As of 2017 there are several consumer hand held Refractometers/Spectrometers/(Lasers) available working in conjunction with SmartPhones providing basic Brix Data that elude to taste/quality of fruit or vegetables....utilizing similar technology, would it be possible to extrapolate the approximate value of Phytonutrients in Fruit/Vegetables as well?
What reference data would be required to accurately acquire such data from said subject?
Would the initial reference data need to be acquired using standard lab techniques?
Maybe. It depends on the chromophores present, the assay method used, and a bunch of other factors. And that's before you talk about the instrument.
Refractometers are usually used to measure sugar ( often present in the % range). If you nutrients fall in this range, a refractometer is an option.
It's not well known, but blood analyzers were basically single beam spectrometers, but with lots of bells and whistles added. Heck, maybe some still are.
Here is a device ( https://www.consumerphysics.com/business/ )we have considered using as it offers a self contained hand held unit suitable for consumers and businesses alike. Acquistion of the necessary Phytonutrient data points is the initial issue to properly calibrate the unit in question as well as its support IOS interface.
The device referenced has very mixed reviews on the internet. And it does seem pricey. As a suggestion, borrow or rent one first. Try it and see how it works for your application. Let everyone know what you find out.