**4. Conclusions**

This work demonstrates the potential to control biocompound release from freeze-dried gellan gum gels by modifying the pH of the substrate during gel formation, and prior to the encapsulation stage. As an exemplar of a relevant biocompound, riboflavin (i.e., vitamin B2) was used.

Freeze-drying kinetics, as well as release mechanisms, were experimentally investigated and modelled. Five different drying kinetics models were discriminated by accuracy and goodness-of-fit using statistical measures (i.e., RMSE, *<sup>R</sup>*<sup>2</sup>*adj*, *AICC* and *BIC*). For samples at natural pH (pH 5.2), the Page model provided the most accurate description of freeze-drying kinetics, while the Wang and Singh model predicted more accurately, the kinetics at acidified pH (i.e., 4 and 2.5).

Results revealed consistent differences in the behaviour of substrates at pH 4. Such differences reflect slower drying and release kinetics, as well as a different delivery mechanism—samples at natural pH (pH 5.2) exhibited Fickian transport, while acidified samples (pH 4) were characterised by an anomalous release mechanism, but with a predominantly Fickian contribution (80–90%).

Overall, this work shows the potential of modified pH freeze-dried gellan gum gel matrices for controlled riboflavin release, demonstrating that:


**Author Contributions:** Conceptualization, V.P., E.L.-Q.; Experimental work and writing, V.P.; Modelling work and writing, E.L.-Q. Supervision and resources, I.T.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by EPSRC gran<sup>t</sup> no. EP/S023070/1.

**Acknowledgments:** Authors acknowledge financial support from the EPSRC Centre for Doctoral Training in Formulation Engineering (grant number EP/S023070/1) as well as support from the Centre's Director, Prof. Fryer.

**Conflicts of Interest:** The authors declare no conflict of interest
