Antonyms of verb sweeten

1 of 2 senses of sweeten

Sense 1
sweeten, dulcify, edulcorate, dulcorate -- (make sweeter in taste)
       Antonym of sour (Sense 2)
      => sour, acidify, acidulate, acetify -- (make sour or more sour)

Synonyms/Hypernyms (Ordered by Estimated Frequency) of verb sweeten

2 senses of sweeten

Sense 1
sweeten, dulcify, edulcorate, dulcorate -- (make sweeter in taste)
       => change taste -- (alter the flavor of)

Sense 2
sweeten -- (make sweeter, more pleasant, or more agreeable; "sweeten a deal")
       => change, alter, modify -- (cause to change; make different; cause a transformation; "The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue")