Hurdle Technology PDF

HURDLE TECHNOLOGY  DEFINITION  Food is preserved by combination of different preservation factors or techniques to achieve multi target, mild but reliable preservation effects to improve product quality and safety.  Refers to the use of gentle but effective pres...

HURDLE TECHNOLOGY  DEFINITION  Food is preserved by combination of different preservation factors or techniques to achieve multi target, mild but reliable preservation effects to improve product quality and safety.  Refers to the use of gentle but effective preservation method.  Different hurdles (stress factors) in a food often have a synergistic (enchancing) or additive effect.  SYNERGISTIC EFFECT  more effective to use different combination of preservatives in small amount (low concentration) than to use large amount of one preservative because different preservatives may have different target within the microbial cell – if bacteria not only affect cell membrane but also DNA.  50 different hurdles have been identified and used in food preservation  Commonly used hurdles : temperature, pH, water activity (Aw), Eh (redox potential)  Others: ultrahigh pressure treatment, modified atmosphere packaging, edible coatings/film, ethanol and bacteriocins Hurdles disturb homeostasis…  HOMEOSTASIS  Homeostasis is the ability of the microorganism to maintain a stable and uniform internal environment  Homeostasis mechanism: the mechanism whereby microorganism are able to resist the hurdles (stress factors such as Aw, pH, temperature)  The best way to preserve food is by disturbing several homeostatic mechanisms of the microorganism simultaneously. The more hurdles use, make it more impossible for microorganism to grow.  Most stress reactions of microorganisms are active processes and this often involves the expenditure of energy.  to transport protons across the cell membrane, to maintain high cytoplasmic concentrations of ‘osmoregulatory’ or ‘compatible’ solutes, ability to react to stress factors.  The success of hurdle technology depends on ensuring metabolic exhaustion of the microorganism.  Hurdles can disturb one or more of the homeostasis mechanism thereby preventing microorganism from multiplying causing them to remain inactive and even die. PRINCIPLE OF HURDLE TECHNOLOGY  Preservative factors or hurdles disturb the homeostasis of microorganisms  Microorganism 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 illustrate that complex interactions of temperature, water activity, pH etc are significant to the microbial stability Temperature pH Pressure Water Redox activity potential Moisture Content (MC) Water Activity (aw) Quantitative amount of A measure of the energy water in a sample on a wet status of the water in a or dry basis system (qualitative) An extensive property that An intensive property that depends on the amount of does not depend on the materials amount of materials Which way does water move??? MC = 20% MC = 30% aw = 0.733 aw = 0.733  CATEGORIES OF HURDLES  Physical hurdles  Heat (blanching, pasteurising, canning)  Cold (chilling, freezing)  Packaging (vacuum, aseptic, modified atmosphere packaging)  CATEGORIES OF HURDLES  Physico-chemical hurdles  Salt, sugar, dehydration, water activity  pH (fermentation)  Sulphur dioxide, smoke, gases, ethanol, chlorine  CATEGORIES OF HURDLES  Microbially-derived hurdles  Competitive flora within the food micro environment  Starter cultures  Bacteriocins : an antibacterial substance produced by bacteria that is harmful to other bacteria  EXAMPLE OF HURDLES USED TO PRESERVE FOODS Type of hurdles Examples Physical hurdles Aseptic packaging, electromagnetic energy (microwave, radio frequency, pulsed magnetic fields, high electric fields) High temperature (blanching, pasteurization, sterilization, evaporation, extrusion, baking, frying) Ionizing radiation, low temperature (chilling freezing), modified atmospheres, packaging films (including active packaging, edible coatings) Photodynamic inactivation, ultra high pressures, ultrasonication, ultraviolet radiation. Physico-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 suphite, spices and herbs, surface treatment agents. Microbially derived Antibiotics, bacteriocins, competitive flora, protective cultures. hurdles  FACTOR INFLUENCE THE SELECTION OF DIFFERENT COMBINATION OF HURDLES 1. The initial microbial load of the product requiring preservation. 2. How favourable conditions are within the product for microbial growth. 