Exploiting xanthan–guar gum interactions for stable avocado oil emulsions: A multi-stage kinetic and rheological approach

Abstract

Avocado oil offers a valuable source of monounsaturated fatty acids and bioactive compounds, but stabilizing it in food emulsions requires effective thickening and droplet protection. This study explores how xanthan gum (XG) and guar gum (GG), individually and in blends of varying ratios (GG:XG = 1.0:0.0 to 0.0:1.0), impact the stability, texture, and droplet-size evolution of avocado oil emulsions at three oil contents (1 %, 5 %, 10 %) and storage temperatures (5 °C, 25 °C, 45 °C). Emulsion stability was assessed via spectrophotometric turbidity measurements and kinetic modeling to capture the flocculation (k_f) and coalescence (kd) phases, while texture profile analysis revealed time-dependent changes in firmness, cohesiveness, and work of cohesion. Droplet-size distributions were measured by microscopy and analyzed under a log-normal model. Results show that xanthan-enriched (≥0.75 XG) emulsions exhibit slower flocculation onset owing to higher zero-shear viscosity, yet eventually become susceptible to coalescence at elevated temperatures (45 °C) and higher oil fractions (≥5 %). Guar-rich systems initially display rapid droplet flocculation (high k_f), forming transient floc structures that undermine long-term stability. An intermediate ratio (0.5:0.5) balances the flexible thickening of guar with xanthan's more robust network, yielding minimized coalescence rates and stable droplet sizes. A depletion-potential model, incorporating polymer layer thickness and osmotic pressure, confirmed that guar-rich blends experience deep negative potentials (≥10³ kB T), indicative of strong depletion flocculation. Taken together, these findings elucidate that formulating avocado oil emulsions demands precise tuning of XG:GG ratios to avoid excessive depletion flocculation while promoting cost-effective, texture-enhancing synergy.