Characterize Firmness Changes of Nectarine and Peach Fruit Associated With Harvest Maturity and Storage Duration Using Parameters of Force–Displacement Curves

Fruit firmness is a critical attribute for evaluating the quality of peaches and nectarines. The precise measurement of fruit firmness plays a key role in maturity assessment, determining harvest periods, and predicting shelf-life. Texture analyzers are increasingly employed for accurate fruit firmness measurement, offering advantages in reducing operator errors compared to the traditional Magness–Taylor test. However, the parameters defining firmness vary across the literatures. To optimize the parameter(s) for characterizing the firmness of peaches and nectarines, we evaluated 31 parameters derived from force–displacement curves using fruit with various maturity levels and storage durations. Our findings affirmed that the conventional Magness–Taylor measurement effectively delineated firmness changes associated with varying maturity levels, while its ability to capture firmness changes due to storage duration was constrained. On the contrary, parameters extracted from the steady phase (P2), which depict flesh properties after penetrating to a specified depth, exhibited strong performance across diverse maturity stages and storage durations. As effective firmness characterization parameters should differentiate various sample groups based on both maturity and storage duration criteria—pivotal factors influencing softening, the P2-derived parameters are thus deemed more appropriate for firmness characterization. Given the stability of the steady phase (P2) within the force–displacement curve and the high correlation among the P2-derived parameters, it is more recommended to use the end force value of P2, corresponding to the force value at 10 mm depth to represent the firmness of peaches and nectarines.