| Summary: | A relatively new, non-destructive, method for the assessment of optimal blueberry fruit maturity directly on the plant uses a DA-meter (delta absorbance) to measure chlorophyll absorbance (I<sub>AD</sub>). Here, ‘Aurora’ fruit quality parameters (peel color, fruit firmness), chemical composition (individual sugars, organic acids and phenolics) and the relative expression of anthocyanidin synthase (ANS) genes were examined at four different maturity stages (immature, light purple, darker purple, fully ripe). All observed parameters changed significantly during ripening and sometimes exhibited high correlation with I<sub>AD</sub> values, as R<sup>2</sup> values ranged between 0.61 and 0.97. Peel lightness (L*), chroma (C*), fruit firmness and organic acids significantly decreased during ripening, while sugars, sugar/organic acid ratio, total phenolics and relative expression of ANS significantly increased. The current study is the first to determine I<sub>AD</sub> values during different maturity stages of ‘Aurora’ fruit using a DA-meter and to evaluate their correlation with the most commonly used quality parameters of ripe fruit, fruit chemical composition and relative expression of ANS.
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