Evaluation of changes in antioxidant compounds of fruit during their ripening and storage using NIR spectroscopy

Changes in contents of polyphenols and ascorbic acid were evaluated in apples (‘Rubinola’), peaches (‘Redhaven’) and tomatoes (‘Dagmar’) during their ripening and storage. The main harvest criteria were tissue firmness, fruit colour and starch content. Each fruit was measured by a NIR spectrophotometer at harvest. The content of ascorbic acid was measured in each fruit by high performance liquid chromatography (HPLC). Folin-Ciocalteau method was used for the spectrophotometric analyses of the total content of polyphenols. Results were matched to the corresponding spectra and then the calibration arrays were developed. In the course of the storage period, fruit samples were evaluated using these arrays. Fruit were stored at 4°C in normal air atmosphere. All fruit types were stored in the same conditions. The peaches were stored 36 days and every 4 days their spectra were measured by the same method (NIR). Tomatoes were stored for up to 32 days and fruits were measured every 4th day. Apples were stored for 105 days and their spectra were measured every 7th day. The NIR spectroscopy method was used to analyse 25 samples of fruit at a time. In apples, the content of polyphenols went descending continuously during the period of ripening and storage while that of ascorbic acid slightly increased. In tomatoes, contents of polyphenols and ascorbic acid during the period of ripening increased by two-fold. There was a slight increase of polyphenols during storage. In the course of storage, the content of ascorbic acid slightly decreased. The content of polyphenols in peaches increased gradually during the ripening period, while a decrease was monitored when fruits were over ripened or after cold storage. The content of ascorbic acid went slightly descending with the progress of ripening.