'Sour' in the Bible

At mealtime Boaz said to her, “Come over here and eat some bread and dip your bread in the vinegar.” So she sat beside the reapers; and he served her roasted grain, and she ate until she was satisfied and she had some left [for Naomi].

“In those days they will not say again,‘The fathers have eaten sour grapes,And the children’s teeth are set on edge.’

But everyone will die [only] for his own wickedness; every man who eats sour grapes—his [own] teeth shall be set on edge.

“What do you mean by using this proverb concerning the land of Israel,‘The fathers eat sour grapes [they sin],But the children’s teeth are set on edge’?