Study On Physical Properties And Histomorphology Of Collagen From Sea Cucumber Body Wall Stichopus Japonicus

Sea cucumber (Stichopus japonicus) is a precious aquatic economic animal, which has high edible and medical value. However, its heat shrinking, water swelling, elasticity losing and getting soft easily during the storage time bring great difficulties to its deep processing. The tissue changes occurred during the processing depend on the micro-structural changes of collagen, the main component of sea cucumber body wall. So, it is necessary to investigate the tissue morphology and microstructure of sea cucumber body wall and it can provide theoretical foundation for us to improve the processing method and prolong the storage time of sea cucumber.In this study, fresh sea cucumbers were used as object to investigate the variations of volume and collagen content under different processing conditions. At the same time, the changes of morphology and microstructure of sea cucumber body wall during different processing conditions were studied by the methods of light microscope, polarizing microscope and scanning electronic microscope, and the regularity of the changes was investigated. Furthermore, the extraction and separation conditions of sea cucumber body wall gelatin were determined and part of its physicochemical properties was also studied. The results are listed as follow:1. The changes ofvolume and hydroxyproline content of sea cucumber body wall under different processing conditions were determined, which showed the rule of change as below: the content of collagen and the loss of volume increases gradually with the processing temperature increasing, and the changes become evident at80; under certain processing temperature, loss of volume also increased as the processing time prolongs. At first, the collagen content increased. And then, it decreased. The collagen content of sea cucumber body wall achieved to the maximum at8.0h,1.5h,0.5h,0.5h respectively when the temperature reached60℃,80℃,100℃,120℃accordingly. The loss of volume was80%.2. The changes of histomorphology and microstructure were observed by light microscope and scanning electronic microscope. The results illustrated that the collagen fiber of fresh sea cucumber was stripe shape and arrayed equably. Meantime, it had certain directivity. The collage fiber got thicker and shorter, and part of it swelled, ruptured and agglutinated as the temperature hoists; the collagen fibre ruptured and agglutinated obviously at8.0h,1.5h,0.5h when the processing temperature reached60℃,80℃,100℃respectively as the processing time prolongs.3. The effect of hot processing on the spectroscopy characteristics of collagen of sea cucumber body wall was investigated and the results indicated that the bands of A, III of acid amide moves towards high frequency while the bands of I, II moves towards low frequency. The absorption peaks of ultraviolet spectrum are all between235nm and237nm. Its position is not affected greatly, but its intensity augments gradually when the temperature get higher.4. Two different components were obtained after the gelatin of body wall was separated by DEAE-52. Their viscocities are129.60mL/mg and138.62mL/mg respectively. The contents of hydroxyproline were10.9%and9.9%respectively and the contents of essential amino acids account for15.8%and12.8%accordingly.