| It's meat science and technology workers' duties and responsibilities to produce emulsion-type meat sausages with low-fat and low-salt in low temperature conditions to advocate a healthy dietary manner.Normally,the researchers at home and abroad added fat and salt replacers to achieve the desirable sensory properties of the meat products with low-fat and low-salt.In addition,high pressure processing(HPP),as a kind of non-thermal processing technology in food industry,could be used to improve the emulsifying and gel properties of meat batters with low-fat or low-salt.However,there is no relevant study to apply HPP to alter the properties of meat sausages both with low-fat and low-salt.Therefore,this study aims to apply HPP to alter the emulsifying and gel properties of meat sausages with low-fat and low-salt The detailed research contents and results are shown below:1.Changes of gel properties in low-fat and low-salt meat gels with application of HPPCompared with the non-pressure treated control samples(0.1 MPa),changes of gel properties of emulsion-type meat products with 20%fat and 1%salt contents after various high pressure treatment(100?200?300?400MPa)at 10? for 2min were investigated,data of water distribution characteristics,rheological properties of meat batters,and cooked yields,textural properties of meat gels were collected,respectively.The results revealed that pH increased significantly with increasing HPP,especially at 200 and 300MPa.Moreover,the lightness and whiteness increased,but the redness decreased with increasing HPP.In addition,the appearance of the 200 and 300 MPa treated meat products were enjoyable with pink color.The cooking loss of 200MPa treated sausages was the lowest,but all the textural properties except adhesiveness are the highest.Low field-nuclear magnetic resonance suggested that HPP significantly changed the proportion of the three water components,transferring the free water into bound water and immobilized water with the increasing HPP.The rheological properties of G',G" and tan ? exhibited the highest values at 200MPa,which indicated the formation of a more regular and filamentous microstructure.In conclusion,200 MP resulted in the best functional quality of emulsion batters and sausages with low-fat among all the pressure treatments.2.Effects of various pressure levels on functional properties of myofibrillar proteins extracted from meat batters with low-fat and low-saltThe myofibrillar proteins extracted from meat batters were subjected to high pressure from 100 to 400 MPa at 10? for 2 min,protein composition,secondary structures and tertiary structures changes were evaluated to compare with the control(0.1 MPa).The results revealed that HPP decreased the ratios of ?-sheet and p-turn,but increased the ratios of a-helix and random coil.Moreover,the hydrogen bonding,hydrophobic interaction,disulfide bonds and the solubility of myofibrillar proteins first increased from 0.1 to 200 MPa,then decreased up to 400 MPa.In these chemical bonds,the contribution rate of hydrogen bonding was the highest,followed by hydrogen interaction and ionic bonding,respectively.In addition,the lowest particle diameter and protein composition showed by SDS-PAGE indicated the start of depolymerization of parts of proteins start at 200 MPa.In conclusion,200 MPa is a major turning point to make change of the protein composition and structures of myofibrillar.3.Effects of various pressure levels on formation of interfacial protein film(IPF)extracted from meat batters with low-fat and low-saltThe emulsion layer obtained from the meat batters subjected to high pressures from 100 to 400 MPa was assessed,and compared with the control sample(0.1 MPa).The results revealed that the emulsion stability and emulsion activity improved with increasing high pressure,with the best results obtained at 200 MPa.Moreover,firstly,the size of fat particles and emulsified liquid decreased,followed by an increase with increasing the magnitude of pressure,with the lowest values exhibited at 200 MPa.In contrast,firstly,the zeta potential and absorbed protein contents increased,followed by a decrease,with increasing high pressure level,with the highest value exhibited at 200 MPa.In conclusion,IPF changed significantly at 200 MPa to make contribution to the sensory properties of the sausages with low-fat and low-salt.4.Effect of 200 MPa HPP on protein structures and chemical composition of meat emulsion batters and gels with low-fat and low-saltProtein structures of meat batters and gels,as well as physical and chemical properties of meat gels having 20%fat and 1%salt content,subjected to 200 MPa at 10? for 2 min,were evaluated to compare with the control samples(0.1 MPa).The results revealed that,200 MPa pressure altered protein secondary and tertiary structures of meat batters and gels having low-fat and low-salt.The trends of the protein changes were similar with the results exhibited in the second chapter.Moreover,partial free amino acid and fatty acid content of gels were better at the 200 MPa treated samples,compared with the control.5.Gel property improvement of meat gels with low-fat and low-salt with application of 200 MPa instead of adding fat contentsThe effects of 200MPa HPP(10? for 2min)on tenderness and emulsion stability of different added fat content(0,5,10,15,20,25 and 30%)in pork batter gels were investigated,and compared with the control samples(0.1 MPa).The results showed that the application of 200 MPa pressure and increasing fat content were associated with increased lightness and whiteness,decreased redness and yellowness,as well as improved emulsion stability and altered tenderness.Tenderness,water-holding and fat-binding capacity of sausages treated at 200MPa with 15-20%fat content were similar to those of 30%fat content batter at 0.1 MPa,the results were further supported by water distribution characteristics and micro-structures analysis.These findings indicated that HPP exhibited potential to improve eating quality of sausages with low-fat and low-salt. |
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