Study of phosphate diffusion and hydrolysis in longissimus dorsi muscle

The thesis starts with a review of literatures related to the topic. In the beginning, several speculations of water holding capacity (WHC) in meat are reviewed, and the joint effects of salt and phosphate addition on WHC are discussed in detail. In addition, the hydrolysis and diffusion of phosphates in meat are also explained. At the end of the literature review, several methods of phosphate measurement are listed and compared. The aim of this research was to determine an effective pattern for phosphate addition in meat processing by studying the dynamics of the phosphate diffusion in relation to their hydrolysis. To address this aim, the meat stripes were subjected to one-dimensional diffusion in TPP and PP brines (with the same salt and P2O5 content), and the phosphate contents of TPP, PP and MP at three diffusion levels (0.625, 1.875 and 3.125 cm) were analysed after 0.5, 2, 6, 24, or 48 h. Thin-layer chromatography (TLC) was used to determine phosphate contents. In addition, the effects of TPP, PP and MP on WHC of the laboratory scale cooked sausages with 0.5 h standing time were compared as a reference for the impact of different phosphates on improving WHC in meat. It was found that areas on the surface of the meat always had the lowest MP content; in addition, in every diffusion level, the initial MP content always decreased first before an increase took place. These results suggested that MP underwent two-way diffusion under the effect of naturally occurring concentration gradient between the meat and the brine, and the TPP/PP hydrolysis generated MP as products. Moreover, PP displayed higher stability then TPP: PP could be observed in the diffusion level as far as at 3.125 cm, and the PP content at 1.875 cm was stable during 2 days’ PP brine diffusion; on the other hand, no TPP was found at distances of 3.125 cm, and only a small amount of TPP was found in 1.875 cm. In addition, the acidic pH accelerated the phosphate diffusion, while the effect of metal ions on diffusivity was unclear. Within the 1.875 cm diffusion distances, which is the common size of meat cube used in meat industry, TPP did not exert a better effect in enhancing or prolonging the stability of PP, and it is possible that the application of PP can fulfil the task of common production schedules. In the sausage WHC test, MP sausages had the worst appearance, which suggests poor protein extraction and hence poor gelling properties. The appearance of PP and TPP sausages were similarly fine, while PP sausages had the best WHC.