Food preservation by hurdle technology

1. SUBMITTED BY: ROHIT KATIYAR
M.TECH 2nd YR.
*

2. *
*Hurdle technology is the combined use of several preservation
methods to make a product self stable, to improve quality and to
provide additional safety.
*Several preservation methods, such as heating, chilling, freezing,
drying, salting, sugar addition, fermentation, removal of oxygen are
used.
*The most important hurdles used in food preservation are
temperature (high or low), water activity (aw), acidity (pH), redox
potential (Eh), preservatives (e.g., nitrite, sorbate, sulfite),
*microorganisms present (‘at the start’) in a food should not be able
to overcome (‘leap over’) the hurdles present during the storage of a
product,

3. *
*hurdles are deliberately combined to improve the microbial stability
and the sensory quality of foods as well as their nutritional and
economic properties.
*In industrialized countries the hurdle technology approach is
currently of most interest for minimally processed foods which are
mildly heated or fermented.
*In developing countries the application of hurdle technology for
foods that remain stable, safe, and tasty if stored without
refrigeration is of paramount importance.

4. *
*Preservatives factors or hurdles disturbs the homeostasis of
micro-organism.
*Micro-organism should not be able to”jump over” all the
hurdles present in the food product.
*Preservative factors prevents microorganism from multiplying
and causing them to remain inactive or even die.
*The hurdle concept illustrate that complex interaction of
temperature, water activity,pH. etc. are significant to the
microbial stability

5. *
Source: Leistner L. (1992)

6. *
*Homeostasis
* Metabolic Exhaustion
*Stress Reaction
*Multitarget Preservation

7. *
*In food preservation the homeostasis of microorganisms is a key
phenomenon which deserves much attention, because if the
homeostasis of these microorganisms is disturbed by preservative
factors (hurdles) in foods, they will not multiply.
* Preservative factors functioning as hurdles can disturb one or more
of the homeostasis mechanisms, thereby preventing microorganisms
from multiplying and causing them to remain inactive or even die.
* Hurdles included in a food should affect the undesired
microorganisms in several different ways, for example by affecting
the pH, Eh and water activity homeostasis systems.

8. *
*Another phenomenon of practical importance is metabolic
exhaustion of microorganisms, which could cause ‘auto
sterilization’ of a food.
* Due to auto- sterilization in hurdle-technology foods,
which are microbiologically stable, become more safe
during storage, especially at ambient temperatures.
*For example, salmonellae that survive the ripening
process in fermented sausages will vanish more quickly if
the products are stored at ambient temperature.

9. *
The synthesis of protective stress shock proteins is
induced by heat, pH, aw , etc.
*The various responses of microorganisms under
stress might hamper food preservation and could
turn out to be problematic for the application of
hurdle technology.
*the activation of genes for the synthesis of stress
shock proteins, which help organisms to cope with
stress situations, should be more difficult if different
stresses are received at the same time.

10. *
*Multitarget preservation of foods should be the ambitious goal for a
gentle but most effective preservation of foods .
*A synergistic effect could be achieved if the hurdles in a food hit, at
the same time, different targets (e.g. pH,aw, Eh) within the
microbial cells and thus disturb the homeostasis of the micro-
organisms present in several respects.
* It is anticipated that the targets in microorganisms of different
preservative factors for foods will be elucidated, and that hurdles
could then be grouped in classes according to their targets.

11. *
*High Temperature:
1.Pasteurization:
*Mild heat treatment(e.g. 71.5°C for 15 sec for milk)
*High product quality
*Destroys vegetative pathogens
*Reduces total microbial load, increase shelf life.
*Does not destroy spores(dormant stage some bacteria)
*Usually combined with other hurdles(e.g. refrigeration)

12. *complete destruction of micro-organism.
*Severe heat treatment( equivalent to several min. at 121.1°C)
*Destroys spores
*Gives shelf stable product
*Commercial sterilized foods may contain a small no. of heat
resistant bacterial spores, but these will not normally multiply in
the food supply.

13. *
*Blanching is a kind of pasteurization generally applied to fruits and
vegetables.
*Primarily applied to the inactive natural enzyme.
*Commonly practiced when food is to be frozen.
*Depending on its severity, also destroys the microorganism.
.

14. *
1.Refrigeration::
Temperature of a food is reduced to between 1ºC and 8ºC.
Refrigeration temperature is 0°C to 4°C.
Short term preservation ( days to week).
High product quality .
Slow down the microbial growth, respiration, chemical reaction.
Some pathogens can grow(e.g. clostridium botulinum).
Chilling prevents the growth of thermophilic and many mesophilic
micro-organism.
Each of the factors that contribute to the shelf life of chilled foods
can be thought of as ‘Hurdles’ to microbial growth

15. *
*Generally -18°C to -30°C.
*Long term preservation.
*Stops microbial growth, respiration.
*Slow down chemical reaction.
*Must have good packaging.

16. *
*Water activity is a property of a solution and is the ratio of vapour
pressure of solution to vapour pressure of pure water at the same
temperature under equilibrium condition.
*Pathogenic micro-organism cannot grow at aw<0.62.
*Some yeast and molds grow slowly at a water activity as slow as
0.65.in general lower the aw the longer the storage life of food
products.
* The interaction of aw with temperature, pH, oxygen and carbon
dioxide, or chemical preservatives has an important effect on the
inhibition of microbial growth

17. *
*Glucose
*Fructose
*Sucrose
*Sodium Chloride
*Potassium Chloride

18. *
*There are some extremely heat-resistant spores that might survive a
commercial process.
*Acidity slows down of spoilage organism and pathogens.
*Pathogens won’t grow, and spores won’t germinate at pH<4.5
*Above pH 4.5,must sterilize for shelf stability.
*foods are divided into three pH groups:
*High-acids foods with pH values less than 3.7,
*Acid foods with pH values between 3.7 and 4.5,
*Low-acid foods with pH values greater than 4.5.

