Yanwen Shao, Hosahalli S. Ramaswamy,

1
Pressure Resistance Screening of Group I
Clostridium botulinum spores at High Temperature
High Pressure processing conditions
ICEF 8

• Yanwen Shao, Hosahalli S. Ramaswamy,
• John Austin

CSBE Conference July 15, 2008
2
High Pressure Processing

• An emerging and Novel technology
• Originally derived from material science areas
• Introduced by Hite (1899)
• Gaining tremendous popularity only in recent
  years

3
HP Characteristics and Advantages

• Results in fresh-like product

Can destroy microorganisms and inactivate enzymes
Environmentally friendly (less wastage)
Process Independent of product shape and size
4
HP Processing Principles
? Iso-static principle Application of
pressure is instantaneous and uniform through
out the sample
? Le Chatelierss Principle Reactions resulting
in a volume change are influenced by high
pressure applications Reactions resulting in a
volume decrease are accelerated with the
application of HP Reactions resulting in a volume
increase are suppressed by HP.
5
Kinetic Energy and Molecular ordering

• Molecular Ordering
• At constant T, an increase in pressure,
  increases the degree of ordering of the molecules
• Like temperature, the pressure increases the
  kinetic energy associated with the molecules
• Combination of pressure and temperature will
  synergistically accelerate the kinetics

6
High Pressure Processing

• HP mostly affects bio-molecules
• - Destroys microorganisms, especially vegetative
  cells
• - Microbial spores are resistant
• - Inactivates enzymes
• - Alters functional properties
• However, HP treatment generally results in
  minimum changes in nutritional quality
• Color and texture can be affected

7
High Pressure Application Areas

• Pasteurization Juices, milk
• Sterilization High and low acid foods
• Texture modification Fish, egg, proteins,
  starches
• Functional changes Cheese, yogurt , surimi
• Specialty processes Freezing, thawing,
• fat crystallization, enhancing
• reaction kinetics

8
Equipment
Avure
ACB
STANSTED
NC Hyperbaric
Unipress
9
HPP products
Sliced ham
Oysters
10
State of the ArtHigh Pressure Pilot Plant at
McGill
11
High Pressure PasteurizationWell
studiedGuidelines have been developed (USDA -
FDA)Processes now must demonstrate 5 log
reduction in pressure resistant
pathogensExamples Listeria monocytogenes,
E. coli 0157H7, Salmonella spp.1 min at 550
MPa considered adequate (juices) Safe - shelf
stable high quality product
12
Sterilization More
ComplexConsidered as a Novel Process Hence
safety of process must be demonstratedConvention
al kinetics may not apply Hence, new data
needed to for safety demonstration
13
High Pressure Sterilization ProcessTemperature
assisted pressure process (pressure accelerated
destruction)A pressure assisted thermal process
(conventional thermal process)
14
HP Sterilization advantage High pressure
accelerates the destruction kinetics of spores
15
Example HP destruction kinetics of B.
stearothermophilus in water
92C
100C
D 40 min
110C
D 16 min
D 8 min
Conventional D value at 110 C 100 min vs 8 s at
700 MPa
Patazca et al., 2006
16
Geobacillus stearothemophilus in milk (Shao et
al. 2008)
17
HP Destruction kinetics of C. sporogenes 7955 in
ground beef
D (100C) 0.75 min
Zhu, Naim, Shao, Marcotte, Ramaswamy, 2006. A
CRDA Collaboration
18
Clostridum sporogenes 7955 in milk (Shao et al.
2008)
19
Clostridum sporogenes 7955 in salmon (Shao et al.
2008)
20
A pressure assisted thermal process (conventional
thermal process) Can be established based on
thermal processing principlesEstablishment of a
designated process lethalityCommon sterility
levels accepted Fo 5 minUse adiabatic
heating/cooling to quickly achieve the
sterilization conditionsGood quality product

21
HP sterilization Process
Load sample and quickly pressurize chamber to 700
900 MPa
Compression heating increases sample temperature
to 120-130C
Pack and Bring initial temperature to 90C
Delivery of target lethality - Safe productRapid
heating cooling - High quality product
Hold until sterility is achieved 0.5 - 5 min
Depressurize. Sample cools to 90C instantaneously
22
Restriction

• Need to assure that the pressure processing
  conditions provide equal to or better destruction
  of the most resistant, pathogenic and anaerobic
  spore former Clostridium botulinum

23
Objectives

• Screening of Group I Clostridium botulinum spores
  for pressure resistance
• Gathering destruction kinetics data and comparing
  with possible surrogates like C. sporogenes
  spores

24
Spore Selection and Preparation

• 10 strains selected for testing
• Standard enumeration procedures (established by
  Health Canada)
• HP treatment at selected conditions to identify
  the pressure resistant strains
• Establishment of destruction kinetics for the
  most resistant strain

25
Pressure Resistance of Clostridium botulinum
spores (Shao et al., 2008)
Higher the survivor count, higher the resistance
26
More severe pressure conditions
27
PA9508B HO9504A CK-2A
28
Clostridum botulinum PA9508B in milk (Shao et al.
2008)
29
Conclusions

• Confirmation of conservative spore kinetics under
  processing conditions need to be established
• Clostridium botulinum spores are more resistant
  than C. sporogenes and Bacillus stearothermphilus
  spores
• Important to keep behind the cross over point!

30
Keep behind the cross over point
Conventional thermal destruction
HP destruction kinetic
(Shao et al., 2008)
31
Thank you for your attention!