Food processing and preservation principles and methods.

1. FOOD PROCESSING
• It is a branch of food technology which covers:
1. General characteristics of raw food materials
2. Principle of food preservation
3. Processing factors which influence quality
shelf life and packaging
4. Water and waste management

2. Physiological functions
1. To provide energy to body
2. To provide foods for building, maintenance and
repair of body
3. Regulate activities of body like breathing
maintenance of body temperature, muscle
contraction etc.
4. Maintenance of health
Psychological functions
1. Satisfy emotional needs, such as security, love and
attention
2. Convey friendship, hospitality and acceptance
3. Use as a treat

3. Social functions
1. Used to celebrate various stage of life, festivals and
religious functions
2. To express welcome
3. Food is a status symbol
4. Food is a source of power

4. Classification of food
• Food classified into diff. group based on nutritive value,
function and Ph
 Based on nutritive value
Basic four- Basic five-
1.Cereals, millets & pulses
2. Fruits & veg. 1. Cereals & grains
3. Milk & milk pdts 2. Pulses & legumes
& animal foods 3. Milk & meat pdts
4. Fats & oil, nuts 4. Fruits & veg.
& oilseeds 5. Fats & sugars

5. Basic seven-
1. Green & yellow veg.
2. Orange, grapes, tomato,
raw cabbage
3. Potatoes, other veg. & fruits
4. Milk & milk pdts
5. Meat, poultry, fish & egg
6. Bread, flour & cereals
7. Butter or fortified margarine
Basic eleven-
1. Cereals & millet
2. Pulses & legumes
3. Nuts & oilseeds
4. Veg.
5. Fruits
6. Milk & milk pdts
7. Egg
8. Meat, fish & other animal food
9. Fats & oils
10. Sugar & confectionaries
11. Spices & condiments

6.  Based on function
• Energy yielding
• Body building
• Protection and regulation
• Maintenance of health
 Based on Ph
• Acid foods
Ph < 4.5
eg: Pickle, juices, tomato pdts.
• Non acid foods
Ph > 4.5
eg: Milk, meat, veg. soup etc.

7. Food group Percentage Example
Low acid foods 5 & above Fish meat, milk corn,
cabbage, meat pdts,
peas
Medium acid foods 5 – 4.5 Veg., sausages, soup
Acid foods 4.5 – 3.7 Mango, citrus fruit,
papaya, guava
High acid foods Below 3.7 Pickle, grape, citrus
fruit, tomato pdts

8. Major causes of food spoilage
1. Biological
2. Chemical
3. Physical
 Biological causes:
Microbial spoilage- growth & activities of bacteria, yeast,
mold
Infestation- by insects, parasites and rodents

9. • Microbial spoilage
• MO generally found in everywhere- soil, water air, on skin of
cattle, feathers of poultry, intestine of animal body, skin and peels
of fruits, hull of grains, shell of nuts, processing equipments…
• Not all MO cause food spoilage
• They are not found in healthy cells. If the skin is weakened by
disease or death, MO may digest skin and penetrate to it.
• Many bacteria cause food intoxication and some transmit disease.
• Staphylococcus aureus, Clostridium botulinum produce toxin
• Clostridium perfringens, Staphylococcus pyogens, Salmonella,
Shigella spp. transmit food born diseases

10. •Infestation
1. Insect:
• Insects destroy 5-50% of total grain, fruit & veg.
production
• They damage foods and facilitate the microbial infection
• Insects egg may be laid in the food
2. Parasites:
• Pigs eat uncooked food waste. The parasiting nematode
penetrates its intestine and the live worm can infect man
if the pork is not thoroughly cooked.
• A parasite worm belonging to genus Anisakis is found in
fish. If such fish is eaten raw it can infect man
• Entamoeba histolytica, responsible for anaerobic
dysentery. Infected water and poor hygiene spread the
parasite
• Cooking kills most of these parasites.

