Effects Of Different Heating Technologies On Water Holding Capacity Of Pork Meat

Heating processing technology is an important factor affecting the quality traits of meat products.Exploring the influences of different heating methods on meat quality is the key to develop a new heating processing technology.In the present study,the Longissimus thoracis et lumborum muscle of porcine was used as experimental material,and low field nuclear magnetic resonance（LF-NMR）and magnetic resonance imaging（MRI）techniques were used to study the effects of different thermal processing methods on the evolution of water status.The microstructure and protein characteristics of pork were analyzed by scanning electron microscopy（SEM）,the projection electron microscopy（TEM）,differential scanning calorimeter（DSC）and Fourier transform infrared spectroscopy（FTIR）,and the relationship between pork structure and protein characteristics and meat quality was analyzed.Quantitative proteomics technique was used to explore the proteome of pork meat cooked by different methods and their relationship with meat quality were analyzed,and Parallel reaction monitor technique was used to determine the biomarkers related to meat quality.Furthermore,by analyzing the proteome of juice losses of pork during cooking processes,the formation mechanism of cooking loss during different cooking process was clarified.The specific results of this research are as follows:Different cooking methods had significant effects on meat quality.Compared with boiling cooking,steam cooking significantly increased the proton relaxation intensity and the proportion of immobilized water,and decreased the proportion of cooking loss and free water.The volume shrinkage and microstructure damage of meat samples cooked by steaming treatment were lower than those of boiling cooking treated-meat samples.Compared with boiled meat sample,steamed meat sample had higher protein solubility and lower surface hydrophobicity.In addition,under the same thermal processing,the salted meat samples had higher water retention than those of unsalted meat samples.Salting treatment increased the swelling of the fiber structure in pork samples.In summary,whether the meat samples were salted or not,steamed meat retained more water than boiled meat.A two-dimensional low-field nuclear magnetic resonance（LF-NMR）T₁-T₂ relaxation technique was developed to contrast the water status evolution during different cooking processes（steam and boiling cooking）.Meat quality,water distribution,microstructure and protein properties were determined.The results showed that steamed meats had lower cooking loss and shear force,but higher redness,proton relaxation intensity（T₁ and T₂）and proton density than boiled meats.The differences in water distribution between the two cooking procedures appeared at approximately40°C,with acceleration at 60°C,and the most remarkable difference was shown at 80°C.Boiling resulted in more damage to muscle structure and greater protein denaturation than steam cooking.Meanwhile,α-helixes andβ-turns increased,butβ-sheets and random coils decreased in steamed meats compared with boiled meats.Changes in microstructural and protein properties were closely associated with water status evolution in cooked meat during cooking.A DIA-based quantitative proteomic strategy was used to investigate the effects of different cooking procedures（steaming and boiling）on pork meat quality.Results showed that steamed meats had higher redness,cohesion,springiness,but lower lightness,yellowness,shear force,hardness,chewiness and cooking loss than boiled meats.In total of 1608 proteins were identified and 103proteins exhibited significant difference（fold change>1.5,P<0.05）.These DAPs mainly involved in protein structure,metabolic enzyme,protein turnover and oxidation stress.ALDOC,PVALB,PPP1R14C,AMPD1,CRYAB and SOD1 were validated as potential indicators of color variations in cooked meat.CFL1,COL1A1,COL3A1,RTN4,NRAP,NT5C3A,and SOD1 might be potential biomarker for texture changes of cooked meats.Moreover,these validated proteins exhibited significant（P<0.05）correlation with cooking loss and could be serve as candidate predictors for cooking loss changes of meats in different cooking procedures.Exudates released from meat has been regarded as a practicable media to evaluate the changes of meat quality.In order to investigate the potential impact of different cooking procedures（steam and boiling cooking）on meat quality,the DIA and PRM-based quantitative proteomics were applied to observe the proteome changes of cooking exudates.Meanwhile,the morphologic changes of cooked meat samples were evaluated by hematoxylin-eosin staining.A total of 1289 proteins were identified in both steaming and cooking pork samples,of which 216 proteins were identified as differential abundant proteins（fold change≥1.5,P<0.05）.The expression abundance of 101 proteins in steam cooking group were higher than that in boiling cooking group,and these proteins mainly included REDOX enzyme,metabolic enzymes and hydrolase.Additionally,the expression abundance of 115proteins in the boiling cooking group were higher than that in the steam cooking group,and these proteins mainly included structural proteins,signaling proteins and transporters proteins.The microstructure of meat samples was seriously damaged by boiling cooking treatment,and the muscle fiber structure became more loose than steamed meat samples.The structural proteins dissolved out with water,which probably increased cooking loss and reduced the water retention capacity of meat samples.