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Hurdle technology:

1.  
This is also method of dairy
product preservation.

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2.    Leistner in 1976 introduced term hurdle effect.

3.   Factors used for food
preservation is known as hurdles

                   4.  The
products whose storage life and microbiological safety are extended by use of
preservation factor, non of which individually would be lethal towards spoilage
or pathogenic microbes are known as HT product.

                   5. In this technology three or more hurdles (preservatives) are
employed in a suitable combination and every hurdle is used at an optimum level
so that damage to the overall quality of food is kept to the minimum.

                  6. There is a great scope of
using bacteriocin in combination with other preservatives factors to get hurdle
effect.

  Hurdle technology has great potential for
preservation of indigenous dairy product because,

§ 
No change in sensory
/nutritional characteristic of the product.

§ 
Can be used at room
temperature.

§ 
Reduced energy consumption.
Less susceptible to non enzymatic browning or lipid oxidation.

  Need for hurdle technology

  
       Consumer
demanding for fresh, natural, minimally processed food products.

           Ongoing trends has been eat out and
to consume ready to eat foods.

               New
ecology routes for microbial growth evolved.

                      A crucial phenomenon in
hurdle technology is known as the homeostasis of microorganisms .

                       This multi-targeted
approach is the essence of hurdle technology.

                     It is more effective than
single targeting and allows hurdles of lower intensity, improving product
quality.   

                        There is the further
possibility that different hurdles in a food not only have an added effect on
stability, but can act synergistically.

Principles
for hurdle technology    

            1. Preservative factors or hurdle disturb
the homeostasis of microorganisms

           2. Microorganisms
should not be able to jump over all hurdles present in food product

           3. Preservative factors prevent
microorganisms from multiplying or causing them to remain inactive or even die

           4. Hurdle concept illustrates that
complex interactions of temperature, water activity, pH etc are significant to
microbial stability

               

 

 

PRINCIPLES HURDLE USED FOR PRESERVATION

Parameter

symbol

application

High temperature

 F

 Heating

Low temperature

 T

 Chilling, freezing

Reduced water activity

aw

Drying, curing, conserving

Increased acidity

 pH

 Acid addition or formation

Reduced redox potential

Eh

Removal of oxygen or addition of
ascorbate

Biopreservatives

 Competitive ?ora such as
microbial fermentation

Other preservatives

Sorbets, sul?tes, nitrites

 

 

Types of hurdles

There are mainly three types of hurdles used i.e

1.   Physical

2.   Physico chemical

3.   Microbial

1. Physical hurdles: there are many physical
hurdles routinely used some of them are

¢ Aseptic packaging

¢ electromagnetic energy
(microwave, radio frequency, pulsed magnetic ?elds, high electric ?elds)

¢  high temperatures, (blanching, pasteurization,
sterilization, evaporation, extrusion, baking, frying)

¢ ionizing radiation

¢  low temperature (chilling, freezing)

¢  modi?ed atmospheres, packaging ?lms (including
active packaging, edible coatings)

¢  photodynamic inactivation, ultra high
pressures, ultrasonication, ultraviolet radiation

2.physic chemical hurdles

¢ Carbon dioxide, ethanol,
lactic acid, lactoperoxidase, low pH, low redox potential, low water activity,

¢ Maillard reaction
products, organic acids, oxygen, ozone, phenols, phosphates, salt, smoking,
sodium nitrite/nitrate, sodium or potassium sulphite, spices and herbs, surface
treatment agents

3. Microbial hurdles

                 
The microbial hurdles compete with the bacteria for survival

                  Antibiotics,

                      Bacteriocin,

                      Competitive ?ora,

                      Protective cultures.

