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M Hendrickx

Publications and source records attributed to M Hendrickx.

17 recordsLinked to original sources
PubMed2004

Comparative study on pressure and temperature stability of 5-methyltetrahydrofolic acid in model systems and in food products.

A comparative study on the pressure and temperature stability of 5-methyltetrahydrofolic acid (5-CH(3)-H(4)folate) was performed in model/buffer systems and food products (i.e., orange juice, kiwi puree, carrot juice, and asparagus). Effects of pH and ascorbic acid (0.5 mg/g) on 5-CH(3)-H(4)folate stability in buffer systems were studied on a kinetic basis at different temperatures (from 65 to 160 degrees C) and different pressure/temperature combinations (from 100 to 700 MPa/from 20 to 65 degrees C). These studies showed that (i) the degradation of 5-CH(3)-H(4)folate in all model systems could be described by first-order reaction kinetics, (ii) the thermostability of 5-CH(3)-H(4)folate was enhanced by increasing pH up to 7, (iii) 5-CH(3)-H(4)folate was relatively pressure stable at temperatures lower than 40 degrees C, and (iv) ascorbic acid enhanced both the thermo- and barostabilities of 5-CH(3)-H(4)folate. In food products, temperature and pressure stabilities of 5-CH(3)-H(4)folate were studied at different temperatures (70-120 degrees C) and different pressure/temperature combinations (from 50 to 200 MPa/25 degrees C and 500 MPa/60 degrees C). 5-CH(3)-H(4)folate in orange juice and kiwi puree was relatively temperature (up to 120 degrees C) and pressure (up to 500 MPa/60 degrees C) stable in contrast to carrot juice and asparagus. Addition of ascorbic acid (0.5 mg/g) in carrot juice resulted in a remarkable protective effect on pressure (500 MPa/60 degrees C/40 min) and temperature degradation (120 degrees C/40 min) of 5-CH(3)-H(4)folate.

Ascorbic Acid↗
PubMed2003

Model studies on the stability of folic acid and 5-methyltetrahydrofolic acid degradation during thermal treatment in combination with high hydrostatic pressure.

Stability of folic acid and 5-methyltetrahydrofolic acid in phosphate buffer (0.2 M; pH 7) toward thermal (above 65 degrees C) and combined high pressure (up to 800 MPa)/thermal (20 up to 65 degrees C) treatments was studied on a kinetic basis. Residual folate concentration after thermal and high pressure/thermal treatments was measured using reverse phase liquid chromatography. The degradation of both folates followed first-order reaction kinetics. At ambient pressure, the estimated Arrhenius activation energy (E(a)) values of folic acid and 5-methyltetrahydrofolic acid thermal degradation were 51.66 and 79.98 kJ mol(-1), respectively. It was noticed that the stability of folic acid toward thermal and combined high pressure thermal treatments was much higher than 5-methyltetrahydrofolic acid. High-pressure treatments at room temperature or higher (up to 60 degrees C) had no or little effect on folic acid. In the whole P/T area studied, the rate constant of 5-methyltetrahydrofolic acid degradation was enhanced by increasing pressure, and a remarkable synergistic effect of pressure and temperature on 5-methyltetrahydrofolic acid degradation occurred at temperatures above 40 degrees C. A model to describe the combined pressure and temperature effect on the 5-methyltetrahydrofolic acid degradation rate constant is presented.

Drug Stability↗
PubMed2003

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

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.

Consumer Product Safety↗
PubMed2002

Purification, characterization, thermal, and high-pressure inactivation of pectin methylesterase from bananas (cv Cavendish).

Pectin methylesterase (PME) was extracted from bananas (cv Cavendish) and purified by affinity chromatography on a CNBr-Sepharose-PME inhibitor (PMEI) column. A single protein and PME activity peak was obtained. For banana PME, a biochemical characterization in terms of molar mass (MM), pI, and kinetic parameters was performed. In a second step, the thermal and high-pressure stability of the enzyme was studied. Isothermal inactivation of purified banana PME could be described by a first-order kinetic model in a temperature range of 65 degrees to 72.5 degrees C, whereas its isobaric-isothermal inactivation followed a fractional-conversion model. Banana PME was found to be more thermally stable compared with PMEs extracted from orange, tomato, and apple.

