The effect of mitochondrial mutants on beer fermentation

ABSTRACTMSC. THESISTHE EFFECT OF MITOCONDRIAL MUTANTS ON BEERFERMENTATIONGülten YAĞMURDEPARTMENT OF FOOD ENGINEERINGINSTITUTE OF NATURAL AND APPLIED SCIENCESUNIVERSITY OF CUKUROVASupervisor: Assoc. Prof. Dr. Hüseyin ERTENYear: 2006, Pages: 56Jury : Prof. Dr. Ahmet CANBAŞProf. Dr. H. brahim EK ZAssoc. Prof. Dr. Hüseyin ERTENThe objective of this study was to determine the effect of mitochondrialmutants of bottom fermentation yeast of Saccharomyces carlsbergensis NCYC 1056and top fermentation yeast of Saccharomyces cerevisiae NCYC 1006 on beerquality.Wort inoculated with mitochondrial mutants at 1x107 cell/mL. Wortinoculated with main yeasts at 1x107 cell/mL was used as control. During thefermentation the yeast growth and fermentation rate were measured. Specific gravity,ethyl alcohol, pH, titration acidity, total and reducing sugars and aroma compoundswere determined in the beers.According to the results obtained, fermentation rate and growth of yeastdecreased in the samples produced by mitochondrial mutants. In addition,mitochondrial mutants produced lower amounts of ethyl alcohol and aromacompounds than the main yeasts. The amount of diacetyl which is off flavour andplay an important role on the beer quality were found higher in the samples producedby mitochondrial mutant of Saccharomyces cerevisiae NCYC 1006 than that ofcontrol.Key Words: Beer, Mitochondri, Mitochondrial Mutant, Mutation, Saccharomyces spp.II