Lecture 11: Preservation

Question 1

What is the mechanism behind why nitrites act as a preservative in food products like bacon?

Answer 1

See slide 6; remember how nitrites react with Fe, and how this is significant both for preserving color and inactivating microorganisms.

Question 2

What is the Code of Federal Regulations?

Answer 2

See the pre-class story from this lecture for a description.

Question 3

How does the Code of Federal Regulations define a low acid food, and an acidic food?

Answer 3

See slide 4; I would recommend that you know the table on this slide.

Question 4

Why are nitrates/nitrites more effective at killing microorganisms in acidic foods?

Answer 4

See slide 6 for a full description (has to do with the pKa)

Question 5

What are two functions of ascorbate/isoascorbate in foods supplemented with nitrites?

Answer 5

1) favors the reduced form; 2) limits production of nitrosamines.

Question 6

The most common food ingredient added, that allows food manufacturers to label “no nitrate/nitrite added”, while actually increasing the level of these compounds, is _______

Answer 6

Celery salt

Question 7

What is the mechanism of killing of sulfites?

Answer 7

Targets membranes, protein synthesis, DNA….is a general inhibitor

Question 8

What enzyme do sulfites inhibit that reduces browning in fruits?

Answer 8

polyphenol oxidase