Yanwen Shao, Hosahalli S. Ramaswamy, John Austin

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 Chateliers’s 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. Fruit Juice (USA) Jams, Fruit topping (Japan) Fruit Juice (Japan) Avomax (USA) Fruit Juice (FRANCE) Meat (SPAIN) 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 0157:H7, 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 demonstratedConventional kinetics may not applyHence, new data needed to for safety demonstration

13. High Pressure Sterilization Process:Temperature 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. sporogenes7955 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 PA9508Bin 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!