L. Ludikhuyze

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.

Effects of combined pressure and temperature on enzymes related to quality of fruits and vegetables : From kinetic information to process engineering aspects

ABSTRACT Throughout the last decade, high pressure technology has been shown to offer great potential to the food processing and preservation industry in delivering safe and high quality products. Implementation of this new technology will be largely facilitated when a scientific basis to assess quantitatively the impact of high pressure processes on food safety and quality becomes available. Besides, quantitative data on the effects of pressure and temperature on safety and quality aspects of foods are indispensable for design and evaluation of optimal high pressure processes, i.e., processes resulting in maximal quality retention within the constraints of the required reduction of microbial load and enzyme activity. Indeed it has to be stressed that new technologies should deliver, apart from the promised quality improvement, an equivalent or preferably enhanced level of safety. The present paper will give an overview from a quantitative point of view of the combined effects of pressure and temperature on enzymes related to quality of fruits and vegetables. Complete kinetic characterization of the inactivation of the individual enzymes will be discussed, as well as the use of integrated kinetic information in process engineering.

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.

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.

Kinetics for Isobaric−Isothermal Inactivation of Bacillus subtilis α-Amylase

Isobaric−isothermal inactivation of Bacillus subtilis α‐amylase (BSA, 15 mg/mL in Tris‐HCl at pH 8.6) in the pressure range 1–750 MPa and the temperature range 25–85 °C could be accurately described by a first‐order kinetic model. The kinetic parameters (k, Ea, and Va) were calculated at different pressure and temperature levels. At reference temperature (40 °C) and reference pressure (500 MPa), isobaric−isothermal inactivation was characterized by an Ea value of 74.8 kJ/mol, a Va value of −23.6 cm3/mol, and an inactivation rate constant of 0.0343 min−1. The influence of 15% glycerol on thermal and pressure−temperature stability of BSA was investigated. In both cases, a stabilizing effect of this additive was found, since the kref value was significantly reduced. Furthermore, a pressure−temperature kinetic diagram, indicating the possible synergistic and antagonistic effects of pressure and temperature on the inactivation of BSA, was constructed. Based on this diagram, a model describing the dependence of the inactivation rate constant on pressure and temperature, in the pressure range 250–750 MPa, was formulated.

Inactivation kinetics of alkaline phosphatase and lactoperoxidase, and denaturation kinetics of β-lactoglobulin in raw milk under isothermal and dynamic temperature conditions

A detailed kinetic study of alkaline phosphatase, lactoperoxidase and beta-lactoglobulin was carried out in the context of identifying intrinsic time-temperature indicators for controlling the heat processing of milk. The heat inactivation or denaturation of alkaline phosphatase, lactoperoxidase and beta-lactoglobulin under isothermal conditions was found to follow first order kinetics. Experimental results were analysed using both a two step linear regression and a one step non-linear regression method. Results obtained using the two statistical techniques were comparable, but the 95% confidence interval for the predicted values was smaller when the one step non-linear regression method was used, indicating its superiority for estimating kinetic parameters. Thermal inactivation of alkaline phosphatase and lactoperoxidase was characterized by z values of 5.3 deg C (D60 degrees C = 24.6 min) and 4.3 deg C (D71 degrees C = 38.6 min) respectively. For the denaturation of beta-lactoglobulin we found z values of 7.9 deg C (D7.5 degrees C = 49.9 min) in the temperature range 70-80 degrees C and 24.2 deg C (D85 degrees C = 3.53 min) in the range 83-95 degrees C. Dref and z were evaluated under dynamic temperature conditions. To estimate the statistical accuracy of the parameters, 90% joint confidence regions were constructed.

The activity of myrosinase from broccoli (Brassica oleracea L. cv. Italica): Influence of intrinsic and extrinsic factors

The potential of some intrinsic (MgCl2, ascorbic acid, pH) and extrinsic (temperature, pressure) factors for controlling/altering activity of myrosinase from broccoli was investigated in this paper. A combination of MgCl2 and ascorbic acid was found to enhance enzyme activity. Concentrations resulting in optimal activity were determined as 0.1 g/liter and 2 g/liter, respectively. Both in the absence and presence of this enzyme activator, the optimal pH was situated between 6.5 and 7, corresponding to the natural pH of fresh broccoli juice. At atmospheric pressure, the enzyme was optimally active at a temperature about 30 degrees C. Application of low pressure (50 to 100 MPa) slightly enhanced the activity while at higher pressure (300 MPa), the activity was largely reduced. Future work should focus on the extension of this work to real food products in order to take cellular disruption into account. In intact vegetable tissues, the enzyme myrosinase is present in compartments separated from its substrate, the glucosinolates. Hence, enzymatic hydrolysis can merely occur after cellular disruption. In this respect, processes such as cutting, cooking, freezing, or pressurizing of the vegetables will have a large effect on the glucosinolate hydrolysis by myrosinase. This work could then be the basis for controlling glucosinolate hydrolysis in food preparation and processing.

Thermal and combined pressure--temperature inactivation of orange pectinesterase: influence of pH and additives.

Inactivation of commercially available orange pectinesterase (PE) was investigated under isothermal and isothermal-isobaric conditions. In both cases, inactivation data could be accurately described by a fractional conversion model. The influence of enzyme concentration, pH, Ca(2+) concentration, and sucrose on the inactivation kinetics was studied. Enzyme stability against heat and pressure increased by increasing enzyme concentration. An increased Ca(2+) concentration caused sensitization to temperature and increased the residual fraction active PE after thermal treatment. To the contrary, in the case of pressure treatment, decreasing Ca(2+) concentrations increased pressure inactivation. The remaining fraction active PE after pressure treatment was not influenced by the addition of Ca(2+) ions. Acidification accelerated thermal as well as pressure-temperature inactivation, whereas in the presence of sucrose an increased temperature and pressure stability of orange PE was observed. Sucrose had no influence on the remaining activity after thermal treatment, but it increased the residual fraction after pressure treatment. The remaining fraction was for all additives studied independent of the pressure and temperature level applied except for the inactivation in an acid medium, when a decrease of the residual fraction was observed with increasing temperature and pressure.