Lecture 12: Fermentation

Question 1

What are three ways that amino acids or amino acid metabolism can positively impact flavor in cheese?

Answer 1

See slide 11.

Question 2

What is the primary starter organism for Cheddar

cheese? For yogurt?

Answer 2

See slide 5.

Question 3

What are non-starter organisms (in relation to cheese), and why do they outcompete the starter Lactococcus lactis for growth?

Answer 3

See slide 9.

Question 4

What is the difference between homofermentative and heterofermentative metabolism?

Answer 4

I don’t expect you to know all the biochemical steps, but you should appreciate the end products of both (see slides 6-7 and 15-16), and what are the positive and negative ways heterofermentative organisms impact cheese during aging (negative: slide 16, positive: slide 17)

Question 5

What do we mean by “adjuncts” in terms of cheese making?

Answer 5

Slide 18 had an example of a Lactobacillus helveticus adjunct in the product “Cougar Gold”. Basically, they are organisms added other than the starter, for the purpose of accelerating flavor development. In this example, L. helveticus is an organism that is highly proteolytic, so it chews up milk caseins into free amino acids really well, providing precursors to flavor compounds.

Question 6

What is the 60-day aging rule, and what is the current controversy surrounding it?

Answer 6

Revisit slide 19.

Question 7

What is the current debate/issue concerning aging of cheeses on wooden shelves?

Answer 7

Revisit slide 20. Remember this isn’t so much a “debate” as an issue that resurfaces every so often. The argument that nobody seems able to settle, is whether the FDA’s requirement that “all utensils and equipment should be cleanable” allow or does not allow for the use of wooden shelves.

Question 8

What are 4 common defects in Cheddar cheese, and what is the mechanism by which they occur?

Answer 8

See slide 13 for discussion.