Effects And Its Application Of Combined High-pressure Processing And CaCl₂ On Properties Of Sodium-reduced Myofibrillar Protein Gels

The development of sodium-reduced meat products is important to promote the Healthy China Action.How to keep the quality characteristics of sodium-reduced meat products in an acceptable manner is urgent in the field of meat science.In this study,the two technologies?salt substitution and non-thermal processing?for reducing the NaCl content were integrated,the mechanism for the effects of combined calcium chloride?CaCl₂?and high pressure processing?HPP?on properties of sodium-reduced?0.3 M NaCl?myofibrillar protein?MP?gels was revealed,as well as the synergistic effect of the combination was verified in the in the sodium-reduced emulsified sausages?1.25%NaCl,w/w?with main raw meats?chicken,pork and beef?.The objective of this research was to provide technical support and theoretical basis for developing low-temperature meat products with reduced sodium content.The main research contents and results are as follows:?1?Low concentration?20 mM?of CaCl₂ combined with HPP of 200 MPa synergistically improved the WHC and strength of the MP gel,but high concentration?100 mM?of CaCl₂ combined with HPP of 200 MPa produced an antagonistic effect on WHC and strength of it.HPP of 200 MPa is the appropriate pressure level to improve the WHC and strength of the MP gel containing low concentration?20 mM?CaCl₂?MP-CaCl₂?.?2?The WHC and strength of the MP gel were positively correlated with hydrogen content,ionic content,disulfide bond content,?-sheet content,the relaxation peak area proportion of immobilized water?A27?,solubility and solubilized amount of myosin heavy chain?MHC?,and were negatively correlated with the normalized intensity of tryptophan?760 cm-1 and 1339 cm-1?Raman bands,the normalized intensity of the aliphatic amino acid residues CH bending?1450 cm-1?and stretching?2935 cm-1?vibrations Raman bands,?-helix content,turbidity and average particle size.?3?Low concentration?20 mM?of CaCl₂ combined with HPP of 200 MPa could significantly increase the A21 value of the gel?P<0.05?,significantly increase the disulfide bond content and hydrogen bond content?P<0.05?,significantly decrease the normalized intensity of 760 cm-1,1339 cm-1,1450 cm-1 and 2935 cm-1 Raman bands of MP gels?P<0.05?,induce the decrease of ?-helix content and the increase of ?-sheet content,promote the formation of dense,homogeneous and continuous gel network structure,synergistically improve the solubility of MP,significantly reduce the average particle size and turbidity of MP?P<0.05?,depolymerize the protein filaments,moderately unfold the tertiary structure of MP,and thus resulting in a synergistic effect on the gel properties of MP.High concentration?100 mM?of CaCl₂ significantly reduced the hydrogen bond content in pressurized MP gel?P<0.05?,significantly increased the normalized intensity of 1339 cm-1 Raman band of pressurized MP gel?P<0.05?,induced the formation of loose,porous and discontinuous structure in pressurized MP gel,reduced the solubilizing effect of HPP on MHC,significantly reduced the thermal transition temperature of myosin in pressurized MP?P<0.05?,promoted the formation of disulfide bonds and non-disulfide cross-linking of myosin S-1 subfragments in pressurized MP,and therefore producing an antagonistic effect with HPP on the gel properties of MP.Excessive pressure?>200 MPa?reduced hydrogen-bonding in MP-CaCl₂ gel,increased the embedding level of tryptophan residues,induced the formation of coarse gel structure with low cross-linking degree in MP-CaCl₂,significantly increased the turbidity and average particle size of MP-CaCl₂?P<0.05?,induced the reformation of protein filaments,excessively unfolded protein tertiary structure,significantly reduced the Ca2+-ATPase activity?P<0.05?,promoted the disulfide cross-linking of myosin S-1 subfragments,and thus leading to decreased gel properties of MP-CaCl₂.?4?HPP of 200 MPa combined with CaCl₂?0.2%,w/w?could significantly increase the A21 value of emulsified sausages?P<0.05?,reduce the fat droplets size,promote the homogeneous distribution of the fat,and form dense and continuous network structure,thus synergistically improving the cooking loss,hardness and chewiness of the three kinds of sodium-reduced emulsified sausages.Meanwhile,this combination treatment enabled the sodium-reduced emulsified sausages obtaining comparable quality characteristics?water and fat binding capacity,texture,sensory and color?that emulsified sausages with high salt content?2.5%NaCl?had,indicating that the quality deterioration problems of emulsified sausages caused by salt reduction were effectively be solved.In conclusion,the synergistic effect between moderate HPP?200 MPa?and low concentration of CaCl₂?0.2%,w/w?exhibits a great potential in the development of sodium-reduced meat products.