Optimised ultrasound-assisted alkaline extraction and rheology of chia mucilage with co-solutes

Chia mucilage is a promising food additive with applications in food systems. However, its attachment to seeds hinders the extraction and utilisation of the mucilage. Therefore, the study aims to optimise chia mucilage extraction using ultrasound and alkaline treatment to enhance yield, hue angle, and apparent viscosity and evaluate its rheological behaviour in the presence of co-solutes (sucrose and sodium chloride). Chia seeds were dispersed in distilled water, and the suspension was modulated to various pH values (7-9) in an ultrasound bath at varying temperatures (50-70 °C) and duration (30-60 minutes). Response Surface Methodology identified the optimum conditions (67.2 °C, 32.7 minutes, pH 9), yielding 79.62% with a hue angle of 74.79° and viscosity of 0.82 Pa.s. The optimised (M2) chia mucilage solution (CMS) was validated and showed higher yield and hue angle than the macerated (M1) samples. Rheological evaluation with incorporation of sucrose (0-20%) and NaCl (0-250mM) showed non-Newtonian pseudoplastic behaviour, with 20% sucrose exhibiting the lowest k value in M1, yet the highest in M2. The relatively stable consistency coefficient value in M2, despite the addition of sucrose from 1 to 20%, indicates the suitability of ultrasonication and alkaline pH during the extraction process. Moreover, the addition of salt exerted a significant negative effect on the apparent viscosity of M1 samples while exerting the opposite effect on M2 CMS. These findings demonstrate that ultrasound-assisted alkaline extraction improves both yield and functional stability of chia mucilage, and its rheological properties were strongly influenced by sucrose and salt concentrations, indicating strong potential as a functional food hydrocolloid for diverse food formulation applications.

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