In transmission spectra of milk, low scattering gave rise to low absorbance.

"The original NIR spectra of the milk samples having high, medium and low fat contents are shown in Figure 3. The spectrum of milk shifted upward with an increase of fat content. In raw milk, the fat exists in the form of globules from 1 mm to 12 mm in diameter, which act as a scattering material. As fat content increases, the number of fat globules increases, and the scattering effect becomes more severe.”

(Chen, J.Y., Iyo, C., Terada, F. and Kawano, S. 2002. Effect of multiplicative scatter correction on wavelength selection for near infrared calibration to determine fat content in raw milk, Journal of Near Infrared Spectroscopy. 10, 301-307.)

High resolution: is it useful for broad band NIR?

"I have to add something to what David Hopkins said: in the early days of NIR (say, from the mid-1970s to the mid-1980s) the major applications were in the agricultural areas. The absorbance bands corresponding to the key materials in those types of samples were in fact, inherently broad: moisture, starch, and protein all have absorbances that are intrinsically broad due to the effects Dave mentioned. Therefore there was little or no incentive for the instrument manufacturers to design instruments with high spectral resolution, because the applications of them, at that time, did not justify expending the engineering time and resources to improve the resolution. Nowadays, of course, many more different types of applications exist, some of which include measurements of materials with the sharp bands that Dave also described. It is the change in the measurement requirements that drove the technologies in the direction of high spectral resolution devices." (Howard Mark, http://www.impublications.com/discus/messages/5/2147.html?1163283835)