Moisture content and SSC remained essentially constant, while the firmness decreased and pH
increased with maturity. No obvious correlations were found between permittivity and firmness,
moisture content or pH. The linear relationship between surface permittivity and SSC was poor
(R2 < 0.2). The best R2 for linear regression between loss tangent of tissue and SSC and between dielectric
constant of juice and SSC was 0.61 and 0.67, respectively, at 4500 MHz. Further studies are needed to
assess the potential usefulness of dielectric properties for sensing apple maturity or internal quality.