Lengthening the life of milk
Louis Pasteur made a few discoveries concerning fermentation as there are many different kinds. He used fermentation with milk and beet-root alcohol. Louis Pasteur invented pasteurization in order to have liquids containing yeast and sugar to have a longer shelf life. He discovered that lactose changed into lactic acid, that's what causes milk to spoil. Pasteur concluded from all his research that microbes or microscopic organisms, cause fermentation, and that specific kinds of microbes cause specific types of fermentation. Also, he concluded that the living yeast cells were causing the alcohol to form from the sugar. If it weren't for the invention of pasteurization and discovery of fermentation, milk and alcohol could be spoiling at a higher rate than if it was pasteurized.