Effect of ultrasonic pretreatment on the rheology and structure of grass pea (Lathyrus sativus L.) protein emulsion gels induced by transglutaminase.

In this study, emulsion gels were prepared by sonicated grass pea protein isolates (GPPI) at different ultrasonic amplitudes (25, 50 and 75 %) and times (5, 10 and 20 min). Formation of emulsion gels was induced by transglutaminase. Enzymatic gelation of emulsions stabilized by sonicated GPPI occurred in two stages. A relatively fast stage led to the formation of a weak gel which was followed by a slow stage that strongly reinforced the gel structure. Emulsion gels fabricated by sonicated GPPIs showed a homogeneous and uniform droplet distribution with higher elastic modulus compared to the native protein. A stiffer emulsion gel with a higher G' was formed after the protein was treated at 75 % amplitude for 10 min. After sonication of GPPI, the water holding capacity (WHC) of emulsion gels increased in accordance with the mechanical properties. Higher intermolecular cross-linking within the gel network increased the thermal stability of emulsion gels fabricated by sonicated GPPI. Although sonicated-GPPI emulsion gels clearly displayed homogenous microstructure in comparison to that made with native GPPI, the microstructures of these gels were nearly identical for all sonication amplitudes and times.

Ultrasound-modified protein-based colloidal particles: Interfacial activity, gelation properties, and encapsulation efficiency.

Proteins are natural amphiphilic polymers that often have good emulsifying, gelling, and structure forming properties. Consequently, they can be used to assemble protein-based colloidal delivery systems for bioactive agents, such as nanoemulsions, protein nanoparticles, or microgels. However, the functional performance of some proteins is limited because of their poor water-solubility, a tendency to aggregate, and or low surface activity, which limits their application for this purpose. Therefore, physicochemical modification is often necessary to improve their technofunctional characteristics. High-intensity ultrasound (HIU) is a non-thermal processing method that has considerable potential for the modification of the structural, physicochemical, and functional properties of proteins. In this article, we review the impact of sonication on the properties of proteins, including their size, charge, surface hydrophobicity, flexibility, solubility, free sulfhydryl groups, and disulfide bond formation. In addition, the influence of sonication on the emulsifying, foaming, gelling, and encapsulation properties of proteins is reviewed. Previous studies show that high-intensity ultrasound treatments have a strong influence on the molecular characteristics of proteins (increasing their solubility, flexibility, and functionality), which improves their ability to form colloidal delivery systems.

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 ß-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.