Hurdle technology for food preservation by exploiting the best of the present techniques at various stages

1. -Ammar Babar
-11FET1009.

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Hurdle technology is the combined use of several preservation methods
to make a product shelf-stable, to improve quality and to provide
additional safety.
Also known as “combined method technology”.
Leistner in 1976, introduced the term “hurdle effect”.
NEED FOR HURDLE TECHNOLOGY
Consumers are demanding for fresh, natural and minimally processed
food products.
Ongoing trend has been eat out and to consume ready to eat foods.

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Preservative factors or hurdles disturb the homeostasis of
microorganisms.
Microorganisms should not be able to “jump over” all the hurdles
present in the food product.
Preservative factors prevents microorganisms from multiplying and
causing them to remain inactive or even die.
The hurdle concept illustrates that complex interactions of temperature,
water activity, pH etc are significant to the microbial stability.

4. 
1) PASTEURIZATION
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mild heat treatment (e.g., 63oC for 30 min; 100oC for 12sec)
high product quality
destroys vegetative pathogens (disease-causing microbes)
reduces total microbial load, increases shelf-life
does not destroy spores (dormant stage of some bacteria)
usually combined with other hurdles (e.g., refrigeration)
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2) STERILIZATION
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complete destruction of microorganisms
severe heat treatment (equivalent to several
min at 121.1oC)
destroys spores
gives "shelf-stable" product
some nutrient, quality destruction (colour,flavour, texture)

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3) BLANCHING
blanching is a kind of pasteurization generally applied to fruits and
vegetables.
primarily applied to inactivate natural enzymes
commonly practiced when food is to be frozen
depending on its severity, also destroys microorganisms

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Vegetative cells, as well as, viruses are destroyed at temperature
60°C to 80°C
Higher temperature may be needed for killing of thermophilic
microorganisms
Vegetative cells are killed in 10 minutes at 100°C and many
spores in 30 minutes at 100°C

7. 
1) Refrigeration
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ideally 0oC to 4oC for most foods
short-term preservation (days to weeks)
high product quality (fresh, minimally processed,
slows down microbial growth, respiration,enzyme/chemical reactions
some pathogens can grow (e.g., C. botulinum (typeE), Listeria).
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2) Freezing
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generally -18oC to -30oC
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quality depends on product, time,temperature
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long-term preservation (months to years)
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stops microbial growth, respiration slows
down chemical reactions
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must have good packaging.
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3) Reduced water activity
aw is water "availability"
water is required for microbial growth, enzyme/chemical reactions
pathogenic microorganisms cannot grow at aw < 0.86
yeast & moulds cannot grow at aw <0.62
free water can be removed by concentration,
dehydration and freeze drying
in general, the lower the aw, the longer the storage life

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Recommended substances to reduce water activity.
Glucose
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Fructose
Increased acidity
Potassium
chloride
Sucrose
Sodium
chloride
acidity slows down growth of spoilage organisms and pathogens
pathogens won't grow, spores won„t germinate at pH<4.5
(e.g., fruit juices, sauerkraut)
above pH 4.5, must sterilize for shelf stability
below pH 4.5, can pasteurize
citric acid
malic acid
tartaric
acid
benzoic
acid
lactic
acid
propionic
acid

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Sequence of hurdles ensures stability at each stage. All hurdles decline
with time except aw.
Nitrite inhibits pathogens.
growth of other bacteria depletes oxygen
Low oxygen favours acid-producing competitive flora
Acid decreases pH
Aw hurdle gradually increases due to drying.

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Pasteurized .
These products have pH > 4.5 and aw > 0.85.
Should have to comply with the low-acid canned food regulations (i.e.,
commercial sterilization).
However, for quality reasons, these products cannot be given a
sterilization process.
Instead, the spreads are stabilized by moderate levels of salt, decreased
pH and moisture.

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Improves product quality and microbial safety.
Save Money, Energy & Several other Resources.
Foods remains stable & safe, high in sensory & nutritive value due to
gentle process applied.
Doesn't effects the integrity of food pieces (fruits).
Applicable in both Large & Small Industries.