The agro-food industries are responsible for the creation of vast amounts of by-products. With sustainability in mind, the valorisation of these residues is of the utmost importance. One of the many ways these residues can be valorised is by extracting bioactive compounds, namely phenolic compounds¹. These compounds are abundant in plants and have remarkable bioactivities, namely antioxidant activity. Hence, they are much sought after in several industries, such as the nutraceutical, cosmetic and biomedical industries².

The aim of this work was to extract phenolic compounds from several types of by-products from different agro-food industries and quantify their antioxidant activity through TPC, DPPH^•, and ABTS^•+ scavenging activities, and FRAP assay. The highest extraction yields obtained were for the pineapple core (64.70%), oat concentrate (59.92%), and mango peel (55.65%). The post-distillation residue of Cistus ladanifer L. stems and leaves and spent coffee grounds were the samples presenting the highest TPC values (134.64 ± 14.73 - 201.16 ± 4.02 mg gallic acid/ g dry extract), as well as those displaying the strongest DPPH^• (569.64 ± 78.08 - 831.04 ± 92.51 mg TROLOX eq/ g dry extract) and ABTS^•+( 1060.99 ± 173.59 - 2998.99 ± 353.70 mg TROLOX eq/ g dry extract) scavenging activities. For the FRAP assay, the highest values obtained were for the spent coffee ground, frozen coffee silverskins, and dried Stevia rebaudiana Bertoni (22.32 ± 3.25 - 86.06 ± 5.74 μmol ascorbic acid eq/ g dry extract).

The results obtained offer valuable information that demonstrates the potential for valorisation of these by-products.

References

1. Gil-Martín, E. et al. Influence of the extraction method on the recovery of bioactive phenolic compounds from food industry by-products. Food Chemistry 378, 131918 (2022).
2. Alara, O. R., Abdurahman, N. H. & Ukaegbu, C. I. Extraction of phenolic compounds: A review. Current Research in Food Science 4, 200–214 (2021).