42 CHEESE MAKING. 
88. Pepsin as a Substitute for Rennet Extract. 
Scale pepsin has been used as a substitute for rennet in 
cheese making. It is made from stomachs of hogs. It both 
eurdles and digests milk and so raises the question whether the 
eurdling and digesting are not really after all two properties of 
one ferment. Scale pepsin solutions do not curdle very sweet 
milk as readily as the rennet extracts do. In milk containing .2 
per cent acid no difference can be observed. In such milk five 
grams or 75 grains of the scale pepsin is equal to four ounces of 
Hansen’s rennet extract. Pepsin makes cheese of excellent 
flavor and texture. Enough cheese has been made to establish 
the value of pepsin in the making of Cheddar cheese.* 
QUESTIONS ON CHAPTER IV. 
1. What are the two general classes of ferments? 2. What 
are enzymes and where do they originate? 3. What is the effect 
of temperature on enzymes? 4. Who discovered galactase and 
where is it found? 5. Describe galactase. 6. What is a rennet? 
7. How are rennets preserved? 8. What is rennet extract? 9. 
Where do the best rennets come from? 10. How is rennet ex- 
tract made? 11. Why are reliable brands of commercial ex- 
tracts to be preferred to homemade extracts? 12. What is the 
effect of heat and acidity on rennet action? 138. On what three 
factors is the rapidity of rennet action dependent? 14. Who 
invented the rennet test? 15. Why are glass graduates used in 
a rennet test inaccurate? 16. Describe the Monrad rennet test. 
17. Describe the Marschall rennet test. 18. In what respect may 
Marschall tests differ? 19. What errors are to be avoided in 
using a Marschall test? 20. What is scale pepsin? 21. What is 
the effect of acidity of milk upon the curdling power of pepsin? 
22. How does scale pepsin compare in strength with Hansen’s 
rennet extract? 
*Experiments with pepsin ir. cheese making have beer conducted at Ont. 
Agric. College (Reports 30, p. 74 and 32, p. 108). 
