Use Of Microorganims And Enzymes

Question 1

Describe the process of producing cheese

Answer 1

Heat treatment of milk, pasteurised and then cooled to 31 and pumped to cheese vats
Starter culture added (lactocococcus lactis) which sours the milk converting the milk sugar lactose to lactic acid. The acid act as preservative and flavour
Rennet is added which causes the milk to clot about 30 mins after starter and the cheese begins to set
Moulds may added artificially for cheeses such as blue cheese eg. Penicillium
Enzymes have the function of producing ammonia which gives the characteristics flavour of the blue cheeses and creamy texture of white cheeses such as Camembert

Question 2

How is yogurt produced?

Answer 2

Concentrated milk with added milk
Bacteria added(lactobacillus bulgaricus and streptococcus thermophilus) they convert lactose into lactic acid.
Must be in equal amounts and one must not outgrow the other or a bitter or too acid product will result
The milk is pasteurised for 15 to 30 minutes between 85-95 degrees which stabilises the proteins in the milk and creates an almost sterile environment
Milk is cooled to between 40 and 43 ideal for bacteria growth
Starter is added to ferment lactose in the milk to give lactic acid and diacetyl which gives yogurt its creamy buttery flavour until pH 5.5 and oxygen is reduced
The inoculated milk is incubated 4 to 6 hours at 37 degree and cooled to 4.5 degree stopping lactic acid production. Yogurt may be heated to destroy bacteria