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Model decay using an enzyme
Required practical 10 investigates temperature and milk decay through pH change. The suggested classroom model adds lipase to fresh milk made alkaline with sodium carbonate. Lipase breaks down milk fat, producing fatty acids that lower pH. This models an enzyme-controlled part of decay; it does not require growing unknown microorganisms. Natural microbial souring produces lactic acid, but the lipase model tests enzyme activity rather than microbial population growth.
