Pectolytic enzyme reduces the concentration of colloidal particles in wine due to changes in polysaccharide structure and aggregation properties.

To explore the effect of pectolytic enzyme application on polysaccharide size and colloidal interactions, rosé
wines were prepared from pressed Shiraz grape juice, and red wines were made from the same juice by the addition
of skins and seeds from fresh pressings. A pectolytic enzyme preparation containing primarily
polygalacturonase and side-activities of arabinase and pectin lyase was used. Enzyme treatment enhanced the
contribution of high molecular weight (? 200 kDa) polysaccharides rich in mannose and glucose
(mannoproteins) and removed arabinose-rich polysaccharides of intermediate (?40 kDa) size. Enzyme application
reduced the molecular weight average of a class of smaller polysaccharides of approximately 6 kDa
(rhamnogalacturonan II). All wines had similar particle sizes, but enzyme treatment markedly reduced particle
concentration in wines, particularly in rosé wines. Wine polysaccharides were purified and when reconstituted
in model wine, showed reduced particle concentration in response to enzyme treatment. Aggregation of polysaccharide
in the presence of seed tannin was also markedly reduced by enzyme treatment. The results indicated
that changes in structure introduced by the enzyme affected wine colloidal properties, potentially increasing
polysaccharide solubility.