This document discusses near infrared reflectance spectroscopy (NIRS) and its principles. NIRS is a nondestructive technique used to evaluate food quality by determining components like protein, moisture, starch and lipids. It works by measuring the absorption of near infrared light as it interacts with molecular bonds in organic materials. Different bonds like C=H, C=O and N=H absorb different wavelengths. The absorbed energy is detected to create a spectral profile that can be analyzed using chemometrics to quantify various chemical components through calibration.