This ppt describes different types of food processing techniques conducted at ambient temperature

1. AMBIENT-TEMPERATURE
PROCESSING

2. Introduction
• Consumers demand processed foods to have a
more ‘natural’ flavour and colour, with a shelf
life that is sufficient for distribution and home
storage before consumption
• These methods do not significantly heat the
food and are thus able to retain to a greater
extent their nutritional quality and sensory
characteristics

3. • Traditionally, fermented foods have many of
these characteristics.
• Irradiation is another example
• Adopted in some countries as a minimal method
of food preservation/minimal processing
• Other novel methods to achieve mild
preservation, for example processing using
electric fields, high hydrostatic pressure, pulsed
light and ultrasound

4. • Each minimal processing method destroys or
inhibits microbial growth, and in some cases
enzyme activity, but there are no substantial
increases in product temperature
• Little damage to pigments, flavour compounds
or vitamins and, in contrast to heat
processing, the sensory characteristics and
nutritional value of foods are largely retained

5. Irradiation
• Ionising radiation takes the form of gamma
rays from isotopes or, commercially to a lesser
extent, from X-rays and electrons
• They are able to break chemical bonds when
absorbed by materials
• The products of ionisation may be electrically
charged (ions) or neutral (free radicals). These
then further react to cause changes in an
irradiated material known as radiolysis
• These reactions destroys MOs, insects and
parasites

6. Mode of Action
• In foods that have a high moisture content, water
is ionised by radiation. Electrons are expelled
from water molecules and break the chemical
bonds. The products then recombine to form
hydrogen, hydrogen peroxide, hydrogen radicals
(H.), hydroxyl radicals (OH.) and hydroperoxyl
radicals (HO2.)
• The radicals are extremely short lived (less than
10-5 s) but are sufficient to destroy bacterial cells.

7. Ionization of water in food

8. 8
• Irradiation disrupts the development of any insects that
may be concealed within produce
• This means that any eggs or larvae present either do not
develop into adults
• If adults do emerge they are sterile and unable to produce
viable offspring. Insects can not multiply further
• Irradiation is not specifically used to kill insects, but
rather to disrupt their reproduction. Therefore live insects
(e.g. fruit fly larvae) may be found on or inside fruit or
vegetables that have been successfully treated

9. 9
• Causes disruption of internal metabolism of cells by
destruction of chemical bonds of insects or bacteria
• DNA destruction results in loss of cells ability to reproduce
• “DNA considered “radiation sensitive” portion of cells

10. Units
• Grays (Gy): Absorbed dose (where 1 Gy is the
absorption of 1 J of energy per kilogram of
food)
• Previously rads (radiological units) were used
where 1 rad 102 J kg1. 1 Gy therefore equals
100 rads

11. Measurement of radiation dose
• Polyvinylchloride (PVC) dosimeters are
impregnated with a dye. Hydrogen chloride is
released from the PVC by irradiation and it
produces a qualitative or quantitative change
in the colour of the dye to indicate the dose
received.

13. Radiation Sources
• Radionuclide or radioactive materials that give
off ionizing gamma rays
– Cobalt-60 Sealed in container - never touches food
Can be recycled
– Cesium-137
• Machine sources of ionizing radiation
– Electron beam accelerators
– X-rays generators

14. Countries commercially applying food irradiation
Worldwide, almost 40 countries permit the use of
irradiation on over 50 different foods, and an
estimated 500,000 tons of food are irradiated annually

15. Bangladesh Potato, onion, fish, pulses
Belgium Spices, dry vegetables
Canada Spices
China Vegetables (D & F), spices, apples, garlic, etc.
Netherlands
Spices, rice, egg powder, dry vegetables, packed
food
South Africa Spices, onion, fruits, onions etc.
America Fruits, vegetables, spices

16. Countries That Have Signed the regulations
for irradiation of Agri Commodities
• Peru
• Philippines
• India
• Thailand
• Viet Nam
• Malaysia
• South Africa
• Mexico
• Pakistan
• Laos

17. Advantages of Irradiation
• There is little or no heating of the food and therefore
negligible change to sensory characteristics
• Packaged and frozen foods may be treated
• Fresh foods may be preserved in a single operation,
and without the use of chemical preservatives
• Energy requirements are very low
• Changes in nutritional value of foods are comparable
with other methods of food preservation
• Processing is automatically controlled and has low
operating costs
• High energy conversion efficiency (> 95%)

