Moreover, the non-use of degreening often meets an objective of differentiation via superior organoleptic quality, as described by Belmin et al. This is particularly the case with organic farming products ( European Union, 2007) which prohibit the use of chemical synthesis products. In some specialized sectors, producers avoid or can’t use ethylene degreening and harvest fruit when orange color is naturally reached on the tree. In many citrus sectors, post-harvest degreening (ethylene application in a controlled atmosphere chamber) is used to artificially accelerate the coloration of green harvested fruit ( Porat, 2008). In this context, citrus fruits are often not accepted by consumers because they are considered too green, even though internal quality is obtained ( Zampini et al., 2008). In many cases, the internal maturity of citrus fruit is reached before external maturity ( Lado et al., 2014 Qin et al., 2015 Deshmukh et al., 2016). However, in citrus fruit, internal and external maturities are not always obtained simultaneously. Clementine can only be sold when all three criteria are met. In the case of clementine ( Citrus clementina hort, ex Tanaka), the commercial maturity of fruit is defined by the United Nations Economic Commission for Europe Standard FFV-14 Citrus Fruit ( United Nations, 2017), based on several criteria: orange epidermis on at least one third of the surface, minimum juice content of 40% and minimum sugar/acid ratio (E/A) of 7. To be marketed according to international standards, fruit must meet many quality criteria concerning their external visual aspects (color, texture, size, etc.) and their internal characteristics (sugars, acidity, juice, etc.). The fruit acidity model obtained in this study will be extended to a practical application tool to predict fruit acidity and quality for a better-controlled harvest management. Our results show that: (i) the dynamics of acidity drop during maturation are similar from one plot to another but staggered in time (ii) fruit coloring occurs at different times during acidity drop (iii) the synchronization between the coloring process and acidity drop determines both the quality of harvested fruit and the period during which orchards are harvestable, which we called the “harvestability window.” This study sheds new light on the quality of citrus harvested without fruit degreening and leads to propose actions to anticipate internal maturity evolution according to the coloring and spreading of the harvest period. Our study was based on a monitoring of the color and acidity of Protected Geographical Indication “Clémentine de Corse” orchards of producers in 20. However, for some sectors where degreening is not authorized, such as organic farming or up-market, it is important to understand the co-occurrence between fruit coloration and internal ripening, and its impact on fruit quality and harvesting management. On citrus, the internal maturity of fruit is often reached prior and independently to their external maturity, inducing the use of degreening practices to artificially color fruit. The commercial quality of fruit is the result of a combination of internal (acidity, sugars, juice, etc.) and external characteristics (shape, size, color, visual defects, etc.). 3UMR SADAPT, National Institute for Agricultural Research, AgroParisTech, Thiverval-Grignon, France.2Research Laboratory on Livestock Development, National Institute for Agricultural Research, Corte, France.1UE Citrus, French National Institute for Agricultural Research, San-Giuliano, France. Laurent Julhia 1*, Raphaël Belmin 2†, Jean-Marc Meynard 3, Olivier Pailly 1 and François Casabianca 2
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