Evaluation of kinetics and estimation of temperature-dependent mass transfer coefficients for pectin extraction from watermelon rind

Background: Understanding how biopolymers are extracted and
creating accurate models for these processes represents a
fundamental advancement in optimizing extraction techniques.
Objective: This research focused on examining the kinetics of
extraction and evaluating mass transfer coefficients during the
production of pectin from watermelon rind.
Materials and Methods: Pectin was extracted using a standard
acid-based approach at three temperatures (70, 80, and 90 °C) over
several time intervals (15, 30, 45, 90, and 120 minutes). The
experimental design enabled analysis of extraction kinetics via a
second-order kinetic model and estimation of essential mass
transfer parameters. Results: The highest pectin yield obtained was
17.45%, observed at 90 °C after 90 minutes. All experimental
conditions yielded high-purity pectin, with galacturonic acid
content consistently above 79%. Analysis of mass transfer and the
Biot number indicated that internal resistance was the controlling
factor under the applied conditions. Models derived from Fick’s
second law were effectively applied to determine the effective
diffusion coefficient, and experimental data provided a reliable
basis for calculating pectin extraction rates. The effective diffusion
coefficient was varied between 1.82 × 10⁻¹⁴ and 4.19 × 10⁻¹⁴ m²/s
across all three-temperature studied.
Conclusion: Temperature significantly influences extraction rates
and modifies mass transfer coefficients. This study confirms that
pectin extraction using the conventional method is mainly
controlled by intra-particle diffusion mechanisms.