Marc Hendrickx

Effects of high pressure on enzymes related to food quality

An important issue in the application of high pressure technology in the food preservation/processing industry is regulatory approval, which focuses upon microbiological and toxicological safety of food products. High pressure preservation processes should reduce the microbial load to the same level achieved by traditional technologies, while delivering higher-quality products. Combination of high pressure with other treatments (e.g., mild temperature elevation, refrigerated storage, acidification) during processing and storage is a likely route the food industry will take, as the inactivation of bacterial spores and some pressure-resistant enzymes at room temperature cannot be achieved by pressure alone. Several authors suggest that the most safe and economically feasible use of high pressure is in combination with moderately elevated temperature (Gould & Sale, 1970; Knorr, 1993). From the point of view of those who define hazard analysis of critical control points (HACCP) guidelines (risk analysis method carried out to guarantee safety and quality of food products throughout the production chain) or “novel food” regulations (directives that have to be taken into account when introducing new products, new ingredients, or new processing techniques on the market), and also from an engineering point of view, methods to determine the impact of pressure processes on food safety and quality are indispensable. A variety of methods could be evaluated for this purpose: (1) the in situ method, in which the change of an intrinsic food component is measured before and after treatment; (2) the physical mathematical method, in which the actual temperature-pressure-time profile is combined with the kinetics of the attribute under consideration; or (3) the use of process history indicators, which are devices that mimic the change of the attribute under consideration when submitted to the same temperature-pressure-time profile. All these methods rely largely on kinetic models. In this context, quantitative kinetic studies on the combined effect of pressure and temperature on several aspects of food safety and quality (pathogenic/spoilage microorganisms, enzymes related to food quality, nutritional and sensorial quality characteristics) are required. From an engineering point of view, such kinetic data are very important for evaluation of process uniformity, for process validation, and for process optimization.

Ultra high pressure treatments of foods

Contributors. Preface. Acknowledgments. Part I: Fundamental Aspects Of Treating Foods With High Pressure. 1. The Evolution of High Pressure Processing of Foods G.W. Gould. Introduction. Preservation Technologies. Evolution of High Pressure Processing. Conclusion. 2. The Effects of High Pressure on Biomaterials K. Heremans. Introduction. Pressure versus Temperature Effects. Stability Phase Diagrams of Food Macromolecules. Structure Property Relationship in Food Biopolymers. Conclusion. Part II: Effects Of High Pressure On Food Attributes. 3. Effects of High Pressure on Vegetative Microorganisms J.P. Smelt, J.C. Hellemons, M. Patterson. Introduction. Mode of Action of Temperature and Pressure on Microorganisms. Classes of Heat Resistance and Pressure Inactivation. The Effects of Food Constituents on Pressure Resistance. Design of Safe Pasteurization Conditions. Conclusion. 4. Effects of High Pressure on Spores V. Heinz, D. Knorr. Introduction. Pressure and Temperature. Microbiological Aspects. Modeling Approach. Spores under Pressure. Conclusion. 5. Effects of High Pressure on Enzymes Related to Food Quality L. Ludikhuyze, A. Van Loey, Indrawati, S. Denys, M.E.G. Hendrickx. Introduction. Mechanisms and Kinetics of Pressure Inactivation of Enzymes. The Effect of High Pressure on Enzymes Related to Food Quality. Kinetic Models To Describe Pressure-Temperature Inactivation of Enzymes Related to Food Quality. From Kinetic Information to Process Engineering. Conclusion. Glossary. 6. Effects of High Pressure on Chemical Reactions Related to Food Quality L. Ludikhuyze, M.E.G. Hendrickx. Introduction. The Effect of High Pressure on the Color of Food Products. The Effects of High Pressure on the Flavor of Food Products. The Effects of High Pressureon Texture of Food Products. The Effects of High Pressure on Nutritive Value and Health Components of Food Products. The Effect of High Pressure on Lipid Oxidation in Food Products. Conclusion. 7. Effects of High Pressure on Protein- and Polysaccharide-Based Structures M. Michel, K. Autio. Introduction. Pressure-Related Alterations in Food Raw Materials. Behavior of Starch Dispersions under Pressure. Influence of Pressure on Pectin. Pressure Effects on Protein Functionality. Structure Engineering by Pressure in Protein-Pectin Mixtures. Conclusion. 8. Effects of High Pressure on Water-Ice Transitions in Foods S. Denys, O. Schluter, M.E.G. Hendrickx, D. Knorr. Introduction. The Uses of Pressure in Freezing and Thawing. Modeling Heat Transfer during Processes with Phase Transitions at High Pressure. Conclusion. Part III: Food Products And Processes. 9. Industrial-Scale High Pressure Processing of Foods P. Rovere. Introduction. High Pressure Processing: State of the Art. Effects of Pressure on Real Foods. The Development of Combined Processing. Conclusion. 10. High Pressure Processing of Dairy Products E. Needs. Introduction. Milk Proteins. Dairy Foams, Emulsions, and Gels. Application of High Pressure in Cheese Production. Milk Enzymes. Conclusion. 11. High Pressure Equipment Designs for Food Processing Applications R.W. van den Berg, H. Hoogland, H.L.M. Lelieveld, L. van Schepdael. Introduction. Equipment for High Pressure Processing. Major Manufacturers of High Pressure Processing Equipment. Economics of High Pressure Processing. Conclusion. Index. About the Editors. List of Sources.

