The present subject matter relates to methods of high-speed analysis of product samples. Light is directed to a portion of a product under analysis and reflected from or transmitted through the product toward an optical detector. Signals for the detector are compared with reference signals based on a portion of the illuminating light passing through a reference element to determine characteristics of the product under analysis. Temperature within the analysis system is monitored and the output signals of the optical detectors are compensated or corrections are made within the analysis calculations to compensate or correct for the system temperature. The products under analysis may be stationary, moved by an inspection point by conveyor or other means, or may be contained within a container, the container including a window portion through which the product illuminating light may pass.