J. Laverse

Assessment of intramuscular fat level and distribution in beef muscles using X-ray microcomputed tomography.

In the present research, the X-ray microtomography (muCT) technique was used to quantify intramuscular fat content and to study fat distribution in different breeds and commercial meat joints. Two different breeds, Podolian vs. Charolaise, chosen to exhibit variability in terms of visible structure of fat, were used. High Pearson correlation coefficients (r=0.92-0.99, P<0.001) were found between fat content, expressed as percentage object volume (POV) determined by muCT and fat content analysed by an official method. Useful information was provided from quantitative three-dimensional parameters describing the fat structure, such as the structure model index (SMI), the object structure/ volume ratio (OSVR) and the structure separation (SS). Charolaise breed showed higher POV and SS (P<0.01) values than Podolian. X-ray microtomography allows a rapid estimation of intramuscular fat of meat and provides a more accurate description of the fat microstructure and meat quality.

X-ray microtomography to study the microstructure of cream cheese-type products

In this work, the imaging x-ray microtomography technique, new to the field of food science, was used for the analysis of fat microstructure and quantification of the fat present in cream cheese-type products. Five different types of commercially produced cheeses, chosen for their variability of texture, were used for this experiment: sample A, sample B, sample C, sample D, and sample E. Appropriate quantitative 3-dimensional parameters describing the fat structure were calculated (e.g., the geometric parameter percentage of fat volume was calculated for each image as a representation of the percentage of total fat content within the sample). The dynamic-mechanical properties of these samples were also studied using a controlled-strain rotational rheometer. Storage modulus and loss modulus were determined in a frequency range of 0.01 to 10 Hz. The strain value was obtained by preliminary strain sweep oscillatory trials to determine the linear viscoelastic region of the cream cheese-type products. Statistical correlation analysis was performed on the results to help identify any microstructural-mechanical structure relationships. The results from this study show that microtomography is a suitable technique for the microstructural analysis of fat in cream cheese-type products, as it does not only provide an accurate percentage of the volume of the fat present but can also determine its spatial distribution.

Feasibility of X-ray microcomputed tomography for microstructure analysis and its relationship with hardness in non-acid lean fermented sausages.

X-ray microcomputed tomography (μCT) was used for microstructure analysis on four different types of non-acid pork lean fermented sausages, three of them supplemented with 5% pork back fat, sunflower oil or diacylglycerols (DAGs). The data from the μCT analysis were related to instrumental texture (hardness). Although μCT analysis identified fat particles and air holes, the technique was not accurate enough to distinguish between pork lean and fat when these constituents were emulsified. Only μCT geometrical parameters related to the meat matrix (emulsion of pork lean and fat) provided useful information on the microstructure of the product. Parameters such as percent object volume (POV), object surface/volume ratio (OSVR), degree of anisotropy (DA), structure thickness (ST) and number of objects (NO) were correlated with instrumental hardness.

X-Ray Microtomography for Food Quality Analysis

In an effort to understand the physical and rheological behavior as well as the mechanical and sensory attributes of foods, processing focus and emphasis have shifted to the microstructure level. Microstructure elements such as air bubbles or cells, starch granules, protein assemblies and food biopolymer matrices contribute greatly to the identity and quality of foods (Aguilera, 2005). The microstructure of food has an influence over the key attributes of a product as evaluated by consumers. Many of these properties are synergetic, therefore having multiple interactions, and are poorly understood as a result. Advances in the last decade in microscopy techniques, along with an improvement in computing capabilities, has made it possible to understand a food’s structure; its relation to physical properties (so called structure-property relationships) and how to engineer and control these properties (Aguilera, 2005). Structure-property relationships can strongly affect the physiochemical, functional, technological and even nutritional properties of foods. For example, with regards to solid food foams like bread, extruded cereals, biscuits and cakes, the consumer appreciation of these products is strongly linked to the texture. For texture, sensory properties of solid food foams are related to both mechanical properties and cellular structure. In this context, determining the relationships between a given mechanical property and the cellular structure is thus of prime importance. It has also been found that the structural organization of the components of cheese, especially the protein network, affect the texture of cheese: in particular the stress at fracture, the modulus and work at fracture could be predicted very well from the size of the protein aggregates (Wium et al., 2003). Cheeses having a regular and close protein matrix with small and uniform (in size and shape) fat globules show a more elastic behavior than cheeses with open structure and numerous and irregular cavities (Buffa et al., 2001). The mechanical properties of cocoa butter are strongly dependent from its morphology at microscopic level and, in particular, from the polymorphic transformation of the fat crystals and the coexistence of different polymorphic forms (Brunello et al., 2003). Thorvaldsson et al. (1999) studied the influence of heating rate on rheology and structure of heat-treated pasta dough. They found that the fastheated samples had pores smaller than the slowly heated one and that the pore dimension affects the energy required to cause a fracture. In particular, the energy required to determine a fracture in the samples having the smallest pores was more than for the

Applications of tomography in food inspection

Given the enormous success of X-ray computed tomography in medical applications and material science, it is not surprising that in recent years much attention has been focused on extending this imaging technique to food science as a useful technique to aid in the study of food microstructure. This chapter uses four case studies to show how X-ray microtomography can be used in food inspection and also to help understand the correlation between the physical aspect and microstructural properties of food products. These studies also demonstrate how the application of X-ray microtomography can aid in the study of cellular food microstructure such as breads, wheat and coffee beans by imaging and visualizing the internal structure.