PALLVI DHOTRA PALLVI DHOTRA PALLVI DHOTRA PALLVI DHOTRA ROLL No. 06ROLL No. 06ROLL No. 06ROLL No. 06

FOOD SCIENCE & TECHNOLOGYFOOD SCIENCE & TECHNOLOGYFOOD SCIENCE & TECHNOLOGYFOOD SCIENCE & TECHNOLOGY

� Hurdle technology is the combined use of several Hurdle technology is the combined use of several Hurdle technology is the combined use of several Hurdle technology is the combined use of several preservation methods to make a product shelfpreservation methods to make a product shelfpreservation methods to make a product shelfpreservation methods to make a product shelf----stable, stable, stable, stable, to improve quality and to provide additional safety.to improve quality and to provide additional safety.to improve quality and to provide additional safety.to improve quality and to provide additional safety.

� Also known as “combined method technology”.Also known as “combined method technology”.Also known as “combined method technology”.Also known as “combined method technology”.

� Leistner in 1976, introduced the term “hurdle effect”. Leistner in 1976, introduced the term “hurdle effect”. Leistner in 1976, introduced the term “hurdle effect”. Leistner in 1976, introduced the term “hurdle effect”.

NEED FOR HURDLE TECHNOLOGY

� Consumers are demanding for fresh, natural and Consumers are demanding for fresh, natural and Consumers are demanding for fresh, natural and Consumers are demanding for fresh, natural and minimally processed food products.minimally processed food products.minimally processed food products.minimally processed food products.

� Ongoing trend has been eat out and to consume ready Ongoing trend has been eat out and to consume ready Ongoing trend has been eat out and to consume ready Ongoing trend has been eat out and to consume ready to eat foods.to eat foods.to eat foods.to eat foods.

� New ecology routes for microbial growth have emergedNew ecology routes for microbial growth have emergedNew ecology routes for microbial growth have emergedNew ecology routes for microbial growth have emerged....

� Preservative factors or hurdles disturb the Preservative factors or hurdles disturb the Preservative factors or hurdles disturb the Preservative factors or hurdles disturb the homeostasis of microorganisms.homeostasis of microorganisms.homeostasis of microorganisms.homeostasis of microorganisms.

� Microorganisms should not be able to “jump over” Microorganisms should not be able to “jump over” Microorganisms should not be able to “jump over” Microorganisms should not be able to “jump over” all the hurdles present in the food product.all the hurdles present in the food product.all the hurdles present in the food product.all the hurdles present in the food product.

� Preservative factors prevents microorganisms from Preservative factors prevents microorganisms from Preservative factors prevents microorganisms from Preservative factors prevents microorganisms from multiplying and causing them to remain inactive or multiplying and causing them to remain inactive or multiplying and causing them to remain inactive or multiplying and causing them to remain inactive or even die.even die.even die.even die.

� The hurdle concept illustrates that complex The hurdle concept illustrates that complex The hurdle concept illustrates that complex The hurdle concept illustrates that complex interactions of temperature, water activity, pH etc interactions of temperature, water activity, pH etc interactions of temperature, water activity, pH etc interactions of temperature, water activity, pH etc are significant to the microbial stability.are significant to the microbial stability.are significant to the microbial stability.are significant to the microbial stability.

High TemperatureHigh TemperatureHigh TemperatureHigh Temperature

i. Pasteurizationi. Pasteurizationi. Pasteurizationi. Pasteurization

� mild heat treatment (e.g., 63mild heat treatment (e.g., 63mild heat treatment (e.g., 63mild heat treatment (e.g., 63ooooC for 30 min; 100C for 30 min; 100C for 30 min; 100C for 30 min; 100ooooC for 12 C for 12 C for 12 C for 12 sec)sec)sec)sec)

� high product qualityhigh product qualityhigh product qualityhigh product quality

� destroys vegetative pathogens (diseasedestroys vegetative pathogens (diseasedestroys vegetative pathogens (diseasedestroys vegetative pathogens (disease----causing microbes)causing microbes)causing microbes)causing microbes)� destroys vegetative pathogens (diseasedestroys vegetative pathogens (diseasedestroys vegetative pathogens (diseasedestroys vegetative pathogens (disease----causing microbes)causing microbes)causing microbes)causing microbes)