18. Disadvantages
• The process could be used to eliminate high bacterial
loads to make otherwise unacceptable foods saleable
• If spoilage micro-organisms are destroyed but pathogenic
bacteria are not, consumers will have no indication of the
unwholesomeness of a food
• There will be a health hazard if toxin-producing bacteria
are destroyed after they have contaminated the food
• Possible development of resistance to radiation in MOs
• Loss of nutritional value
• Until recently, inadequate analytical procedures for
detecting whether foods have been irradiated
• Public resistance due to fears of induced radioactivity

19. Effective dose of Irradiataion?
• Low Dose (<1 kGy)
– Control insects
– Inhibit maturation
– Inhibit sprouting
• Medium Dose (1-10 kGy)
– Extend shelf life (radurisation)
– Reduce microorganism level (radicidation)
• High Dose (> 30 kGy)
– Sterilize - analogous to canning (radappertisation)
– Decontaminate certain food additives, e.g., spices

20. Crop Minimum (kGy) Maximum (kGy)
Mango 0.25 0.75
Apricot, peach, nectarine 0.10 0.20
Apple 0.10 0.15
Onion 0.03 0.09
Potato 0.06 0.15
KRUSHAK
(Krushi Utpadan Sanrakshan Kendra)
Lasalgaon, Maharashtra

21. India tops list of pest-exporting nations
In May 2014, the European Union banned the import of all
mangos as well as four vegetables from India ($4 bn/y),
because last year pests were discovered in at least 207
consignments of produce.
EU inspectors found fruit flies and tobacco white flies in the
infested shipments. Neither is harmful to humans, but both
pose a serious threat to European tomato and salad crops,
which are worth hundreds of millions of dollars annually.
Despite warning India of the problems, officials say the
number of infested shipments kept rising in 2013, and a ban
became necessary.
EU's ban Indian mango to counter pests

22. Sprout inhibition
Potato, onion, garlic, ginger
Quarantine
Fruits
Pathogen reduction
Spices
Insect disinfestations
Cereal, pulses, dry fruits
Shelf life extension
Meat, fish

23. • Some foods (for example dairy and meat products)
are unsuitable for irradiation owing to the
development of rancid off-flavours
• Reactive oxygen and its derivatives are produced in
foods by peroxidases, xanthine oxidase and amino
acid oxidase.
• The presence of oxygen accelerates this process
• Therefore they are irradiated in vacuum packs
Caution

24. What Can Irradiation Do?
• Prevent Food Poisoning By Reducing
– E. Coli )157:H7 (Beef)
– Salmonella (Poultry)
– Campylobacter (Poultry)
– Parasites
• Prevent Spoilage by Destroying Molds, Bacteria
and Yeast
• Control Insects and Parasite Infestation in
grains
• Increase Shelf Life by Slowing Ripening of Fresh
Fruits and Vegetables. Eg Mango, strawberries,
banana, tomato etc.

25. 25
Irradiation as GRAS
• Radiolytic byproducts products by irradiation
are the same as those produced by traditional
processing methods whose status as GRAS
• The radiolytic byproducts in biological systems
are safe and does not effect the human health

26. Are irradiated foods safe to eat?
• Foods cannot become radioactive at energies
used in irradiation
• Below 10 kGy there are no known
toxicological, microbiological, or nutritional
problems

27. Labeling Criteria
• The FDA requires that irradiated foods bear
the radura label and state on the label
“Treated with radiation” or “Treated by irradiation”

28. Regulations: Eligible Commodities
Ghana Eggplant, Okra, Pepper
Hawaii
Abiu, Atemoya, Banana, Breadfruit, Capsicum spp.,
Carambola, Cucurbita spp, Dragon Fruit, Eggplant, Jackfruit,
Litchi, Longan, Mango, Mangosteen, Melon, Moringa pods
(Drumstick), Papaya, Pineapple, Rambutan, Sapodilla, Sweet
Potato, Tomato
India Mango
Malaysia Rambutan, Papaya
Mexico
Carambola, Clementine, Grapefruit, Guava, Mango, Chile
Manzano, Sweet Lime, Sweet Orange, Tangelo, (Figs, Pitayah,
Pomegranate)
Pakistan Mango
South Africa Grapes, Stone Fruit, Pears, Persimmons, Litchi
Thailand
Litchi, Longan, Mango, Mangosteen, Pineapple, Rambutan
Dragon Fruit,
Viet Nam Dragon Fruit, Rambutan, (Litchi, Longan)

29. HIPEF
• When an electric field of strength 12-35 kV/cm
is applied to a liquid food placed between two
electrodes in a short pulse (1–100 µs), there is
a pronounced lethal effect on micro-organisms
• During 1990s, a variety of liquid foods,
including fruit juices, soups, liquid egg and milk
were used to destroy MOs and the technology
were termed ELSTERIL and ELCRACK.

