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Browsing by Subject "Water-holding"

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  • Effect of different ions and pH values on the surface hydrophobicity of myosin S1 units 
    Wu, Qimeng (2015)
    The literature review deals with water distribution in meat, the structure of the myofibrillar matrix, and the aspects related to the water-protein interaction. Special focus was given to the large water accessible area of myosin S1 units, surface hydrophobicity of proteins and factors affecting the hydrophobicity. Also the possible mechanisms of water-holding in meat were briefly introduced. The aim of the thesis was to study the effect of different ions and pH values on the surface hydrophobicity of the myosin S1 units, adding knowledge to the understanding of the interaction between myosin S1 units and water. Myosin S1 units were prepared from porcine longissimus dorsi muscle 48 h postmortem. Obtained myosin S1 units were subjected to 0.2 M, 0.4 M and 0.6 M ionic strength of NaCl and KCl and to pH 5.0, 5.5, 6.0, 6.5 and 7.0. The surface hydrophobicity of myosin S1 units was measured by fluorescent molecular probe (cis-Parinaric acid) method. The method of purifying myosin S1 units from porcine longissimus dorsi muscle 48 h postmortem was established under the conditions of our laboratory. Surface hydrophobicity was found to increase with increasing ionic strength of both KCl and NaCl. Concerning the different ions studied, only at 0.6 M, significantly higher surface hydrophobicity of myosin S1 units was measured in KCl compared to NaCl. This phenomenon is in accordance with chaotropic effect of K+ and Cl- and kosmotropic effect of Na+. Regarding the effect of pH, within KCl samples, more hydrophobicity myosin S1 unit was detected towards to the more acidic direction pH values than pH 6.0. For NaCl samples, at pH 5.5 and 6.0, surface hydrophobicity was significantly higher than at pH 5.0, 6.5 and 7.0. Differences may have been induced by the changes in the net charges of protein, and further in protein conformation. Considering the property of the protein surface, more hydrophobic protein results in less water-protein interaction. However, to look at the whole scenario of the interaction between myosin S1 units and water, changes of net charges of myosin S1 units and water structure at vicinity of them should be further studied.
  • Study of phosphate diffusion and hydrolysis in longissimus dorsi muscle 
    Wang, Xiaoqing (2015)
    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.

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