MICROBIOCIDAL HURDLES THAT REDUCE MICROBIOLOGICAL LOAD
| Hurdle Technology For Milk Products

The principles of the most common Hurdles within this category are:

1.  
Bactofugation: The removal of microbial cells of high density from milk using
high centrifugal forces.

2.  
Competitive micro flora: The reduction of the number of undesirable microorganisms by
lowering the pH, consumption of nutrients, and production of bacterial
antimicrobial substances (such as nisin, other bacteriocins and hydrogen
peroxide). Usually, this Hurdle is applied by choice of starter cultures.

3.  
Microfiltration: Removal of microbial cells, clumps and somatic cells by
recirculation over a micro filter.

4.  
Ripening (ageing): The holding for such time, at such temperature, and under such
conditions as will result in the necessary biochemical and physical changes
characterizing the cheese in question. When applied as a Hurdle, the
multifactorial, complex system developing in cheese (pH, antagonistic flora,
decreased water activity, metabolism of bacteriocin and organic acids) is
utilized to influence the microenvironment in and on the food and consequently
the composition of the micro flora present.

5.  
Thermization: The application to milk of a heat treatment of a lower intensity
than pasteurization that aims at reducing the number of microorganisms.
Thermized milk is alkaline phosphatase positive.

6.  
High-pressure treatment: Application of high hydrostatic pressures
(> 3000 Bar) to irreversibly damage the membranes of vegetative cells.

7.  
Ultrasonication: The application of high intensity ultrasound (18-500 MHz) that
cause cycles of compression and expansion as well as cavitations in microbial
cells. Implosion of microscopic bubbles generates spots with very high
pressures and temperatures able to destroy cells.

