Modification of Grass Pea Protein Isolate (Lathyrus Sativus L.) Using High Intensity Ultrasound Treatment: Structure and Functional Properties

In this study the effect of different high intensity ultrasound (HIU) amplitudes (25, 50 and 75%) and sonication times (5, 10 and 20 min) on the structure and functional properties of grass pea protein isolate (GPPI) was investigated. A higher sonication amplitude and longer time improved the protein solubility and surface hydrophobicity and reduced the particle size of GPPI. These physicochemical alterations in GPPI enhanced the protein adsorption at the oil-water interface, reduced the interfacial tension and increased the EAI and ESI values. SDS-page demonstrated that sonication did not change the primary structure of the protein. However, CD spectroscopy indicated a reduction in α-helix and an increase in the content of β-sheet and random coil structures in the sonicated GPPI. The free SH groups content and UV-vis absorbance intensity increased after the sonication. However, prolonged sonication up to 20 min reduced the free SH content in GPPI due to the oxidation of susceptible SH groups. HIU increased the thermal degradation of GPPI and lowered the least concentration needed for gelatinization of GPPI (LGC). Therefore, less protein powder was needed to form a strong gel compared to the non-sonicated GPPI. Sonicated GPPIs showed higher gel strength especially when 75% amplitude used for 10 min. These results showed that the HIU is a promising approach for modification of the functional properties of GPPI for food applications.