QUALITY ATTRIBUTES, PECTOLYTIC ENZYME ACTIVITIES AND PHYSIOLOGICAL CHANGES DURING POSTHARVEST RIPENING OF NECTARINE

The postharvest ripening at 20C and 90–95% RH for 10 days of ‘Armking’ nectarine grown in a greenhouse was investigated over two seasons. Firmness, titratable acidity, ascorbic acid, pH and maturity index were all adequate to stablish the rate of ripening. However, soluble solids content and reducing and non-reducing sugars showed no significant changes. It took about 10 days for very early ripening fruit (100 g weight and 82 N firmness) and 6 days for normal early ripening fruits (115 g weight and 46 N firmness), both harvested at preclimacteric stage, to become eating ripe (near 20 N). Total weight loss and decay after 10 days was approximately 11%. During ripening there was a temporal coincidence among higher rates of ethyleneproduction, higher pectinmethylesterase (PME) and polygalacturonase (PG) activities, lower firmness and acidity and higher maturity index. PME and PG activities increased during ripening, with a highly negative linear correlation between activities of the two enzymes and firmness. In very early ripening fruit, PME activity was more closely related to softening than PG, whereas in normal early ripeningfruit, PG activity was slightly more closely linked to the loss offirmness than PME.     

FACTORS RESPONSIBLE FOR WHITE FILM FORMATION ON CUT SURFACES OF DRYCURED HAMS

White surface film that forms on cut surfaces of country-style ham was identified as crystalline L-tyrosine. Free L-tyrosine averaged 287.3 μmoles/g (5.2% by weight) in the film and 6.1 μmoles/g in ham tissue from which film had been removed. It is concluded that the film forms because the concentration of free L-tyrosine and certain other free amino acids in ham is greater than solubility levels; therefore, crystals form on the cut surface. The absence of surface film on knuckle muscles and film formation on other muscles of the same slice was attributed to higher NaCl (P < 0.05) of the former which decreased catheptic activity.     

How hygiene happens: physics and chemistry of cleaning

Cleaning is a commonplace but poorly understood operation in the dairy industries. This paper describes recent work to identify and quantify the critical factors that control cleaning. Experiments have used micromanipulation probes to remove deposits from surfaces; these probes can measure the force required to remove deposits, and allow simple models of cleaning to be produced.     

On efficiency of both single fuel cells and stacks II

The model developed in the first part of this work is used to predict the cell potentials and the irreversible Gibbs free energy of a stack of 15 cells. The model starts from a phenomenological equation of a polarization curve with the extent of reaction as the independent variable. Two extreme kinds of flow of reagents, defined as Chain and Separate Flows respectively, are considered. The cell potentials are obtained by a combination of the potential of the two extreme cases of flow. The stack cell potentials and the efficiencies, estimated by the model, reproduce the general characteristics obtained by the experiments.     

Photo-physical properties of Ca2+-indicator dyes suitable for two-photon fluorescence-lifetime recordings

We analyzed the suitability of various Ca²⁺-indicator dyes for quantitative two-photon fluorescence-lifetime imaging. Although fura-2, fluo-3, BTC and calcein did not show useful Ca²⁺-dependent lifetime changes, calcium orange, calcium green-1, oregon green-2 and -5N, as well as magnesium green allowed to quantify the Ca²⁺-free and Ca²⁺-bound dye fractions by a double-exponential lifetime analysis. For the latter dyes, we derived calibration formalisms that correct for lifetime distortions by dye impurities and Ca²⁺-dependent extinction coefficients.     

Adaptive limits for pc-based inventory control

The paper reports work on the development of a decision support system to implement the adaptive control limits approach within a transaction-oriented pc-based inventory control system. The system developed offers ways for an automatic adjustment of the inventory control parameters when the sales forecasts are updated or management adjusts its expected customer service level. Technical aspects of the approach used to generate the adaptive limits are presented along with an illustrative case example of its application.     

