Effects of High Intensity Ultrasonication on Molecular Characteristics and Emulsifying Properties of Rambutan Seed Protein

Rambutan seed protein untreated (No-US) and treated (US) with high intensity ultrasonication (~ 320 W 20 min) had been characterized. LC-MS/MS analysis revealed that molecular sizes of proteins identified in rambutan seed protein were in a range of 4.1 to 318.9 kDa. US protein had higher fractions of small molecular weight proteins than No-US protein, suggesting US disrupted polypeptide structures into smaller units. No-US protein and US protein displayed similar band patterns on SDS PAGE gels. The surface hydrophobicity, the denaturation temperature, and the enthalpy of heat denaturation of No-US protein and US protein were not significantly different. The applied ultrasonication was suggested to not have a strong effect on the protein tertiary conformation. Rambutan seed protein had a relatively high amount of hydrophobic amino acids of 40.2% promoted strong intra-hydrophobic interaction. Emulsions prepared by US protein had lesser bridging flocculation and higher creaming stability than prepared by No-US protein.