This document provides an overview of various food preservation principles and methods. It begins by defining food preservation and its objectives, including increasing shelf life and retaining nutritional value. The key principles of preservation are inhibiting microbial growth through methods like reducing temperature, moisture, or increasing acidity. Physical methods include thermal processes like pasteurization and sterilization, and non-thermal methods like drying, freezing, irradiation, and packaging techniques. Chemical preservation uses antimicrobials, while biological preservation involves fermentation. A variety of pathogens, spoilage causes, and food classifications are also discussed at a high level.

1. ADVANCES IN FOOD PROCESS TECHNOLOGY
(FT 505)
“PRINCIPLE AND METHODS OF FOOD PRESERVATION”
PRESENTED BY-
KRATIKA SINGHAM
INT.FOOD TECHNOLOGY

2. INTRODUCTION
 Food preservation is known as the “ science which deals with the process of prevention of
decay or spoilage of food thus allowing it to be stored in a fit condition for future use”.
 The state in which any food may be retained over a period of time without being
contaminated by pathogenic organisms or chemicals, without losing optimum qualities of
colour, texture, flavour and nutritive value”.
 Preservation ensures that the quality, edibility and the nutritive value of the food remains
intact.
 Making food safe for consumption
 Removal of unwanted matter
from food
 Increases digestibility
 Enhance flavour, color & taste
 Improves texture and consistency
 Minimize nutrient loss
 Extending shelf life
OBJECTIVES
 Increase the shelf life of food
 Retain the quality of food (colour, texture,
flavour, nutritional value)
 Increase food supply
 Adds variety to the foods
 Decrease wastage of food
 Make food available in off season
IMPORTANCE

3. PRINCIPLE
 Inhibit or delay of microbial decomposition
 Keeping out micro-organisms (asepsis)
 Removal of micro-organisms,i.e., by filtration
 Hindering the growth of activity of micro-organisms, i.e., by low
temperature, drying, anaerobic conditions etc.
 Killing the micro-organisms,i.e., by heat or radiations.
 Preservation or delay by Self -decomposition of food
 Destruction or inactivation of food enzymes (phenolase)eg-: blanching
 Inhibit or delay of chemical reactions (non-enzymatic browning) eg:-
preservation of oxidation by means of an antioxidant.
 Prevention of damage caused by insects & rodents
 Prevention against losses due to mechanical causes

4. 1. Bacteriocidal method- (killing /inactivation of micro-organisms)
2. Bacteriostatic method- (inhibition of growth)

5. CLASSIFICATION OF FOOD

6. CAUSES OF FOOD SPOILAGE

7. METHODS OF FOOD PRESERVATION

8. PHYSICAL METHODS
(A) THERMAL METHODS
Blanching- Destruction of enzymatic activity, maintain color,
texture, flavour and nutritive values in fruits & vegetables .It is a pre-treatment done
before canning, drying and freezing. Temperature is below 100˚c
Boiling - Destroys vegetative cells of bacteria, yeast and moulds.
Temperature is 100˚c
Pasteurization- It is a mild heat treatment in which food is heated below
100˚c. Effective for kiling pathogenic micro-organisms
• low acid foods(pH>4.5)- minimize pathogenic microbes & extend shelf life at (90.5˚c)
• Acidic foods(pH=<4.5)- destruction of spoilage microbes(yeast &moulds) , inactivate
enzymes at (79.5˚c to 85˚c)

9. Types of pasteurization
 Thermization- 57 ˚c to 68˚c for 15 minutes
 Batch/(LTLT )pasteurization- 63˚c for15 minutes
 Flash pasteurization/(HTST)- 72˚c to 74˚c for15 to 20seconds
 Ultra high temperature (UHT) - 135˚c to 140˚c for 2-4 seconds
STERILIZATION
It is a controlled heating process used to completely eliminate all living micro- organisms
including thermo- resistant spores .
 Moist Heat
(HTLT): 110-130˚c,for 20 -40 minutes .
In autoclave 121˚c for 20min
(LTST): 80-100˚c for 10 minutes
 Dry Heat
(HTLT):160-180˚c for 2 hrs
(UHT) : 135-150˚c for few seconds

