Multiscale analysis of meat products using multimodal and multispectral imaging

The meats we eat are generally processed before consumption. The first transformation results from the evolution of the muscle after slaughter. From the end of the bleeding process, muscle cells will survive using the energy released by ATP hydrolysis, which is itself regenerated as hydrolysis proceeds, thanks to the anaerobic breakdown of the cell's glycogen reserves. The end products of these reactions are protons and lactate, which accumulate in the cells in the absence of blood circulation. When glycogen reserves are depleted, the pH of the meat decreases and stabilizes, reaching a value generally between 5.5 and 6, depending on the muscle, species and pre-slaughter stress. These biochemical changes lead to modifications in muscle structure, resulting in hardening of the meat, exudations and changes in color, the variations in which depend on the amplitude and speed of the pH drop in the muscle. During cold storage, the muscle continues to evolve. Endogenous proteases, released into the environment, find themselves in favorable conditions to degrade muscle structures and tenderize the meat. All these modifications are dependent on: pre-slaughter stress, carcass cooling kinetics, carcass storage conditions (temperature, duration) and muscle characteristics, with repercussions on the sensory qualities (color, flavor, texture, juiciness) and technological qualities (suitability for processing, juice losses during cooking, ham slicing losses, etc.) of meats.

Meat is then subjected to various types of technological processing designed to enhance its microbiological and sensory qualities, developing pleasant flavors and improving the texture, color and juiciness of meat products.

There are two types of processing: cold processing (marinating, salting, drying, smoking) and hot processing, which generally involves cooking. Some meat products, such as cooked ham, combine cold processing (salting) with hot processing (long cooking at low temperature).

So, from the live animal to the resulting meat product, many factors can influence the quality of the final product.

A significant part of the evolution of these qualities is linked to gradual variations in muscle structure and composition, at different stages of technological transformation. Imaging tools have evolved considerably in recent years, enabling us to characterize not only the morphological structure of tissues, but also their molecular structure and chemical composition. While each technique provides information of interest, it is the coupling of different methods, enabling multi-scale characterization, that brings significant added value to the understanding of phenomena generated by technological treatments. Correlative approaches make it possible to link structural...