Non thermal processing and thermal processing, concept, mechanism and application

1. M.Venkatasami,
Ph.D. (Processing and Food Engineering)
Department of Food Process Engineering
AEC&RI, TNAU.
NON THERMAL PROCESSING AND
THERMAL PROCESSING, CONCEPT,
MECHANISM AND APPLICATION

2.  Low acid: pH ≥ 4.6; Acid: pH < 4.6 (C. botulinum)
Classification of foods based on pH
Low acid:
pH > 5.3
 Red meat
 Poultry
 Seafood
 Milk
 Corn
 Peas
 Lima beans
 Potatoes
 Cauliflower
Medium acid:
4.5 < pH < 5.3
 Spaghetti
 Soups
 Sauces
 Asparagus
 Beets
 Pumpkin
 Spinach
 Green beans
 Turnip
 Cabbage
Acid:
3.7 < pH < 4.5
 Tomato
 Pear
 Fig
 Pineapple
 Apricot
 Yogurt
 White cheese
 Beer
High acid:
pH < 3.7
 Sauerkraut
 Pickles
 Berries
 Citrus
 Rhubarb
 Wine
 Vinegar
 Plums
 Currants

3.  Importance of aw: Honey at 20% mc is shelf stable, while potato at 20% is not
Classification of Foods Based on MC or 𝑎𝑤
 Fruits
 Vegetables
 Juices
 Raw meat & fish
High moisture foods
(50+% -- 70-99%)
 Bread
 Hard cheeses
 Sausages
Intermediate moisture
foods (15-50%)  Dehydrated
vegetables
 Grains
 Milk powder
 Dry soup mixes
Low moisture foods
(0-15%)

4. Classification of Bacteria
Aerobes
 Need oxygen for growth
Anaerobes
 Grow in the absence of 𝑂2
 Based on oxygen
 Micro-aerophile:
 Need only small amount of oxygen for
growth
 Obligate:
 Oxygen prevents growth
 Facultative:
 Can tolerate some degree of oxygen
 Based on temperature
 Based on salt, acid, water activity (aw), osmotic pressure

5. Based on Temperature
Psychrophiles
 Grow best from
50 - 58 °F
 Grow slowly at
refrigerator temp
Mesophiles
 Grow best from
86 - 98 °F
 Warehouse temps
Thermophiles
 Optimum: 122 - 150 °F
 Spores can survive 250
°F for 1+ hr
 Psychrophiles: Aeromonas, Alcaligenes, Flavobacterium, Pseudomonas, Serratia and Vibrio
 Mesophiles: E. coli, Salmonella spp., and Lactobacillus spp.
 Thermophiles: Bacillus, Clostridium, Alicyclobacillus, Geobacillus, and Thermoanaerobacter

6. Based on salt, acid, water activity (𝑎𝑤), osmotic
pressure
Halophiles
 Can not grow in absence of salt
Acidophiles
 Can grow in high acid conditions
 Even at pH of 2.0
Xerophiles
 Can grow in low aw conditions
Osmophiles
 Can grow in high osmotic pr.
Conditions, high sugar foods

7. Blanching Pasteurization
Ultra-Pasteurization
UHT
Hot Fill Aseptic/Sterilization
Thermal Processing

8. Inactivate enzymes
Reduce microbial
load
Wilt vegetables for
efficient packing into
cans
Blanching
 Mild heat treatment (~90 °C) for few minutes
Heating medium Water or steam
 Purposes
 Continuous hot water blanchers
 Screw or chain conveyors move product through a tank of hot water
 Continuous steam blanchers
 Complex, convey the product through tank containing steam using a chain/belt conveyor

9. Pasteurization
 Microorganisms may survive
 All vegetative pathogenic organisms inactivated (not spores)
 Public health significance (earlier target: Mycobacterium tuberculosis)
 HTST (Targets veg. state of Coxiella burnetti => Q fever)
 Spoilage organisms that can grow at room temp. are destroyed
15 s at 161 °F (~72 °C)
Equivalent batch (Vat): 30 min at
145 °F (~63 °C)
 If milk product has > 10% fat, is condensed, or is sweetened, Increase temperature
by 3 °C (or 5 °F)

10. “Nearly” sterile
 Filler may not meet aseptic standards
Shelf life: ~3 months
 Longer shipping distances
Products: cream, specialty dairy products
 Becoming more popular for milk
Ultra-Pasteurization
 280 °F (~138 °C) for 2 s
Vegetative organisms killed; not spores Product must be refrigerated
https://horizon.com/

