GLYCOPROTEINS - CHARACTERIZATION IN A HYBRID GRAPE VARIETY (MUSCAT BAILEY-A) JUICE, FERMENTING MUST, AND RESULTANT RED WINE

Elucidation of the differences in properties between unstable and solu ble proteins will assist in developing effective fining of wine and in breeding of grape varieties with fewer unstable proteins. Soluble pro teins from juice, must pressed just after fermentation on skins, and f rom red wines were isolated by ammonium sulfate precipitation and frac tionated by Sephadex G-100 followed by high performance liquid chromat ography. At least 17, 18, and 22 protein fractions were obtained from the juice, fermenting must, and red wine samples, respectively. All of the fractions had sugars in the range of 0.3% to 33.3% of total glyco proteins (the sum of the total sugars and amino acids found in the hyd rosolates). Most of the glycoproteins had less than 10% sugars. The gl ycoproteins differed from grape proteins, generally being rich in the amino acids aspartic acid, glycine, threonine, glutamic acid, and alan ine and in the sugars arabinose, rhamnose, galactose, and glucose. The ir isoelectric points and molecular weights ranged from 3.7 to 4.9 and form 12.1 to 30.8 K daltons, respectively. Differences in the HPLC pa tterns and in the chemical and physical properties of the protein frac tions obtained revealed the presence of several individual glycoprotei ns, their concentrations, and occurrence of specific glycoproteins at each stage of vinification. The proportion of glycoprotein sugars decr eased in the order juice proteins > must proteins > wine proteins - i. e., degradation or modification of the sugar portions of the glycoprot eins occurred during vinification. The origin of wine glycoproteins su ggests roles in aging reactions and other wine characteristics.