Photoprotection of folic acid upon encapsulation in food-grade amaranth (Amaranthus hypochondriacus L.) protein isolate - Pullulan electrospun fibers

•Folic acid was encapsulated in amaranth protein isolate:pullulan matrices.•Electrospinning was the encapsulation technique used.•Very high encapsulation efficiency was obtained (>95%).•Encapsulation led to enhanced folic acid thermal stability.•The biopolymer matrices also protected folic acid from UV photodegradation.

In this work, the ability of amaranth protein isolate (API):pullulan structures obtained through electrospinning for the photoprotection of bioactive compounds was studied. The model bioactive compound encapsulated was folic acid, due to its great sensitivity to UV light exposure. Addition of 100 mg of folic acid per g of biopolymer to the biopolymeric solution used for electrospinning resulted in increased apparent viscosity and, thus, in thicker electrospun fibers. Very high encapsulation efficiency was obtained (>95%) using this encapsulation technology and no specific chemical interactions were established between the vitamin and the matrix materials as inferred from FTIR analysis. Encapsulation within the API:pullulan structures increased thermal stability of folic acid, which may be useful for food processing applications. Furthermore, no degradation of the encapsulated compound was observed after 2 h of UV exposure, while the characteristic UV-Vis spectrum from the photodegradation compounds of folic acid was observed after UV irradiation of the unprotected vitamin.