10. Canning- food content is sealed in an airtight containers(jars,steel and tin
cans). During heating process air is driven out of the jar and as it cools a vaccum
seal is formed.This vacuum seal prevents air from getting back into the product
bringing with it contaminating microbes.
 Enhances shelf life (upto5 yrs)
 Suitabe for high & low acidic foods
 Hot water canning - 212˚F at sea level, time varies with product
 Pressure canning- 240˚F

11. Drying- inhibits the growth of bacteria, yeasts and moulds .
sufficient moisture is removed (aw), which is essential for enzyme activity& microbes.
Examples:- raisins, guava, apple, dates,papaya,figs
 Natural methods - shade drying
 Mechanical methods – oven ,kiln, tunnel , belt trough ,fluidized bed ,foam mat,
spray, vacuum puffing ,drum, microwave, freeze, pneumatic dryers
Factors affecting drying rate:
• Temperature
• Velocity of air
• Surface area
• Size of the product
• Tray load
• Relative humidity of air
• Atmospheric pressure and vacuum
• Moisture content of food

12. LOW TEMPERATURE PRESERVATION
 Freezing – inhibit microbial growth by lowering water activity
 Air freezing- air blast freezers, fluidized bed freezing ,tunnel freezing
temperature = (-18˚c to -40˚c), velocity =1.5- 6 m/s
 Plate freezing
 Liquid immersion freezing
 Cryogenic freezing – liquid NO2
 Deep and quick freezing
 Freeze drying
 Chilling- temperature(0 to-5˚c), reduction in free liquid water activity thud depriving
micro-organisms of the water they need to metabolize.
 Immersion chilling
 Air chilling
 Refrigeration - tempertaure (-15 to -25˚c)
 Bulking
 Shelfing
 Boxing

13. TYPES OF NON THERMAL PRESERVATION TECHNIQUES

14. IRRADIATION
 Exposing food to inonizing radiation, such as gamma rays, X-rays or electron beam without direct
contact to the food product.
 Destroys micro-organisms causing spoilage and food borne illness and inhibiting sprouting/ ripening
and control insects and invasive pests.
Depending upon the dosage:
 Micro-organism destroys
 Slowed down
 Incapable of reprodution
 Ex: sprouting in potato, onion ,garlic
DOSES
 Inhibit sprouting= (0.06-0.2 kGy)
 Delay in ripening=(0.5-1.0 kGy)
 Prevent insect infestation=(0.15-1.0 kGy)
 Parasite control= (0.3-1.0 kGY)
 Extend shelf life (raw meat)=(1.0-5.5 kGy)
 Extend shelf life(frozen meat)=(4.5-7.0 kGy)
 Pathogenic &spoilage microbes=(1.0-7,=.0 kGy)
 Reduction in cooking time(dried veg)=(3.0-7.0)kGy
 Enzymes =(10.0 kGy)
 Sterilization (spices,veg seasonings)=10.0 kGy
 Sterilization foods (NASA)= (44.0 kGy)
 Packaging sterilization=(10-25 kGy)

15. Ultrasound
Microbial inactivation - cavitation process (changes the pressure and temperature )
break down of cell walls, disruption and thinning of cell membranes and DNA damage.
 Transient cavitation
 Stable cavitation-
Methods:-
 Ultrasonication
 Thermosonication
 Manosonication
 Manothermosonication-
DOSES
 Microorganism inactivation= ultrasonic waves (20kHz,D value=4.3min) and (200kPa,1.5-1.0 min)
 Spore inactivation =500kPa for 12 min(manosonication), 20kHz at 300kPa(sonication)
 Enzyme inactivation=1000Pa at 5000K(lipoxygenase and polyphenol oxidase)
APPLICATIONS
 Filteration&drying
 Freezing
 Mixing & homogenization
 Defoaming
 Crystallization of fats,sugars
 Cutting
 Degassing