� reduces total microbial load, increases shelfreduces total microbial load, increases shelfreduces total microbial load, increases shelfreduces total microbial load, increases shelf----lifelifelifelife

� does not destroy spores (dormant stage of some bacteria)does not destroy spores (dormant stage of some bacteria)does not destroy spores (dormant stage of some bacteria)does not destroy spores (dormant stage of some bacteria)

� usuallyusuallyusuallyusually combined with other hurdles (e.g., refrigeration)combined with other hurdles (e.g., refrigeration)combined with other hurdles (e.g., refrigeration)combined with other hurdles (e.g., refrigeration)

ii. ii. ii. ii. SterilizationSterilizationSterilizationSterilization

� complete destruction of microorganismscomplete destruction of microorganismscomplete destruction of microorganismscomplete destruction of microorganisms

� severe heat treatment (equivalent to several severe heat treatment (equivalent to several severe heat treatment (equivalent to several severe heat treatment (equivalent to several min at 121.1min at 121.1min at 121.1min at 121.1ooooC)C)C)C)

� destroys sporesdestroys sporesdestroys sporesdestroys spores

� gives "shelfgives "shelfgives "shelfgives "shelf----stable" productstable" productstable" productstable" product

� some nutrient, quality destruction (colour, some nutrient, quality destruction (colour, some nutrient, quality destruction (colour, some nutrient, quality destruction (colour, flavour, texture)flavour, texture)flavour, texture)flavour, texture)

iii. iii. iii. iii. Blanching Blanching Blanching Blanching

� blanching is a kind of pasteurization blanching is a kind of pasteurization blanching is a kind of pasteurization blanching is a kind of pasteurization generally applied to fruits and vegetablesgenerally applied to fruits and vegetablesgenerally applied to fruits and vegetablesgenerally applied to fruits and vegetables

� primarily applied to inactivate natural primarily applied to inactivate natural primarily applied to inactivate natural primarily applied to inactivate natural enzymesenzymesenzymesenzymes

� commonly practiced when food is to be commonly practiced when food is to be commonly practiced when food is to be commonly practiced when food is to be frozenfrozenfrozenfrozen

� depending on its severity, also destroys depending on its severity, also destroys depending on its severity, also destroys depending on its severity, also destroys microorganismsmicroorganismsmicroorganismsmicroorganisms

� Vegetative cells, as well as, viruses are Vegetative cells, as well as, viruses are Vegetative cells, as well as, viruses are Vegetative cells, as well as, viruses are destroyed at temperature 60destroyed at temperature 60destroyed at temperature 60destroyed at temperature 60°°°°C to 80C to 80C to 80C to 80°°°°CCCC

� Higher temperature may be needed for Higher temperature may be needed for Higher temperature may be needed for Higher temperature may be needed for killing of thermophilic microorganismskilling of thermophilic microorganismskilling of thermophilic microorganismskilling of thermophilic microorganisms

� Vegetative cells are killed in 10 minutes at Vegetative cells are killed in 10 minutes at Vegetative cells are killed in 10 minutes at Vegetative cells are killed in 10 minutes at 100100100100°°°°C and many spores in 30 minutes atC and many spores in 30 minutes atC and many spores in 30 minutes atC and many spores in 30 minutes at100100100100°°°°CCCC

Low TemperatureLow TemperatureLow TemperatureLow Temperature

iiii. Refrigeration. Refrigeration. Refrigeration. Refrigeration

� ideally 0ideally 0ideally 0ideally 0ooooC to 4C to 4C to 4C to 4ooooC for most foodsC for most foodsC for most foodsC for most foods

� shortshortshortshort----term preservation (days to weeks)term preservation (days to weeks)term preservation (days to weeks)term preservation (days to weeks)

� high product quality (fresh, minimally processed, high product quality (fresh, minimally processed, high product quality (fresh, minimally processed, high product quality (fresh, minimally processed, soussoussoussous vide) vide) vide) vide)

