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High pressure processing

Identification

Key words high hydrostatic pressure, inactivation, enzyme, virus, spore, pasteurization, sterilization, structure modification, phase equilibrium, simulation, p-T diagram, pressure intensifier
Latest version 2012/07/23
Completed by DIL

How does it work?

Primary objective Microbial inactivation, stabilization, structure modification, preservation
Working principle Thermodynamic: Thermodynamic properties and phase equilibrium of any media such as thermal conductivity, viscosity or diffusivity show a functional relationship to pressure and temperature. Hydrostatic pressure may be generated by the addition of free energy, e.g., heating at constant volume or mechanical volume reduction. Under (high) pressure all reactions of low- and macromolecular compounds follow the principle of Le Chatelièr. Reactions with a negative reaction volume indicate an increasing product formation with increasing pressure. For example dissociation reactions often show a negative volume-difference and are enhanced during pressure application. The physicochemical and biological effects of high pressure application include structural changes of macro-molecules by coagulation, swelling, denaturation and auto-oxidation. (1, 2, 3, 10, 11, 12)

Biological Effects:

  • Inactivation: In general, vegetative cells are inactivated at low pressure levels, around 400-600MPa, while more resistant bacterial spores can survive pressures higher than 1.000 MPa. High pressure affects the permeability of the cellular membrane, which is responsible for the nutrient and respirative transport mechanisms of the cell. The modified permeability of the cellular wall results in a disturbed transport mechanism which may cause a loss of vitality. The extent of inactivation depends on several parameters such as type of micro-organism, pressure level, processing temperature and time, pH and composition of the product or treated media. In general gram- negative bacteria were found to be more sensitive than gram-positive bacteria. A combination of pressure and other inactivation mechanisms or antimicrobial hurdles allows a reduction of processing intensity or enhanced inactivation, e.g. also in inactivation of pressure and thermo-resistant spores. (5, 17, 7, 15, 14, 12)
  • Effects on Proteins: Pressure levels higher than 300 MPa induce modification of the tertiary structure of proteins, characterized by modification of hydrogen bonds and disruption of hydrophobic bonds, often resulting in modified functionality and reactivity of proteins and enzymes. Some studies also describe an impact of pressure on secondary protein structures. In summary when increasing pressure structural changes such as disintegration of micelles, protein dissolution and structure modification such as unfolding or aggregation can occur. These denaturation process typically increase with increasing pressure, temperature and treatment times. (8, 5, 16, 10)
  • Effects on Lipids: By pressure phase equilibria of lipids are subject to change, often a higher amount of crystalline-structures is observed. In some studies lipid oxidation by pressure is reported, which may results from enzymatic as well as chemical reactions. These equilibria and the extent of other desired or undesired reactions such as oxidation depend on the media composition (lipid type and structure, saturation, presence of oxygen).(9)
  • Effects on Polymers: The properties (MW, isostatic index, density, crystallinity…) and the phase equilibria of (bio-)polymers such as starch or cellulose are pressure and temperature dependent. The investigation of melting and crystallization of polymers by pressure is interest due to its potential to induce structure modification. E.g. for starch a potential to achieve a physical structure modification is observed (10)
Images
Additional effects
  • Enzyme inactivation
  • Textural changes (polymers)
  • Vitamin, flavour and colour retention
  • Structure modification
  • “Cold cooking”
  • Swelling
  • Gelation
  • Minimisation of thermal energy stress
Important process parameters
  • Pressure
  • temperature
  • treatment time
Important product parameters
  • pH
  • protein, lipid, salt or sugar content
  • water activity

What can it be used for?

Products Liquid, semi-liquid and solid products in a final or processing package. Meat, fish, chicken, shellfish, vegetable and fruit (apple, carrot and celery) products
Operations Preservation and structure formation, f.e. starch gelation by High Pressure

Can be used for pasteurisation, low temperature process, sterilisation (packaging material for sterilisation) is still under investigation.

Solutions for short comings Preservation of heat sensitive products, reduction of processing time, “cold cooking”, structure formation in protein and carbohydrate based material.

What can it NOT be used for?

Products Dry products such as powders. Due to discoloration fresh meat treatment is limited.
Operations Can be used for pasteurisation, sterilization is still under investigation.
Other limitations
  • Often applied as a batch process with limited capacity of 4t/h
  • High investment cost and maintenance costs e costs
  • Choice and adaptation of appropriate packaging geometry and material required.
  • Undesired changes of functional and technological properties of polymers (proteins) are possible
Risks or hazards Pressure resistance of target strains different from heat resistance, processing uniformity (mainly temperature distribution) is still an issue for sterilization applications.

Implementation

Maturity Industrially available up to pressure levels of 600 MPa. About 130 industrial equipments have been installed worldwide with vessel volumes ranging up to 420 L and production volume of more than 120.000 tons. Most of these applications (about 31%) are found in the meat industry.
Modularity /Implementation Inactivation in the final package, scalable by use of multiple machines or pressure vessels. Short processing times allow a simple implementation of the technique, but often high efforts for loading/unloading of products are required.
Consumer aspects Consumers perceive the technique as environmental friendly and are positive to naturalness of the product. HPP products are seen as positive because the natural texture is retained better, fresher taste and environmental friendliness.

