3.2.2. Reduced Scattering Coefficient

Compared with absorption coefficient, the reduced scattering coefficient displays different changing patterns in the spectral region of 905–1600 nm (Figure 3c,d). The μ- *s* spectral was flatter and steadily decreased with increasing wavelength. In addition, the μ*'s* spectral changed consistently as storage time progressed, which was in accordance with studies of He et al. [28] and Cen et al. [31]. The scattering coefficient at 905–1600 nm was in 0.34–1.40 mm<sup>−</sup>1, which was smaller than μ- *s* of Royal Gala (1.00–1.50 mm−1) [33]. This may be related to different apple cultivars [43]. Within the short wave near infrared region (905–1100 nm), the scattering property was still stronger than the absorption property. μ- *<sup>s</sup>* was more than seven times the value of μ*a*, ranging from 0.80 to 1.40 mm−<sup>1</sup> at 25 ◦C, and from 0.04 to 0.11 mm−<sup>1</sup> at 0 ◦C. This result was also reported in Wei et al. [36]. In the range of medium wave near infrared (1100–1600 nm), the scattering property gradually declined, and the absorption became the dominant optical property as the wavelength increased [33].
