HURDLE TECHNOLOGY-Ammar Babar-11FET1009.

Introduction Hurdle technology is the combined use of several preservation

methods to make a product shelf-stable, to improve quality and to provide additional safety.

Also known as “combined method technology”. Leistner in 1976, introduced the term “hurdle effect”.

NEED FOR HURDLE TECHNOLOGY Consumers are demanding for fresh, natural and minimally

processed food products. Ongoing trend has been eat out and to consume ready to eat

foods.

PRINCIPLE Preservative factors or hurdles disturb the homeostasis of

microorganisms. Microorganisms 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 illustrates that complex interactions of

temperature, water activity, pH etc are significant to the microbial stability.

High Temperature 1) PASTEURIZATION mild heat treatment (e.g., 63oC for 30 min; 100oC for 12sec) high product quality destroys vegetative pathogens (disease-causing microbes) reduces total microbial load, increases shelf-life does not destroy spores (dormant stage of some bacteria) usually combined with other hurdles (e.g., refrigeration) 2) STERILIZATION complete destruction of microorganisms severe heat treatment (equivalent to several min at 121.1oC) destroys spores gives "shelf-stable" product some nutrient, quality destruction (colour,flavour, texture)

3) BLANCHING blanching is a kind of pasteurization generally applied to fruits

and vegetables. primarily applied to inactivate natural enzymes commonly practiced when food is to be frozen depending on its severity, also destroys microorganisms

EFFECT OF HEAT AEROBIC AND ANAEROBIC BACTERIA YEAST & MOULDS.

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

Higher temperature may be needed for killing of thermophilic microorganisms

Vegetative cells are killed in 10 minutes at 100°C and many spores in 30 minutes at 100°C

Low temperature 1) Refrigeration ideally 0oC to 4oC for most foods short-term preservation (days to weeks) high product quality (fresh, minimally processed, slows down microbial growth, respiration,enzyme/chemical

reactions some pathogens can grow (e.g., C. botulinum (typeE), Listeria). 2) Freezing generally -18oC to -30oC quality depends on product, time,temperature long-term preservation (months to years) stops microbial growth, respiration slows down chemical reactions must have good packaging.

3) Reduced water activity aw is water "availability" water is required for microbial growth, enzyme/chemical

reactions pathogenic microorganisms cannot grow at aw < 0.86 yeast & moulds cannot grow at aw <0.62 free water can be removed by concentration, dehydration and freeze drying in general, the lower the aw, the longer the storage life

Recommended substances to reduce water activity.

Increased acidity acidity slows down growth of spoilage organisms and pathogens pathogens won't grow, spores won‘t germinate at pH<4.5 (e.g., fruit juices, sauerkraut) above pH 4.5, must sterilize for shelf stability below pH 4.5, can pasteurize

citric acid

malic acid

tartaric acid

benzoic acid

lactic acid

propionic acid

Glucose

Fructose

Potassium

chlorideSucrose

Sodium chloride

Fermented dry salami

Sequence of hurdles ensures stability at each stage. All hurdles decline with time except aw.

Nitrite inhibits pathogens. growth of other bacteria depletes oxygen Low oxygen favours acid-producing competitive flora Acid decreases pH Aw hurdle gradually increases due to drying.

PROCESSED CHEESE SPREADS Pasteurized .

These products have pH > 4.5 and aw > 0.85. Should have to comply with the low-acid canned food

regulations (i.e., commercial sterilization). However, for quality reasons, these products cannot be given a

sterilization process. Instead, the spreads are stabilized by moderate levels of salt,

decreased pH and moisture.

Significance Improves product quality and microbial safety. Save Money, Energy & Several other Resources. Foods remains stable & safe, high in sensory & nutritive value

due to gentle process applied. Doesn't effects the integrity of food pieces (fruits). Applicable in both Large & Small Industries.