This Brief reviews the chemistry behind the production of yoghurt
through acidification of milk. It quantifies the changes in physical and
chemical properties of yoghurt during fermentation with microbial
organisms (such as Lactobacillus bulgaricus and Streptococcus
thermophilus). It has been found that this symbiosis has an optimal
development at a temperature of ca. 45°C with the transformation of
lactose into lactic acid and small amounts of acetaldehyde, diacetyl and
volatile acids. This Brief explains the chemical and physical results of
the fermentation process, such as precipitation of proteins and the acid
coagulation of milk with a clot formation in the final semi-solid mass.
The Brief sheds light on the accomplishments of the fermenting
organisms: they are responsible for the biochemical reactions of
carbohydrate metabolism, proteolysis, lipolysis and flavour production
in the process of yoghurt production. It also briefly reviews
formulations and food additives used in the modern yoghurt producing
industry.