Kristof Mertens

New approach of testing the effect of heat stress on eggshell quality: mechanical and material properties of eggshell and membrane

1. The effect of high temperature on eggshell quality was investigated by measuring the mechanical and material properties of shell and membranes. 2. Heat exposure resulted in a decrease in zootechnical performance and eggshell thickness, increase in egg breakage, and unchanged egg shape index. 3. The static stiffness (K stat), dynamic stiffness (K dyn) and modulus of elasticity of the eggshell were not significantly affected by high temperature. Membrane prolongation increased significantly while membrane attachment strength and breakage strength tended to decrease and increase, respectively. The relationships between these variables were changed by high temperature. 4. Neither K stat nor K dyn could give a reasonable explanation for the changed eggshell quality induced by heat stress. The decreased eggshell thickness and changed properties of shell membrane may be responsible, at least partially, for the decreased shell quality of eggs from heat-stressed hens.

Eggshell Penetration of Various Types of Hens' Eggs by Salmonella enterica Serovar Enteritidis

Egg weight, shell thickness, number of pores, cuticle deposition, eggshell strength (dynamic stiffness and damping ratio), and the ability of Salmonella enterica serovar Enteritidis (SE) to penetrate the eggshell were determined. Penetration was assessed by filling the eggs with a selective medium that allowed viewing of Salmonella growth on the inside of the shell and membrane complex. After inoculation of each shell with on average 2.71 log CFU, the eggs were stored for up to 14 days at 20 degrees C and 60% relative humidity. Commercially available eggs were used. At 14 days of storage, only 6.0% of the eggs from free-range hens and 16.0% of the generic (i.e., eggs from hens in conventional battery cages that were given standard feed) white eggs were penetrated. The generic brown, organic, and omega-3-enriched eggs were penetrated at a frequency of 30 to 34%. In a second experiment it was shown that the layer strains of the hen (ISA-Brown Warren versus Bovans Goldline), which were kept in furnished cages, did not affect eggshell penetration by SE. For Bovans Goldline hens, the housing system (furnished cage versus aviary) did not affect penetration, while a trend was visible toward a higher fraction of penetrated eggshells when hens were fed corncob mix rather than standard feed. Eggshell penetration was observed more frequently in the absence of cuticle spots and for eggs having lower dynamic stiffness values. Shell contamination at the end of storage was highly correlated with SE penetration.

The transmission color value: A novel egg quality measure for recording shell color used for monitoring the stress and health status of a brown layer flock

Stress and diseases have the potential to influence the deposition of eggshell pigmentation during egg formation. Therefore, defining the shell color of eggs on a daily basis could be a representative method for monitoring stress or health status of a flock and maintaining good performance. A novel way of measuring eggshell color based on visible-near infrared transmission spectroscopy transmission spectra was defined: the transmission color value (TCV). The TCV was calculated as the ratio between the transmission at 643 nm (maximum absorbance of the pigmentation molecule protoporphyrin IX) and the transmission at 610 nm (a reference wavelength). Experiments were carried out to investigate the relevance of TCV for monitoring flock stress and health or even anticipating any factors unfavorable to performance. In 2 small experimental flocks, deliberate heat stress challenges were applied. A medium-scale experimental flock in an aviary was monitored on a daily basis during the whole productive period. From the deliberate heat stress challenges, it was seen that stress had a significant effect on eggshell pigmentation. This observation was confirmed in a daily monitored flock, in which, for example, an infectious bronchitis infection occurred. These stress situations were quickly reflected by an increased TCV value: more transmission due to less pigmentation and hence less absorbance at the pigmentation wavelength. Furthermore, for the observed problems in the daily monitoring, the TCV value signaled the problem earlier (4 d) than the average egg weight or even signaled when the other parameters did not signal anything. Measuring the TCV of all eggs produced on a daily basis provides relevant information on the stress or health status of a flock of brown layers. This could be used as an early detection of stress situations or emerging diseases, even before important quality and health damage can occur.

The assessment of viscosity measurements on the albumen of consumption eggs as an indicator for freshness

Viscosity values of albumen reported in the literature are difficult to compare because different shear rates and different methods of sample preparation have been adopted. Therefore, we first investigated the effect of shear rate on the viscosity measurements of thick albumen. For intact albumen, a large intersample fluctuation in viscosity with increasing shear rate was observed. Furthermore, a large hysteresis effect was observed, indicating that the structural properties were substantially altered by the rotational behavior of the rotor. From this, we concluded that to obtain reliable measurements, the albumen needed to be mixed. After mixing, a smooth evolution in viscosity with increasing shear rate was observed. Compared with intact albumen, the hysteresis effect was smaller but still present. We next investigated the correlation between albumen viscosity and Haugh units. For this, we compared the viscosity of fresh eggs with the viscosity of eggs stored for 24 d at a temperature of 18°C. The Haugh units were first determined, and the viscosity was next determined on mixed albumen at a shear rate of 200 rad/s. Mean viscosity equaled 0.0304 and 0.0181 Pa/s for fresh eggs and eggs stored for 24 d, respectively. The decrease in viscosity during storage was significant (α = 0.05). Furthermore, we observed that the correlation between Haugh units and viscosity measured on the same egg was low. Fresh eggs having comparable Haugh units differed substantially in their measured viscosities, whereas for stored eggs, the Haugh units differed substantially but the viscosities were comparable. It is unlikely that the very large variation in rheological properties observed among fresh eggs reflects the natural variation in albumen freshness present after lay. Results suggest that these differences were partly due to the structural changes caused by albumen sampling and by the turning motion of the rotor. We conclude that determination of the rheological properties of albumen is practically infeasible and that albumen viscosity cannot be used as an index for albumen freshness.

