Changes Of Collagen Structure In Sea Cucumber (Stichopus Japonicus) Body Wall During Heating And Rehydration

As a traditional processing method of sea cucumber,the rehydration process has continued to this day.Sea cucumber should be heated before rehydration,then placed in pure water to soak.Different heating temperatures and heating times will make the sea cucumbers have different water absorption capacities,and thus rise to different sizes,and their texture characteristics and sensory qualities are also different.At present,the rehydration technology of sea cucumber has matured,but the relationship between the change of body wall collagen tissue and water distribution during sea cucumber heating and rehydration is still unclear.The purpose of this paper is to clarify the mechanism of change in this process.Theoretical support for quality control in the rehydration process.In this study,fresh sea cucumber was used as raw material,and the pretreated sea cucumber was heated at 100 °C for 30 min,60 min,90 min,120 min,150 min,180 min,and then immersed in deionized water for 48 h.The changes of water absorption characteristics,water distribution,water holding capacity and texture characteristics of sea cucumber body wall(SCBW)after soaking were investigated.Scanning electron microscopy and transmission electron microscopy were used to observe the microstructure of SCBW in different cooking time.Explain the relationship between microstructural changes and water absorption characteristics.The results showed that the water absorption capacity of the SCBW increased significantly with the increase of cooking time.The absorbed water was found to exist inside the SCBW in two forms,physisorbed water,which entered the sea cucumber via diffusion and could be easily removed,and associated water,which formed association with the sea cucumber structure,evidenced by the difference in mobility determined by low field nuclear magnetic resonance(LF-NMR)spectroscopy.Study of the microstructure of the SCBW showed that the collagen fibers in the SCBW gradually depolymerized and degraded,resulting in the formation of inter-fiber pores and gaps which became internal space that could accommodate more and more water as the cooking time increased.This water wasmainly physisorbed with high mobility.The texture characteristics of the SCBW negatively correlated with the accumulation of physiosorbed water.The rehydration time also has a very important influence on the quality of sea cucumber.The heated sea cucumbers were placed in deionized water to rehydrate.The different soaking time will make the sea cucumbers have different states,and the texture characteristics and sensory quality are also significantly different.In the experiment,the water absorption characteristics,water distribution,water holding capacity,texture characteristics and microstructure of sea cucumber were studied by means of texture profile analyzer,nuclear magnetic resonance analyzer and cryo-emission scanning electron microscopy.The results showed that the water absorption rate of SCBW grew slowly in the first 10 hours and then increased rapidly.Compared with before rehydration,the shearing force decreased significantly after soaking for 16 h,and the hardness,elasticity and chewiness all appeared at the maximum when immersed for24h;Scanning electron microscopy picture shows the "sponge-like structure".With the extension of the soaking time,the "sponge-like structure" has larger holes.Image analysis software(ImageJ 1.46r)was used to perform morphometric analysis of the SEM images and found that the porosity increased by 36.51% during soaking.Significant changes in texture characteristics due to increased porosity during soaking.The above results indicate that proper heating time and rehydration time are essential for the quality of sea cucumber.At the same time,the microstructure and texture characteristics of sea cucumber in rehydration process are closely related.The change of microstructure will directly affect the texture characteristics.This result is great significance for improving the quality of sea cucumber products and enriching the basic theory of sea participation.