| Emulsion technology plays a key role in the quality of emulsion-type meat products. The myofibrilla structure and protein conformation have different effect when used the different emulsion technology, and the changes of myofibrilla structure and protein conformation are influence of the emulsify stability, texture, rheology character and sense quality of meat batter. Salt is a necessary material to produce the meat batter, it is a key factor in the solubilisation of the myofibrillar proteins, and determine the quality and flavour of batter. However, over consumption of salt can rise hypertension and lead to cardiovascular disease. For reducing the salt of batter, most researchers have demonstrated the possible utilization methods, such as used of salt substitutes, natural flavor enhancer. To our known, no research reported that utilized the emulsify technology to lower the salt, and we do not have a thorough understanding of the underlying mechanisms. Therefore, the study was basis on the effects of myofibrilla structure and protein conformation by the chopping and beating, to research the effect of processing technology, salt, fat, protein content and different sources of muscles on the emulsified meat quality characteristics and protein conformation, and investigate the content in different processes, different salt, protein and fat condition, the relationship between the myofibrillar structure and protein conformational changes and emulsified meat texture, emulsion stability and other quality characteristics, and then to provide a theoretical basis for lowering the amount of salt added emulsified meat products and improve the quality of products. The study includes five parts, the contents and results are as follows:1. Effect of chopping and beating on the changes of myofibril structure and protein conformationBy the chopping and beating pork batters as the research object, to study the effect of chopping and beating on the damage degree of myofibril, particle-size of meat batter and protein conformation. When using phase-contrast microscopic examination, found that the processes shattered the muscle. Much longer myofibrils and still connected (bigger particles) for muscle homogenized by the chopping process, however, when used the beating process, the myofibrils were shorter, even many muscle myofibrils were disrupted less than 10 sarcomeres. The result was agreement with the particle-size analysis. The major peaks of the beating and chopping treatments located at 15 u.m and 138 μm, respectively. However, the shoulder peaks located at 91 μm and 20 μm, respectively, and the values of D 32, D 4,3, D 0.1, D 0.5 and D 0.9 were significantly (P< 0.01) decreased in the beating treatments. The results indicated that beating treatments had smaller diameters particles volume than the chopping. In the micrographs of chopped meat batter, muscle clusters were aggregated, and the cut surfaces were in good order, muscle myofibrils and endomysium were complete. However, in the beaten batter, muscle bundles were in disordered, myofibrils and endomysium were breakdown and generated some thin fibres, and the thin fibres were cross linking with myofibrilla.The heat process was significant effect (P< 0.05) the protein secondary structure contents. The α-helices content of heated samples were lower, and had a higher P-sheet, β-turn, random coil content. There were significant effects of chopping and beating process on the values of secondary structural percentages content and local environment. Compared with the chopping, the use of beating process could cause more α-helices structures unfolding, and then transformation into β-sheet, β-turn and random coil structures. The results were coincidence with the secondary structure informations of amide III band. The beating and heat treatment caused partially transition from ganche-ganche-ganche and/or trans-ganche-trans conformations to ganche-ganche-trans conformation. The results indicated that beating process and heat treatment had similar effect of S-S stretching, and had higher potential energy conformation. Compared with chopping process, the use of beating process made more hydrophobic microenvironment become exposed to the polar aqueous solvent, but no significant (P> 0.05) differences were showed in the normalized intensity of the Raman band near 760 cm-1 (the tryptophan residues ring) as a function of thermal treatment. Chopping and beating process caused tyrosine residues of proteins exposed to the aqueous or polar environment, the beating has lower the value of doublet tyrosine bands ratio (1850/1830) and thermal stability. After heated, the value of 1850/1830 was significant (P< 0.05) decreased in the chopping. Chopping and beating process also caused the Raman bands of C-H stretching vibrations had a trend of shifting to high wavenumber.2. Effect of chopping and beating process on characteristics of pork batter with various amount of saltThe research studied the effect of chopping and beating process on characteristics and protein secondary structure of batter. Improved salt levels resulted in higher L-values, cooking yield, salt-soluble proteins (SSP) concentration, storage module (G1) and firmer texture, however, there were no significant effects (P> 0.05) of salt content on the a-helical content with the same processing method. The reason was improved the salt content, it was benefit of solubilisation of the myofibrillar proteins, and increased the SSP concentration. Compared with the chopping, the used of beating resulted in higher L*-values, SSP concentration, emulsion stability, G’, cooking yields and improved the|3-sheet content of the proteins, and lower the Tanδ. The batters with 1% and 2% salt by beating had similar L*-values, SSP concentration, hardness, springiness, and higher than the chopping with 2% salt. From the changes of G’ and Tanδ of beating batters, the result in that beating process could decrease the effect of denaturation of the myosin tails and destruct the gel network structure.The beating could decline the a-helix content, increase the β-sheet content, and the changes were salt and thermal stability. It also improved