Principles and Methods of food preservation

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