Hurdle technology

Question 1

What is hurdle techonology

Answer 1

an intelligent
combination of hurdles that secures the
microbial safety and stability as well as the
organoleptic and nutritional quality and the
economic viability of food products.

Question 2

The need for hurdle technology

Answer 2

• Not all microbes are equally inhibited by processing.
• Demand is increasing for fresh, natural, and minimally
  processed food products.
• Also. an increasing trend of going out to eat and ready to eat
  foods.
• Leads to change in processing practices.
• Suggests there are new opportunities for microbes to
  dominate a batch of a particular product.

Question 3

Microbial ecology of foods

Answer 3

• Microbes in foods can: Grow,
  Survive, or Die
• Depends on:
  Food composition (e.g.
  additives, antimicrobials)
  o Other microbes in foods
  o Processing steps
  o Storage conditions
  etc
  o Each stable and safe food must have a set of hurdles.
  o They may differ in intensity depending on the particular product.
  o In any case, the hurdles must keep the “normal” population of microorganisms
  in this food under control.
  o The microorganisms present (“at the start”) in a food should not be able to
  overcome (“leap over”) the hurdles present during the storage of a product,
  otherwise the food will spoil and/or cause food borne illness.
  o Food preservation implies putting microorganisms in a hostile environment, in
  order to inhibit their growth or shorten their survival or cause their death.
  o 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.

Question 4

Types of hurdles used for food preservation: Physical

Answer 4

Example:
Aseptic packaging, electromagnetic energy (microwave, radio
frequency, pulsed magnetic fields, high electric fields), high
temperatures (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

Question 5

Types of hurdle used for food preservation: Physicochemical

Answer 5

Example:
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

Question 6

Types of hurdle used for food preservation: Microbial

Answer 6

Example:
Antibiotics, bacteriocins, competitive flora, protective cultures

Question 7

Water activity aw

Answer 7

• Free water – inside cells, maintains properties of water, may be
  removed by pressure
• Bound water – part of molecular structures, reduced mobility
  (therefore fluidity), does not retain the characteristics of water
• Water activity – amount of free water in a product as opposed to
  bond water.
• Ratio of the vapour pressure of water in a food at a specified temperature
  to the vapour pressure of pure water at the same temperature
• An extremely important hurdle
• Most bacteria do not grow at water activities below 0.91 and most moulds
  do not grow at water activities below 0.8

Question 8

Hurdle technology:
combining bacteriocin-containing films
and HPP

Answer 8

Effective in reducing L.
monocytogenes and eliminating
Salmonella in vacuum packed cooked
ham.
The antimicrobial effects of HPP are
strongly dependent on food water
activity. Therefore, the synergistic
antimicrobial effect might be
compromised in meat products with aw
values below 0.9 such as some dry
cured hams and fermented sausages.

Question 9

HPP and mild heat

Answer 9

Conditions required to achieve a 106 reduction of E. coli O157 in poultry
meat (15 min. treatment)
Combination treatments:
Combination of HPCD with other preservation techniques
Hurdle technology may enhance the lethal effects of non-thermal processing
Synergistic effect of combination treatments

Question 10

HPCD and mild heat

Answer 10

HPCD treatment alone at
moderate temperature
(20-40C) is often not
sufficient for substantial
spore reduction.

Question 11

Combination of hurdles

Answer 11

Combination of hurdles
Application of PEF at moderately high temperatures (55C) in combination with the antimicrobials
nisin and lysozyme resulted in greater reduction of Salmonella in orange juice.
PEF and mild heat (55ºC) and antimicrobials (nisin and lysozyme)