X-ray tomography using the full complex index of refraction.

We report on x-ray tomography using the full complex index of refraction recorded with a grating-based x-ray phase-contrast setup. Combining simultaneous absorption and phase-contrast information, the distribution of the full complex index of refraction is determined and depicted in a bivariate graph. A simple multivariable threshold segmentation can be applied offering higher accuracy than with a single-variable threshold segmentation as well as new possibilities for the partial volume analysis and edge detection. It is particularly beneficial for low-contrast systems. In this paper, this concept is demonstrated by experimental results.

Specific and selective biosensor for Salmonella and its detection in the environment.

The specific and selective detection of Salmonella typhymurium based on the use of a polyclonal antibody immobilized by the Langmuir-Blodgett method on the surface of a quartz crystal acoustic wave device was demonstrated in liquid samples. These biosensors were selective to S. typhymurium in the presence of large concentrations of Escherichia coli O157:H7. They were also specific to S. typhymurium since bacteria preincubated with free antibody produced no signal. Dark-field and electron microscopy showed that two different antibodies, polyvalent somatic O and flagellar H7, were immobilized on the sensor surface producing two distinct attachments of bacteria at the liquid-solid interface. The somatic O antibody exhibits a rigid, binding, while the flagellar H7 antibody forms a flexible connection allowing a large degree of freedom. When the attachment of bacteria was rigid and strong, the responses of the acoustic wave sensors correlated with changes in the mass of bacteria present at the liquid-solid interface. In contrast, when attachment was flexible, the sensor signals were inversely proportional to the additional mass of bound bacteria. This difference is probably determined by the interfacial viscoelasticity and by acoustic and electromagnetic coupling. The signals of environmentally aged sensors with either predominantly rigid or flexible positioning of bacteria were correlated with changes in mass at the liquid-solid interface. Sensors with O or H type of binding could be used for analytical purposes.

The effect of stress during lairage and stunning on muscle metabolism and drip loss in Danish pork.

The effect on meat quality of a low stress handling system (LSS) compared with a traditional handling system (TS) was investigated in Duroc×(Landrace×Yorkshire; n=117) and (Hampshire×Duroc)×(Landrace×Yorkshire) pigs (n=110) under commercial conditions. In the low-stress handling system the pigs were kept in groups of 15 during lairage and movement up to the stunner. Before the stunner the groups were divided into three groups of five pigs for the CO(2)-stunning in a specially designed set-up. The pH and temperature were determined in m. longissimus dorsi (LD) and m. biceps femoris (BF) at various times post mortem. Immediately after exsanguination a biopsy was taken from the LD and analysed for the concentration of glycogen, lactate and creatine phosphate. The day after slaughter the pH was determined in the LD, BF, m. semimembranosus (SM) and m. semispinalis capitis (SC). The temperature was determined in the LD and BF, the internal reflectance was determined in the LD, SM and BF, the colour was determined in LD, the drip loss was determined in LD and BF, and the amount of blood splashing/bruising was evaluated in LD. There was a tendency for a higher concentration of creatine phosphate in the LSS-group (P=0.06). The pH in both the LD and BF on the day of slaughter decreased more slowly from 5 min post mortem to 40 min post mortem in the LSS-group than in the TS-group (P<0.001). From 40 min to 6 h post mortem the rate of the pH decline was similar in the two groups producing the lowest pH-level in the TS group. The day after slaughter the pH was similar in the two groups in the LD and SC, whereas in the BF and SM it was lower in the LSS-group than in the TS-group. The drip loss was lower in the LSS-group in both LD (P<0.01) and BF (P<0.05) whereas the internal reflectance was only different in LD with the lowest value in the LSS-group (P<0.001). The lightness (L*) was higher in the LSS-group (P<0.05). There was no effect of stunning system on the amount of blood splashing/bruishing in the LD. The study showed that by using a low stress stunning system it is possible to decrease drip loss, possibly by increasing the concentration of creatine phosphate and thereby delaying the acceleration of pH fall in muscles after death.

Determination of lean meat in pig carcasses with the Autofom classification system.