16. Pulse electric field
short pulses of high electric fields(few micro-milliseconds) with intensity in the range of (10-80kV/cm) for
microbial inactivation and causes minimal detrimental effect on food quality attributes.
o Gram +ve are more resistant than gram –ve
o Spores are highly resistant
o Yeast more sensitive than bacteria
o PEF inactivates yeast, pathogens & spoilage M.O
Mechanism:
1. Electrical breakdown
2. Electroporation
Uses- milk & dairy products, juices, enhancement of juice extraction
Juice processing- increase mass transfer coefficient due to cell membrane permeabilisation.
Applications:
 Sugar processing- disintegration and destruction of cell membrane at 70-78˚c
 Plant oil extraction- oil recovery improved by 7.4%at 1.3kV/cm
soya bean oil – iso-flavonoid content increases
 Meat & fish- improve mass transfer and accelerate, curing

17. Ohmic Heating
Food material , which serves as an electrical resistor,is heated by passing electricity
through it. Electrical energy is dissipated into heat, which results in rapid and uniform
heating.
 Heating rate = 1 to 10˚c/s
Mechanism:
1. Thermal inactivation
2. Electroporation (50-60Hz)
uses
 Meat processing- Reduce cooking time of brine cured meat(>0.5Kg/min)
Quicker and uniform thawing
 Milk processing- HTST ohmic pasteurization(goat milk)
 Fruit &vegetable processing- reduces loss of solid (upto50%)
ohmic blanching-enhance water and surface transfer

18. High pressure processing(HPP or pascalization)
Food products are processed under very high pressure, leading to the inactivation of certain micro-
organisms (vegetative cells)and enzymes
o Range for Food – (400-600MPa) for 2 minutes or greater
o Temp of product rises 3-6˚c for every 100 Mpa
Principle:
 Le chateliar’s principle
 Isostatic principle
DOSES
 Inactivation of (milk) enzymes= (1000MPa)
 Commercial food products= (600MPa)
 Increasing milk shelf life = 600MPa for 60 min(4 days)
Inactivates:
• parasites
• Vegetative cells
• Fungal spores
• Food borne viruses
• Selected enzymes
Suitable for:
 Low medium moisture,semi-solid, vacuum foods
 High moisture,solid foods, vacuum packed
 High moisture ,liquid foods in plastic bottle/flexible packaging

19. Filteration
Reduces microbial population or sterilizes solutions of heat sensitive materials by
removing micro-organisms.
1. Depth filters
Thick fibrous / granular filters that removes micro-organisms by physical
screening, entrapment or adsorption
2. Membrane Filters
porous membrane with defined pore sizes that removes micro-oraganisms primarily
by physical screening.
Antimicrobials
 Bactericide: chemical that destroys bacteria(not spores)
 Fungicide: chemicals that kills fungal spores,hyphae, yeasts
 Virucide: chemical that inactivate virus
 Sporicide: can destroy bacterial endospores
 Germicide and microbicide: kills micro-organisms
 Bacteriostatic: prevent growth of bacteria
Examples- methyl,ethyl,propyl and butyl arabens, sorbic acid ,Na,K& Ca
sorbate,Benzoic acid ,Na,K&Ca benzoate, sodium Metabisulphite, propylene glycol,
BHT, BHT, benzaldehyde , essential oils, phenol and mercury compounds

20. CHEMICAL PROCESS
Preservatives
Chemicals used to retard food spoilage caused by micro-organisms &prolong shelf life.
1. Traditional:
 Salting- contains chlorine, harmful for microbes(causing dehydration)
 Sugaring- increase osmotic pressure , Aw=<0.845(prevent mesophile yeast&mold)
 smoking- prevent bacterial and fungal growth
2. Aciludants- benzoic (yeast) , sorbic (<0.3%)and lactic acid(decreases pH levels)
3. Gaseous preservatives- SO2 and sulphites(dec pH <4), CO2(inhibits psychrotrophic m.o, retard
yeast & mold growth )
4. Antioxidants- BHA,BHT,propyl gallate, Tocophenols(vit E),Ascorbic acid, lecithin (prevent
rancidity)
5. Color additives- sunset yellow(110),tartrazine(102),carmoisine(122), allura red (129),brilliant
blue(133),Amaranth purple(123)
6. Flavour additives – Nitrates and nitrites(prevent clostridium botulinum)
7. Sweeteners -(aspartame(951), alitame,sucrose ),
8. Emulsifier- lecithin(milk,egg,soyabean)