Early warnings from automatic milk yield monitoring with online synergistic control

Sensors play a crucial role in the future of dairy farming. Modern dairy farms today are equipped with many different sensors for milk yield, body weight, activity, and even milk composition. The challenge, however, is to translate signals from these sensors into relevant information for the farmer. Because the measured values for an individual cow show nonstationary behavior, the concepts of statistical process control, which are commonly used in industry, cannot be used directly. The synergistic control concept overcomes this problem by on-line (real-time) modeling of the process and application of statistical process control to the residuals between the measured and modeled values. In this study, the synergistic control concept was developed and tested for early detection of anomalies in dairy cows based on detection of shifts in milk yield. Compared with the combination of visual observation and milk conductivity measurements, the developed strategy had a sensitivity of 63% for detecting clinical mastitis. Consequently, this technique could have added value on many farms, as it extracts practical information out of inexpensive data that are already available. As it can be easily extended to other measured parameters, the technique shows potential for early detection of other nutrition and health problems.

Developments in understanding and assessment of egg and egg product quality over the last century

The hens egg, in the form of table eggs and egg products, forms a staple part of the worlds total protein consumption. In the last century, there has been considerable research effort focusing on ways of improving egg production and enhancing the quality of eggs. More recently, and with the development and application of new molecular technologies, our understanding and knowledge of how an egg is formed, what it actually consists of, in terms of its major versus minor components, and what the functional roles of each of these components might be, have been greatly enhanced. For example, new previously unknown molecules with specific activity or functional properties have been discovered in the egg albumen and yolk, some of which have potential uses in pharmaceutical and other food related applications. This review paper, which is the collaborative effort of members of Working Group 4 - Quality of Eggs and Egg Products - of the European Federation of WPSA, describes the scientific research behind a number of these major advances and provides some insight to the focus of current research in this area.

Assessment of embryonic growth in chicken eggs by means of visible transmission spectroscopy.

During this work, it was investigated whether spectral measurements can be used to monitor embryonic growth. An experiment was conducted in which both the transmission spectra and embryonic weight were determined on 240 eggs (Cobb, 37 weeks) between Day 5 and Day 10 of incubation. The spectral data were linked to embryonic weight by means of a partial least squares analysis. Different preprocessing procedures were compared during this work, that is, smoothing, multiplicative scatter correction (MSC), and first‐ and second‐order derivative. Compared to the remainder of the preprocessing procedures, MSC leads to a considerable improvement of the prediction capability of the embryonic weight. The ratio of performance to deviation obtained for the MSC spectra equaled 4.5 indicating that a very accurate prediction of embryonic weight is feasible based on the VIS/NIR transmission measurements. Important regions for the prediction are situated around 685–740 nm. It is suggested that the spectral changes in these spectral regions result from the displacement of carotenoids from the yolk into the blood circuitry.

The importance of choosing the right validation strategy in inverse modelling

Inverse modelling techniques, such as principal component regression, partial least squares regression and support vector machines, are very powerful multivariate calibration strategies which are widely used in near infrared spectroscopy. However, these techniques are so efficient in finding correlations between the spectral variables and the parameter to be predicted that great care should be taken to avoid over-optimistic results by use of a proper validation strategy. In this study, different validation strategies were investigated on a dataset that was acquired during various measurement days. The goal was to predict albumen freshness based on spectral measurements. Validation procedures frequently applied in practice, i.e. 10-fold cross-validation (10-fold CV) and validation based on random subdivision in calibration and validation set (RS) were compared to a cross-validation across measuring day (MD). Whereas 10-fold CV and RS validation suggested that prediction of albumen freshness is possible, MD validation on the same dataset indicated that albumen freshness cannot be predicted from the spectral measurements. It is shown that inverse modelling is very sensitive to unspecific correlations between the spectral measurements and the dependent variable, which might be artifacts of the measurement protocol and will not be persistent in the future. Therefore, selection of the right validation strategy for a given application and critical evaluation of the obtained results are crucial steps in inverse modelling to obtain useful calibration models. More specifically, in the context of process analytical technology where spectra are acquired over time, great care should be taken to break the unspecific correlation between the dependent variable and the variations in the spectral measurements over time.

Eggs and Egg Products

To a great extent eggs and egg products used in the food industry are bought in either the frozen or dried state. The objective of either drying or freezing is to retain the native characteristics of the raw egg to the greatest possible extent. Egg yolks and whole eggs are spray-dried commercially, while egg whites may be either spray-dried (powder) or pandried (flaked).

Advances in egg defect detection, quality assessment and automated sorting and grading

Abstract: Efficient control of the quality of eggs for human consumption facilitates the production of enough eggs that meet consumer requirements. The development of techniques for assessing the different quality aspects of eggs is an essential prerequisite for achieving this goal of quality. Novel technologies which are fast, automated and reliable offer the possibility of assessing quality in all individual units instead of relying on the evaluation of a subsample. Factors affecting the choice of techniques include consistency within a single product, measurement speed, instrumentation cost and the sorting efficiency required. This chapter reviews available techniques, focusing on advances, for the assessment of egg quality.