Impact of freezing and freeze-drying processes on changes in phytochemicals and antioxidant capacity of blackberry fruit

Blackberry (Rubus subg. Rubus Watson) is highly valued for its nutritional properties, which may be linked to its high content of primary and secondary metabolites. This study evaluates the effect of freezing and freeze-drying processes on the phytochemical content and antioxidant capacity of the ʻČačanska Bestrna’ blackberry cultivar, comparing these changes with the quality of fresh blackberry fruit. Primary metabolites, including soluble solids content (SSC), total and reduced sugars (TS, RS), total sucrose (TS), and total acids (TA) content, were determined in freeze-dryed, frozen and fresh blackberry fruits. Among the secondary metabolites, the content of total phenolics (TPC), and total anthocyanins (TAC) was analyzed as phytochemicals responsible for the antioxidant capacity of the fruit, which was also determined using the DPPH method. The results showed that the applied preservation methods positively affected the examined fruit parameters. Freeze-dried blackberry fruits showed superior levels of SSC (90.63%), TS (52.25%), RS (45.83%), and TA (6.10%) compared to frozen and fresh fruits. TPC values did not demonstrate significant variations between the two preservation methods and fresh fruit. In this regard, further research should be focused on increasing the efficiency of preserving beneficial phytonutrients in final blackberry products that are essential for human health, thereby ensuring better quality and high nutritional value.