Effects of ultrasound treatment on the structure, function properties and in vitro digestion of Sipunculus nudus protein

Sipunculus nudus (S. nudus), an edible marine invertebrate, is rich in myofibrillar proteins. However, its extremely low water solubility and relatively firm texture limit its practical applications. This study aimed to investigate the consequences of different ultrasound amplitude treatments on the structure, functional properties, and digestive characteristics of S. nudus salt soluble protein (SSP). The results showed that ultrasound treatment significantly reduced the particle size, surface tension, and the unordered structure of SSP, while having not impact the zeta potential. Additionally, the results of infrared spectroscopy and intrinsic fluorescence spectrum revealed that ultrasound treatment enhanced the hydrogen bonding and hydrophobic interaction within the components of SSP, leading to a more compact and uniformly distributed protein structure. These changes increased the solubility (increased from 12.07 % to 37.59 %) and optimized the functional properties of SSP (foamability and emulsifiability). Further, the results of in vitro digestion simulation revealed that the antioxidant proteopeptides of SSP were mainly produced in the small intestine, with the ABTS