Reflection is due to three different phenomena. Specular
reflection causes gloss, whereas external diffuse reflection is
induced by rough surfaces. Both only provide information about
the surface of the sample. Scattering results from multiple refractions
at phase changes inside the material. The main scattering
elements in fruit and vegetables are the cell wall interfaces since
they induce abrupt changes in refractive index (McGlone et al.,
1997), but suspended particles, such as starch granules, chloroplasts
and mitochondria may also induce scattering caused by
diffraction at the particle surface where the refractive index is
different from that of the surroundings (Il’yasov and Krasnikov,
1991). The scattering is also dependent on the size, the shape
and microstructure of the particles. Scattering may also appear
due to heterogeneities, such as pores, openings, capillaries that
are randomly distributed through the sample. Multiple scattering
events largely determine the intensity of the scattered
light that is emitted (McGlone et al., 1997). The scattering process
affects the intensity level of the reflected spectrum rather
than the shape; the latter is more related to the absorption
process.
(Nicolai et al., (2007) Postharvest Biology and Technology 46, 99–118)
ไม่มีความคิดเห็น:
แสดงความคิดเห็น