Effect of acetic acid fermentation on the stability of anthocyanin pigments

Stability of anthocyanin pigments (AN) prepared from sweet potato (Ipomoea batatas Poir.) "Ayamurasaki" and other plants (elderberry, strawberry, grap e juice and perilla) were investigated during acetic acid fermentation. (1) The ethyl alcohol contents before fermentation was 6%. Acetic acid content s after fermentation at 21 days was 5.0 similar to 5.5%, and pH was decreas ed to an average of 2.27. (2) The browning rate changed a little during ace tic acid fermentation. (3) Increasing acetic acid contents, and the relativ e absorbance (525 nm) of various anthocyanins were higher and became highes t after 21 days of fermentation. (4) A-value and b-value of the Hunter's di agram shifted to positive after 21 days of fermentation. (5) Major anthocya nins of elderberry, strawberry and grape juice were identified as cyanidin 3-sambubiose, pelargonidin 3-glucoside and delphinidin 3-glucoside, respect ively, by LC/MS analysis. (6) Sweet potato AN was more stable than the pigm ents of elderberry, strawberry and grape juice for acetic acid fermentation . Sweet potato AN was stable, meaning probably the intermolecular copigment ation of two organic acid with peonidin aglycone. Compared with sweet potat o anthocyanin, perilla (shiso) was instable, suggesting the decomposition t o shisonin.