Kinetics of combined pressure-temperature inactivation of avocado polyphenoloxidase

Irreversible combined pressure-temperature inactivation of the food quality related enzyme polyphenoloxidase was investigated. Inactivation rate constants (k) were obtained for about one hundred combinations of constant pressure (0.1-900 MPa) and temperature (25-77.5 degrees C). According to the Eyring and Arrhenius equation, activation volumes and activation energies, respectively, representing pressure and temperature dependence of the inactivation rate constant, were calculated for all temperatures and pressures studied. In this way, temperature and pressure dependence of activation volume and activation energy, respectively, could be considered. Moreover, for the first time, a mathematical model describing the inactivation rate constant of a food quality-related enzyme as a function of pressure and temperature is formulated. Such pressure-temperature inactivation models for food quality-related aspects (e.g., the spoilage enzyme polyphenoloxidase) form the engineering basis for design, evaluation, and optimization of new preservation processes based on the combined effect of temperature and pressure. Furthermore, the generated methodology can be used to develop analogous kinetic models for microbiological aspects, which are needed from a safety and legislative point of view, and other quality aspects, e.g., nutritional factors, with a view of optimal quality and consumer acceptance.

A modeling approach for evaluating process uniformity during batch high hydrostatic pressure processing: combination of a numerical heat transfer model and enzyme inactivation kinetics

Abstract A numerical conductive heat transfer model for calculating the temperature evolution during batch high hydrostatic pressure (HHP) processing of foods was tested for two food systems: apple sauce and tomato paste. Hereto, relevant thermal and physical properties of the products were determined. For a comprehensive evaluation, both ‘conventional’ HHP processes with gradual, step by step pressure build-up and pressure release were simulated. In all cases, satisfactory agreement between experimental and predicted temperature profiles was obtained. The model provides a very useful tool to evaluate batch HHP processes in terms of uniformity of any heat- and/or pressure-related effect. Uniformity of inactivation of Bacillus subtilis α-amylase and soybean lipoxygenase during batch HHP processing was evaluated. Hereto, a theoretical as well as an experimental approach was used. The residual enzyme activity distribution appeared to be dependent on the inactivation kinetics of the enzyme under consideration and the pressure–temperature combinations considered. Good agreement between the theoretical considerations and experimentally obtained activity retentions was found for Bacillus subtilis α-amylase. In case of soybean lipoxygenase, less agreement was found. This work presents a first step in the development of indicators to assess process uniformity in HHP processing of foods.

Evaluation of the integrated time-temperature effect in thermal processing of foods

In this review, current methods used to evaluate the integrated impact of time and temperature upon preserving a food product by a heat treatment are considered. After identifying the basic premise any preservation scheme shall meet, the central role of a feasible description for the heat activation kinetics of microorganisms, their spores, and other quality attributes are stressed. Common concepts to quantify a thermal process are presented. Shortcomings of the prevalent evaluation methods are highlighted and attention is given to the development, restrictions, and possibilities of time-temperature-integrators as new evaluation tools to measure the impact of a classical in-pack heat treatment and more modern heating techniques such as continuous processing of solid/liquid mixtures on foods.