11. 21CFR108 21CFR113 21CFR114
Ultra High Temperature (UHT)
 UHT = Aseptic
 All pathogenic and spoilage organisms including spores) are killed
 Thermophilic organisms may survive
 Commercially sterile product
 Shelf life: 1-2 years
 UHT milk processing covered under
 Code of Federal Regulations , US FDA
284 °F (140 °C) for 4 s

12. Aseptic Processing
A continuous thermal process in which the product and container are sterilized
separately and brought together in a sterile environment
 Temperature: 125 - 140 °C (257 – 284 °F)
 Components
Pump
Deaerator
Heat exchanger
Hold tube
Cooling unit
Back pressure
device
Packaging unit

13.  Fill processed product in unsterile container
 Acid or acidified product (sterilization)
Shelf stable product
 Low acid product (pasteurization)
Refrigerated product
 Hot product (~90 °C or 194 °F) sterilizes container
 Invert container for 0.5 to 3 min
Sterilize neck area
 Cooling of product: Air cool, Water spray
Hot Fill
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14. Fruit juices
(snapple)
Jams Jellies
Tomato-
based sauces
Isotonics
(gatorade)
Cont…
 Package: Glass or plastic with vacuum panels
 Needs to withstand vacuum during cooling
 Smooth finish needed for good label application
 PET or PET/PEN with UV coating
 Steaming closures for softening closure for tamper-evident band not needed
anymore
 Shelf stable product
 Sodium benzoate or potassium sorbate
 Products:

15.  Peeled & sliced potatoes
 Shredded lettuce & cabbage
 Washed & trimmed spinach
 Chilled peach, mango, melon
 Vegetable snacks: celery & carrot stick
 Cauliflower & broccoli florets
Minimal Processing
Preserve the original wholesome and fresh nature of a food product (flavor,
texture, safety, nutritional value) by subjecting it to mild processing conditions
 Traditional minimal processing
Cleaning washing Trimming Coring Slicing shredding
 Packaged mixed salads
 Cleaned & diced onions
 Peeled & cored pineapple
 Fresh sauces
 Peeled citrus fruits
 Microwaveable fresh vegetable trays

16. Cont…
 Other minimal processing methods
Thermal
 Microwaves
 RF
 Infrared
 Ohmic sous vide
Non-thermal
 Irradiation
 High pressure
 Pulsed light
 PEF
 UV
 Ultrasound
 Antimicrobial agents
 Oscillating magnetic field
 Plasma

17.  Pasteurization – HTST (~161 °F for 15 s)
 Least processing (cooling to ~45 °F)
 Pasteurization – HHST (191 °F for 1.0 s; 212 °F for 0.01 s)
 Cooling to ~45 °F
 UHT = Aseptic = Commercially sterile (~284 °F for 4 s)
 Longest shelf life (cooling to ~70 °F)
 ESL (includes ultra-pasteurization -- ~280 °F for 2 s)
 Anything in between Pasteurization & UHT (cooling to ~45 °F)
 Hot fill (~194 °F for 30 s to 3 min)
 Maximize benefits of pasteurization & UHT -- mainly for acid/acidified products
(cooling to ~70 °F)
Summary of Different Processes

18. Non-thermal food processing techniques
HPP Sanitizers
Cold plasma Super Critical Fluid Extraction
Ozone E beam
Pulsed Light Gamma
UV Ultrasonic
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19. The high pressure [600 MPa] causes the microorganisms membrane to be
disrupted
Target specific pathogens in specific food products such as vibrio spp in oysters,
and listeria spp as post-process treatment on sliced deli meats and juices
The food is largely protected from the damaging force of the pressure since
pressure is uniformly distributed around and throughout the food.
Pressure will depend on type of bacteria to be killed.
Advantage: commercially being used to treat jams/jellies in japan and juices in the
US, can be used in pre-packed food products
Dis-advantage: not proven to kill virus
High Pressure Processing (HPP)

20. Cold plasma is generated by using electricity and a carrier gas, such as air, oxygen,
nitrogen or helium
Ionization of atmospheric air/ moisture
Generate –UV radiation, ozone, charged particles and “supercharged” oxygen and
hydroxyl ions
All of these products work together to kill pathogens (bacteria, virus)
Advantages:
 Water free, Chemical free.
 Can be used in surface treatment of fresh produce,
 Effective against Salmonella and E. Coli
Dis-advantage: Nutritional quality of products to be validated
Cold Plasma Processing

