Encapsulation of blackberry anthocyanins (Rubus spp.) in hydroxypropylmethylcellulose nanofibers using electrospinning technology

Blackberry ( Rubus spp., cv. BRS Cainguá) is a significant source of anthocyanins, especially cyanidin-3-glycoside, compounds recognized for their antioxidant activity, but with limited stability against environmental factors. This study aimed to incorporate blackberry anthocyanins into HPMC nanofibers obtained by electrospinning, with a view to obtaining a nanostructured material capable of preserving the bioactive fraction. Nanofibers were produced without extract (control) and with 5–20% (w/w) extract incorporation. The samples were characterized in terms of morphology, thermogravimetric properties, functional groups, wettability, and antioxidant capacity. The nanofibers presented homogeneous morphology and average diameters between 101 and 191 nm. FT-IR spectroscopy indicated intermolecular interactions between the hydroxyl groups of HPMC and anthocyanins, resulting in encapsulation efficiencies greater than 95% for concentrations up to 15%. TG/DSC analyses showed that encapsulation increased the initial degradation temperature of the extract from 135 °C to 173–175 °C (approximately 30%) and altered the thermal profile, indicating interactions with the HPMC matrix and improved thermal stability. The incorporation of the extract increased the hydrophilicity of the membranes, as reflected in the reduction of the contact angle, although antioxidant activity increased with extract concentration, nanofibers showed lower values than the free extract, suggesting reduced immediate bioactive compound availability due to encapsulation. PCA indicated that the formulation with 15% extract presented the best balance between structural stability and bioactivity. The results demonstrate that HPMC nanofibers incorporated with blackberry anthocyanins constitute a promising system for application as a functional ingredient.