Thermal Processing Flashcards
Who invented canning? When?
Nicolas Appert; early 1800s
What is “retort” processing, and when did it first become used?
Pressure cooking; 1850 (Appert-Chevalier)
When did computerized applications for thermal processing begin?
1960s
What is Louis Pasteur known for?
Discovery of microbiological basis of spoilage
What was the original method of sterilizing?
Boiling water, corked glass bottles
True/False: the Ball formula is still used as an industry standard today.
True
In the 1920s, Bigelow, Etsy, Prescott and Underwood made important developments in…(3)
- classifying acid/low acid foods
- importance of C botulinum
- *created GENERAL METHOD for process calculation
Further improvements on the general method were made by ____ and ____.
Ball
Stumbo
Which is more accurate, Ball or Stumbo method?
Stumbo
What developments were made in the 2000s? (3)
high pressure pasteurization
High pressure + high temperature for sterilization
pulsed electric field (non thermal)
True/False: commercially sterile means there are NO viable microbes in the product.
False; refers to shelf stability
No viable microbes of significance to public health/spoilage concerns
(certain thermophiles may still be present)
Name the key developments in sterilizing equipment in the 1950s (5)
- Continuous Agitating cookers
- Flame sterilization
- HTST or UHT or ASEPTIC processing
- Bulk processing in 55gallon drums
- Storage of sterilized liquid in large steel tanks
When did thermal processing sterilization equipment become fully automated/computerized?
1980s
What factors in canning act to make it commercially sterile? (5)
Heating (or alternative) lowering pH Adding chemicals (preservatives) Lowering Aw Sealing to keep sterile
What are tetra paks, and when did they come into use?
Cartons made from waxed cardboard/plastic material, filled under aseptic conditions (sterile containers and contents) - for dairy or fruit beverages
1960s/70s
The key developments in 1960/70s were: (3)
Tetra-paks
Crateless retorts
Hydrostatic sterilizers
For what types of products would a scraped surface heat exchanger be useful?
Viscous products; scraped to prevent from burning
Why would an agitating system be advantageous over a stationary system?
Faster rate of heat transfer, more even heat distribution
What are the alternative processing treatments established in the 1990s? (3)
Microwave/Radiofrequency heating
Ohmic heating
Acidification + Pasteurization
What are the key developments in sterilizing equipment in the 1980s? (3)
computerized/automated systems
scraped surface heat exchangers
agitating vs stationary systems
Acidic products are notable because they prevent ___ growth.
spore
also prevents most microbes/fungi
What is the “blanching” step? When does it happen, for what products, and what is the purpose?
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
What enzymes are of main concern in plants, and which one is used as an index for measuring inactivation by blanching?
Oxidative enzymes: PO, PPO, catalase, lipase, LOX, pectin esterase
PEROXIDASE used as index; most heat stable and widely present
How might acidification be beneficial to a product in terms of processing?
lowering pH allows for lower processing temperature (100C) for pasteurization, which can help retain quality.
What is the ABCO blancher? Why makes it more efficient?
More efficient blanching equipment
Uses recycled steam
Heat-hold-cool approach: Steam to heat surface, hold to allow heat penetration, cool with humid air
List the methods for peeling (5)
By hand Mechanical (knives) Chemical (Lye, caustic soda NaOH) Abrasive High Pressure steam/water
Blanching (IS/IS NOT) a highly energy intensive process, and requires about ___% of the total energy for processing.
is; 35
Describe the process of chemical peeling:
Lye or NaOH is applied to dissolve the skin
Application done with dip/spray
product then neutralized by ACID dip
Potatoes may be peeled using: (2)
abrasive; high pressure steam
What % of energy is lost during blanching?
66%
What heat transfer media can be used for blanching?
Steam, Water, Microwaves, Air
What is headspace and why is it important (3)?
Unfilled portion of can
gives room for expanding contents during heating (maintain can shape/integrity)
better vacuum
better agitation
The _____ in canned foods is important and must be declared.
Fill Weight
What are the benefits/negatives of peeling?
Good: better texture, hygiene
Bad: removing nutrients/minerals, extra step in process
True/False: high acid foods treated at low temperatures (<100C) can still be shelf stable.
True: if pH is below 4.5
True/False: if a pasteurized product is sealed, it will be shelf stable.
False; bacteria spores still active, and pathogens are only reduced in number. These products require refrigeration and have a shorter shelf life.
The main goals of thermal processing is to? (2)
Prevent growth of:
spoilage bacteria
pathogens
What pasteurized products will still require refrigeration? Why?
Low acid foods (>4.5)
only pathogens are CONTROLLED (reduced number); spores still active, so refrigeration needed to prevent fast growth
What considerations should be made when calculating processing time in order to prevent overcooking? (5)
Integrate thermal destruction effect over entire process
Consider pH of food
Consider final storage temperature/storage life
Heating behaviour of food
Microbial destruction kinetics
The simple act of vacuum sealing a can will prevent growth of _____.
Obligate aerobes
What is the temperature range for sterilization?
100-150C (121 is reference)
The main pathogen of concern in canned low acid food is _____. The process needed to ensure safety from this pathogen is ____.
Clostridium botulinum Bot cook (12D reduction)
What process removes most of the air in headspace from cans?
Exhausting
why should cans be stored at cool temperatures (<30C)?
To prevent thermophilic bacteria from growing (may not have been as affected by thermal processing)
Why would air in the headspace be an issue? (2)
Growth of aerobic bacteria
expanding air will cause can swelling
How are dimensions of cans described?
2 three digit numbers, representing diameter and height respectively
1st digit is INCHES, 2nd is sixteenths of inch
ex: 401x411
What are the 3 exhausting methods?
thermal exhausting
steam closing
mechanical vacuum sealing
Most molds require ____ for growth. This makes them ____ _____.
oxygen; obligate aerobes
What strains are there of C. botulinum, and what conditions do they grow in?
Anaerobic, low acid
Mesophilic (strains A and B)
Psychrophilic (E)
What step must take place after pasteurization?
Cool to below 4C within 2 hours
What are the different temperature classes of bacteria?
psychrophiles (<5 to 35C)
mesophiles (10 to 40)
thermophiles (35 to 55C)
The temperature range for pasteurization is:
55-100C
What are the pH classifications of food?
low acid >4.5
medium acid 3.7-4.5
high acid <3.7
What does the success of thermal processing depend on? (5)
Removal of oxygen Proper heat treatment pH control Sealed in sterile container Proper storage
What are can lacquers used for?
To prevent chemical reactions that may erode the can
The classes of microbes based on oxygen requirements are:
Obligate aerobes
Obligate anaerobes
Facultative anaerobes
What types of products may need can laquers? (3)
- high acid (AR)
- Sulfur resistant (SR)
- contains pigments (R)
How are standard cans sealed? What are some factors to judge if it is a proper seal?
Double seaming
countersink depth, width, overlap
____ _____ can grow in complete absence or small presence of oxygen.
Facultative anaerobes
