# Influence of pH and Heat Treatment on the Physicochemical, Interfacial, and Emulsifying Properties of Hemp Seed Protein Dispersions

## TL;DR

This study shows how pH and heat treatment affect the ability of hemp seed proteins to stabilize oil-water emulsions.

## Contribution

The study reveals the impact of pH and heat on hemp seed protein interfacial behavior and emulsifying properties.

## Key findings

- HPI dispersions at pH 10 showed high solubility and interfacial viscoelasticity, forming stable emulsions.
- Acidic conditions (pH 2) also promoted stable emulsions with smaller droplet size and high interfacial elasticity.
- Heat treatment improved emulsifying stability at alkaline pH but reduced it in neutral conditions.

## Abstract

This study reports the effect of pH (2, 7, 10) and heat treatment (80 °C for 30 min) on the oil–water (o/w) interfacial behavior of hemp seed protein isolate (HPI) aqueous dispersions. The physicochemical, interfacial adsorption, rheology, and emulsifying properties of protein dispersions were evaluated. HPI dispersions at pH 10 exhibited the highest water solubility (60%), the greatest net charge (−27 mV), and the lowest hydrophobicity (~5 a.u.), promoting o/w interfacial pressure (π) and interfacial viscoelasticity. Strong interfacial viscoelastic protein layers (E* = 25 mN/m) were also observed under acidic conditions (pH 2), where proteins exhibited high solubility (40%), a high positive net charge (21 mV), and increased hydrophobicity (46 a.u.). HPI dispersions in their neutral state (pH 7) were not able to form stable o/w emulsions due to their poor physicochemical properties such as low solubility (18%), low surface charge (−18 mV), and hydrophobicity (~5 a.u.). Heat treatment significantly increased the charge and hydrophobicity of both neutral and alkaline proteins (~30 mV and ~10 a.u., respectively), increasing their particle size distribution and ultimately reducing their interfacial protein layer elasticity (E* = 20 and 13 nM/m, respectively). While particles at acidic conditions showed high thermal resistance, heat treatment improved the emulsifying stability in alkaline conditions while further reducing it in the neutral state. Overall, HPI dispersions demonstrated the ability to form stable emulsions at both alkaline and acid pHs, with those formed at pH 2 exhibiting a lower droplet size and superior stability.