Modeling Conductive Heat Transfer and Process Uniformity during Batch High-Pressure Processing of Foods

A numerical model for predicting conductive heat transfer during batch high hydrostatic pressure (HHP) processing of foods was developed and tested for a food simulator (agar gel). For a comprehensive evaluation of the proposed method, both “conventional” HHP processes, HHP processes with gradual, step‐by‐step pressure buildup and pressure release, and pressure cycling HHP processes were included. In all cases, good agreement between experimental and predicted temperature profiles was observed. The model provides a very useful tool to evaluate batch HHP processes in terms of uniformity of any heat‐ and/or pressure‐related effect. This is illustrated for inactivation of Bacillus subtilis α‐amylase, an enzymatic model system with known pressure‐temperature degradation kinetics.

Quantitative evaluation of thermal processes using time-temperature integrators

Abstract The further development of new heating technologies, process assessment and process optimization in the thermal processing of foods is limited by the applicability of currently used process evaluation methodologies. Therefore, considerable effort has been and will continue to be put into the development of specific sensors — time-temperature integrators (TTIs) — which can allow faster, easy and correct determination of the impact of a process on a product attribute without the need for detailed knowledge of the actual time-temperature history of the product. This article presents the current state of the art regarding TTI development to monitor thermal processes, as well as a discussion of the possible applications and limitations of several types of TTI systems.

Inactivation kinetics of polygalacturonase in tomato juice

a ¸ ´´ ˜ ´ Abstract The inactivation kinetics of polygalacturonase (PG) in tomato juice was studied during thermal and high-pressureythermal processing. In the temperature range of 55-70 8C the thermal inactivation of polygalacturonase in tomato juice followed a fractional conversion model, with a thermostable fraction of approximately 14%. Under conditions of combined high-pressurey thermal processing, 200-550 MPay5-50 8C, PG inactivation presented first order kinetics. A mathematical model to describe the inactivation rate constant as a function of pressure and temperature was formulated. Industrial relevance: Polygalacturonase is responsible for the decrease of viscosity in tomato-based products. However, little research on thermal and high pressure ythermal inactivation kinetics of tomato Polygalacturonase has been reported. This research clearly shows that it is possible to selectively inactivate PG by high pressureythermal processing without applying high temperatures. This leads to tomato-based products with improved functional properties while other quality attributes (color, flavor, nutritional value ) are maintained. 2002 Elsevier Science Ltd. All rights reserved.

Influence of pH, Benzoic Acid, EDTA, and Glutathione on the Pressure and/or Temperature Inactivation Kinetics of Mushroom Polyphenoloxidase

The pressure and/or temperature inactivation of mushroom polyphenoloxidase (PPO) in the absence and presence of EDTA, benzoic acid, and glutathione was studied on a kinetic basis. In addition, the effect of pH was evaluated. The temperature stability of PPO at atmospheric pressure increased with increasing pH up to pH 6.5. The pressure stability of PPO at room temperature (25 °C) also increased with increasing pH. EDTA slightly increased the thermal stability of the enzyme but did not alter the pressure stability of PPO. Benzoic acid protected the enzyme toward temperature but caused sensitization toward pressure when used at a concentration of 50 mM. Glutathione produced sensitization to both temperature and pressure. It is suggested that the sensitizing effect of glutathione is due to an interaction with a disulfide bond of the enzyme.

Modeling conductive heat transfer during high-pressure thawing processes: determination of latent heat as a function of pressure.

A numerical heat transfer model for predicting product temperature profiles during high‐pressure thawing processes was recently proposed by the authors. In the present work, the predictive capacity of the model was considerably improved by taking into account the pressure dependence of the latent heat of the product that was used (Tylose). The effect of pressure on the latent heat of Tylose was experimentally determined by a series of freezing experiments conducted at different pressure levels. By combining a numerical heat transfer model for freezing processes with a least sum of squares optimization procedure, the corresponding latent heat at each pressure level was estimated, and the obtained pressure relation was incorporated in the original high‐pressure thawing model. Excellent agreement with the experimental temperature profiles for both high‐pressure freezing and thawing was observed.