Research On The Texture Changes And Mechanism Of Abalone Muscle During Freezing And Frozen Storage

Abalone is the precious seafood in China.Because of its rich nutritional content,delicious taste and unique chewy,it is extremely popular all over the world.In this study,abalone was used as the experiment object.Firstly,the histology characteristics of muscle was studied,and the effect of liquid nitrogen frozen treatment on microstructure and protein distribution of different parts of muscle from abalone was explored.Finally,the adductor muscle was selected as the experiment object to explore the effect of freeze-thaw cycles,frozen temperature and time on adductor muscle texture.The study was in order to provide theoretical support and practical basis for high value processing of abalone and other aquatic products.?1?In order to better understand the raw material properties of abalone,the nutrient composition,protein composition and distribution of the three parts muscle?the adductor muscle,the transition muscle and the skirt muscle?from Haliotis discus hannai were determined and analyzed,and the tissue structure of the three parts muscles was observed by light microscope.From the perspective of nutrition,the water distribution and the distribution of protein and fat showed the opposite trend,with the center to the edge,and the water content gradually increased,while the protein and fat content gradually decreased.Although the crude fat content in the adductor muscle was very high,it was still far lower than other shellfish aquatic products;From the point of protein content and distribution,the adductor muscle and transition muscle of water-soluble protein,salt-soluble and basic protein,the types and contents of protein are more than the skirt muscle.But in terms of matrix proteins,the protein bands of skirt muscle were richer than the former two,which was three times of the adductor muscle and two times of the transition area;From the perspective of microstructure,the yellow area corresponding to myofibril gradually decreased,while the red area corresponding to collagen fiber gradually increased from the center to the edge,which was consistent with the results of protein content determination above.In addition,it could be found that there was a certain difference between cross section and longitudinal section of the same part of the muscle.?2?In order to explore the effect of freezing methods on the protein distribution and microstructure,liquid nitrogen freezing,which was the commonly industrial processing way,was selected to investigate the changes of water retention,water distribution,protein distribution changes of the three parts muscle?the adductor muscle,the transition muscle and the skirt muscle?from Haliotis discus hannai,and the tissue structure of the three parts muscles was observed by light microscope.From the perspective of water retention,the water retention of the three parts of muscles after freezing treatment was significantly reduced.Comparing the three parts,it was found that the water retention of the adductor muscle was better,which may be due to the higher myofibrillar protein content in it;From the perspective of protein distribution,SDS-PAGE showed that the four proteins were degraded after quick-freezing treatment,and the corresponding protein bands became lighter,especially the myosin heavy chain,paramyosin,actin,and tropomyosin were more obvious;LF-NMR showed that there was no significant change in the water content in the three muscles,which may be due to the fast freezing speed,shorter treatment time,less muscle damage,which had not caused the migration of water;It can be found in the light micrograph that the amount of myofibrillar protein in the unit field of vision of the adductor muscle has decreased,which was speculated that protein degradation may occurred.There was no significant change in the transition muscle.The muscle fibers of the skirt muscle became disorder and twist from the original arrangement.It was subject to rapid freezing treatment,which was consistent with the water retention results.In general,the effect of liquid nitrogen quick-freezing on the three muscles was small,and it was a very good quick-freezing method.?3?In order to explore the effect of temperature fluctuations on the texture of shellfish muscle,the commercial quick-frozen abalone was selected as the research object,and the texture,water-holding,field nuclear magnetic resonance and protein oxidation of 5 times freeze-thaw cycles were determined.From the perspective of texture changes,the results showed that the stiffness,elasticity,and chewiness of the muscles decreased significantly with the increase of freeze-thaw times?P<0.05?,which decreased to 11.21,3.03,and 10.04%respectively after 5 cycles.On the contrary,the shear force increased significantly?P<0.05?;From the perspective of water retention,the thawing loss,and cooking loss of muscles increased significantly?P<0.05?from2.28,16.09 and 38.51%to 10.50,28.53 and 43.67%,respectively;From the perspective of hydration characteristics,LF-NMR showed that the bound water was hardly affected during the freeze-thaw cycles and the relaxation times T₂₂ and T₂₃ of the immobilized water and free water shifted significantly to the right,and the corresponding peak area ratio P₂₂significantly increased and P₂₃significantly decreased?P<0.05?;From the perspective of protein oxidation,changes in protein structure and function have an adverse effect on muscle texture.It was found that hydrophobicity increased first and then decreased,and carbonyl content decreased significantly while active sulfhydryl content increased significantly?P<0.05?during the freeze-thaw cycles,which has a significant impact on muscle texture,Color and so on have important effects.?4?In order to investigate the effect of frozen storage temperature and time on the texture of abalone,the adductor of commercial quick-frozen abalone was selected as the research object,and the shear force,p H,water distribution and salt-soluble protein content during the frozen storage were integrated,and then combined with this index,the quality evaluation model was established.The p H value changed in a“V”shape and the rate of change at-40?was lower than that of the-18?;LF-NMR showed that the water distribution changed during the frozen storage;There was no significant difference in the shear force under these two temperatures for 5 months,but the value was still slightly higher at-40?than the-18?group,indicating that the effect of low temperature storage on texture during a short period of time was not significant;The relaxation time of the three types of water increased significantly,and the P₂₁ decreased with time,while P₂₂ and P₂₁ both increased and the rate of change at-40?was slower than the-18?group;In the first 3 months,the salt-soluble protein content at-40?was lower than-18?.However,the change occurred in the 4th month,and the salt-soluble protein content of-40?became higher than that of-18?;The principal component analysis?PCA?was performed by integrating these major indicators,and the comprehensive evaluation model finally obtained was F=0.680F₁+0.164F₂+0.157F₃.