Diaa Sharedeh (thesis defended the 21st of may 2015)

Marinating and brining improve shelf-life, tenderness and juiciness of meat and fish. As a supplement massaging or tumbling is often applied to meat pieces before cooking. The main aim of this study was to assess the impacts of the processing conditions on the biochemical and structural changes in the meat tissue; a great part is focussed on massaging. In the marinating trials the pH and NaCl content of thin samples of beef Semimembranosus muscle were set at 6.5, 5.4 or 4.3 and at 0,9 or 2 % (w/w), respectively; an ANOVA have shown the effect of these two parameters on the cells and extra cellular space sizes, the oxidation of lipids and proteins and the protein surface hydrophobicity. A brining-massaging simulator built by the laboratory was used to apply controlled successions of deformations (number from 350 to 2500, compression ratio from 10 to 30 %) to Semimembranosus (SM) ou Rectus femoris (RF) pork muscles. Mechanical treatments similar to those existing in industrial tumblers of various diameters were so reproduced. The main conclusions are: (1) massaging clearly increases the NaCl apparent diffusivity, on the one hand, by a modifying the tissue structure (+20%) and, on the other hand, by adding convection to diffusion (+200%); (2) the mechanical treatment promotes by itself an increase in protein solubility, known to affect processed meat quality, from 20 to 50 % in comparison with salted or unsalted reference samples; (3) it also increases moderately protein hydrophobicity; (4) the endomysium degradation, used as an indicator of structural changes, was more pronounced in the muscle periphery than in the middle and all the more marked than massaging was strong and long.