Carboxylic Ester Hydrolases↗
PubMed2000

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.

Ascorbic Acid↗
PubMed1999

Development of a novel methodology To validate optimal sterilization conditions for maximizing the texture quality of white beans in glass jars

Optimal thermal processes were designed for white beans in glass jars heated in a still and end-over-end rotary pilot water cascading retort. For this purpose, isothermal kinetics of thermal softening of white beans were studied in detail using a tenderometer and a texturometer. The fractional conversion model was applied in both cases to model the texture degradation. The Arrhenius equation described well the temperature dependence of the reaction rate constant. With regard to the heat transfer, heat penetration parameters (fh and jh) were experimentally determined from 100 containers under static as well as rotational (end-over-end) conditions at 4, 7, 10, and 15 rpm. Theoretical optimal temperatures, maximizing volume average quality retention, were calculated using a computer program valid for conduction heating foods. Experimental verification of the calculated results was conducted. Considering the finite surface heat transfer coefficient, theoretical and experimental optimal temperatures were of the same order of magnitude, around 130 degrees C, while for an infinite surface heat transfer coefficient the calculated optimum temperature was much lower than the experimental value. The type of reaction kinetic model, fractional conversion or first-order models, does not significantly affect optimal sterilization temperatures. Although some differences were found, the developed theoretical approach was successfully applied to convective and mixed heating mode products. The use of the correct surface heat transfer coefficient is crucial to design optimal processing conditions.

Journal Article↗
PubMed1999

Kinetic study of the irreversible thermal and pressure inactivation of myrosinase from broccoli (Brassica oleracea L. Cv. italica).

Thermal and pressure inactivation of myrosinase from broccoli was kinetically investigated. Thermal inactivation proceeded in the temperature range 30-60 degrees C. These results indicate that myrosinase is rather thermolabile, as compared to other food quality related enzymes such as polyphenol oxidase, lipoxygenase, pectinmethylesterase, and peroxidase. In addition, a consecutive step model was shown to be efficient in modeling the inactivation curves. Two possible inactivation mechanisms corresponding to the consecutive step model were postulated. Pressure inactivation at 20 degrees C occurred at pressures between 200 and 450 MPa. In addition to its thermal sensitivity, the enzyme likewise is rather pressure sensitive as compared to the above-mentioned food quality related enzymes. By analogy with thermal inactivation, a consecutive step model could adequately describe pressure inactivation curves. At 35 degrees C, pressure inactivation was studied in the range between 0. 1 and 450 MPa. Application of low pressure (<350 MPa) resulted in retardation of thermal inactivation, indicating an antagonistic or protective effect of low pressure.

Brassica↗
PubMed1997

A critical analysis of mathematical procedures for the evaluation and design of in-container thermal processes for foods.

Kinetic data on thermal destruction of spoilage and quality factors coupled with the temperature history of a product during a heat sterilization cycle are the basic information needed for the evaluation and the design of thermal processes through a physical-mathematical approach. A critical review on the available physical-mathematical procedures used for thermal process calculations of in-container processed foods is presented. The origin and the limitations of each method are discussed. The equations associated with each method, for internal product temperature predictions, are explicitly given. The relative performance of selected methods under identical processing conditions is illustrated. Several problems associated with thermal process calculations are discussed.

Food Handling↗
PubMed1996

Covalent enzyme immobilization on paramagnetic polyacrolein beads.

An optimized procedure of covalent glucose oxidase, urease, Bacillus subtilis alpha-amylase and Bacillus licheniformis alpha-amylase immobilization on paramagnetic, non-porous, polyacrolein beads is presented. The resulting insolubilized enzymes can be employed for extended periods of time without loss of activity. The conditions were optimized for maximizing the activity of the linked enzyme. Coated beads bearing up to 15 micrograms active enzyme/mg(beads) were obtained on reproducible basis. The paramagnetic feature of the particles facilitates the enzyme handling. In the magnetic field, the enzyme separation is fast and complete. Thus, the paramagnetic beads represent an excellent carrier for immobilized enzymes.

