The Effect of pH on the Precipitation of the Anthocyanins of Wine as Their Lead Salts

Abstract

The precipitation of anthocyanin pigments from wine by lead acetate was studied at pH 4.7, 6.1, and 9.4. Ninety to 95% of the anthocyanins least stable to alkaline conditions, delphinidin and petunidin glycosides, were precipitated at pH 4.7. At pH 6.1 approximately 95% of the cyanidin glycosides, 75% of the malvidin monoglucosides, and 50% of the peonidin monoglucosides were precipitated. The anthocyanins remaining in solution following pnecipitation at pH 6.1 were removed at pH 9.4. Partial fractionation of the pigments by pH and lead salt precipitation appeared to be dependent upon the structure of the aglycone. Whether the wine anthocyanins were monoor diglucosides made little or no difference in their completeness of precipitation, but the substitution pattern of the aglucone was important. A basic medium was required for complete precipitation of the anthocyanins devoid of vicinal hydroxyl groups, malvidin and peonidin glycosides. Complete precipitation of the anthocyanins was accomplished by means of a sequential precipitation procedure using three separate pH levels. Calculated recovery by this procedure ranged between 94 and 102%.