Changes in Body Wall of Sea Cucumber (Stichopus japonicus) during a two-Step Heating Process Assessed by Rheology, LF-NMR, and Texture Profile Analysis

Sea cucumber (Stichopus japonicus) is regarded as a highly priced delicacy in Japan and China owing to its unique elasticity and palatability. Heating is an essential step to process sea cucumber with desired texture. In the present study, sea cucumber body wall was pre-heated at 40 degrees C, followed by post-heating at 80 degrees C. Changes in body wall were assessed by rheology, LF-NMR, and texture profile analysis. The small strain rheological analysis indicated that there were significant structural changes of body wall at about 40 degrees C during pre-heating. Large strain texture profile analysis and the storage modulus showed a good correlation. LF-NMR analysis displayed only one water population in samples preheated at 40 degrees C for up to 120 min, and the population did not change significantly with the heating duration. This demonstrated that structural changes and moisture loss from the inter collagen fibrils were not significant. As for samples postheated at 80 degrees C, three distinct peaks were found and the T-2 relaxation time and area of the bulk water decreased significantly, revealing significant changes of internal structures and loss of water-holding capacity. T-2 parameters had a good correlation to texture profile analysis parameters for samples after both pre-heating and post-heating.