A fully automatic classification equipment called Autofom for use at pig abattoirs has been developed and tested. It measures fat- and meat depth in carcasses by use of ultrasound. Measurement with Autofom is very fast (measuring up to 1250 carcasses per hour). It is non-invasive and low maintenance costs can be expected due to lack of moving parts. The repeatability and reproducibility have been estimated. An equation for calculating lean meat percentage on the basis of Autofom measurements has been calculated. The accuracy of the equation, expressed by residual mean square error and by standard error of prediction, is 1.84 and 1.95, respectively. A functionality test shows that, when installed on-line at the abattoir, 99% of the carcasses can be classified by Autofom. The equipment will be a suitable alternative to automatic on-line determination of lean meat percentage in pig carcasses.

Effect of early post-mortem cooling on temperature, pH fall and meat quality in pigs.

The aim of this study was to investigate how early cooling of carcasses after slaughter by showering with cold water affected the rate of the pH fall post mortem, protein denaturation and drip loss. Eighty pigs were selected in pairs at debleeding according to sex and farm of origin. All pigs were halothane genotyped and glycolytic potential in LD analysed. One of each pair was cooled 30 min post mortem by showering with 10-12 °C water for 12 min. The control pig was treated normally except for the same delay before batch chilling commenced. The initial pH fall in LD and BF did not depend on the glycolytic potential in LD but at 5 to 6 and 24 hr post mortem pigs with the lowest glycolytic potential had the highest pH. Weight and lean meat content did not affect the cooling curve, i.e. the temperature fall. The results showed that it was possible to reduce the temperature in BF and LD by cooling at slaughter. The maximum difference in temperature between control and cooled carcasses 2hr post mortem was 2 and 1 °C in LD and BF respectively. The lowering of the muscle temperature early post mortem resulted in a reduced rate of the pH fall and a higher pH from 2 to 6 hr in the cooled carcasses. The rate of the pH fall in LD and BF seemed to be independent of temperature at levels above approximately 37 °C, but decreased linearly as the temperature dropped below approximately 37 °C. The cooling procedure used here did not result in a significant reduction in protein denaturation or drip loss, although there was a tendency towards lower drip loss in LD and BF in cooled carcasses.

Comparison of Dehiding versus Scalding and Singeing: Effect on Temperature, pH and Meat Quality in Pigs.

The aim of this work was to investigate the temperature and pH changes taking place at the slaughter line and during the chilling process, and the subsequent effect on meat and eating quality in pig carcasses that had either been scalded and singed or dehided. Both processes were followed by fast chilling. 219 halothane-gene-free Duroc Sire and Landrace-Yorkshire pigs were delivered from three farms and slaughtered over 2 weeks at either a dehiding or a scalding singeing slaughterhouse. Temperature and pH were measured at intervals from exsanguination until 6 hours post mortem. Ultimate pH, internal reflection, drip loss and colour (Minolta) were measured the day after slaughter. Colour (JPCS scale) was evaluated after freezing and thawing, and eating quality was estimated on unaged and aged (4 days at 4°C) m. longissimus dorsi (LD), using a trained taste panel. At the slaughter line the dehided carcasses had an almost constant and lower temperature compared to the scalded and singed carcasses. During chilling there is a shift in temperature curves between treatments, where the scalded carcasses had the lowest muscle temperature in LD and m. biceps femoris (BF) from 2hr post mortem and throughout the measuring period. In spite of the shift in temperature, the dehided carcasses had the highest pH in LD and BF from exsanguination and throughout the measuring period. The rate of pH fall in LD and BF was slowest in the dehided carcasses from exsanguination until 3 and 2hr respectively, post mortem. Dehided carcasses showed a 40% lower drip loss, a darker meat colour and a lower internal reflection in LD and BF compared to scalded and singed carcasses, thus indicating less protein denaturation in dehided carcasses. Scalding and singeing, however, lead to increased tenderness compared to dehiding, and this difference persisted even after ageing for 4 days at 4°C. The differences in toughness may be caused by increased proteolysis by released lysosomal cathepsins.