Comparative characteristics of some complex indicators of the degree of apple fruit maturity in determining the technical degree of maturity for juice

Currently, there are no direct methods for determining the degree of fruit maturity, and researchers use complex indicators that take into account several parameters. The purpose of our work was to give comparative characteristic to some complex indicators of apple fruit maturity when determining technical degree of a maturity for juice and to define the most reliable. The article presents data of the comparative study of integrated indicators of the degree of apple fruit maturity - Strerf index, Yager index and FARS index, which was conducted on 11 apple varieties breeding in the All-Russian Research Institute of Fruit Crops Breeding when determining the technical maturity for juice. The studied apple varieties were of various terms of maturing, immune to scab and included in the State register of breeding achievements admitted for use. As control variety was used the Antonovka Obyknovennaya, everywhere widespread in fruit plantations and widely used in processing. When calculating Streif index, Yager index and FARS index we used the following parameters: firmness (density) of pulp, starch-iodine index, total soluble solids, total titratable acidity. It has been found that the Streif index and FARS index in most varieties had the same value (0.1) at the maximum juice yield, characterizing the optimal technical degree of maturity for the juice. The Yager index was characterized by high lability of the values of optimal technical degree of fruit maturity for juice - on the average, from 1.2 in ‘Veniaminovskoye’ and to 3.9 in ‘Orlovim’ varieties. The average values of the Streif index, Yager index and FARS index during the studies were 0.12, 2.12 and 0.10, respectively. On the basis of the obtained data, the most reliable indicators of the technical degree of maturity of apple fruit for juice should be considered complex indicators of fruit maturity: the Streif index (0.10) and FARS index (0.10).

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