Question

____________ measures the amount of volatile insoluble fatty acids.

• A. Saponification number
• B. Reichert meissl number
• C. Polenske number
• D. Iodine number

Hint:

Remember the difference between these two volatile fatty acid indices:
- Reichert-Meissl (RM) number \(\rightarrow\) Volatile, Water-Soluble fatty acids.
- Polenske number \(\rightarrow\) Volatile, Water-Insoluble fatty acids.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The purity and composition of fats and oils (especially butterfat and coconut oil) are characterized by several chemical indices.
Some of these indices measure volatile fatty acids obtained by steam distilling saponified fats.

Step 2: Detailed Explanation:
Let us analyze the chemical indices provided in the options:
- Saponification number (A): Measures the milligrams of potassium hydroxide (KOH) required to saponify 1 gram of fat or oil, reflecting the average fatty acid chain length.
- Iodine number (D): Measures the grams of iodine absorbed by 100 grams of fat or oil, reflecting the degree of unsaturation.
- Reichert-Meissl (RM) number (B): Measures the milliliters of 0.1 N alkali required to neutralize the volatile, water-soluble fatty acids (primarily butyric and caproic acids) distilled from 5 grams of fat.
- Polenske number (C): Measures the milliliters of 0.1 N alkali required to neutralize the volatile, water-insoluble fatty acids (primarily caprylic, capric, and lauric acids) distilled from 5 grams of fat.
These water-insoluble, steam-volatile fatty acids are separated from the water-soluble ones by filtration during the analysis.
The Polenske number is particularly useful for detecting the adulteration of butterfat with coconut or palm kernel oils, which contain high levels of these volatile, water-insoluble fatty acids.
Therefore, the Polenske number is the correct index.

Step 3: Final Answer:
The chemical index that measures volatile, water-insoluble fatty acids is the Polenske number.