While initially skeptical myself, I found a bit of information on Consumer Physics' site stating that they use near-infrared spectroscopy. Doing a little initial research, it seems plausible that they could glean a number of useful traits from agricultural products, including soluble solids (i.e. sugar content in fruits), acidity, moisture content and more.

https://www.consumerphysics.com/myscio/technology/

https://en.wikipedia.org/wiki/Near-infrared_spectroscopy#Agr...

http://www.intechopen.com/books/developments-in-near-infrare...