Lactic Acid - 88%, Lowers pH in mash. Add 1 teaspoon per cup of water. Can use up to 4 teaspoons. This food grade lactic acid (88% solution) is used for artificially adding a sour flavor to your beer without having to use bacteria that can contaminate your equipment. It is also used to lower the pH of your brewing water if it is too alkaline for the yeast to thrive.