In the investigation of the amount of pectinase, the amount of pectinase should be used as the independent variable, strictly control the irrelevant variables, that is, the temperature and pH are controlled in the optimal conditions, but also to control the reaction within a certain time.

(2) ① take six test tubes, numbered 1 to 6, were added to an equal amount of apple puree, adjust the pH to 4.8;

② to 1 to 6 test tubes were added to a different volume of pectinase solution, and then placed into the 45 ℃ thermostatic water bath device holding the same time.

③ Filter the apple puree and record the volume of juice.

(3) Results and conclusions: please describe how to determine a certain amount of pectinase is the most suitable amount based on the experimental data?

With the increase in the amount of pectinase, the volume of juice obtained by filtration also increases, when the amount of pectinase increased to a certain value, and then increase the amount of pectinase, the volume of juice obtained by filtration is no longer increased, then this value (i.e., juice is no longer increasing the amount of pectinase) is the most suitable amount of pectinase.

The answer is: (1) the amount of pectinase

(2) ① equal amount of apple puree ② different volumes of pectinase solution, holding the same time ③ filter the apple puree and record the volume of juice

(3) with the increase in the amount of pectinase, filtration to obtain the volume of juice increases, when the amount of pectinase increased to a certain value, and then increase the amount of pectinase. The volume of the juice obtained by filtration is no longer increased, then this value (i.e., the amount of pectinase that the juice is no longer increased) is the optimum amount of pectinase