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Structure formation through pressure-induced protein denaturation

Identification

Key words High pressure processing (HPP), high pressure homogenization (HPH), protein modification, enzyme inactivation, protein and food functionality, improved protein functionality
Latest version 2013/08/02
Completed by DIL

How does it work?

Primary objective To modify the protein spatial structure whereby protein functionality is affected.
Working principle he application of high pressure (100 – 1000 MPa) has a disruptive effect on intra-molecular hydrophobic and electrostatic interactions with minimum impact on covalent bonds in proteins. This makes pressure an ideal tool to tune non-covalent interactions, such as hydrogen bonds, and destabilize the hydrophobic effect. Thus, it leads to modification of quaternary and tertiary structure of the proteins by a proposed unfolding mechanism, with negligible effect on their secondary structure. It can also dissociate protein subunits (1).

Based on the protein modification induced by the application of high pressure, different degrees of coagulation and gelation take place, whereby new textures are created. For instance, if you apply High Pressure Processing (HPP) to solid mixtures like meat, an increase in the consistency and a decrease in the drip loss of cooked meat products, compared to standard processing, can be achieved (2, 3). Protein solutions can be submitted to High Pressure Homogenization (HPH) with the aim of improving protein functionality (4, 5, 6). For instance, if HPH is applied to whey protein solutions, better foaming and stabilizing properties can be obtained (7, 8).

The main advantage of pressure is that it is transmitted instantaneously through the entire system and thus a uniform effect takes place. However, both in High Pressure Processing (HPP) and High Pressure Homogenization (HPH), the pressure increase leads to a temperature increase. Overall, pressure processing can lead to globular protein denaturation, and to different states of aggregation, surface hydrophobicity and gelation depending on the protein system, treatment temperature, solution conditions, and magnitude and duration of the applied pressure. Optimization of treatment conditions on a case-basis is required in order to obtain the desired functionality. Protein stability or coagulation zones can be explained in pressure/temperature denaturation graphs where it is possible to separate native and coagulated proteins.

Images
Additional effects
Important process parameters Pressure level, treatment time (i.e. holding time for static-HP or flow and number of cycles for dynamic-HP) and temperature.
Important product parameters Type of protein, protein concentration, pH, ionic force, solubility, protein interactions, water content, initial structure (air voids)

What can it be used for?

Products
  • All solid or liquid foodstuffs can be submitted to HPP; on condition they contain sufficient moisture for transmittance of pressure and not too many air voids. All kinds of dispersions which are sufficiently liquid and thus pumpable can be submitted to HPH.
  • Emulsions or foam-structured foodstuffs can be treated by high pressure but the amount of air and the degree of organization will determine the stability after the HP treatment.
  • Protein dispersions or solutions can also be treated by the technologies.

In general, the application of HPP appears effective in improving meat (2, 3, 9), egg (10) or soy (11) protein gelation properties, as well as the coagulating properties of milk (6, 7, 12, 13, 14). This fact can be transferred to products with improved texture using fewer additives such as emulsifiers (11, 16), stabilizers (7, 8, 11, 16), texturizers (2, 9, 10, 12, 13, 14, 15) and water retention intended additives like phosphates or gums (2, 8, 13). As an example, in meat products, HPP has shown potential in the production of sausages with lower salt content and equivalent or enhanced water holding capacity and texture, as the gelation properties of the meat batter are improved (2, 3, 9). Dairy proteins can also be submitted to HPP to induce gel formation (10, 14), or to HPH to improve protein functionality like foaming or stabilizing properties (7, 8).

Operations Structure formation by texture modification, preservation
Solutions for short comings
  • New texture development
  • Clean labelling: less additives such as emulsifiers, stabilizers, texturizers etc… will be needed.

What can it NOT be used for?

Products
  • HPP cannot be used for dry products, or products with a highly porous structure.
  • HPH cannot be used for solid food products or for products with high viscosity as those are not pumpable, but they can be processed by HPP.
  • For some products, the formation of gels at the applied pressures might obstruct the pipe in HPH. In general, the higher the protein concentration, the temperature and the pressure, the higher the probability of obstruction.
Operations
Other limitations Initial investments in equipment may be high. A feasibility study is recommended before investment.
Risks or hazards Under normal operating conditions the risks for operators of the equipment are negligible.

From a consumer standpoint, no risks have been identified or associated with the use of HPP so far. In any case, these products must comply with the legal requirements described in the section “legal aspects”.

Implementation

Maturity Static HPP equipment is commercially available. These can apply pressures to a maximum of 600 MPa. Industrial-scale HPH HPH units are also available, but usually the application pressure range is lower (up to 350 MPa).

Research is still needed to better understand the mechanisms by which the structure formation or the improved functionality is achieved as well as to discover potential future applications.

Modularity /Implementation Standardized procedures are already established in industry for HPP and HPH.

Static HPP is applied in a batch system, whereas HPH equipment is inare continuous systems.

Consumer aspects Generally, physical processing of foodstuffs has good acceptability by the consumer. The technologies do not have to be declared on the label and has potential to contribute to a clean labelling.