11. 3. Rodents:
• Rodents like rat consume large quantities of food and
contaminate them.
• The urine and droppings of rodents cause several kinds of
disease producing bacteria.
• They spread human diseases such as typhus fever, plague

12. Factors affecting microbial growth
 Intrinsic factors:
1. Composition of food
2. Ph
3. Water availability
4. Oxidation reduction potential
5. Physical structure
6. Presence of antimicrobial substances
(eg: poly phenols, allicin, lysozyme, aldehydic & phenolic
compounds)
 Extrinsic factors:
1. Temperature
2. Relative humidity
3. Atmosphere

13. • Chemical spoilage
1. Self spoilage – Activities of food enzymes and
other chemical reactions within food itself
2. Cross contamination – from storage area
3. Contamination from pollutants

14. • Physical spoilage
1. Temperature
• Heat and cold cause deterioration of food, if not
controlled
• Up to a level, rate of enzymatic and non enzymatic
reaction doubled for rise in temperature
• Extensive heat cause denaturation of protein, breaks
emulsion, destroy vitamins
• Uncontrolled cold cause discolouration, changes in
texture or cracked skin
2. Reaction with light
• Light destroy vitamin B2, A and C.
• Affect many food colours
• Cause surface discolouration of meat pigments

15. 3. Physical stress
• High pressure
• Vacuum
• Physical damage
4. Reaction with oxygen
• Air and oxygen causes number of destructional
changes in food, such as destruction of food
colours, flavour, vitamin A and C
• Oxygen is necessary for the growth of microbes,
therefore it is excluded from food in course of
processing, by deaeration, vacuum packaging
and flashing containers with nitrogen or CO2 or
by the use of oxygen absorbing chemicals

16. 5. Moisture
• Presents and absence of excess moisture in food
leads to food spoilage
• Moisture is required for chemical reactions and
microbial growth
• Food with high percentage of water will spoil fast
6. Time
• All food spoilage factors considered as time
dependent
• Larger the time, greater the destructive
influences, except certain food like wine and other
fermented foods which improves with aging up

17. Principles of food preservation
1. Prevention or delay of microbial
decomposition.
 By keeping out microorganisms (asepsis)
 By removal of m.o eg: by filtration
 By hindering the growth and activity of mo
(low tempt, drying, antibiotics etc.)
 By killing the mo (by heat or radiation)

18. 2. Prevention or delay of self-decomposition of
the food
By destruction or inactivation of enzymes, eg:
by blanching
By prevention or delay of chemical reactions
eg: prevention of oxidation using antioxidants.
3. Prevention of damage by insects, animals,
mechanical causes etc.
 By using proper insecticides, pesticides etc.

19. METHODS OF FOOD PRESERVATION
• Asepsis
• Preservation by high temperature
• By low temperature
• By chemicals
• By drying
• By filtration
• By carbonation
• By sugar, salt, acids
• By fermentation
• By antibiotics
• By oils and spices
• By irradiation

20. 1. Asepsis:
• Absence of infection
• Preventing the entry of mo
• Maintaining of general cleanliness while picking,
grading, packing and transporting of fruits and veg.
increases their keeping quality
• The pdts prepared from them will be of superior
quality
• Protective covering of food materials prevent
penetration of mo. Packaging of food is a widely
used application of asepsis

21. 2. Removal of mo.
• It maybe accomplished by means of filtration,
centrifugation, washing, trimming etc.
• Washing: removes organisms, dirt, dust..some
microbes from soil may be resistant to heat treatment.
• Trimming: Spoiled food portions have to be trimmed
prior to processing or preservation
• Filtration: Juices are clarified by settling or by using
ordinary filters, then passed through special filters
which are capable of retaining yeast and bacteria.
(germ proof filters used).
• Filters are made of unglazed porcelain, diatomaceous
earth, membrane etc.
• Used for physically removing mo from particularly
liquid foods like fruit juices, beer, soft drink, wine,
water, milk..

22. • Centrifugation: Centrifugal force is used to
sediment and separate the unwanted substances
• Maintenance of anaerobic conditions:
• By sealing or packaging
• By evacuating the unfilled space (vacuum
packaging)
• Replacement of air by inert gas

23. 3.Thermal processing:
Cooking
– The process of subjecting food to the action of heat
is termed as cooking and it includes at least six forms of
heating- baking, broiling, roasting, boiling, frying and stewing.
– Baking, broiling and roasting usually require dry heat at relatively
high temp. ( 100C).
– Boiling and stewing done by placing in boiling water.
– Frying involves cooking oil and temp much greater than 100C.
– Refrigerated storage following cooking is a common household
method of preservation
– Two imp. Preservative changes: destruction/ reduction of mo and
inactivation of undesirable changes. Other changes are-
– Destruction of potentially hazardous toxins present naturally or
through mo
– Alteration of colour, flavour and texture
– Improved digestibility of food components
– Undesirable changes may also occur, such as degradation of nutritive
components and sensory attributes