� slows down microbial growth, respiration, slows down microbial growth, respiration, slows down microbial growth, respiration, slows down microbial growth, respiration, enzyme/chemical reactionsenzyme/chemical reactionsenzyme/chemical reactionsenzyme/chemical reactions

� some pathogens can grow (e.g., some pathogens can grow (e.g., some pathogens can grow (e.g., some pathogens can grow (e.g., C. C. C. C. botulinumbotulinumbotulinumbotulinum (type (type (type (type E), E), E), E), ListeriaListeriaListeriaListeria)

ii. ii. ii. ii. FreezingFreezingFreezingFreezing

� generally generally generally generally ----18181818ooooC to C to C to C to ----30303030ooooCCCC

� quality depends on product, time, quality depends on product, time, quality depends on product, time, quality depends on product, time, temperaturetemperaturetemperaturetemperature

� longlonglonglong----term preservation (months to years)term preservation (months to years)term preservation (months to years)term preservation (months to years)� longlonglonglong----term preservation (months to years)term preservation (months to years)term preservation (months to years)term preservation (months to years)

� stops microbial growth, respiration stops microbial growth, respiration stops microbial growth, respiration stops microbial growth, respiration

� slows down chemical reactionsslows down chemical reactionsslows down chemical reactionsslows down chemical reactions

� must have good packagingmust have good packagingmust have good packagingmust have good packaging

Reduced Water Activity (aReduced Water Activity (aReduced Water Activity (aReduced Water Activity (awwww))))� aaaawwww is water "availability"is water "availability"is water "availability"is water "availability"

� water is required for microbial growth, water is required for microbial growth, water is required for microbial growth, water is required for microbial growth, enzyme/chemical reactionsenzyme/chemical reactionsenzyme/chemical reactionsenzyme/chemical reactions

pathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at a < < < < � pathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at apathogenic microorganisms cannot grow at awwww < < < < 0.860.860.860.86

� yeast & moulds cannot grow at ayeast & moulds cannot grow at ayeast & moulds cannot grow at ayeast & moulds cannot grow at awwww <0.62<0.62<0.62<0.62

� free water can be removed by concentration, free water can be removed by concentration, free water can be removed by concentration, free water can be removed by concentration, dehydration and freeze dryingdehydration and freeze dryingdehydration and freeze dryingdehydration and freeze drying

� in general, the lower the ain general, the lower the ain general, the lower the ain general, the lower the awwww, the longer the storage , the longer the storage , the longer the storage , the longer the storage lifelifelifelife

� GlucoseGlucoseGlucoseGlucose

� FructoseFructoseFructoseFructose

� SucroseSucroseSucroseSucrose� SucroseSucroseSucroseSucrose

� Sodium chlorideSodium chlorideSodium chlorideSodium chloride

� Potassium chloridePotassium chloridePotassium chloridePotassium chloride

Increased Acidity (lowered pH)Increased Acidity (lowered pH)Increased Acidity (lowered pH)Increased Acidity (lowered pH)� acidity slows down growth of spoilage acidity slows down growth of spoilage acidity slows down growth of spoilage acidity slows down growth of spoilage

organisms and pathogensorganisms and pathogensorganisms and pathogensorganisms and pathogens

� pathogens won't grow, spores won't pathogens won't grow, spores won't pathogens won't grow, spores won't pathogens won't grow, spores won't germinate at pH<4.5germinate at pH<4.5germinate at pH<4.5germinate at pH<4.5

� pathogens won't grow, spores won't pathogens won't grow, spores won't pathogens won't grow, spores won't pathogens won't grow, spores won't germinate at pH<4.5germinate at pH<4.5germinate at pH<4.5germinate at pH<4.5(e.g., fruit juices, sauerkraut)(e.g., fruit juices, sauerkraut)(e.g., fruit juices, sauerkraut)(e.g., fruit juices, sauerkraut)

� above pH 4.5, must sterilize for shelf above pH 4.5, must sterilize for shelf above pH 4.5, must sterilize for shelf above pH 4.5, must sterilize for shelf stabilitystabilitystabilitystability

