Biological Processes in Fermentation: PTE Listening: Fill in the Blanks practice questions

During the production of yogurt, specific bacterial cultures convert lactose into lactic acid through a natural metabolic pathway. This biochemical change increases the of the milk, which causes the liquid proteins to coagulate and form a thicker texture. The lower pH level also serves an essential role by inhibiting the growth of harmful microorganisms that would otherwise spoil the product. Modern industrial facilities carefully monitor the ambient to ensure that the bacteria remain active throughout the entire batch. Consequently, this controlled environment delivers a consistent flavour and extends the commercial of the finished dairy goods.

In the brewing industry, yeast cells consume dissolved sugars and convert them into ethanol and carbon dioxide under anaerobic conditions. When oxygen levels drop, the metabolic pathways shift to sustain energy without cellular respiration. Brewers must regulate the concentration of in the liquid broth, as excessive amounts can hinder enzymatic activity and slow the conversion rate. In addition, secondary compounds such as esters are produced during this phase, contributing subtle fruit aromas to the beverage. Maintaining uniform throughout the large stainless steel vessels ensures that the yeast remains healthy, resulting in a predictable profile across every production cycle.