contains pigments (R)
58
Q

How are standard cans sealed? What are some factors to judge if it is a proper seal?

A

Double seaming

countersink depth, width, overlap

59
Q

____ _____ can grow in complete absence or small presence of oxygen.

A

Facultative anaerobes

food processing (17 decks)

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