Lipase is a digestive enzyme that hydrolyses the ester bonds of triglycerides to release fatty acids and glycerol (propylene glycol). As the reaction proceeds, the pH decreases as a result of the rising concentration of carboxylic acids. This means it is very convenient to monitor the progress of the reaction by measuring pH. To get a visual result, phenolphthalein can be used as an indicator. The slightly alkaline starting pH causes the indicator to appear pink, but this changes to colourless as the reaction proceeds. With this enzyme, we suggest using full cream milk as the source of triglycerides.
This particular type of Lipase is sensitive to pH. If the reaction mixture is made too alkaline (pH greater than 10), the enzyme will be denatured and rendered ineffective. For this reason, it is very important to ensure that only the required amount of Na2CO3 is used. Adding any more than is necessary can cause problems.
SOURCE: Rhizopus oryzae