INTERNAL BROWNING IN 'KANZI®' APPLES - REASONS AND POSSIBILITIES TO REDUCE THE DISORDER

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‘Kanzi’® (‘Nicoter’) apple shows a high sensitivity to internal browning disorders during CA-storage. To investigate the reasons and to develop optimal storage conditions for the ‘Kanzi’ apple, storage experiments have been carried out for five 5 years. Fruit were picked from different orchards at up to four different harvest dates. After harvest apples were stored at various temperatures (1, 2, 3 or 5°C), and at different O2- (1 and 3 kPa) and CO2-partial pressures (0.7, 1.5, 2.0 and 3.0 kPa). In addition, a delayed establishment of CA conditions (7 or 21 days) was compared with a CA, employed immediately after harvest. After 4 to 8 months storage plus 7 d shelf-life at 20°C the influence of the tested factors on storability and fruit quality attributes (firmness, TA, TSS and skin colour) as well as on the incidence of browning disorders was investigated. Mineral analyses were carried out to find possible correlations between the mineral status of the fruit and the occurrence of internal browning. Results showed that ‘Kanzi’ apple is very sensitive to low temperatures and to increased CO2 partial pressure during CA storage. Apple stored at 3°C showed significantly less incidence of internal browning compared to fruit from 2 or 1°C, respectively, without having a negative influence of the increased temperature on fruit quality attributes. In a similar manner, increasing CO2 partial pressure (>1.5 kPa) led to an increase of the browning symptoms compared to apple stored at 0.7% CO2. The application of delayed CA-conditions did not show any positive effect in reducing the symptoms, but the sensitivity for internal browning was significantly increased with later harvest dates. Fruit mineral status did not appear to be correlated with sensitivity to internal browning symptoms. For ‘Kanzi’ apples, from the Lake Constance region, storage temperatures of 3°C, 1 kPa O2, E‚1 kPa CO2 and a CA start immediately after room filling seem to be suitable to reduce the occurrence of internal browning and to maintain fruit quality during long term storage.