21. CONTROLLING pH
Low acid foods= (pH>4.6)spores killed by heating & canning)
 ex:- vegetable, meat & poultry foods
 canned low acid foods - spores are heat resistant .
so, (temp >=115.6˚c )is applied for 20 min
Acid foods= (pH<=4.6) prevent growth of clostridium botulinum
 ex:- fruits- orange, mango, guava
pH range (4to4.3)=pasteurization 90.5˚c (kills bacteria not spores)
pH range (4.3-4.5) =pasteurization 99˚c(kills bacteria not spores)
High acid foods= (pH<=3.5 )
 ex:-jams, jellies, pickles
 pasteurization temperature= 85˚c

22. BIOLOGICAL PROCESS
Fermentation
 fermented foods are those which are subjected to action of micro-
organisms(bacteria, yeast , molds) or enzymes to get desirable biochemical
changes and causes significant modification in food.
 fermentation often preserves a raw material , improving safety with regard to
food borne pathogens and increasing shelf life .
(LAB), Lactic Acid Bacteria
 antimicrobial effects
 chelate ferrous ions
 Degrade nitrite & cholestrol
 Inhibition of foodborne pathogens
ex:- lactococcus lactis (prevent spoilage & pathogenic bacteria)
LAB Antibacterial strains:
o L. plantarum
o L. pentosus
o L. paracasei
All these are highly heat resistant (65˚c to 121˚c),acidity(pH=2 to 6)

23. PACKAGING METHODS
MODIFIED ATMOSPHERE PACKAGING (MAP)
Modifying the composition of the internal atmosphere
of a package in order to improve the shelf life.
i. control the humidity level
ii. Modify gas composition
 Reduce lipid oxidation reaction , maintains respiration ,
inhibit growth of aerobic bacteria
 Modification process generally lowers the oxygen (O2),in the headspace of the package.Oxygen can
be replaced with nitrogen (NO2), a comparatively inert gas, or carbon dioxide(CO2)
Types
1. Active modification (also called gas flushing ) involoves displacing the air with controlled desired
mixture of gases
2. passive modification occurs as a consequence of food’s respiration and metabolism of
microorganisms present inside it.
 used with chilling
packaging Material
 flexible films( fresh produce, meat, fish, bread) providing suitable permeability for gases and water
vapour
 LDPE, PVC,OPP(oriented polipropylene,EVA(ethylene vinyl acetate) are not suitable for fresh cut
produce , broccoli, mushrooms
 permeable films- fruits and vegetables
 Barrier films- meat and fish (non- respiring)

24. CONTROLLED ATMOSPHERE PACKAGING (CAP)
 Concentration of oxygen, carbon dioxide and nitrogen as well as temperature
and humidity of a storage room are regulated
 oxygen is reduced to 1.5–2% by replacing it with nitrogen and a little bit of
carbon dioxide, which is produced by fruits ( apple and pear)
 control insects and pests- (>30%CO2), temp (<15˚c)
 Disinfestation of dry grains=(<13% m.c) with CO2 ar approx 25˚c
Ex:- grains, legumes , oilseeds

25. FUTRURE TRENDS
Cold plasma: innovative Technology for Decontamination of foods
 flexible antimicroial process
 Effectively reduces human pathogens like E. coli, Lysteria monocytogenes,
salmonella, s. aureus and shigella
 Reactive products-(O , O3 , NOX), charged particles (heavy ions or electrons)
Applications:
• contamination of the produce by potentially harmful biocide residues
• disinfection of high moisture foods and granular foods
• enzyme inactivation
• packaged food and packaging material disinfection