Encapsulation of β-carotene into food-grade nanofibers via coaxial electrospinning of hydrocolloids: Enhancement of oxidative stability and photoprotection

Εncapsulation of β-carotene in two different food hydrocolloid matrices, pure pullulan (PUL) and its blend with whey protein isolate (WPI) at a weight ratio of WPI:PUL 30:70, via coaxial electrospinning, was investigated. Τhe encapsulation efficiency of β-carotene in the generated WPI:PUL (30:70 w/w) and PUL nanofibers has reached up to ∼90% and ∼95%, respectively. Among the various operating parameters examined, the factor which had the greatest impact on encapsulation efficiency was the oil-β-carotene solution (core material) flow rate. More uniform thread-like nanofibers were obtained using pure pullulan as wall material, while the WPI:PUL (30:70 w/w) blend resulted in formation of nanostructures with bead-shaped morphologies periodically along the fiber axis. The β-carotene degradation kinetics followed an apparent first-order reaction model, showing highest values of the rate constants at an intermediate water activity level (aw = 0.53) for all matrices and storage temperatures (25 °C, 35 °C, 45 °C) examined. The degradation kinetics did not seem to be directly related with the molecular mobility of the fiber polymeric components (i.e., physical state of the amorphous wall material), as β-carotene losses were evident even at temperatures below their glass transition temperatures (Tg). The electrospun WPI:PUL nanofibers were more suitable as carriers in delaying oxidation of β-carotene under different storage temperatures, aw levels and exposure to UV–Vis irradiation, compared to pure PUL. Overall, the coaxial electrospinning process using the mixture of WPI:PUL (30:70 w/w) as an encapsulation vehicle appears to be an effective technique to fabricate functional foods or dietary supplements enriched with β-carotene.