Science, Tech, Math › Science What Acid Is in Vinegar? Vinegar Chemical Composition Share Flipboard Email Print =. Cacycle, Wikipedia Commons Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 06, 2019 What acid is in vinegar? Vinegar contains 5-10% acetic acid, one of the weak acids. Acetic acid is produced by the fermentation process used to make vinegar. Most of the remainder of the liquid is water. Vinegar may also contain sweeteners or flavorings added after the fermentation process.