21. 10 to 30 PPB is good enough for a sanitizing action
Ozone is a powerful sanitizer, similar to chlorine
It kills pathogens and leaves no residues
Advantages:
 Powerful sanitizing action
 Decomposes to Oxygen hence does not get carried along with food.
Dis-advantages:
 Human / workmen safety to be taken into consideration.
 Works mainly for surface treatment
Ozone

22. Pulsed light (PL) uses short, intense pulses of white light which includes ultraviolet,
infrared and visible light.
It is like a camera flash that is used to take pictures but far more intense.
When this light is flashed on a food, it kills microorganisms but has minimal impact
on the food
The UV light kills pathogens by disrupting the DNA.
Advantages:
 Presently approved by FDA (21 CFR179.41)
 Helps in surface sterilization even for packaging materials
Dis-advantages: Surface treatment
Pulsed Light (PL) Processing

23. Radiation from UV range of spectrum 100 to 400 nm
UV irradiation strength:1800 to 2000mW
At high levels, UV light causes damage to a microorganism’s DNA
Advantages:
 UV processing is being used in the juice and cider industries for pasteurization
without heat targeting E. coli O157:H7 and Cryptosporidium parvum.
 commonly employed for water treatment systems.
 It’s easy to use.
Dis-advantages: People safety to be taken into consideration
Ultra-Violet (UV) Light

24. Super critical carbon dioxide is used to deactivate bacteria and enzymes
Advantages:
Used in bio-active compounds like carotenoids, flavonoids and fruits and
vegetables
Dis-advantages:
Chemicals -human / workmen safety to be taken into consideration
Super Critical Fluid Extraction

25. Sanitizers with surfactants are being found to be effective .
Surfactant improves potency of the sanitizer by detaching microbial cell
from food.
Food grade surfactants are being worked upon.
Advantages: Lower cost in use
Dis-advantages: Chemicals -Human / workmen safety to be taken into
consideration
Sanitizers

26. Electron beam irradiation (E-beam)
High energy accelerated electrons (close to the speed of light) are aimed at solid or
liquid foods, reducing the number of or eliminating pathogens, pests or insects
An electron beam generator uses electricity as the energy source and can be turned
on and off.
E-beam work against pathogens such as viruses and bacteria by breaking the
linkages in DNA or RNA
Advantages: Tried on packaged dry meat to kill E. coli.
Dis-advantages: Limited penetration depth, High initial cost.
E-Beam

27.  Cobalt 60, properly shielded, is primarily used as the gamma irradiation source
 Doses used must be established for each specific food product taking into
account product composition, texture, density and impacts on quality
Advantages:
Used in lettuce, spinach, mushrooms , fresh fish and Spices
Food is safer without compromising texture, taste and nutrition and can be
used effectively on frozen products
Dis-advantages: Irradiation labeling, safety considerations.
Gamma Irradiation

28. High frequencies in the range of 0.1 to 20 MHz, pulsed operation and low power levels
(100 mW)
Ultrasonic treatment is a sterilization method that uses alternating high-frequency
electric currents, amplified and applied via an ultrasonic probe, to produce cavitation
and shear forces.
When sonicating liquids at high intensities and amplitudes, the sound waves that
propagate into the liquid media result in alternating high-pressure (compression) and
low-pressure (rarefaction) cycles, with rates dependent on the frequency–Disrupt
cellular structure
Advantages: Suitable for liquid, slurry or paste products
Dis-advantages: Technology cost is high
Ultrasonic treatment

29. Techniques of non-thermal processing
 MAP/CAP
 Waxing
 Reducing water activity
 Altering pH
 Antimicrobial agents and
preservatives
 Emulsification
 Microwave –Thermal/Non-thermal
 High Pressure Processing (HPP)
 Gases (ozone, chlorine dioxide, cold
plasma)
 Light (ultraviolet, pulsed light)
 Chemical (chlorine, surfactants)
 Ionizing radiation (gamma
irradiation, electron beam)
 Combination of one or more above

30. Reference
 Holdsworth, S. Donald, ricardo simpson, and gustavo V. Barbosa-cánovas.
Thermal processing of packaged foods. Vol. 284. New york: springer, 2008.
 Chauhan, o. P., Ed. Non-thermal processing of foods. CRC press, 2019.

31. THANK YOU