EFFECT OF PH, SULFUR DIOXIDE, INSOLUBLE SOLIDS, AND IMMOBILIZED LEUCONOSTOC OENOS PSU-1 ON THE INDUCTION OF MALOLACTIC FERMENTATION IN TABLE WINES

Malolactic fermentation, the conversion of L-malic acid to L-lactic acid and carbon dioxide, was induced in table wines by inoculation with a malolactic bacteria Leuconostoc oenos PSU-1. The rate of malolactic fermentation was influenced by the must pH and level of sulfur dioxide. Low pH and a high level of sulfur dioxide reduced the population of malolactic bacteria. This decreased the rate of malolactic fermentation in the wines. In white wines, grape insoluble solids was found to be stimulatory to malolactic fermentation. Results indicated that the insoluble solids affected the sulfur dioxide content of the musts and wines. Musts and wines with highest insoluble solids tended to be lowest in sulfur dioxide.;Induction of malolactic fermentation was also studied with immobilized cells of L. oenos PSU-1. Bacterial cells were entrapped in a carrageenan gel, and were inoculated into wines to compare their activity with freely suspended cells. The immobilized bacteria were able to induce malolactic fermentation in both red and white wines with pH values as low as 3.0. In contrast, no malolactic fermentation was observed in wines inoculated with freely suspended cells. Results also indicated that the alcohol content of wines decreased after malolactic fermentation by immobilized bacteria, apparently due to the addition of carrageenan gel.