The Effect of Grape Skin Treatments on Induced Malo-Lactic Fermentation in Ohio Wines

¹ Department of Horticulture, The Ohio State University, Columbus, Ohio, 43210
² The Ohio Agricultural Research and Development Center, Wooster, Ohio

Induced malo-lactic fermentation was attempted in grape musts prepared by cold pressing, hot pressing, and fermentation "on the skins" for 1, 3, and 5 days before pressing. The musts were inoculated with the malo-lactic bacterium Leuconostoc citrovorum (ML 34) and otherwise treated by a standard vinification procedure. Results revealed that fermentation "on the skins" had a profound effect on the occurrence and rate of malo-lactic fermentation. The grape musts prepared by cold pressing, hot pressing, and fermentation "on the skins" for one day supported only limited growth of the inoculated bacteria, and no malo-lactic fermentation was defected after one year. The wines that were fermented "on the skins" for 3 days underwent an incomplete malo-lactic fermentation. Wines that were fermented 5 days "on the skins" completed malo-lactic fermentation by 11.3 weeks after the bacterial inoculation.

In addilion, model grape musts were prepared which simulated the grape musts prepared by hot and cold pressing as well as by fermentation "on the skins." Isolates prepared from these model musts were demonstrated to contain substance(s) stimulatory to the growth of L. citrovorum (ML 34). Microbiological assays indicated that the isolates from the skins caused a greater growth stimuation than the isolates from the model musts stimulating hot- and cold-pressed musts.