24. • Blanching:
• Fruits and veg. are blanched prior to canning,
freezing, or dehydration
• Aims of blanching include:
– to inactivate the native enzymes and to destroy enzyme
substrates such as peroxides
– To reduce the microbial load in food raw material
– To soften and shrink the food facilitating the filling into
containers
– Expel cellular gases thereby reducing can-corrosion and
improve the texture particularly of dehydrated foods
• However, loss of heat sensitive vitamins and
leaching out of water soluble nutrients may occur
• Over blanching damages the texture of pdt

25. • Pasteurization:
• Comparatively low order of heat treatment
generally done at temp. below bp of water.
• Two primary objectives are:
– Destruction of majority of but not necessarily all
pathogenic and other spoilage mo in liquid foods such as
milk and liquid egg. In the case of milk used for cheese
making, pasteurization destroys all mo that would
compete with the desired fermentation process at a
later stage
– Extending the pdt shelf life from a microbial and
enzymatic point of view (beer, wine, fruit juice..)

26. • It will inactivate the natural enzymes present in
food
• Pasteurized food will contain many living org.
capable of growth thus limiting the storage life of
foods compared to commercially sterile foods
• Types of pasteurization include :
1. LTLT : Low temp. long time 63C 30 minutes
– Batch / holding past.
2. HTST : High temp. short time 72C 15 seconds
– Continuous / flash past.
3. UHT : Ultra high temp. 130 -135C 1 - 2 second

27. • Sterilization:
• The complete destruction of viable mo
• Treatment at 121C of wet heat for 15 minutes or its
equivalent is necessary for sterilization
• Most of the bottled and canned pdts are sterile.
• Commercially sterile canned foods have a shelf life of 2 years
or more
• Time and temp. vary with type of food
• Fruit and tomato pdts should be heated at 100C for 30
minutes so that spore forming bacteria which are sensitive to
high acidity maybe completely killed
• Veg. like green peas, okra, beans, being non-acidic and
containing more starch than sugar require higher temp. to kill
spore forming org. (116C for 30 to 90 minutes).
• Before using, empty cans and bottles should be sterilized for
about 30 minutes by placing them in boiling water
• Temp. above 100C obtained by using steam pressure
sterilizers like pressure cooker and autoclaves.

28. 4. By low temperature:
• Microbial growth and enzyme reactions are retarded in foods
stored at low tempt.
• Lower the tempt., greater the retardation
• Low tempt. Can be produced by:
– Cellar storage
– Refrigeration or chilling
– Freezing
• Cellar storage (about 15C)
• Temp in cellar (underground rooms) where surplus food is
stored in many villages is usually not much below that of
outside air and is seldom lower than 15C
• It is not low enough to prevent the action of many spoilage
mo or of plant enzymes.
• Root crops, potatoes onions, apples and similar foods can be
stored for limited periods during the winter months.

29. • Refrigeration or chilling (0 TO 5C)
• Fruits, veg. and their pdts can be preserved for a few days to many
weeks when kept at this temp.
• Best storage temp for many foods is slightly above 0C but vary
with pdt
• Besides temp. RH and composition of air can affect preservation of
food
• Freezing (-18 to -40C)
• Most harmless method
• Microbial growth is inhibited and rate of chemical reaction is
slowed down at low temp.
• Activity of meat enzymes is stopped while plant foods have to be
blanched before freezing to avoid undesirable quality changes
• Most perishable foods can be preserved for several months if the
temp is brought down quickly
– Placing them in contact with the coil through which refrigerant flows
– Blast freezing in which cold air is blown across the food
– Dipping in liquid nitrogen

30. 5. By chemicals
• Preservative is a substance which is capable of
inhibiting, retarding, or arresting the process of
fermentation, acidification or other decomposition
of food.
• Inhibitory action of preservatives is due to their
interfering with the mechanism of cell division,
permeability of cell membrane and activity of
enzymes.
• Two imp. chemical preservatives permitted are:
– Sulphur dioxide (including sulphites)
– Benzoic acid (including benzoates)

31. 6. By drying:
• Mo need moisture to grow. So when the
concentration of water in food is brought down
below a certain level, they are unable to grow
• Moisture can be removed by the application of heat
as in sun-drying or by mechanical drying
(dehydration).
• Sun drying is the most popular and oldest method
of preservation
• Artificial heat under controlled conditions of temp.,
humidity and air flow is provided and fruit and veg.
like green peas, mango, cauliflower etc are dried to
such an extent that the mo present in them fail to
survive.