The main benefits linked to HPP technologies are the health-related, taste-related (products’ naturalness) and environment-related benefits(20, 21, 22). According to several researches HPP has been judged to be relatively similar to conventional process technologies in terms of overall consumer acceptability. (23)

Legal aspects HPP foods fall in the scope of Regulation (EC) 258/97 on novel foods and novel food ingredients, article 1, item f. Among other categories, this legislation applies to foods and food ingredients to which a production process not currently used has been applied, and evaluates possible changes in nutritional value, metabolism and level of undesirable substances (19). In January 14th 2008, EU published a proposal for the amendment of Regulation (EC) 258/97 (18).

The competent authorities of the member states agreed in 2001 that the national authorities should decide on the legal status of high pressure treated foods, as it was no longer considered to be a novel process. Case-by-case assessment by national authorities must ensure the products’ safety.

Environmental aspects Energy efficient, waste free technique

Further Information

Institutes KU Leuven LFT, DIL, IRTA, TU Berlin, Wageningen UR - FBR
Companies Hiperbaric, Resato, Uhde-HPT, APA Processing
References 1. Ardia, A. (2004). Process considerations on the application of high pressure treatment at elevated temperature levels for food preservation. Ph.D thesis, Berlin, Berlin University of Technology, 94.

2. Ardia, A., Knorr, D. & Heinz, V. (2004). Adiabatic heat modelling for pressure build-up during high-pressure treatment in liquid-food processing. Food and Bioproducts Processing, 82(C1), 89-95.

3. Bridgman, P. W. (1911). Water in the liquid and five solid forms, under pressure. Proc. Amer. Acad. of Arts and Sciences, 47, 441-558.

4. Bridgman, P. W. (1912). Water in the liquid and five solid forms under pressure. Proc. Amer. Acad. of Arts and Sciences, 47(13), 439-558.

5. Cheftel, J. C. (1992). Effects of high hydrostatic pressure on food constituents: An overview. In C. Balny, R. Hayashi, K. Heremans & P. Masson. High Pressure and Biotechnology (pp. 195-209). John Libbey Eurotext, Montrouge.

6. Cheftel, J. C. (1995). Review: High pressure, microbial inactivation and food preservation. Food Science and Technology International, 1, 75-90.

7. Heinz, V. & Knorr, D. (2002). Effects of high pressure on spores. In M. E. G. Hendrickx & D. Knorr. Ultra high pressure treatments of foods (pp. 77-114). Kluwer Academic/ Plenum Publishers, New York.

8. Heremans, K. (1982). High pressure effects on proteins and other biomolecules. Annual Review of Biophysics and Bioengineering, 11, 1-21.
9. Kato, M. & Hayashi, R. (1999). Effects of high pressure on lipids and biomembranes for understanding high-pressure-induced biological phenomena. Biosci. Biotechnol. Biochem., 63(8), 1321-1328.

10. Knorr, D., Heinz, V. & Buckow, R. (2006). High pressure application for food biopolymers. Biochimica et Biophysica Acta, 1764, 619–631.

11. Mathys, A. (2008). Inactivation mechanisms of Geobacillus and Bacillus spores during high pressure thermal sterilization. PhD thesis, Berlin, Technische Universität Berlin, 161.

12. Mathys, A., Reineke, K., Heinz, V. & Knorr, D. (2008). High pressure thermal sterilization- Development and application of temperature controlled spore inactivation studies. High Pressure Research, in press.

13. Mathys, A. & Knorr, D. (2009). The Properties of Water in the Pressure–Temperature Landscape. Food Biophysics, 4(2), 77-82.

14. Patterson, M. F. (2005). A Review: Microbiology of pressure-treated foods. Journal of Applied Microbiology, 98, 1400–1409.

15. Setlow, P. (2003). Spore germination. Current Opinion in Microbiology, 6, 550–556.

16. Smeller, L. (2002). Pressure-temperature phase diagram of biomolecules. BBA - Biochimica et Biophysica Acta, 1595, 11-29.

17. Smelt, J. P. P. M. (1998). Recent advances in the microbiology of high pressure processing. Trends in Food Science & Technology, 9, 152-158.

18. European Union (2008). 5 COM(2007)872: Proposal for a Regulation of the European Parliament and of the Council on novel foods and amending Regulation (EC) No xxx/xxxx common procedure.

19. European Union (1997). European Parliament and of the Council. Regulation (EC) No 258/97 of the European Parliament and of the Council of 27 January 1997 concerning novel foods and novel food ingredients. OJL 043, 14/02/1997, p. 0001-6.

20. Cardello A.V. et al. (2007). Consumer perceptions of foods processed by innovative and emerging technologies: A conjoint analytic study Original Research Article Innovative Food Science & Emerging Technologies, Volume 8, Issue 1, 73-83

21. Nielsen H.B. et al. (2009). Consumer perception of the use of high-pressure processing and pulsed electric field technologies in food production, Appetite 52: 115–126

22. lsen, N.V. et al. (2010). Consumer acceptance of high-pressure processing and pulsed-electric field: a review. Trends in Food Science & Technology, 21: 464-472

23. Sorenson, D. & Henchion, M. (2011). Understanding consumers’ cognitive structures with regard to high pressure processing: A means-end chain application to the chilled ready meals category, Food Quality.

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Created by Hte irta on 3 February 2012, at 11:55