Ultrasound assisted extraction modeling of fructans from agave (Agave tequilana Weber var. Azul) at different temperatures and ultrasound powers

• Ultrasound treatment increased the extraction of water soluble carbohydrates from agave.
• Ultrasound treatment at low temperatures resulted in significant fructan extraction.
• Thermal and ultrasound treatment caused agave cell-wall disruption.
• Mass transfer parameters were increased mainly by the sonication treatment.
• A general model to predict the fructans ultrasound-assisted extraction was developed.

The effect of ultrasound power and temperature on the extraction of carbohydrates from agave was evaluated. Extraction kinetics of fructans (F), total carbohydrates (TC) and reducing sugars (RS) were obtained at different ultrasound powers (28–49 mW/mL) and temperatures (20–40 °C). The mass transfer coefficients of F, TC and RS were calculated and a model using the production functions of Cobb–Douglas was developed. Microstructural analysis was performed to evaluate the effect of ultrasound and temperature on carbohydrates extraction. Ultrasound and temperature had impact on F, TC and RS extractions. After 5 min, no increases in carbohydrates content were observed, showing an asymptotic tendency. Results showed a strong sonication effect in carbohydrate extraction at any extraction temperature. The maximum F, TC and RS contents were 7.2, 7.79 and 0.54 g/100 g d.m., respectively, at 49 mW/mL and 40 °C. The fructans volumetric mass transfer coefficients ranged from 0.0585 ± 4.2 × 10−4 to 0.0834 ± 12.51 × 10−4 s−1 (R2 = 0.86–0.92). An overall model was developed based on the Cobb–Douglas function, which was adjusted adequately to estimate the fructans extraction assisted with ultrasound (R2 = 0.954). Tissue structural changes were present due to cell-wall modifications and breakdowns of sonicated agave samples, which have enhanced the carbohydrates extraction.

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