The main benefits linked to HPP technologies are the health-related, taste-related (products’ naturalness) and environment-related benefits (17, 18). According to several researches HPP has been judged to be relatively similar to conventional process technologies in terms of overall consumer acceptability (17, 18, 19, 20)

Legal aspects As a physical treatment, the process can be applied. EU: novel food legislation to be observed, but at present, results do not indicate substantial changes of product composition.

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 (21). In January 14th 2008, EU published a proposal for the amendment of Regulation (EC) 258/97 (22). 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 HPP is considered environmentally friendly, but no real environmental footprint has been calculated, in terms of waste generated and energy consumption (19).

Further Information

Institutes DIL, IRTA, SP, KU Leuven LFT, Wageningen UR - FBR, University of Reading, University of Copenhagen
Companies Hiperbaric, APA Processing, Stansted Fluid Power, Resato, Uhde-HPT, ZDAS, Avure, Tetra Pak, GEA Niro Soavi
References 1. Aertsen, A., Meersman, F., Hendrickx, Marc, E.G. Vogel, R.F., & Michiels, C.W. (2009). Biotechnology under high pressure: applications and implications. Trends in Biotechnology, 27, 434-441.

2. Bajovic, B., Bolumar, T. & Heinz, V. (2012). Quality considerations with high pressure processing of fresh and value added meat products, Meat Science, 92, 280-289.

3. Tintchev, F., Bindrich, U., Toepfl, S., Strijowski, U., Heinz, V., and Knorr, D. 2013. High hydrostatic pressure/temperature modeling of frankfurter batters. Meat Science 94:376-387.

4. Dumay, E., Picart, L., Regnault, S., & Thiebaud, M. (2006). High pressure–low temperature processing of food proteins. Biochimica et Biophysica Acta, 1764, 599-618.

5. Dumay, E., Chevalier-Lucia, D., Picart-Palmade, L., Benzaria, A., Gràcia-Julià, A., Blayo, C. (2012) Technological aspects and potential applications of (ultra) high-pressure homogenisation. Trends in Food Science and Technology. In press. http://dx.doi.org/10.1016/j.tifs.2012.03.005

6. Galazka, V.B., Dickinson, E., Ledward, D.A. (2000). Influence of high pressure processing on protein solutions and emulsions. Current Opinion in Colloid & Interface Science, 5, 182-187.

7. Bouaouinaa, H., Desrumauxa, A., Loisela, C., & Legrandb, J. (2006). Functional properties of whey proteins as affected by dynamic high-pressure treatment. International Dairy Journal, 16, 2006, 275–284.

8. Lim, S.Y., Swanson, B. G., & Clark, S. (2008). High Hydrostatic Pressure Modification of Whey Protein Concentrate for Improved Functional Properties. Journal of Dairy Science, 91, 1299–1307.

9. Sun, X.D., & Holley, R.A. (2010). High hydrostatic pressure effects on the texture of meat and meat products. Journal of Food Science, 75, R17-R23.

10. Ngarize, S, Adams, A., & Howella,N. (2005). A comparative study of heat and high pressure induced gels of whey and egg albumen proteins and their binary mixtures. Food Hydrocolloids, 19, 984-996.

11. Roesch,R.R., & Corredig, M. (2003). Texture and microstructure of emulsions prepared with soy protein concentrate by high-pressure homogenization. Lebensmittel Wissenschaft und Technologie, 36, 113-124

12. Considine, T., Patel, H.A., Anema, S.G., Singh, H., & Creamer, L.K. (2007). Interactions of milk proteins during heat and high hydrostatic pressure treatments — A Review. Innovative Food Science and Emerging Technologies, 8, 1–23.

13. Ciron, C.I.E., Gee, V.L., Kelly A.L., & Auty, M.A.E. (2010). Comparison of the effects of high-pressure microfluidization and conventional homogenization of milk on particle size, water retention and texture of non-fat and low-fat yoghurts. International Dairy Journal 20 314–320.

14. Venir, E., Marchesini, G., Biasutti, M., & Innocente, N. (2010). Dynamic high pressure-induced gelation in milk protein model systems. Journal of Dairy Science, 93, 483–494.

15. Bader, S., Bez, J., & Eisner, P. (2011). Can protein functionalities be enhanced by high-pressure homogenization? – A study on functional properties of lupin proteins. 11th International Congress on Engineering and Food (ICEF11). Procedia Food Science, 1, 1359-1366.

16. San Martin-Gonzalez, M.F., Roach, A, & Harte, F. (2009). Rheological properties of corn oil emulsions stabilized by commercial micellar casein and high pressure homogenization. LWT - Food Science and Technology, 42, 307–311.

17. 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

18. 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

19. Olsen, N.V., Grunert, K.G., & Sonne, A.-M. (2010). Consumer acceptance of high-pressure processing and pulsed-electric field: a review. Trends in Food Science & Technology, 21: 464-472.
20. 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 and Preference 22: 271–280.

21. European Union. European Parliament and of the Council. (1997). 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) http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31997R0258:EN:HTML.

22. 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]. http://ec.europa.eu/food/food/biotechnology/novelfood/index_en.htm



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Created by Claudia Siemer on 2 August 2013, at 12:51