A New Strain of Leuconostoc Oenos for Induced Malo-Lactic Fermentation in Eastern Wines

Abstract

A bacterium, isolated from a red table wine made in the laboratory from French-hybrid grapes grown in Pennsylvania following a spontaneous malo-lactic fermentation, was characterized as <i>Leuconostoc oenos</i> and was given the strain designation, PSU-1. It was found to be quite similar in most biochemical characteristics to <i>L. oenos</i> ML-34, a commonly studied strain which was isolated from a California wine. ML-34 and PSU-1 were compared for their growth characteristics in a complex laboratory medium modified to simulate some of the conditions which limit the growth of bacteria in wine. It was found that ML-34 always grew as well as or slightly better than PSU-1 with variations in pH, added ethanol, added sulfur dioxide and different incubation temperatures. Two separate experiments were conducted to compare the strains for induced malolactic fermentation by pure culture inoculation into Pennsylvania red table wines. In the first experiment, three wines made from blends of hot-pressed Pennylvania musts were passed through 0.5 µm filters prior to inoculation. PSU-1 induced malo-lactic fermentation in two of these wines within 11.9 and 15.3 weeks following inoculation, while ML-34 failed to induce malo-lactic fermentation within 50 weeks in all three wines. In the second experiment, bacteria were inoculated into three varietal red Pennsylvania wines made using traditional vinification procedures. Two of the three varieties inoculated with PSU-1 completed malo-lactic fermentation considerably faster than identical wines inoculated with ML-34. In the other variety, wines inoculated with both organisms completed malo-lactic fermentation at about the same time which was much faster than the uninoculated control lots. Sensory evaluation of the varietal wines treated identically, except for the bacterial strain inoculated, revealed that no detectable differences existed in the wines.