High pressure and pasteurization effect on duck foie gras

The effects of combined high pressure (300 and 400 MPa) and low temperature (50°C) treatments on the microbial contamination of duck foie gras samples were compared with those of classical thermal pasteurization (85°C at the coldest point). A multilayer packaging film (PE/PA/PE) was selected from two films commonly used for these types of food, by preliminary tests showing its ability to limit microbiological development in such samples. In each experiment, microbiological contamination was analysed on treated and untreated samples, and results were systematically compared with those obtained from a classically pasteurized sample of the same liver. A pasteurization type effect (drastic reduction of vegetative mesophilic and psychrophilic contaminations, destruction of coliforms and of Staphylococcus aureus ) was obtained at this temperature with samples pressurized at 400 MPa for at least 10 min.     

Orientational analysis of planar fibre systems observed as a Poisson shot-noise process

We consider two‐dimensional fibrous materials observed as a digital greyscale image. The problem addressed is to estimate the orientation distribution of unobservable thin fibres from a greyscale image modelled by a planar Poisson shot‐noise process. The classical stereological approach is not straightforward, because the point intensities of thin fibres along sampling lines may not be observable. For such cases, Kärkkäinen et al. (2001) suggested the use of scaled variograms determined from grey values along sampling lines in several directions. Their method is based on the assumption that the proportion between the scaled variograms and point intensities in all directions of sampling lines is constant. This assumption is proved to be valid asymptotically for Boolean models and dead leaves models, under some regularity conditions. In this work, we derive the scaled variogram and its approximations for a planar Poisson shot‐noise process using the modified Bessel function. In the case of reasonable high resolution of the observed image, the scaled variogram has an approximate functional relation to the point intensity, and in the case of high resolution the relation is proportional. As the obtained relations are approximative, they are tested on simulations. The existing orientation analysis method based on the proportional relation is further experimented on images with different resolutions. The new result, the asymptotic proportionality between the scaled variograms and the point intensities for a Poisson shot‐noise process, completes the earlier results for the Boolean models and for the dead leaves models.     

Optimization of multiphoton excitation microscopy by total emission detection using a parabolic light reflector

We have constructed a device that maximizes the probability of collecting all of the scattered and ballistic light isotropically generated at the focal spot of multiphoton excited emissions (MPE) to optimize the signal-to-noise ratio (SNR) for micro-imaging. This was accomplished by optically coupling a parabolic reflector (that surrounds the sample and top of the objective) to a pair of collimating lenses (above the sample) that redirects emitted light to a separate detector. These additional optics, combined with the objective, allow the total emission detection (TED) condition to be approached. Numerical simulations suggest an approximately 10-fold improvement in SNR with TED. Comparisons between the objective detection and TED reveal an enhancement of 8.9 in SNR (77% of predicted) for GFP-labelled brain slices and similar results for fluorescent beads. This increase in SNR can be used to improve time resolution, reduce laser power requirements/photodynamic damage, and, in certain cases, detection depth, for MPE imaging techniques.     

Sampling theory and automated simulations for vertical sections,applied to human brain

In recent years, there have been substantial developments in both magnetic resonance imaging techniques and automatic image analysis software. The purpose of this paper is to develop stereological image sampling theory (i.e. unbiased sampling rules) that can be used by image analysts for estimating geometric quantities such as surface area and volume, and to illustrate its implementation. The methods will ideally be applied automatically on segmented, properly sampled 2D images – although convenient manual application is always an option – and they are of wide applicability in many disciplines. In particular, the vertical sections design to estimate surface area is described in detail and applied to estimate the area of the pial surface and of the boundary between cortex and underlying white matter (i.e. subcortical surface area). For completeness, cortical volume and mean cortical thickness are also estimated. The aforementioned surfaces were triangulated in 3D with the aid of FreeSurfer software, which provided accurate surface area measures that served as gold standards. Furthermore, a software was developed to produce digitized trace curves of the triangulated target surfaces automatically from virtual sections. From such traces, a new method (called the ‘lambda method’) is presented to estimate surface area automatically. In addition, with the new software, intersections could be counted automatically between the relevant surface traces and a cycloid test grid for the classical design. This capability, together with the aforementioned gold standard, enabled us to thoroughly check the performance and the variability of the different estimators by Monte Carlo simulations for studying the human brain. In particular, new methods are offered to split the total error variance into the orientations, sectioning and cycloid components. The latter prediction was hitherto unavailable – one is proposed here and checked by way of simulations on a given set of digitized vertical sections with automatically superimposed cycloid grids of three different sizes. Concrete and detailed recommendations are given to implement the methods.