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

Anna Skic,Monika Szymańska-Chargot,Andrzej Kurenda,Monika Chylińska,Artur Zdunek,Piotr Pieczywek,Beata Kruk,Krzysztof Rutkowski

doi:10.3390/s16050661

Abstract

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.

Highlights

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 [1,2,3,4,5,6]
Determination of titratable acidity is rarely used in commercial practice, it is usually performed in research projects evaluating storage conditions [8,44]
Apples harvested at the 6th picking date showed the best storage capabilities, which was indicated by the smallest decrease in firmness

Summary

Introduction

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 [1,2,3,4,5,6]. When apples are harvested immaturely they do not develop their full ripeness after storage, which leads to a small size, poor fruit colour, sour and starchy flavour and a weak aroma. They are more susceptible to scald, bitter-pit and internal breakdown. Apples harvested when over-mature are vulnerable to mechanical injury and disease, and sensitive to low temperature breakdown or watercore [11]. All these physiological processes take place even under optimum conditions, which complicates storage [12,13]. Determination of the optimum harvest date (OHD) is a crucial issue for growers to ensure the high post-storage apple quality expected by consumers

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Results

Discussion

Conclusion