Changes

The sensory analysis showed that all of the fresh beers with or without gallic acid scored positively by tasters, although they preferred the beers with gallic acid because of their "fullness of taste and mouthfeel". After 5 days of storage at 40°C, the beers with gallic acid continued to rate high while the non-gallic acid beers began to show signs of staling (darker in color, cardboard flavor, slight sweetness, and a sharp unpleasant bitterness), and at 10 days the non-gallic beers were clearly more oxidized. These results were confirmed by storing the beers for one year at 4°C in the dark; the beers with gallic acid were always more preferred by tasters. The beers with gallic acid added during the mashing and sparging had better flavor stability, and better stability of hop compounds such as iso-alpha acids. They also had a higher polyphenol content from the malts (only hop extract was used, so the polyphenol content had to come from the malts). The lipoxygenase activity ('''LOX'''), which is the mechanism by which lipids are oxidized to create off-flavors, was also decreased in the beers with gallic acid added. They also found that the "Strecker" and "Maillard" derived aldehydes phenylacetaldehyde, furfural, benzaldehyde were reduced by the use of gallic acid (fatty-acid derived aldehydes were not reduced, but there is evidence that these are already present in malt and are not formed during the mashing process, unlike the previously mentioned aldehydes). Trans-2-nonenal (papery, cardboard staling flavors) was also reduced in beers brewed with gallic acid. The study found that mashing with gallic acid at 62°C and 5.3 pH had the most positive impacts on both flavor stability and the prevention on off-flavor development <ref name="Aerts_2004" />.

===Hop Compounds===