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Sensors 2016, 16(5), 661;

Determination of the Optimum Harvest Window for Apples Using the Non-Destructive Biospeckle Method

Faculty of Production Engineering, Department of Mechanical Engineering and Automatics, 28 Głęboka St 20-612 Lublin, Poland, University of Life Sciences, Akademicka 13, 20-950 Lublin, Poland
Institute of Agrophysics, Polish Academy of Sciences, Doswiadczalna 4, 20-290 Lublin 27, Poland
Research Institute of Horticulture, Pomologiczna 18, 96-100 Skierniewice, Poland
Author to whom correspondence should be addressed.
Academic Editor: Simon X. Yang
Received: 16 March 2016 / Revised: 29 April 2016 / Accepted: 3 May 2016 / Published: 10 May 2016
(This article belongs to the Special Issue Sensors for Agriculture)
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Determination of the optimum harvest window plays a key role in the agro-food chain as the quality of fruit depends on the right harvesting time and appropriate storage conditions during the postharvest period. Usually, indices based on destructive measurements are used for this purpose, like the De Jager Index (PFW-1), FARS index and the most popular Streif Index. In this study, we proposed a biospeckle method for the evaluation of the optimum harvest window (OHW) of the “Ligol” and “Szampion” apple cultivars. The experiment involved eight different maturity stages, of which four were followed by long cold storage and shelf life to assist the determination of the optimum harvest window. The biospeckle activity was studied in relation to standard quality attributes (firmness, acidity, starch, soluble solids content, Streif Index) and physiological parameters (respiration and ethylene emission) of both apple cultivars. Changes of biospeckle activity (BA) over time showed moderate relationships with biochemical changes during apple maturation and ripening. The harvest date suggested by the Streif Index and postharvest quality indicators matched with characteristic decrease in BA. The ability of biospeckle method to characterize the biological state of apples was confirmed by significant correlations of BA with firmness, starch index, total soluble solids and Streif Index, as well as good match with changes in carbon dioxide and ethylene emission. However, it should be noted that correlations between variables changing over time are not as meaningful as independent observations. Also, it is a well-known property of the Pearson’s correlation that its value is highly susceptible to outlier data. Due to its non-selective nature the BA reflected only the current biological state of the fruit and could be affected by many other factors. The investigations showed that the optimum harvest window for apples was indicated by the characteristic drop of BA during pre-harvest development. Despite this, at the current state of development the BA method cannot be used as an indicator alone. Due to rather poor results for prediction in OHW the BA measurements should be supported by other destructive methods to compensate its low selectivity. View Full-Text
Keywords: biospeckle; apple; maturity index; Streif; optimum harvest window; postharvest quality biospeckle; apple; maturity index; Streif; optimum harvest window; postharvest quality

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Skic, A.; Szymańska-Chargot, M.; Kruk, B.; Chylińska, M.; Pieczywek, P.M.; Kurenda, A.; Zdunek, A.; Rutkowski, K.P. Determination of the Optimum Harvest Window for Apples Using the Non-Destructive Biospeckle Method. Sensors 2016, 16, 661.

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