Abstract: The microflora changes of yoghurt during processing and storage are analyzed by using selective media and the variation of the microbiological standards of yoghurt are studied by GB methods. The results indicate that Pseudomonas, Enterbacteriaceae and lactic acid bacteria are dominant floras in raw materials; lactic acid bacteria becomes dominant flora after fermentation; molds and yeasts become secondary organisms after one week in storage and the aerobic bacterial count increases obviously after three weeks. The molds, yeasts and bacteria are main microorganisms causing spoilage of yoghurt.

Key words: yoghurt, microflora, hygiene standards, changes