Acrolein↗
PubMed1996

Potential Bacillus subtilis alpha-amylase-based time-temperature integrators to evaluate pasteurization processes.

Thermal inactivation kinetics of Bacillus subtilis alpha-amylase (BSA) in different environmental conditions was studied by performing isothermal experiments. As a response property, residual enzymic activity and residual heat of enzyme deterioration were chosen. A comparison of processing values determined from the read-out of a system with actual integrated processing values revealed the potentials of these systems as time-temperature integrators to be used in the pasteurization domain (temperatures of 70 to 100 degrees C) for target attributes with z-values ranging from 6 to 12 degrees C.

Bacillus subtilis↗
PubMed1995

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.

Food Handling↗
PubMed1993

Revision of total hip arthroplasty using the R.M. isoelastic prosthesis.

A cemented revision of failed total hip arthroplasty is prone to early mechanical failure. Cementless revision seems to be much more promising. We present our 2 year follow-up of 19 cementless revisions using the R.M. isoelastic stem. During follow-up special attention focused on the restoration of bone stock on the femoral side of the arthroplasty. Bone stock deficiencies encountered during the operation were managed with grafts. Other complications to solve during the procedure were encountered frequently. The average follow-up was 58 months. Rating the results following Merle d'Aubigné and Postel showed very good or good result only in half of the cases, one case needed a revision. Nevertheless good restoration of bone stock was observed in nearly all cases. A greater number of patients should be followed for a longer period of time to establish the exact role of this prosthesis design.

Adult↗
PubMed1993

Surgical treatment of spinal metastases.

Between 1985 and 1991, thirty-one patients with spinal metastases were operated in our department. The aim of the surgical treatment is to abolish pain and instability caused by neurological involvement and bony invasion. Anterior decompression with fixation by means of a methylmethacrylate cement block was used. In some cases additional posterior fixation was used in a second procedure. Pain was reduced in 78% of the patients, and 70% underwent improvement of their neurological status. The quality of life was improved, but the short survival confirms the palliative nature of this kind of surgery.

Adult↗
PubMed1991

Effects of hypothermic ischemia on purine catabolism in canine, primate, and human myocardium.

After hypothermic cardiac arrest, creatine phosphate (CrP) and adenine nucleotide catabolism was compared in myocardium from dogs (n = 7), baboons (n = 5), and man (n = 7; patients undergoing cardiac transplantation) during cold (0.5 degree C) storage for up to 24 hours. Although hypothermia delayed the catabolism in dog myocardium it still remained very extensive. CrP dropped to virtually nil and ATP fell to below 15% of the total purines within 6 hours. The majority of the adenine nucleotides was broken down to adenosine (ADO; 32% of total purines) and inosine (INO; 21%). Apart from the delay (7 to 9-fold), hypothermia also reversed the ratio between ADO and INO when compared to normothermia, suggesting a profound effect of temperature on the nucleoside transporter. In human myocardium even after 12 hours of hypothermia ATP still contributed more than 60% to the total purines. Concomitantly, nucleoside formation proceeded slowly with almost no intermediate ADO. Under similar conditions, the catabolism of ATP in baboon myocardium occurred at a higher rate than in man but still far below canine metabolism. Irrespective of the relatively higher fall in ATP, ADP and AMP accumulated more in baboon myocardium indicating a limited dephosphorylation of the nucleotides. Only in the baboon myocardium did inosine monophosphate increase above the detection limits. In none of the species did purine catabolism proceed beyond hypoxanthine and even this could hardly be detected in the primates. It is concluded that considerable species differences do exist in the rate as well as in the pattern of nucleotide catabolism even during storage of the myocardium at low temperature.

Adenine Nucleotides↗
PubMed1970

[Not Available].

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Belgium↗
PubMedDate not supplied

[Heparin-associated thrombocytopenia].

Thrombocytopenia and heparin. Heparin associated thrombocytopenia (HAT), more specially type 2, is an important complication of anticoagulant treatment in clinical practice. Diagnosis may be difficult and requires special laboratory techniques. Platelet count should be performed every two days. Severe complications may occur in 23% of type 2 HAT patients and is associated with a high mortality. Until now there are no prophylactic measurements for high risk patients.

Female↗