## 3 Results and Discussion  
### Preparation and PXRD Analysis  
The solids (CT_MA and CT_TA) were prepared through the slurry process in ethanol, to obtain multifunctional solid mixtures, in which the properties of the single components remain unchanged. In particular, MA and TA were chosen for their baking activity, whereas catechin was selected for its well-known antioxidant properties [40]. Therefore, in analogy with the well-known studies of drug-excipients compatibility [41; 42] physical and chemical interactions between the single components within the CT_MA and CT_TA solid mixtures are undesired since they could affect the individual properties. The commercially available CT, according to its characteristic PXRD profile (Figure 2, black line), consists in the \(\beta\)-monohydrate form, which, unfortunately, displays poor water solubility [23] and therefore poor bioavailability. However, it is well known that water recrystallization of CT in its \(\beta\)-monohydrate polymorph can induce a phase transition into the tetrahydrate form [24]; moreover, additional catechin polymorphs, with different water solubility, have been observed, including several hydrates [25], an anhydrous form and methanol solvate form. On this basis, before preparing the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Descriptor** & **Definition** \\ \hline \multirow{4}{*}{**Appearance**} & Glossy & Presence of glossy crust \\  & Embrowned & Presence and intensity of crust browning \\  & Open surface & Irregularities and openings in crust surface \\  & Arched & Shape of muffin top surface \\ \hline \multirow{2}{*}{**Olfactory**} & Typical flavor & Product typical flavor intensity \\  & Sweet flavor & Sweetness intensity \\ \hline \multirow{4}{*}{**Taste**} & Typical taste & Product typical taste intensity \\  & Intensity & General taste intensity \\  & Sweet taste & Sweet taste intensity \\  & Caramel & Caramel taste intensity \\  & Bitter & Bitter taste intensity \\  & Aftertaste & General aftertaste intensity \\ \hline \multirow{4}{*}{**Texture**} & Adhesiveness & Adhesion rate to mouth during test \\  & Toughness & Chewing resistance rate \\ \cline{1-1}  & Dryness & Dry mouthfeel impression \\ \cline{1-1}  & Bubbling & Presence of empty areas inside product \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Muffin sensory descriptor list. baking powders formulation, the flavonoid \(\beta\)-monohydrate polymorph was slurred individually in ethanol, with the aim of investigating if a polymorphic transition occurs and, eventually, which solvate and/or hydrated form is generated. The eventual formation of the ethanol solvate would represent a great improvement in the CT bioavailability, since, according to the general rules of polymorphs solubility [26] the ethanol solvate should be more soluble than the monohydrate phase. The resulting microcrystalline powder was analyzed through Powder X-Ray Diffraction, in order to determine the eventual CT structural modification induced by the slurry process. Indeed, the PXRD profile of CT after slurry in ethanol is found different from that of the \(\beta\)-monohydrate form, indicating the occurred solid state phase transition (Figure 2, red line). However, the new PXRD pattern corresponds to the tetrahydrate form of catechin [23], excluding the formation of a new ethanol solvate form. It is important to highlight that the tetrahydrate form of catechin displays higher water solubility than the \(\beta\)-monohydrate. Since, to the best of our knowledge, water solubility quantitative measurements of the catechin tetrahydrate form have never been reported, the water solubility of the obtained resulting powder was measured and compared with that of the \(\beta\)-monohydrate form; in particular the solubility values in water are 4.6 mg mL\({}^{-1}\) for catechin \(\beta\)-monohydrate and 8.0 mg mL\({}^{-1}\) for catechin tetrahydrate.