CRC Food Processing and Engineering 2

Question 1

What does the D-value of a microorganism represent?

Accepted Answer

Time at a given temperature to reduce the population by 90% (one log)

Answer

The D-value is the decimal reduction time, i.e., minutes at a constant temperature for a 1-log reduction.

Question 2

The z-value describes which relationship?

Accepted Answer

Temperature change required to change the D-value by a factor of 10

Answer

The z-value is the temperature increase that reduces D by 90% (tenfold).

Question 3

Above which pH is a canned food classified as low-acid under US regulations?

Accepted Answer

4.6

Answer

Foods with finished equilibrium pH above 4.6 (and aw above 0.85) are low-acid foods requiring a botulinum-safe process.

Question 4

A 12D process for low-acid canned foods is designed to reduce which organism?

Accepted Answer

Clostridium botulinum spores

Answer

The botulinum cook delivers a 12-log reduction of C. botulinum spores.

Question 5

Which are typical HTST pasteurization conditions for fluid milk?

Accepted Answer

72°C (161°F) for 15 seconds

Answer

HTST milk pasteurization is at least 72°C (161°F) for 15 seconds.

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