19. *
* The redox potential(removal of oxygen) affects the speed of
weathering reactions and the growth of microorganisms.
Depending on their requirements in oxygen, microorganisms are
classified into four categories:
The strict aerobes (Pseudomonas, Micrococcus, Bacillus) are
microorganisms that can grow in the presence of oxygen.
The aerobic optional (Enterobacteria, Staphylococcus) are
microorganisms that can grow in the presence and absence of
oxygen.
Strict anaerobes (Clostridium, Bacteroides, ...): Are the
microorganisms that can grow in the presence of oxygen.
Micro-Aérophile (Lactobacillus, Streptococcus, ...): Are the
microorganisms that can grow in the presence of low amounts of
oxygen.

20. *
*For the control of redox potential of a product several techniques
are used:
Vacuum packaging
Modified atmosphere packaging
Controlled atmosphere

21. *
*inhibit the bacteria, yeast and mold.
Recommended chemical preservatives
*Sulpher dioxide and sulphites
*Nitrites and nitrates
*Sorbates
*Propionates
*Sodium benzoates

22. *
Steps for food design:
*For the modified and novel food product the desired sensory properties are
tentatively defined.
*A feasible technology for the production of this food must be outlined
*The food is manufactured according to this technology, and the resulting
products is analyzed for pH, aw, preservatives,
*For testing the preliminary microbial stability of the food products
*The product is challenge with toxigenic and spoilage micro-organism
*If necessary, the hurdles in the products are modified,
*The food is again challenged with relevant micro-organism,
*After the established hurdles of the modified foods are exactly defined,
including tolerance.
*The designed food should not be produced under industrial condition
*For the industrial process the critical control point and their monitoring
must be established .

23. *
*Lowering the calories content or the fat, sugar, salt content of
the food some additives tend to be removed and replaced by
natural ingredients.
*Fresh like products are more perishable
*strong need from food processer for new or improved mild
preservation methods that allow the production of fresh like but
stable and safe food.

24. *
*Dairy products
*Meat products
*Vegetables and fruits products
*Cereal products

25. For an example: Dairy products:
( Dr. k. Jayraj Rao, in the “German federal center for meat
research, kulambach”,)
*A mildly heated paneer in cans with the desired flavor(like freshly
prepared),colour (no browning) and texture (not to hard),was
developed.
* This product was stabilized by hurdle technology and thus is stable
and safe for several weeks without refrigeration. The following
combination of hurdle proved effective with this product;
aW=0.97,pH=5.0 and heating to an F value of 0.8 alternatively
aw=0.96 ,pH=5.0.F=0.4,
*The product with gravy was packed in tins or retort pouches and a
set of hurdle, i.e.F=0.8,aw=0.90.95,pH=5.0,and 0.1% potassium
sorbate,was choosen, which had a maximum lethal and
inhibitory effects on micro-organism and minimum effects on
textural and chemical characteristics.(Natrajan, 2000)

26. *The water activity of paneer and gravy was lowered by using
humectants, such as dahi, skim milk powder, salt and glycerol.
*The pH was adjusted by changing the dahi :skim milk powder ratio.
*The resultant product had a keeping quality of one month at 30°C
and over 3 month at 15°C.
*The product was compared with fresh samples from restaurants and
was and found to be equally acceptable.

27. High Moisture fruit product(HMFP) Preservation: Recently process
have been developed for the preservation of HMFP(aw>0.92) and
have been applied for peach halved, pineapple slices, mango
slices, and purees, papaya slices, banana puree.etc.
The new technologies were based on the combination of a mild heat
treatment(blanching for 1-2 min in saturated steam).
Slightly reduction in water activity(to 0.97 -0.92) by the addition of
glucose and sucrose
Lowering of pH(to 4.0 -3.0, by the addition of citric or phosphoric
acid)
And the addition of antimicrobial(potassium sorbate or sodium
benzoate,and sodium sulfite or sodium bisulfite.
After the implementation of these hurdles the product then placed
at 30°C for three month.
And resulting fresh like product scored high, with consumer panels
for taste ,flavour, colour .(Leistner,1996).

28. Due to blanching process the initial microbial counts were
substantially reduced and during the storage of the stabilized HMFP
the number of bacteria, yeast and mold further decreased.
Uses:
In confectionary dairy and bakery products or for the preservatives.
 In Jam and jellies.
Fruit pieces can also be utilized as ingredients in salads ,pizza and
fruit drink simulation.

29. *
* The physiological responses of microorganisms during food
preservation (i.e., their homeostasis, metabolic exhaustion, and
stress reactions.
*The novel and ambitious goal for optimal food preservation is the
multitarget preservation of foods.
*The concept of hurdle technology may also contribute to improving
the organoleptic quality or total quality of foods as perceived by
consumer.
*It may be expected that hurdle technology foods with a relatively
high water activity will partially replace intermediate moisture
foods.
*hurdle technology should be applied without sacrificing the
microbial stability and safety of the foods in developing countries
especially if stored without refrigeration.