the micrographs of batters, and formed more compact and continuous structures. The chopping could flatter the fat, reduced the particle size. However, the beating had little effect on the fat, so the particle size was bigger than the chopping, reduced the SSP which was required to surround the fat globules and formed firm gel. After heated, the batters prepared by beating had a uniform network, and showed a more of spongy structure with more cavities formation. Because the beating could improve the SSP concentration and change the secondary structure of protein, the micrographs was better than the chopping. Panelists found that the addition of 3% salt to kung-wan resulted in excessive saltiness, causing the batters to have low scores for overall acceptance. Due to the worse texture, lower hardness and springiness, the batters with 0.5% salt were not accepted by panelists. Among all samples, the batters with 2% and 3% salt by beating had the highest scores for overall acceptance because they had suitable color, texture, juiciness, and odor.3. Effect of chopping and beating on the quality and protein conformation of low protein concentration pork batters with various amount of saltWhen add water, the protein concentration of batter was lower from 15.92% to 12.94%. The influence of chopping and beating on the quality and protein conformation of pork batters based on water and various amount of salt added was investigated. Increased salt content from 1% to 2% increasing cooking yield, hardness, and springiness, and not significant effects (P> 0.05) of the L*-value, a*-value and b*-value. Compared with the chopping, the batters of beating had higher L*-value, b*-value, cooking yield, hardness, and springiness, and the batter of beating with 1% salt had a higher L*-value, cooking yield, hardness, and springiness than the chopping with 2% salt. That indicated the used of beating could improve the water hold capacity of the batter.The strongest intensity of the 1658 cm-1 and 1660 cm-1 band in the Raman spectra (1600-1700 cm-1) of cooked batters produced by chopping and beating process, respectively. The results implied that pork meat proteins were attributable to proteins with high a-helix content. A significant (P< 0.05) decrease in a-helix, companied by a significant (P< 0.05) increase in (3-sheet percentage when using the beating process, because transformation of α-helical structures into β-sheet structures during the protein denaturation. The results were concordance with the percentages of secondary structure obtained from the amide III Raman spectra profile (1600-1700 cm-1). No significant differences (P> 0.05) were found in the intensity of the Raman band of tryptophan residues near 760 cm-1, that indicated salt content and emulsion technology had little effect. Salt contents were not effect of the tyrosine residue is solvent exposed or buried. Compared to the chopping, the doublet bands ratio ranges in beating batters were significantly increased (p< 0.05), which indicates that more tyrosine residues are exposed to the aqueous or polar environment. Improved salt content and used beating process induced more changes in pork protein structures of batters and the proteins cross-linking could be largely.4. Effect of the beating on characteristics of low-salt and low-fat pork battersThe physico-chemical properties during the processing, and antioxidant activity during the storage of batter with 1% salt by beating as affected by replacing pork back-fat with pre-emulsified sesame oil were investigated. Decreased fat content by the replacement of pork back-fat with pre-emulsified sesame oil, improved the content of water and protein content of the cooked batters, and declined the fat content and energy. Meanwhile increased the L*-value of raw and cooked batters, and there was not effect of emulsion stability, that indicated the batters contented pork back-fat or/and pre-emulsified sesame oil had similar water and oil hold capacity and thermal stability. Due to the protein concentration increased, the batter which contented pre-emulsified sesame oil had higher hardness and springiness (P<0.05). The overall acceptance scores of cooked batters were decreased significantly (P <0.05) when increasing the SE over 50%. The reason is added exceed sesame oil while product the dominating oily smell of cooked batters, so some panelists were unacceptable. Due to the presence of sesamolin, sesamin, sesamel, and a-tocopherol in sesame oil, the batter which contented pre-emulsified sesame oil had better oxidative stability during the storage.5. Effect of the beating on characteristics of low-salt batters with various amount of pork and chicken meatThe used of pork leg meat and chicken breast meat as material, the objectives of this study were to evaluate the quality attributes of batters with various mixtures of pork leg meat and chicken breast meat, ranging from 0 to 100%, including instrumental color, protein solubility, emulsion stability, texture profile analysis, dynamic rheological properties and sensory evaluation. When increased the content of chicken breast meat of the batters, pH and protein solubility was increased. The effects of various mixtures of pork leg meat and chicken breast meat on the color, dynamic rheological properties and emulsion stability were different. The emulsion stability of mixer meat batters were lower, L*-values and G’ of 80 ℃ increased with chicken breast meat increasing, and the batter of 100% pork leg meat had the lowest lower initial G’.L*-values and hardness of cooked batters increased with chicken breast meat increasing. According to the result of sense evaluation, extremely hard texture had negative effect on the sensory qualities of cooked batter. The results showed that the kung-wan with 50% chicken breast meat, and 50% pork leg meat improved the quality of batters.In conclusion, the beating could shatter the myofibrilla shorter, changed the protein conformation, amended the process characteristics of meat protein, enabled lowering of the salt content, and improved the quality of the emulsion-type meat products. |
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