� below pH 4.5, can pasteurizebelow pH 4.5, can pasteurizebelow pH 4.5, can pasteurizebelow pH 4.5, can pasteurize

� Organic acidsOrganic acidsOrganic acidsOrganic acids

citric acidcitric acidcitric acidcitric acid

malic acidmalic acidmalic acidmalic acid

tartaric acidtartaric acidtartaric acidtartaric acid

benzoic acidbenzoic acidbenzoic acidbenzoic acid

lactic acid lactic acid lactic acid lactic acid lactic acid lactic acid lactic acid lactic acid

propionic acidpropionic acidpropionic acidpropionic acid

� Inorganic acidsInorganic acidsInorganic acidsInorganic acids

� Fermentation byFermentation byFermentation byFermentation by---- productsproductsproductsproducts

Controlling OxygenControlling OxygenControlling OxygenControlling Oxygen� low oxygen inhibits growth of many low oxygen inhibits growth of many low oxygen inhibits growth of many low oxygen inhibits growth of many

spoilage organismsspoilage organismsspoilage organismsspoilage organisms

but:but:but:but:

� anaerobic conditions required by some pathogens anaerobic conditions required by some pathogens anaerobic conditions required by some pathogens anaerobic conditions required by some pathogens

(e.g., (e.g., (e.g., (e.g., C. botulinumC. botulinumC. botulinumC. botulinum))))(e.g., (e.g., (e.g., (e.g., C. botulinumC. botulinumC. botulinumC. botulinum))))

PreservativesPreservativesPreservativesPreservatives� inhibit bacteria, yeasts, mouldsinhibit bacteria, yeasts, mouldsinhibit bacteria, yeasts, mouldsinhibit bacteria, yeasts, moulds

� used at low levels (mg/kg) for specific applicationsused at low levels (mg/kg) for specific applicationsused at low levels (mg/kg) for specific applicationsused at low levels (mg/kg) for specific applications

� e.g., benzoate (soft drinks), propionate (baked e.g., benzoate (soft drinks), propionate (baked e.g., benzoate (soft drinks), propionate (baked e.g., benzoate (soft drinks), propionate (baked goods),goods),goods),goods),

nitrites (meats), sulfites (wine), ascorbate (juices)nitrites (meats), sulfites (wine), ascorbate (juices)nitrites (meats), sulfites (wine), ascorbate (juices)nitrites (meats), sulfites (wine), ascorbate (juices)

� Sulphur dioxide and SulphitesSulphur dioxide and SulphitesSulphur dioxide and SulphitesSulphur dioxide and Sulphites

� Nitrites and NitratesNitrites and NitratesNitrites and NitratesNitrites and Nitrates

� SorbatesSorbatesSorbatesSorbates

� Propionates Propionates Propionates Propionates

Sodium benzoateSodium benzoateSodium benzoateSodium benzoate� Sodium benzoateSodium benzoateSodium benzoateSodium benzoate

Competitive MicroorganismsCompetitive MicroorganismsCompetitive MicroorganismsCompetitive Microorganisms

� "good" bacteria inhibit "bad" (spoilers, pathogens)"good" bacteria inhibit "bad" (spoilers, pathogens)"good" bacteria inhibit "bad" (spoilers, pathogens)"good" bacteria inhibit "bad" (spoilers, pathogens)

May act byMay act byMay act byMay act by::::� "crowding out""crowding out""crowding out""crowding out"� "crowding out""crowding out""crowding out""crowding out"

� producing acidproducing acidproducing acidproducing acid

� producing antibiotics (bacteriocins)producing antibiotics (bacteriocins)producing antibiotics (bacteriocins)producing antibiotics (bacteriocins)

� e.g., lactic acid bacteria (sauerkraut, yogurt)e.g., lactic acid bacteria (sauerkraut, yogurt)e.g., lactic acid bacteria (sauerkraut, yogurt)e.g., lactic acid bacteria (sauerkraut, yogurt)

� Sequence of hurdles ensures stability at each Sequence of hurdles ensures stability at each Sequence of hurdles ensures stability at each Sequence of hurdles ensures stability at each stage. All hurdles decline with time except astage. All hurdles decline with time except astage. All hurdles decline with time except astage. All hurdles decline with time except awwww....

