Chr. Hansen A/S in Denmark has patented genetically modified lactic acid bacteria, Leuconostoc pseudomesenteroides. Specifically the invention provides novel genetically modified strains of lactic acid bacteria that are modified to have enhanced or reduced diacetyl reductase activity, acetoin reductase activity and/or butanediol dehydrogenase activity. Such modified bacteria are particularly useful as freeze-dried starter cultures in the manufacturing of food products for reducing or completely removing diacetyl in beverages including beers, fruit juices and certain types of wine, where the presence of diacetyl is undesired.