2. Introduction
A combination of food preservation technique is called
hurdle technology
Factors used for food preservation are called ‘hurdles’
The concept of combining several factors has been
developed by Leistner(1995)
3. Raising factors for hurdle
technology
Consumer demands for healthier foods
Shift to ready-to-eat and convenience foods
Consumer preference for more natural food
6. Basic aspects
Food preservation implies putting microorganisms in a
hostile environment, in order to inhibit their growth or
shorten their survival or cause their death.
The feasible responses of microorganism to this hostile
environment determine whether they may grow or die.
8. Homeostasis
Microorganisms react homeostatically to stress
factors.
Microorganisms undergo many important
homeostatic reactions.
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.
Food preservation is achieved by disturbing
the homeostasis of microorganisms.
9. Metabolic exhaustion
Metabolic exhaustion of microorganisms cause
autosterilization of a food.
This was first observed by Leistner and Karan-
Djurdjic, 1970 in experiments with mildly
heated liver sausage adjusted to different
water activities by the addition of salt and
fat, and the product was inoculated with
Clostridium sporogenes and stored at 37*C.
Clostridial spores surviving the heat treatment
vanished in the product during storage.
10. Stress reactions
synthesis of protective stress shock proteins is induced
by several stresses including heat, pH, aw, ethanol,
oxidative compounds,.
stress responses of microorganisms might hamper food
preservation and become problematic for the
application of hurdle technology.
The use different stresses at the same time prevent
the synthesis of those protective proteins may cause
the microorganisms to become metabolically
exhausted.
This antimicrobial action of combining hurdles is
known as multitarget preservation.
11. Multitarget preservation food
An important aspect for efficient and effective
preservation of targeted food material.
Hurdles applied in the targeted food material might not
just have effects on microbial stability but they could act
synergistically.
Synergistic effect could be achieved in the targeted food,
if the hurdles affects different targets such as pH, aw, Eh,
enzyme systems simultaneously within the microbial cell
and thus disturb the homeostasis of the microbes
rendering it difficult for the microbes to synthesize
different stress shock proteins and to maintain their
homeostasis.
Application of several hurdles simultaneously would lead
to an optimal microbial stability and effective food
preservation.
13. Example 1 represents a food containing six
hurdles: high temperature during
processing (F value), low temperature during stor
age (t value), water activity (aw),
acidity (pH), redox potential (Eh), and preservativ
es (pressure).
The microorganisms present cannot
overcome these hurdles, and thus the food is micr
obiologically stable and safe.
17. Case study -1
Low cost preservation of cauliflower for 180 days through hurdle
technology
Research objectives
1.To develop a suitable hurdle technology (appropriate concentration &
combinations of preservatives, storage temperatures & storage periods) for
preservation of cauliflower for 180 days.
2.To study the effect of hurdle technology (different concentration &
combinations of preservatives, storage temperatures & storage periods) on the
microbial content of preserved cauliflower.
3.To study the effect of hurdle technology (different concentration &
combinations of preservatives, storage temperatures & storage periods) on the
physical & sensory properties of preserved cauliflower.
4.To estimate the cost of preservation of cauliflower for 180 days by hurdle
technology
18. Method of preservation
First cauliflower head were cut into 5×3×3
cm. then thoroughly washed in tap water
and distilled water.
After washing blanched at 100°C for
60sec. then steeped into different
concentrations & combinations of
preservatives.
20. Then aseptically packed into food grade polyethylene pouches
and stored at two different level of temperatures.
T1 ambient temperature – 30 to 37 °C
T2 refrigeration temperatures – 5 to 7 °C for different time
intervals i.e. 0, 30, 60, 90, 120, 150 & 180 days respectively.
These preserved cauliflowers were studied for their
microbial, physical, sensory, & total cost of
preservation.
21. Results
Treatments in which mean of yeast &
mold count were found lowest with a
storage period of 180 days are P4/T1,
P4/T2 & P5/T2.
Lowest water activity & lowest pH were
found in P4/T2 in a storage period of 180
days.
22. Conclusion of research
All the treatments combination was not effective
for preservation of cauliflower till 180 days of
storage period.
Only 3 treatments - P4/T1, P4/T2 & P5/T2 were
microbial safe till 180 days.
Treatment P4/T2 was found best in physical &
sensory but cost of preservation through
treatment P4/T1 for 180 days of storage period
was found cheapest.
Best hurdle treatment for low cost preservation
of cauliflower for 180 days was P4/T1
combination.
23. Conclusion
The physiological responses of microorganisms
during food preservation (i.e., their homeostasis,
metabolic exhaustion, and stress reactions) are the
basis for the application of advanced hurdle
technology.
The disturbance of the homeostasis of
microorganisms is the key phenomenon of food
preservation.
Microbial stress reactions may complicate food
preservation, whereas the metabolic exhaustion of
microorganisms present in stable hurdle-technology
foods could foster food preservation.
24. The novel and ambitious goal for an optimal food
preservation is the multitarget preservation of
foods, in which intelligently applied gentle hurdles
will have a synergistic effect.
After the targets of different preservative factors
within the microbial cells have been elucidated, and
this should become definitely a major research topic
in the future, preservation of foods could progress
far beyond the state-of-the-art of the hurdle
technology approach as we know it today.
25. References
Basic aspects of food preservation by hurdle
technology by Lothar Leistner. (International Journal
of Food Microbiology).
LOW COST PRESERVATION OF CAULIFLOWER
FOR 180 DAYS THROUGH HURDLE
TECHNOLOGY Jyoti Sinha, Ena Gupta and Ramesh
Chandra (INTERNATIONAL JOURNAL OF FOOD
AND NUTRITIONAL SCIENCES ).
Hurdle Technology in Food Preservation by
Mohammad Shafiur Rahman.