3. Target shelf life. 4. Physico chemical and biochemical reactions that can deteriorate the quality. 5. Type of microorganisms that can be present and develop in the food  EXAMPLE OF FOODS PRESERVED BY HURDLE TECHNOLOGY 1. Salami type fermented sausage  Preserved using a combination of hurdles (salt, nitrate, Eh, pH and Aw) http://t3.gstatic.com/images?q=tbn:ANd9GcTF9jeddJ7yun8XOT6yr7v_7Lxm94E8gH66l9kWCPaxqEIUPru5LWQiB5LX 2. Smoked products  Heat, reduced Aw, salt and antimicrobial chemicals from smoke http://t0.gstatic.com/images?q=tbn:ANd9GcRWsL8pCC2iBpLFMEzuYNj3jidaNAfUcq6djDsmHDZe70pPsEq9u1LUql0 3. Jam  Heat, high acidity, high sugar content, reduced Aw 4. Pickles http://t3.gstatic.com/images?q=tbn:ANd9GcQATPB12E1WHhG-qofF_od6D3gtfK016KRrz55q7W2TD_FXfV0-t0DiJA  Salt, acetic acid, heat and chemical preservatives (benzoate and sorbate)  EXAMPLES OF HURDLE TECHNOLOGIES 1. Thermal processing (blanching) + antimicrobial (sodium benzoate, vanilin)  Thermal resistance of microorganism are reduced, lower temperature / time values to kill microorganisms.  Chemical hurdles that target various cellular components such as membrane, nucleic acid and proteins can therefore be utilized during food processing to enhance the sensitivity of bacteria to heat treatment and to prevent cellular repair mechanisms during storage. EXAMPLES OF HURDLE TECHNOLOGIES 2. High pressure based hurdles + biopreservatives such as natural antimicrobial from garlic (allicin), clove (eugienols), niasin 3. Irradiation + preservatives (organic acids, bacteriocins and natural antioxidants) 4. Modified atmosphere packaging (MAP) + high pressure processing + irradiation  INDUSTRIAL APPLICATIONS OF HURDLE TECHNOLOGY:  Minimally processed fruits and vegetables hurdles.  Temperature (refrigeration), dipping into antioxidant solutions (anti browning ascorbic and citric acids), washing with chlorinated water, anti softening (CaCl) and packaging.  Chilling + disinfection + MAP (modified atmosphere packaging).  Combining UV light + chemical disinfectants +/or MAP on vegetable produce.  INDUSTRIAL APPLICATIONS OF HURDLE TECHNOLOGY:  Combining chlorinated water to disinfect fresh cut fruit and vegetables + UV light treatments + storage in MAP.  UV light combined + mild thermal treatments.  Fungal inactivation to prevent postharvest decay in strawberries and sweet cherries with the UV combined + thermal treatment (15 min at 45oC). http://t1.gstatic.com/images?q=tbn:ANd9GcTkkO_ZqT-K8TKr9oN1o0ND-9dQBnQ9wwkCd2njRvurjsQnQNh4gQoKsr2C  COMBINED METHODS FOR PRESERVING TROPICAL FRUIT WITH MINIMAL PROCESSING Fruit Combined method Temperature(oC) Shelf life (month) Peach, sliced, halves or Blanching (steam, 2 min) 35 3 whole aw = 0.98 (sucrose) pH = 3.7 NaHSO3 = 150 ppm KS = 1000 ppm Peach, halves Blanching (steam, 2 min) 20 or 30 4 aw = 0.94 (glucose) pH = 3.5 NaHSO3 = 150 ppm KS = 1000 ppm Pineapple, sliced or whole Blanching (steam, 2 min) 27 4 aw = 0.97 (glucose) pH = 3.1 NaHSO3 = 150 ppm KS = 1000 ppm KS = potassium sorbate, AA = ascorbic acid, SB = sodium benzoate, SMB = sodium metabisulphite  Fruit Combined method Temperature(oC) Shelf life (month) Mango Blanching (80oC, 10 min) 30-35 3 aw = 0.985 (sucrose) pH = 3.6 SMB = 150 ppm SB = 1000 ppm Papaya Blanching (steam, 3 min) 35 4 aw = 0.98 (sucrose) pH = 4.1 KS = 1000 ppm Plum Blanching (steam, 3 min) 25 4 aw = 0.98 (sucrose) pH = 3.0 NaHSO3 = 150 ppm KS = 1000 ppm KS = potassium sorbate, AA = ascorbic acid, SB = sodium benzoate, SMB = sodium metabisulhite  INTERMEDIATE MOISTURE FOOD  Modifications of traditional intermediate-moisture foods to produce high moisture ambient stable foods.  Easy to prepare and store without refrigeration, energy efficient and relatively cheap.  Disadvantage of traditional IMF: too high sugar, used of additives (nitrite, sulfite, humectant) is health hazard. http://t3.gstatic.com/images?q=tbn:ANd9GcRy_9kBtsVIkNmvBlxtHwiz5RbP1LehGSkQwLxA8_PeqlFTim8pDJe6DGky8g http://t3.gstatic.com/images?q=tbn:ANd9GcQSJqwSKbS4iJvx0EHtTbXPPGpiQJMR4WnSYgLmOzGrDlit-fKr5zbwuIk  Hurdle technology application: to increase moisture content and aw, reduce sugar and salt addition without sacrificing the microbial stability and safety of the product if stored at ambient temperature.  Hurdles : mild heat treatment (blanching), reduce aw, low pH, preservative, anti browning agents, anti softening agent. http://t1.gstatic.com/images?q=tbn:ANd9GcR3ifwobrTX9akiH554NBRv-6yThTwplUZYAVJlSsyrIQaBgqhyldhg9K0x http://t2.gstatic.com/images?q=tbn:ANd9GcR6LsRwTAp0CAqwdd4pJzzGxIcDxgnfs6d3COVqTok0CyLXlGZfSxjLmw