Biochemical composition of berries of some kolomikta kiwi (Actinidia kolomikta) cultivars and detection of harvest maturity

The so called climacteric period with rapid and complicated changes of biochemical composition and skin firmness is characteristic of the berries of Actinidia kolomikta during their maturation. When these changes occur, the suitability of berries for even short-time storage is reduced. The highest content of ascorbic acid in the berries of cultivars 'Lande', 'Pavlovskaja' and 'VIR-1' was found in unripe berries (1120, 840 and 1530 mg/100 g respectively). Later the content decreased at the beginning of maturity (790, 630 and 1020 mg/100 g respectively), and dropped even further in the berries at their full biological maturity (700, 600 and 850 mg/100 g respectively). The percentage of dry soluble solids (DSS) at the beginning of the berry maturity was 10.0, 9.0 and 10.5%, but in berries at their biological maturity it increased to 15.9, 16.2 and 16.0% respectively. Studies of skin firmness (SF) showed that up to the beginning of maturity there are no considerable differences but SIT decreases rapidly when ripening begins. Berries should be picked during the technical maturity phase because they get soft rapidly and their skin starts to break. The main characteristics to decide the optimal harvesting time should be SIT (230-320 N/cm(2)) and the amount of DSS (9-11 degrees Brix). The determination of the beginning and the end of the phenological phases showed that the technical maturity of mid-season kolomikta kiwi cultivars 'Lande', 'Pavlovskaja' and 'VIR-1' starts approximately 5866 days after their full bloom.