Black Queens of Fruits: Chemical Composition of Blackberry (Rubus subg. rubus Watson) and Black Currant (Ribes nigrum L.) Cultivars Selected in Serbia.

Black fruits, especially blackberries and black currants, are highly appreciated by consumers due to their nutraceutical properties, which have reported health benefits. This study aimed to assess the fruit quality of the blackberry (cv. 'Cacanska Bestrna') and black currant (cv. 'Cacanska Crna') created at the Fruit Research Institute, Cacak (Republic of Serbia) by evaluating basic quality parameters (fruit weight, soluble solids), and content of primary (sugars and organic acids) and secondary (phenolic compounds) metabolites. Additionally, the study examined the quality of frozen and long-term frozen storage (6, 9, and 12 months). The results showed that 'Cacanska Crna' contained a high level of total soluble solids (15.23°Bx), sugars (93.06 mg g-1), and a high index of sweetness (159.48) as well as a high content of acids (34.35 mg g-1) in the fruit. Both species were found to contain forty-seven phenolic compounds, including phenolic acids, flavanols, and anthocyanins, analyzed using high performance liquid chromatography-mass spectrometry (HPLC-MS). 'Cacanska Bestrna' had the highest amounts of phenolic acids (66.85 mg 100 g-1) and flavanols (53.99 mg 100 g-1), whereas 'Cacanska Crna' showed the highest levels of flavonols (8.57 mg 100 g-1) and anthocyanins (139.11 mg 100 g-1). Furthermore, the study revealed that anthocyanins were the most abundant phenolic group in both blackberries and black currants, and their levels remained constant during frozen storage. The sugar content in both species remained unchanged, while the acid concentration increased over time in blackberries but remained consistent in black currants. Overall, the findings highlight the superior phenolic content, particularly anthocyanins, of the cultivars with black fruits selected in Serbia. These cultivars have great commercial potential for the fresh market and processing. Moreover, the study suggests that frozen storage is an effective method for preserving their quality and beneficial properties.