Effects Of Superchilled Storage On The Quality Characteristics Of Chilled Fresh Duck Meat And Its Mechanism

Duck has a long history as a meat ingredient in China,and its consumption is only less than that of pork and chicken.With the people’s increasing demand for a better life,the high quality duck meat with bright color,tender taste and pleasant flavor is favored by consumers.Superchilled storage is a new low temperature storage method.Compared with the traditional chilled fresh storage and frozen storage,it has significant advantages,and has been appling in the field of fresh keeping of aquatic products,However,the research and application of superchilled storage in duck meat are rare now.This paper takes chilled fresh duck breast as the research object,explores the change rules of fresh quality characteristics of duck meat during the process of superchilled storage from fresh degree,apparent characteristics,texture,water holding and flavor.The changes of duck meat flavor during storage are characterized by GC-IMS and electronic tongue technology.And further explored the influence mechanism of superchilled storage on duck meat quality characteristics from three aspects:protein biochemical characteristics and degradation law,water distribution state and migration law,and microstructure changes.This study aims to provide theoretical support for the high-quality chilled fresh duck products and the transition and development of duck meat industry to usher in the"ice fresh market".The main results are as follows.（1）The results of the study on the freshness characteristics of duck meat during superchilled storage show that with the increase of the storage time,the sensory score of chilled fresh duck meat decreased,TVB-N value,p H value and microbial quantity increased significantly,and entered to the secondary fresh range in the second week of storage,and the fifth week of storage entered to the corruption stage;adding kojic acid could keep the microbial quantity low during storage,The p H value and sensory score of the fresh-keeping group were lower than those of the blank group,and the fresh-keeping group entered the second degree of freshness at the 6th week of storage.The results showed that the water holding capacity,apparent characteristics and texture of duck meat were significantly affected by superchilled storage.During the storage,the sap loss rate and cooking loss rate increased,the L*value and a*value on the duck surface gradually increased,the b*value gradually decreased,the color gradually changed from bright red to yellow,and the hardness,fracturability,springiness,cohesiveness,gumminess,chewiness and resilience of duck meat texture decreased during storage,the adhesiveness increased.Fresh-keeping group’s change rate of texture and water holding capacity was significantly lower than that of the blank group.During superchilled storage,the adenosine triphosphate（ATP）content in duck meat decreased significantly,and hypoxanthine（Hx）accumulated significantly.Kojic acid treatment can delay the accumulation of Hx;The content of cadaverine,putrescine and histamine showed an upward trend during storage.The content of tryptamine,spermidine and spermine did not change significantly,and the treatment of kojic acid can delay the cadaverine and putrescine’s accumulation in duck meat.The shelf life of chilled fresh duck meat during superchilled storage is 4weeks.After kojic acid treatment,the shelf life can be extended about 4 weeks.Compared with 4℃refrigeration,superchilled storage significantly prolongs the shelf life of chilled fresh duck meat.（2）Based on the electronic tongue technology and GC-IMS Technology,the changes of taste and volatile flavor substances in the process of superchilled storage were analyzed.The results showed that the overall trend of taste characteristics during the superchilled storage was that the sourness decreased,bitterness,aftertaste-bitterness,astringency,aftertaste-astringency,saltiness,umami and richness increased;the change rate of taste characteristic response value in the blank group during the superchilled storage was higher.The response values of bitterness,astringency and aftertaste-bitterness can be used as the key value of electronic tongue to quickly judge the freshness grade of duck meat samples in superchilled storage.With the prolongation of storage time,the types and odor concentrations of volatile flavor substances in duck meat increased.Based on HS-GC-IMS technology,60 volatile flavor compounds were identified from the superchilled duck meat,among which 22 kinds of active intermediates,such as2-nonanone,2-Ethyl-5-methylpyrazine（D）,heptaldehyde,etc.were significant for indicating the degree of freshness of duck meat;The results of PCA analysis showed that the samples with different storage time had good discrimination,and GC-IMS technology could quickly identify the storage time of duck meat.（3）Based on the LFNMR,SEM,SDS-PAGE electrophoresis and FTIR technology,the mechanism of superchilled storage on the quality characteristics of chilled fresh duck meat was studied from the following three aspects:microstructure change,water distribution and migration law,and myofibril biochemical characteristics.The results showed that the water relaxation time T₂ and the relative content of free water increased during the storage.The total peak area of T₂ and the density of ¹H decreased significantly;The myofibrillar protein of duck meat was denatured to some extent during the storage,the carbonyl content gradually increased,and the content of mercaptol decreased;the myosin heavy chain in SDS-PAGE was gradually degraded,the band at 70 k Da disappears gradually,and the band strength increases at 35 k Da and 25 k Da;In the secondary structure of myofibril protein.theα-helix gradually changed to irregular curl,while theβ-fold content increased a little.During the superchilled storage,the formation of ice crystal has irreversible mechanical damage to the microstructure of muscle fibers.The degradation of myofibril leads to the decline of protein hydration capacity,increase of the degree of muscle fiber bundle separation,and deterioration of texture characteristics.The synergistic effect of the two results in the increase of the freedom degree of non-flowing water in the myofibrillar protein grid,The combined water and non-flowing water gradually transformed into free water,and the water holding capacity decreased significantly.Kojic acid treatment can significantly delay the above changes.