� Nitrite inhibits pathogensNitrite inhibits pathogensNitrite inhibits pathogensNitrite inhibits pathogens

growth of other bacteria depletes oxygengrowth of other bacteria depletes oxygengrowth of other bacteria depletes oxygengrowth of other bacteria depletes oxygen� growth of other bacteria depletes oxygengrowth of other bacteria depletes oxygengrowth of other bacteria depletes oxygengrowth of other bacteria depletes oxygen

� Low oxygen favours acidLow oxygen favours acidLow oxygen favours acidLow oxygen favours acid----producing producing producing producing competitive floracompetitive floracompetitive floracompetitive flora

� Acid decreases pHAcid decreases pHAcid decreases pHAcid decreases pH

� AAAAwwww hurdle gradually increases due to drying. hurdle gradually increases due to drying. hurdle gradually increases due to drying. hurdle gradually increases due to drying.

� These products have pH > 4.5 and aThese products have pH > 4.5 and aThese products have pH > 4.5 and aThese products have pH > 4.5 and awwww > 0.85. > 0.85. > 0.85. > 0.85.

� Should have to comply with the lowShould have to comply with the lowShould have to comply with the lowShould have to comply with the low----acid acid acid acid canned food regulations (i.e., commercial canned food regulations (i.e., commercial canned food regulations (i.e., commercial canned food regulations (i.e., commercial sterilization).sterilization).sterilization).sterilization).

� However, for quality reasons, these products However, for quality reasons, these products However, for quality reasons, these products However, for quality reasons, these products cannot be given a sterilization process. cannot be given a sterilization process. cannot be given a sterilization process. cannot be given a sterilization process.

� Instead, the spreads are stabilized by moderate Instead, the spreads are stabilized by moderate Instead, the spreads are stabilized by moderate Instead, the spreads are stabilized by moderate levels of salt, decreased pH and moisture. levels of salt, decreased pH and moisture. levels of salt, decreased pH and moisture. levels of salt, decreased pH and moisture.

� Improves product quality and microbial safety.Improves product quality and microbial safety.Improves product quality and microbial safety.Improves product quality and microbial safety.

� Save Money, Energy & Several other Resources.Save Money, Energy & Several other Resources.Save Money, Energy & Several other Resources.Save Money, Energy & Several other Resources.

� Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & nutritive value due to gentle process applied.nutritive value due to gentle process applied.nutritive value due to gentle process applied.nutritive value due to gentle process applied.

� Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & Foods remains stable & safe, high in sensory & nutritive value due to gentle process applied.nutritive value due to gentle process applied.nutritive value due to gentle process applied.nutritive value due to gentle process applied.

� Doesn't effects the integrity of food pieces (fruits).Doesn't effects the integrity of food pieces (fruits).Doesn't effects the integrity of food pieces (fruits).Doesn't effects the integrity of food pieces (fruits).

� Applicable in both Large & Small Industries.Applicable in both Large & Small Industries.Applicable in both Large & Small Industries.Applicable in both Large & Small Industries.

� Manufacture of new products according to the need Manufacture of new products according to the need Manufacture of new products according to the need Manufacture of new products according to the need of processors and consumers.of processors and consumers.of processors and consumers.of processors and consumers.

BOOKSBOOKSBOOKSBOOKS----� A text book of food preservation A text book of food preservation A text book of food preservation A text book of food preservation ---- BY BY BY BY

NEELAM KHETARPALNEELAM KHETARPALNEELAM KHETARPALNEELAM KHETARPAL....� Food microbiology Food microbiology Food microbiology Food microbiology ---- BY BY BY BY

Food science Food science Food science Food science –––– BY BY BY BY � Food science Food science Food science Food science –––– BY BY BY BY WEBSITESWEBSITESWEBSITESWEBSITES----

<http://www.ifrn.bbsrc.ac.uk/safety/comicro/Culture_25.pdf>

<http://ars.usda.gov/Services/docs.htm?docid=6786