Nondestructive Method For Beef Quality Measurenment During Frozen And Chilling Storage Based On Magnetic Resonance Technology

Beef is one of the common meats in everyday diets.However,beef is also prone to spoilage due to its high moisture and protein content.Frozen storage and refrigeration are still the most two effective methods for preserving meat.The quality of beef is also greatly affected by the freezing and thawing phenomenon which caused by temperature fluctuation during transportation.Due to the long shelf life,it is necessary to monitor the quality of the beef to reduce loss in real time.The quality evaluation methods of beef during storage mainly include sensory evaluation,microbiological and physicochemical tests.However,these methods have been failed to reflect the dynamic changes of beef quality visually and quickly.Magnetic resonance technology is a rapid,non-destructive and non-invasive method for monitoring food internal moisture detection.This article takes beef as the research object,low field nuclear magnetic resonance?LF-NMR?,magnetic resonance imaging?MRI?and scanning electron microscopy as research techniques have been used,combining physical and chemical analysis?including water holding capacity,color,texture,pH,TVB-N,TBARS,etc.?and mathematical statistical analysis?principal component analysis,PCA,partial least squares analysis,PLSR?which provide a theoretical basis for quality nondestructive testing method during beef storage.The main contents and conclusions of this study are as follows:?1?The effects of frozen storage on the moisture status and distribution,myofibrillar protein,microstructure and physichemical properties of beef were studied.And its quality non-destructive testing method was established.During the frozen period,LF-NMR relaxation showed that three water components were distributed into the beef matrix,which were bound,immobilized and free water.During the frozen period,the structure of myofibrillar and myofibrillar protein was destroyed.It was observed that the transverse relaxation time and peak area of the immobiled water in the beef were significantly reduced.The relaxation time of free water is reduced significantly and the peak area is increased significantly(P<0.05.The T₁ image showed a continuous decrease in water intensity of beef,and the T₂ image showed a continuous increase.During frozen period,thawing loss,b*,MetMb content,hardness,chewiness,pH,TVB-N and TBARS values,hydrophobicity of myofibrillar protein surface increased and water holding capacity?WHC?,L*and a*values,springiness,cohesiveness,resilence,myofibrillar protein solubility decreased.The quality of frozen beef which freezing at-18°C changed faster during the early period,and beef freezing at-80°C changed faster later.Based on the relaxation data,the PCA result of beef freezing at-18°C showed that PC1 and PC2 explained 96%and 3%changes,respectively.The PCA result of beef freezing at-80°C showed that PC1 and PC2 explained 90%and 10%changes,respectively.It indicated that LF-NMR could identified beef samples with different frozen times.And through PLSR analysis,strong correlation(the verification coefficient R²_cvv value>0.8000)between original CPMG data and various quality indicators?including pH,TVB-N and TBARS,etc.?was observed.?2?Influences of multiple freeze-thaw?F-T?cycles on water status and distribution,microstructure and physicochemical properties of beef were investigated.And its quality non-destructive testing method was established.With the increase of F-T cycles,the relaxation time and peak area of immobilized water decreased significantly?P<0.05?.T₁ and T₂ magnetic resonance images displayed a continuous decrease of water intensity in beef.The cryo-scanning electron microscopy results revealed repeated F-T cycles resulted in more and more large holes in the beef muscle fiber.The repeated F-T cycles also led to the increase of springiness,cohesiveness and resilience,thawing loss,cooking loss,b*value and TBARS value,and the decrease of pH,water holding capacity,L*value,a*value and hardness.Based on the relaxation data,the PCA results showed that PC1 and PC2 explained 98%and 2%changes,respectively,indicated that LF-NMR could identified beef samples with different freeze-thaw cycles.Through PLSR analysis,it is observed that there is a strong correlation(the verification coefficient R²_cv value>0.8000)between the original CPMG data and various quality indicators including cooking loss,WHC,pH,L*value,cohesiveness,resilence and TRABS value.?3?Freshness has been regarded as an important indicator to estimate the quality of chilled meat.A rapid and non-destructive method for beef freshness was developed by LF-NMR in this study.Both the transverse relaxation time and peak area of immobilized water declined significantly due to the damage in microstructure?P<0.05?.The brightness of the T₁ and T₂ images continued to decrease throughout the storage period,indicating a decrease in moisture content of beef muscle.Refrigeration also caused the increase of cooking loss,L*value,b*value,pH,TVB-N value,TBARS value,and the decrease of WHC,a*value,hardness,springiness,chewiness,cohesiveness and resilience.PC1 explained 99%,and PC2 explained 1%changes,respectively,which demonstrated that LF-NMR could distinguish beef samples with different refrigerating times.The PLSR model based on CPMG data indicated the strong predication ability(verification coefficient R²_cv value>0.8000)of LF-NMR for freshness indicator including pH,TVB-N and TBARS value,and other quality parameters such as cooking loss,WHC,L*,a*and b*values in color,hardness,springiness,cohesiveness and resilience in textural characteristics.