Iron-chelation properties of phenolic acids bearing catechol and galloyl groups

In this study, the capacity of seven phenolic acids and hydroxytyrosol for complex formation with iron was quantified. A metal-chelation mechanism was described by means of spectrophotometry and calculating the binding constants of the complexes. The influence of phosphate buffer, Hepes buffer, Tris buffer and water on this mechanism was investigated. UV–Vis absorption spectroscopy showed that the absorption of phenolic acids changes upon the addition of Fe²⁺, which resulted in several shifts of their spectra. These batochromic shifts were analyzed and evaluated by calculating binding constants. Furthermore, in the presence of different concentrations of EDTA (0–1 mM), a reduction of the constants was observed. However, not all of the phenolic compounds assessed here showed complex formation, those not bearing catechol or galloyl moiety like vanillic acid, syringic acid and ferulic acid, did not show any complex formation in our study. The ability of the phenolic compounds which chelate iron have been ranked in line with the binding constants in ascending order rendering the protocatechuic acid (1.43 M⁻¹) the weakest chelator, followed by hydroxytyrosol (2.66 M⁻¹), gallic acid (4.78 M⁻¹), caffeic acid (8.12 M⁻¹) and chlorogenic acid (20.13 M⁻¹) as the strongest chelator.     

Transient suppression in FRF measurement: Comparison and analysis of four state-of-the-art methods

This paper compares four well selected methods for computing the non-parametric Frequency Response Function (FRF) of a periodically excited linear time invariant system. The suppression of the transient is mandatory when its influence in the data is large. Better suppression of the transient leads to a better non-parametric FRF estimate. A good non-parametric FRF estimate can be used to validate the parametric transfer function model in a second step. The suppression of the transient will be highlighted using the mean squared error of the non-parametric FRF estimate. Temperature transients caused by heat diffusion are used as example. The selected methods consist of two standard windowing methods and two methods based on the Local Polynomial Method (LPM). LPM was designed to find a non-parametric FRF estimate in the presence of nonlinearities. This paper will modify LPM to find a non-parametric FRF estimate for linear systems using a single experiment. The mean squared error of the four non-parametric FRF estimates will be compared and analyzed, based on a simulation and a measurement example.     

Effect of thermal and high pressure processes on structural and health-related properties of carrots (Daucus carota)

In the present study, the effect of thermal and equivalent high pressure processes on structural (texture and microstructure) and health-related (total β-carotene concentration, β-carotene isomerisation and β-carotene bio-accessibility) properties of carrots was investigated. Both a mild and strong pasteurisation process and a sterilisation process were considered.     

B7-1 (CD80), B7-2 (CD86), interleukin-12 and transforming growth factor-beta mRNA expression in CSF and peripheral blood mononuclear cells from multiple sclerosis patients

Injection of formalin into the hind paw of mice produced a biphasic nociceptive response consisting of immediate (first-phase) and tonic (second-phase) components. Although the duration of the first-phase response was significantly longer in diabetic mice than in nondiabetic mice, the second phase was significantly shorter in diabetic mice. The first-phase response was dose-dependently and significantly reduced by pretreatment with calphostin C (0.3 to 3 pmol, i.t.), a specific protein kinase C inhibitor, in diabetic mice. The second-phase response was markedly increased when diabetic mice were pretreated with calphostin C. However, calphostin C (3 nmol, i. t.) had no significant effect on either the first-phase or second-phase response in nondiabetic mice. On the other hand, pretreatment with phorbol-12,13-dibutyrate (50 pmol, i.t.), a protein kinase C activator, significantly enhanced the first-phase response in nondiabetic mice. These results suggest that the change in the formalin-induced nociceptive response in diabetic mice may be due, at least in part, to the modification of nociceptive transmission in the spinal cord by the activation of protein kinase C.     

Guidelines to determine the optimal variables for the MTC measurement by noise analysis

In this paper guidelines will be given in order to determine the required measurement time for a specified precision of the Moderator Temperature Coefficient (MTC) estimate by noise analysis. Until now the discussion of the precision of the MTC estimate was neglected. We will study the relation between the precision, the coherence, the amount of temperature sensors and the measurement time. Based on this relation guidelines to determine the optimal measurement time will be given. Simulations in MATLAB will be used to verify the theoretical analysis. Realistic values for the different influencing variables for a specific measurement setup will be given by use of the analysis of a measurement at a Nuclear Power Plant in Belgium.     

Enzyme infusion and thermal processing of strawberries: Pectin conversions related to firmness evolution

Strawberries were infused with fungal pectinmethylesterase (PME) and/or calcium chloride with the aim of minimising tissue damage during subsequent thermal processing (95 °C). Firmness measurements and micrographs provided information on the extent of tissue damage. These observations were linked to the chemical structure of pectin. When PME was infused in absence of Ca²⁺, the degree of methoxylation of pectin was lowered, but chains remained water soluble, indicating that they were not crosslinked. Thermal processing of PME-infused strawberries resulted in pectin solubilisation and depolymerisation which was reflected in pronounced firmness decrease and tissue damage, comparable to non-infused processed strawberries. On the other hand, when a combination of both PME and Ca²⁺ was infused, an important decrease in processing-related tissue damage was perceived. This can be explained by increased crosslinking of pectin chains with low degree of methoxylation, rendering them insoluble and less susceptible to thermal depolymerisation.     

Lycopene degradation, isomerization and in vitro bioaccessibility in high pressure homogenized tomato puree containing oil: Effect of additional thermal and high pressure processing

In the present study, the effect of equivalent thermal and high pressure processes at pasteurization and sterilization intensities on some health related properties of high pressure homogenized tomato puree containing oil were investigated. Total lycopene concentration, cis-lycopene content and in vitro lycopene bioaccessibility were examined as health related properties. Results showed that pasteurization hardly affected the health related properties of tomato puree. Only the formation of cis-lycopene during intense thermal pasteurization was observed. Sterilization processes on the other hand had a significant effect on the health related properties. A significant decrease in total lycopene concentration was found after the sterilization processes. Next to degradation, significant isomerization was also observed: all-trans-lycopene was mainly converted to 9-cis- and 13-cis-lycopene. High pressure sterilization limited the overall lycopene isomerization, when compared to the equivalent thermal sterilization processes. The formation of 5-cis-lycopene on the other hand seemed to be favoured by high pressure. The in vitro lycopene bioaccessibility of high pressure homogenized tomato puree containing oil was decreased during subsequent thermal or high pressure processing, whereby significant changes were observed for all the sterilization processes.     

Development of an immunological toolbox to detect endogenous and exogenous pectin methylesterase in plant-based food products

An immunological toolbox consisting of five monoclonal antibodies (MA) was developed for the detection of endogenous as well as exogenous pectin methylesterase (PME) in plant-based food products. Based on cross-reactivity with plant PME, the MA were subdivided into two groups. MA of group one recognise exclusively PME from Aspergillus aculeatus (fPME), which could be visualised upon infusion. Three different infusion techniques were compared for three different types of plant tissue, revealing a homogenous distribution of exogenous PME upon pressure-and vacuum-assisted infusion. The MA of group two recognise fPME as well as PME from different plant sources like tomato, carrot, strawberry, broccoli and apple. The use of these antibodies allowed detection of endogenous PME in tomato which revealed an overall presence of PME in the pericarp of tomato fruit. Moreover, the PME detected by the MA of group two in the plant cell wall of tomato coincided with the localisation of two isoenzymes of tomato PME, as detected by isoenzyme-specific MA. The obtained results highlight the versatility of the developed antibodies as probes to detect PME in the context of food processing.