Isinglass, a type of by-product of fish industry is principally used for

Options

A. Feeding cattle, pigs and poultry
B. Preparation of paints and varnishes O
C. Clarification of vinegar, wines and beer
D. Production of insulin

Answer

### Step-by-Step Solution:

1. **Identify the Source of Isinglass**:
- Isinglass is a by-product derived from the fish industry, specifically from the air bladders (also known as swim bladders) of certain fish species.

2. **Understand the Composition**:
- Isinglass is primarily composed of a type of gelatin, which is a whitish, semi-transparent protein substance.

3. **Recognize the Main Fish Source**:
- The most notable fish used for producing isinglass includes sturgeons, which are known for their high-quality swim bladders.

4. **Determine the Principal Uses**:
- The primary application of isinglass is in the clarification process of beverages, particularly wine and beer. It helps in removing impurities and sediments, resulting in a clearer product.

5. **List Other Uses**:
- Besides beverage clarification, isinglass is also used in various other applications such as making purses, books, honeycomb, and ribbons.

6. **Note the Quality Source**:
- The best quality isinglass is known to be produced in Russia, indicating a geographical distinction in quality.

### Final Answer:
Isinglass is principally used for the clarification of wine and beer.

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