Harvest (wine) of wine, winemakers would use the sugar and acid levels of the grape as a guide in determining ripeness. Early winemakers tasted the grapes to gauge ripeness. Modern winemakers use a refractometer to measure high sugar levels and °Brix or titration tests (using an indicator such as phenolphthalein) to determine the titratable acidity within the grape. In recent times there has been more of an emphasis on the "physiological" ripeness of the grape, usually in the form of tannins and other phenolics. Currently, tasting is the only way to measure tannin ripeness, which can take experience and skill to do
The Fox and the Grapes of this transposition to the human situation hinges on the double meaning of 'unripe' ("vert") in French, which could also be used of a sexually immature female. From this emerges the story's subtext, of which a literal translation reads: There is the same sexual ambiguity in the Greek of Babrius. The phrase there is "όμφακες εισίν" ("omphakes eisin"), the word "omphax" having both the literal meaning of an unripe grape and the metaphorical usage of a girl not yet ripe for marriage. Rather than admit his failure to reach the grapes, the fox rationalises that they are not really desirable.