Evaluation of Streif’s Index Values During Maturation of Two Apple Cultivars

Abstract

The paper presents the results of Streif’s Index (SI) expression by new method of harvest date optimization, based on calculation one of its components - starch index (S), by image analysis. Harvest date prediction is a crucial factor in apple storage and subsequent shelf life, making it the main factor of product optimization. Apple fruits (Gloster and Rubin) after harvest were subjected to measurements of firmness, extract, and calculation of starch degradation as the main indicators of fruit storage suitability. The work presents basic changes of maturity indicators to assess credibility of its value in various stages of ripening. The results present that the use of precise digital image analysis reduces inaccuracies of Streif’s Index to more test limits set. Streif’s index value in the range of 0,7 – 0,8 for Rubin apples and 3 – 4 for Gloster, at which harvest of fruits is recommended, was obtained at different harvest dates for image analysis results based on different image filtration thresholds. This type of image analysis inaccuracies emerged as the main factor of SI deviations.