Diacetyl Production in Batch Fermentation Process by Lactic Starter Cultures

In this research diacetyl production as a buttery flavor in food industries by Lactic Acid Bacteria (LAB)، Lactococcus and Leuconostoc genus was investigated. Batch fermentation process accomplished on MRS (De Man، Rogosa and Sharpe medium) broth medium، medium based on whey powder and based on skim milk powder at different conditions of temperature، agitation speed، glucose as carbon source، tri-sodium citrate as precursor of diacetyl production، inoculum، catalase enzyme، bovin blood as heme protein source and CuCl2. Optimum conditions were determined for achivement of highest production yield. This research indicated that the optimum fermentation conditions for diacetyl production by LAB were: 32º C، 180 rpm، glucose 6 g/l،tri-sodium citrate 5g/l، inoculun 5%، catalase enzyme 6 ml/l، bovin blood 4 g/l، CuCl2 15 mg/l. Finally، for production of diacetyl، a fermenter was used with 10 liter volume، inoculum size 5 % (v/v) with working volume of 6. 5 liters. Agitation and temprature were maintained at 180 rpm and 32ºC، respectively. Diacetyl concentration under optimized condition in fermenter was obtained as 945 mg/l.