Question

Which of the following biochemical test function is based on the ability of organisms to produce Acetylmethyl carbinol with creatine?

• A. Horrell Elliker test
• B. Indole test
• C. Creatine test
• D. Methyl red test

Hint:

The Creatine test is a modified Voges-Proskauer (VP) reaction where creatine is added to accelerate and intensify the red color reaction with acetoin (acetylmethylcarbinol), identifying aroma-producing dairy cultures.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Acetylmethylcarbinol (also known as acetoin) is an intermediate compound in the bacterial fermentation of citrate to diacetyl.
The presence of acetoin is commonly used as a diagnostic indicator for aroma-producing bacteria in starter cultures.
The classic biochemical assay for detecting acetoin is the Voges-Proskauer (VP) reaction, which can be modified for dairy starter cultures.

Step 2: Detailed Explanation:
In the standard Voges-Proskauer reaction, acetoin is oxidized in an alkaline environment to diacetyl, which then reacts with guanidine compounds in peptone to produce a pinkish-red color.
To increase the sensitivity of this test, creatine is added to the reaction mixture.
Creatine contains a guanidinium group that reacts directly with diacetyl to form a red complex, acting as a color intensifier.
In dairy microbiology, this modification is known as the Creatine test (or Creatine-naphthol test).
This assay is routinely used to screen starter cultures for the presence of citrate-fermenting, diacetyl-producing bacteria such as L. diacetylactis and Leuconostoc species.
For comparison, the Indole test detects tryptophan degradation, the Methyl Red test measures mixed-acid production, and the Horrell-Elliker test is used to evaluate the activity of lactic starter cultures.
Therefore, the Creatine test is the correct choice.

Step 3: Final Answer
The biochemical test based on the detection of acetylmethylcarbinol using creatine as an intensifier is the Creatine test.