In the wine making process yeast cells are kept short of oxygen. This causes sugars in the grape juice to ferment which forms alcohol and carbon dioxide. In cheese and yoghurt, bacteria perform a similar job, turning lactose into lactic acid. Rennet is then added to separate the curds and whey.
The clip can be used to cover the use of microbes in industry for biology. It could also be used in more general study of food production. Field trips to food producers could take place in which students find out more about the influence of temperature control and other factors in efficiency and the types of reaction that take place. In class use nigrosin stain to visualise bacteria in yoghurt.