Characterization of Heat-Induced Water Adsorption of Sea Cucumber Body Wall.

Different heating conditions could change water absorption capacity of sea cucumbers body wall (SCBW), and subsequently affect the sensory quality of the rehydrated sea cucumbers. In this study, fresh SCBWs were boiled for 30, 60, 90, 120, 150, 180 min, respectively. The boiled SCBWs were then soaked in deionized water for 48 hr. The changes in water absorption ratio (Wabs ), water holding capacity, water distribution, texture and ultrastructure of the SCBW were investigated. With increasing cooking time (from 30 to 180 min) the water absorption capacity is significantly enhanced (from 1.84 times to 3.37 times). The absorbed water was found to exist inside the SCBW in two forms, physisorbed water, which entered the SCBW via diffusion and could be easily removed, and associated water, which formed association with the SCBW 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 was mainly physisorbed with high mobility. The texture characteristics of the SCBW negatively correlated with the accumulation of physiosorbed water. These findings suggest that proper control of heating time could be critical in determining the sensory/eating quality of sea cucumbers. PRACTICAL APPLICATION: Different heating conditions allows sea cucumbers to have different water absorption capacity during the subsequent soaking process, which could greatly affect sea cucumber sensory quality. Understanding the effects of heating on the water absorption characteristics and texture characteristics of sea cucumber body wall will provide knowledge basis and guidelines to optimize the processing parameters for the emerging ready-to-eat sea cucumber industry.