A spectroscopic method, preferably 
Raman scattering, is used to rapidly determine the 
general health or stress status of living plants and 
plant products, including 
agricultural crops, forests, and harvested 
fruits and vegetables. In the preferred embodiments, 
carotenoid levels are used to provide an indication of oxidative deterioration. Based upon the results of the analysis, further action may or may not be taken, for example, in terms of choosing, picking, harvesting or sorting the agricultural product in accordance with the 
carotenoid level. Concentration levels of an 
analyte substance can be determined relative to an external standard, to each other, or relative to another substance in the item being analyzed. Carotenoids such as 
lycopene, beta-
carotene, 
lutein, violaxanthin, neoxanthin, antheraxanthin, and 
zeaxanthin are determined according to the invention, through other 
plant components may be analyzed such as other terpenes, polyenes, 
chlorophyll, proteins, starches, sugars, overall 
nitrogen levels, flavonoids, and vitamins. The hardware associated with the invention may be field portable or mounted on a piece of equipment such as a harvester or sorter.