8.  
Electromagnetic energy treatment: Electromagnetic energy results from high
voltage electrical fields, which alternate their frequency millions of times
per second (< 108 MHz). Examples are microwave energy (thermal effect), radio-frequency energy (non-thermal effects) or high electric field pulses (10 – 50 kV/cm, non-thermal effects). The treatment destroys cells by establishing pores in the cell walls due to the buildup of electrical charges at the cell membrane. 9.   Low-intensity irradiation: The submission of beams of photons/electrons to destroy viable microorganisms. Three basic approaches in dairy for application of hurdles ¢ Use of microbiocidal step without use of other hurdles           eg; in container sterilized milk ¢ use of microbiocidal step as combination with other hurdles, this is wide spread used for all dairy products 1.   Drinking milk- heat treatment and cold chain 2.   Cheese – fermentation, salting, heat treatment, ageing 3.   Butter- heat  treatment, fermentation, salting, water dispersion 4.   Milk powder- heat treatment, water activity ·       Use of hurdle technology without combination with microbiocidal step with or without preventive step at primary production level                 Eg:  production of cheese from micro filtrated and thermized milk                   The first ever hurdle technology in India was made in author's laboratory for preservatives of ready to eat paneer curry. DAIRY PRODUCTS    1. PANEER                   Perishable products highly. The freshness of the paneer remains intact only for three days in refridgeration at room temperature.                   Increasing shelf life hurdle technology involved mild treatment, minor reduction in water activity and acidification extend their shelf life of paneer.                    Use 1% sodium chloride, sucrose, glycerol-?water activity. It leads to extended shelf life of paneer.                    0.1%potassiumsorbate – kept for 1 month it is better quality than heat stabilized product stored under 30°C.                    5% brine ,acidified brine,hydrogen peroxide also used . PACKAGING :    paneer curry shelf life is     30°C – 1 month,                                                    15 °C-3 month. The water activity of gravy was reduced by using suitable humectants. It is prepared by using onions, tomatoes, usual spices , humectants, potassium sorbate. 2. BROWN PEDA             Heat desiccated milk. Caramelized color. Highly cooked flavour.good shelf life compared to other khoa based sweets due to low moisture content, higher amount of sugar severe heat treatment applied during its preparation.               But brown peda is very much susceptible to microbial spoilage due to unhygienic process.               Modified vacuum packaging on sensory, physico- chemical texture, biochemical quality of brown peda during storage for 40 days at 30°C. 3. CURD RICE        It is a traditional product in south India. Shelf life is  24 hrs at 30°C. Incorporating a fresh ginger with other spices in milk and boiled for 2-3 min & then used to preparation for curd rice  extended shelf life 7 days at 37°C & 12 days at refridgeration. 4. KHOA                Packaging of khoa in laminates of paper/aluminum foil have been found be quite satisfactory for khoa. In this shelf life is 10 days at ambient temperature.60 days under refridgeration.                4- poly laminated pouches made of the shelf life khoa can be increased to 14 days at 30°C ,&75 days in cold storage                   Packaging of channa polycel is good, low cost packaging material. 5.GHEE              Ghee generally packaged in lacqured or  unlacqured  tin can of various capacity (250g-5 kg) and ghee packed in polyethylene bags also. 6. BURFI            Burfi prepared by traditional method .sold in paper board box- acceptable for about 1 week room temperature.               Add 0.1 %potassium sorbate into polystyrene containers vacuum packaging –more than 60 days     7. GULABJAMUN              Shelf life of ambient temperature in sugar syrup 5-7 days.               Extended 3 weeks by hot filling in polystyrene cups    0.1 % potassium sorbate. 8. RABRI          Rabri is partially concentrated milk product containing several layers of clotted cream.      Polystrene cups in rabri shelf life is 16 hours at 30°C           9. SHRIKHAND                                                             Shelf life    8°C -35 TO 45 DAYS                    35°C-2 TO 3 DAYS                                                                                   Add 0.5 % potassium sorbate ,post production heat treatment at 70°C for 5 min – shelf life is 15 days at 35-37°C. frozen -6 to 12 months for -18°C POLYSTRENE CUPS                 Various hurdle technologies                             Lactic acid bacteria have long been used as components of hurdle technologies due to their ability to rapidly drop the pH in fermented foods and competitively inhibit the growth of other microorganism, which, in part, is due to their production of broad spectrum bacteriocin.       B             Successful applications have been reported for bacteriocin used with various non thermal hurdles including high hydrostatic pressure (HHP), pulsed electric fields (PEF) and irradiation. HHP treatment disrupts hydrogen bonds, ionic bonds and hydrophobic interactions, which results in sub lethal damage to the bacterial cell membrane that affects the function of ATP-generating and transport proteins.                       Hurdle technologies are essential in the preservation of dairy products. Commonly used hurdles include high temperature, short time (HTST) or ultra high temperature (UHT) pasteurization, refrigeration, salting, reduction in pH due to LAB fermentation and a decreased water activity. ADVANTAGES OF HURDLE TECHNOLOGY                      Hurdle technology used in the correct way is a good tool for achieving safe and tasty products of high quality                      Hurdle technology is used to preserve food for more than a decade, but only recently has it been developed for preserving cosmetics                     One of the greatest benefits of hurdle technology is conquering the tendency of microorganisms to develop resistance to conventional preservation systems such as parabens                    Opportunities to using natural preservation in combination with synthetic preservatives.                     As hurdle technology continues to advance, personal care products will become more natural and less dependent on preservatives that are man-made all without compromising the stability of the product or the health and well-being of the consumer. LIMITATIONS                         Hurdles used in food preservation could provide varying results depending on bacterial stress reactions such as the synthesis of protective proteins.                       These stress reactions or cross-tolerance may not exist when combined hurdles are used. However, although hurdles are applied simultaneously in combined form, there are three possible results whereby the action may be changed by combining two or more preservative factors:                              1. Addition or additive effect,                              2. Synergism or synergistic effect,                              3.  Antagonism or antagonistic effect.                Additive effect denotes that the effects of the individual substances are simply added together.               Synergistic effect is the expression used when the inhibitory action of the combination is reached at a concentration lower than that of the constituent substances separately.                An antagonistic effect is the opposite of this latter, i.e. one where the mixture concentration required is higher than that of the individual constituent.                

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