32. 7. By carbonation:
• Carbonation is the process of dissolving sufficient CO2 in
water or beverage so that the pdt when served gives off the
gas as fine bubbles and has a characteristic taste.
• Fruit juice beverages are generally bottled with CO2 content
varying from 1 to 8 g per liter.
• This concentration is much lower than that required for
complete inhibition of microbial activity (14.6g/liter), it is
sufficient for supplementing the effect of acidity on
pathogenic bacteria.
• Removes air thus creating an anaerobic condition, which
reduces the oxidation of ascorbic acid and prevents browning.
• High carbonation however, should be avoided as it usually
destroys the flavour of juice
• Keeping quality enhanced by adding about 0.005% sodium
benzoate

33. 8. Preservation by sugar:
• Syrup containing 66% or more of sugar do not
ferment
• Sugar absorb most of the available water with the
result that there is very little water for growth of
mo. Hence their multiplication is inhibited.
• Dry sugar does not ferment.
• Sugar act as a preservative by osmosis
• Fruit syrup, jam, jelly, marmalade, preserve, candy,
crystallized and glazed fruit are preserved by sugar

34. 9. By fermentation:
• Decomposition of carbohydrates by mo or enzymes
is called fermentation
• One of the oldest method of preservation
• Foods are preserved by the alcohol or organic acid
formed by microbial action
• Wine, beer, vinegar, fermented drinks, fermented
pickles etc.
• 14% alcohol acts as a preservative in wines because
yeasts cannot grow at that concentration
• About 2% acetic acid prevents spoilage in many
pdts

35. 10. By salt:
• Salt at a concentration of 15 to 25% is sufficient to
preserve most pdts
• It inhibits enzymatic browning and discolouration and
act as an antioxidant
• Salt in the form of brine is used for canning and pickling
of veg which contain very little sugar and hence
sufficient lactic acid cannot be formed by fermentation
to act as preservative
• Preservation action by:
– Causing high osmotic pressure resulting in plasmolysis of
microbial cell
– Dehydrating food as well as mo by drawing out and tying up
the moisture by ion hydration
– Ionizing to yield chloride ion which is harmful to mo
– Reducing the solubility of oxygen in water
– Interfering with action of proteolytic enzymes

36. 11. By acids:
• Low acid foods are spoilt rapidly
• Highly acidic environment inhibits the growth of food
spoilage org.
• Lowering the protein of certain foods by anaerobic
fermentation and action on carbohydrates producing
lactic acid is the method
• Same inhibitory effects by acidic additives like vinegar
(acetic acid abt 2% prevents many) or citric acid (lime
juice)
• Onions are bottled in vinegar with little salt
• Vinegar also added to pickles, chutneys, sauces etc
• Citric acid to many fruit juices, jam and jelly to increase
acidity and prevent mould growth

37. 12. By oil and spices:
• A layer of oil on surface of any food produces
anaerobic condition which prevent the growth of
mould and yeast
• Spices like turmeric, pepper and asafoetida have
little bacteriostatic effect
• Their primary function is to impart characteristic
flavour to food
13. By antibiotics:
• Certain metabolic pdts of mo have germicidal effect
and are termed as antibiotics
• Nisin, subtilin, pimaricin

38. 14. By irradiation:
• When gamma rays or electron beams pass through foods,
there are collisions bw the ionizing radiation and food
particles at atomic and molecular level resulting in the
production of ion pairs and free radicals
• Reactions of these pdts result in physical and chemical
phenomena which inactivate mo in food
• Thus irradiation called as “ cold sterilization” i.e. Food is
preserved without high heat treatment
• WHO and IAEA recommended radiation dose of up to 1 Mrad
is not hazardous
• Different org. sensitive to radiation to diff. extents.
• Uses:
– Used for sterilization in hermetically sealed packs.
– Reduction of spoilage flora in perishable foods.
– Elimination of pathogens in food.
– Control of infestation in stored cereals.
– Prevention of sprouting of potatoes, onion etc.