For the past 200 years foodies and food scientists have found the refractometer (with the BRIX scale) the most accurate and reliable measure of food quality i.e. delicious and nutritious. We have been using them since 2010, Australian and global farmers since circa 1950.
See Store for Prices, etc.
Just drop a few drops of liquid, juice into the "Measuring Slot" and read up to 55 degrees BRIX. Most food and beverage can be measured within the 0-32 degree range as in NutriMeter I.