Currently, there is a general trend towards reutilizing industrial by-products that would
otherwise be discarded or considered as waste, aiming to explore them as alternative sources of
valuable compounds. The apple pomace remaining from cider and apple juice industries represents
a high-potential source of bioactive compounds with putative application in food or pharmaceuticalrelated
products. Accordingly, the work reported herein was conducted to characterize the phenolic
compounds in apple pomace from Belgium and Spain, as well as to evaluate its chemical composition
and particular types of bioactivity. As a proof of concept, a new hydrogel was prepared, incorporated
with the bioactive compounds and pectin extracted from apple pomace, aiming to obtain the most
organic formulation possible. Independently of the extracting agent, it became evident that using
lyophilization as the drying step is a better choice than thermal processes as it yielded a richer phenolic
profile (fifteen individual compounds), with 5-O-caffeoylquinic acid as the major compound (66 to
114 mg/100 g dw) in Belgian samples. In general, the hydroethanolic extracts showed the strongest
antioxidant and antimicrobial (particularly against Propionibacterium acnes: MIC = 2.5 mg/mL)
activities. This result, together with the lipid nature of human skin, led it to be chosen as the extract
type to be incorporated in the hydrogel. In general, apple pomace stood out as a valuable source of
bioactive compounds, especially polyphenols and pectin, with good potential to be incorporated in
dermal formulations.
This research was funded by Foundation for Science and Technology (FCT, Portugal)
through national funds to CIMO (UIDB/00690/2020), the institutional scientific employment program contract for L. Barros and M.I. Dias and through the individual scientific employment program
contract for J. Barreira. Research was also funded by the FEDER Interreg España–Portugal program
through the project TRANSCoLAB 0612_TRANS_CO_LAB_2_P and by the ERDF through the
Regional Operational Program North 2020, within the scope of project Mobilizador Norte-01-0247-
FEDER-024479: ValorNatural® and Project GreenHealth-Norte-01-0145-FEDER-000042.
