Improving functional properties of lupin protein by physical modification: high pressure homogenisation

Summary

Aqueous dispersions of commercially produced lupin protein isolate with pH 5 and 9 were treated using high pressure homogenisation (HPH) at 25‐200 MPa with one to ten homogenisation cycles. Particle size, zeta potential, solubility, molecular weight and rheological properties were analysed. HPH reduced the particle size for lupin protein at pH 5 from 54 μm to 5 μm and from 14 μm to <2 μm at pH 9 at 25‐100 MPa. However, at 200 MPa, the particle size had less reduction. HPH didn't have any significant impact on the zeta potential where it was maintained at ‐13 mV for pH 5 and ‐25 mV for pH 9. After HPH, solubility increased significantly for both pH 5 and 9 lupin protein samples. However, prolonged homogenisation decreased solubility. HPH impacted the viscosity of lupin protein at pH 5 and 9, depending on pressure and homogenisation cycles. The highest viscosity (~10 Pa.s) was achieved at 200 MPa with 10 passes. HPH increased the loss modulus where the viscoelastic properties were improved for both pH 5 and 9 at 200 MPa. The storage modulus profile indicated that HPH improved the gelling properties of lupin protein both at pH 5 and 9 at 200 MPa.