Red Cabbage Extract Contained Sodium Alginate/Poly (Vinyl Alcohol) Nanofibers as  a pH-Responsive Food Packaging

Red cabbage extract is a natural pH indicator, and its use in polysaccharides is applicable to provide smart food packaging. In this study, we investigated the performance of sodium alginate (SA)/poly (vinyl alcohol) (PVA) nanofibers containing red cabbage extract (RCE) prepared by the electrospinning method. The optimum volume ratio of SA: PVA (60:40) and the addition of RCE (2% (w/v)) to the polymeric solution were determined based on morphological uniformity and minimal average diameter of the nanofibers around 212.1 nm and 217.2 nm, respectively. The presence of RCE in the SA: PVA nanofibrous sample was confirmed by appearing stretching carbon double bond at 1648 \({\text{cm}}^{-1}\) ${\text{cm}}^{-1}$ and UV absorption of 310 nm. Moreover, the insertion of RCE in the SA: PVA (60:40) blend nanofibers resulted in increased surface hydrophobicity and significant changes in the crystallinity of the polymers. Eventually, the pH responsibility of the RCE contained SA: PVA nanofibers was evaluated via color alteration against different pH values (2–11). The obtained results revealed that the pH ascending led to a severe color change from light red to purple and then green. These findings showed that the recommended sample has a high potential for use in pH indication applications.