*2.3. Freeze Drying*

The riboflavin-loaded gels were frozen at −20 ◦C for 24h and then freeze-dried at increasing processing times, from 2 h up to 18 h, in a bench top freeze dryer (SCANVAC Coolsafe ™, model 110-4, Lynge, Denmark) with condenser temperature of −110 ◦C and chamber pressure of 10 Pa [14]. The experiments were performed in triplicates, and each batch of freeze-dried samples was weighted to measure the water content.

#### *2.4. Water Activity Analysis*

Water activity (a w) of wet and dried gels was measured using an AquaLab ® dew point water activity meter (model 4 TE, Decagon Devices Inc., Pullman, WA, USA). The temperature-controlled sample chamber was set to 25 ◦C [14,15]. All analyses were carried out in triplicate.

#### *2.5. Vitamin Release Experiments*

Vitamin delivery analyses were performed using a UV–Vis spectrophotometer (Orion Aquamate, Thermo Scientific, UK) at 444 nm. The loaded gels were placed in stirred (250 rpm) distilled water (200 mL) at room temperature. To measure vitamin release, aliquots of 3 mL were withdrawn from the

release medium, analysed with the spectrophotometer and poured back into the release medium. The vitamin content in the release medium was then expressed as normalised vitamin release (NVR), a dimensionless quantity defined as:

$$NVR = \frac{V(t)}{V\_{total}}\tag{1}$$

All analyses were carried out in triplicate.