30. Action
• ELECTROPORATION- Formation of pores in cell
membranes which cause swelling and rupturing of
the cells
• Electrolysis products or highly reactive free radicals
• Induced oxidation and reduction reactions within
the cell structure that disrupt metabolic processes
• Heat produced by transformation of induced
electric energy
• Cell reductions of up to six log cycles

32. Factors affecting
• Type of Food
• pH
• Electric Field – Increase in microbial inactivation with
increase in intensity of electric field
• Temperature- With constant electric field strength,
inactivation increases with an increase in temperature
(35–50°C )
• Pressure Pressure is applied to inhibit the formation of
air bubbles.
• Time of Exposure- Treatment time is defined as the
product of the number pulses and the pulse duration. An
increase in any of these variables increases microbial
inactivation.

33. Applications of HIPEF to foods

34. Advantages
• Kills vegetative cells
• Colours, flavours and nutrients are preserved
• No evidence of toxicity
• Relatively short treatment time

35. Limitations
• No effect on enzymes and spores
• Difficult to use with conductive materials
• Only suitable for liquids or particles in liquids
• Only effective in combination with heat
• Products of electrolysis may adversely affect foods
• Safety concerns in local processing environment
• Energy efficiency not yet certain
• Regulatory issues remain to be resolved
• May be problems with scaling-up process

36. Examples of commercial applications
• For liquid foods
• Pasteurisation of fruit juices, soups, liquid egg
and milk
• Accelerated thawing
• Decontamination of heat sensitive foods

37. Effect on food
• HIPEF results in cell reductions of up to six log
cycles.
• In general, vitamins and enzymes are not
inactivated to any appreciable extent by HIPEF
processing
• Flavour and colour of fruit juices is unaltered
by processing

39. PASCALLIZATION
• When high pressures, up to 1000 MPa (10 000
bar), are applied to packages of food that are
submerged in a liquid, the pressure is distributed
instantly and uniformly throughout the food.
• The high pressure causes destruction of micro-
organisms. Typically, a pressure of 350 MPa
applied for 30 min or 400 MPa applied for 5 min
will cause a ten-fold reduction in vegetative cells
of bacteria, yeasts or moulds

41. • However, when combined with moderate
heating (e.g. to 60°C), spores are destroyed at
pressures of 400 MPa to different extents
• High pressures cause collapse of intracellular
vacuoles, and damage to cell walls and
cytoplasmic membranes
• High pressures only affect non-covalent
chemical bonds (i.e. ionic, hydrogen and
hydrophobic bonds), leaving covalent bonds
intact

42. • This permits destruction of microbial activity
without significantly affecting food molecules
that contribute to the texture or flavour of the
food
• The process does not require the use of
chemical preservatives to achieve an adequate
shelf life of processed products
• Temperature control in commercial operations
can be achieved by pumping a heating/
cooling medium through a jacket that
surrounds the pressure vessel.

43. Methods of processing
• There are two methods of processing foods in
high pressure vessels: in-container processing
and bulk processing
• Conventional plastic and foil pouches are
suitable

44. Comparison

45. Advantages
• Kills vegetative bacteria (and spores at higher
temperatures)
• No evidence of toxicity
• Colours, flavours and nutrients are preserved
• Reduced processing times
• Uniformity of treatment throughout food
• Desirable texture changes possible
• In-package processing possible
• Potential for reduction or elimination of chemical
preservatives
• Positive consumer appeal

46. Disadvantages
• Little effect on food enzyme activity
• Some microbes still survive
• Expensive equipment
• Foods should have approx. 40% free water for
anti-microbial effect
• Batch processing
• Limited packaging options
• Regulatory issues to be resolved

47. Effect on food
• The pressure causes unfolding of the molecular
structure and then aggregation with either different
proteins in a food or into a different form, resulting
in changes to the texture of the food
• Gel formation is observed in some proteins, such as
soya, meat, fish and egg albumin
• Compared to heat treated gels, pressure induced gels
maintain their natural colour and flavour and are
described as smooth, glossy and soft, and having
greater elasticity
• Fruit products are reported to retain the flavour,
texture and colour of the fresh fruit

48. Applications
• Tempering chocolate, where the high pressures
transform cocoa butter into the stable crystal
form (Chapter 23), preservation of honey and
other viscous liquids, seafoods, dairy products
such as unpasteurised milk and mould ripened
cheese
• Tenderisation of meat processing at 103 MPa and
40–60ºC for 2.5 min improves the eating quality
• Pressure-processed salted raw squid and fish
sausages