Anthocyanin profiles and biological properties of caneberry (Rubus spp.) press residues.

Background: The global interest in natural food colours shows increasing attention towards new product development to replace synthetic colourants, because of the strengthening of legislative rules and consumer awareness of synthetic additives and chemicals in food. This study was designed to evaluate anthocyanin content and biological activities of press residues from four caneberries: two raspberry (Rubus idaeus, cv. 'Meeker' (RM) and 'Willamette' (RW)) and two blackberry (Rubus fruticosus, cv. 'Thornfree' (BT) and 'Čačanska bestrna' (BC)) cultivars.

Results: Analysis by high-performance liquid chromatography-diode array detection-electrospray ionization-tandem mass spectrometry identified cyanidin glycosides in all press residues, cyanidin 3-glucoside being prevalent in BC (1360.6 mg kg(-1)) and BT (1397.7 mg kg(-1)), and cyanidin 3-sophoroside in RM (349.2 mg kg(-1) ) and RW (581.0 mg kg(-1)). Antioxidant capacity (AC), evaluated by ABTS (2,2'-azino-bis(3-ethyl benzothiazoline-6-sulfonic acid) assay, reducing power (RP) and α-glucosidase inhibitory potential (α-GIP) was higher in blackberry press residues. Total anthocyanin content was in good correlation with AC (r = 0.953; P < 0.05), RP (r = 0.993, P < 0.01) and α-GIP (r = 0.852, P < 0.15).

Conclusion: This study has revealed the potential for valorization of juice production byproducts for further industrial use as a rich source of bioactive compounds and natural colourants (mainly anthocyanins). Also, they can provide health-promoting effects beyond their general organoleptic acceptance in food product development.