Answer:

tartest

Answer	Crossword Clue
TARTEST	Most cutting
TARTEST	Most likely to elicit a pucker
TARTEST	Most sour

TARTEST	Most tangy
TARTEST	Cutting to the max
TARTEST	Most acidic
TARTEST	Least sweet
TARTEST	Most lemony
TARTEST	Maximally tangy
TARTEST	Most puckery
TARTEST	Sharpest.

TARTEST	Most mouth-puckering.
TARTEST	Most acerb
TARTEST	Maximally sharp
TARTEST	Most like rhubarb, flavorwise
TARTEST	Tangiest