Effect of high pressure homogenization on acid-induced gelation of sesame protein isolate

Protein gelation plays a vital role from living organisms to food preparation and is used in many industrial applications. In this study, the effects of high-pressure homogenization (HPH) on the gelation property of sesame protein isolate extracted from sesame cake by acidification with glucono-δ-lactone (GDL) were investigated. For this purpose, homogenization was applied to the sesame protein solution prepared at 8% concentration at 0 (control), 25, 50, 100, and 150 MPa pressures, and then 2% GDL was added to the samples, and gelation properties were determined. This study examined acidification and gelation kinetics, physicochemical, structural, rheological properties, and intermolecular forces of the gels. The applied homogenization process affected acidification kinetic parameters such as Vmax, Tmax, T5, and T4.5. The maximum Vmax (0.062 pH units/min) value was determined in the sample with 100 Mpa pressure applied. However, the high pressure applied caused the protein's gelation time (T4.5) to decrease. It was observed that as the applied homogenization pressure increased, the particle size decreased, especially before gelation, and this played a role in the formation of lower particle size aggregates after gelation. The water binding capacity of the gels improved significantly with the applied HPH, and the highest value (69.02%) was detected in the sample where 100 MPa pressure was applied. While a significant tendency to increase the whiteness index of gels was observed by increasing the homogenization pressure up to 100 MPa, the highest total color difference (ΔE) was detected at 50 Mpa pressure. The G′ value of the samples tended to increase with time and with the high pressure applied, which indicated a significant improvement in the elasticity of the sesame protein gel and was found to increase the gel strength. All gel samples exhibit shear thinning behavior due to decreasing viscosity with increasing shear rate. Hydrophobic interactions were dominant in the gel samples, and the highest value (8.28 mg/mL) was determined in the sample where 100 MPa pressure was applied. This study revealed that the properties of sesame protein gel obtained using GDL can be improved with HPH and that 100 MPa pressure application is ideal.