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Abstract
Under the research study, the changes were determined in the quality of persimmon (Diospyros kaki) fruits stored under the shelf life conditions. The following physical parameters were determined: colour, firmness, vegetation index (NDVI), anthocyanins index (NAI), and chemical composition. Also, there were determined the correlations between the selected indices so as to develop rapid methods for assessing the quality of fruits. The research was conducted at the West Pomeranian University of Technology in Szczecin and at the Research Station of the Agricultural University in Plovdiv, Bulgaria, where the fruits of five persimmon cultivars: ‘Sharon’, ‘Moro’, ‘Jiro’, ‘Kaki Tipo’, and ‘Hyakume’ came from. The cultivars were characterized by a varied chemical composition and a variable response to storage. During storage, the fruits became darker (the value of L* parameter decreased from 58.2 to 39.8) and redder (the value of a* parameter increased from 16.8 to 35.0). The firmness of the fruits decreased as did their resistance to mechanical damage. After 6 days of storage, a considerable acceleration was reported of changes in the indices, which characterized the ripening of fruits. The fruits of the ‘Kaki Tipo’ cultivar were the firmest and, at the same time, the most resistant to mechanical damage after the whole storage period. The persimmon fruits of ‘Sharon’ cv. were characterized by good quality parameters and they contained: polyphenols: 308 mg GAE kg-1; L-ascorbic acid: 105 mg kg-1; total acids: 7.84 g kg-1; provitamin A: 0.86 mg·kg-1; and vitamin E: 38.1 mg·kg-1. During storage the acidity level and the content of L-ascorbic acid decreased in the fruits, whereas the content of vitamin E increased. The firmness (r = -0.82) and the colour of fruits (r = – 0.82) turned out to be significantly (p=0.05) correlated with the NDVI vegetation index. A significant (p=0.05) correlation was also reported between the anthocyanic index (NAI) and the content of polyphenols, both at the beginning (r = 0.92) and at the end (r = 0.93) of the storage period. The correlations found confirm the possibility to use non-destructive methods for the assessment of the quality of persimmon fruits.
Keywords
persimmon (Diospyros kaki), fruits, firmness, colour, vitamins, polyphenols, NDVI, NAI