Effect of ultrasound assisted rehydration on the quality of dried sea cucumber

Sea cucumbers (Holothuria scabra), also known as beche-de-mer, are highly valued as a luxurious food item and have been utilized as a traditional tonic food in various Asian countries for centuries. The body walls of sea cucumbers are the main edible part, which are primarily composed of glycosaminoglycan (GAG). The rehydration of dried sea cucumber is a crucial step prior to further processing. The aim of this study was to assess the impact of ultrasound-assisted rehydration (UAR) on the quality of dried sea cucumbers. The experiment used four different rehydration methods, including conventional methods at 27°C (KV27°C) and 15°C (KV15°C), as well as a combination of ultrasound at 27°C with conventional at 15°C (UAR27 + KV15°C) and ultrasound at 15°C with conventional at 15°C (UAR15 + KV15°C). Results indicated that the rehydration rate (RR) was significantly affected by both the rehydration method and the temperature used (p < 0.05). UAR27 + KV15°C was identified as the most effective method in terms of rehydration behavior and quality characteristics of dried sea cucumber, with a RR of 0.58 ± 0.53 gH2O/hour and reduced rehydration time of up to 28 hours. Moreover, the UAR27 + KV15°C method demonstrated superior rehydration potential, nutritional value (proximate composition and sulfate content), color, lower energy, and microstructure properties compared to the other methods. The sulfate content and yield of sulfated GAGs were determined to be 89.4 mg/g and 52.8 μ/g, respectively. Confirmation of the absorption band of the sulfate group showed the presence of 3-N-acetyl galactosamine at a wavelength of 1,269 cm−1 and C-O-S at 860 cm−1. The sea cucumbers treated with UAR exhibited a GAG content approximately 2.9 times higher than those rehydrated with the conventional method. Eventually, the combination of UAR at 27°C with conventional at 15°C methods can significantly accelerate the rehydration of sea cucumber without negatively affecting its physical quality properties.