Crude fiber calculation involves determining the indigestible plant material in food. It's not a direct measurement of total dietary fiber, which encompasses a wider range of substances. The traditional method relies on a weight difference before and after specific chemical treatments.
Calculating Crude Fiber: The Traditional Method
The process typically involves these steps:
- Weighing: Accurately weigh a sample of the food.
- Acid Digestion: Boil the sample in acid (e.g., dilute sulfuric acid) to dissolve non-fiber components.
- Alkali Digestion: Then, boil the remaining material in alkali (e.g., dilute sodium hydroxide) to remove additional non-fiber components.
- Filtering and Washing: Filter the residue to remove soluble substances. Thoroughly wash the remaining fiber.
- Drying: Dry the filtered residue in an oven until a constant weight is achieved.
- Ashing: Heat the residue in a furnace to burn off any remaining organic matter. (This step is crucial; Heat the crucible with electrical bunsen in order to ash the residue. Continue the heating till you obtain a whitish ash.)
- Weighing and Calculation: Weigh the ash and the dried residue before ashing. The difference in weight represents the crude fiber content. (The difference in weight of the crucible before and after ashing is reported as the crude fiber content of the feed taken.) This weight difference is expressed as a percentage of the initial food sample weight. (% crude fiber in ground sample= Loss...)
Example:
- Initial sample weight: 10 grams
- Weight after drying and ashing: 1 gram
- Crude fiber content: (10 - 1) / 10 * 100% = 90%
Important Note: The above method is a crude fiber determination. It doesn't capture all forms of dietary fiber. Modern methods, such as those using Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF) analyses, provide more comprehensive assessments of fiber content. (Crude fiber is only 1/7 to 1/2 of total dietary fiber.) These methods are described in standards like ISO 6541:1981. (Reference: ISO 6541:1981 Agricultural food products - Determination of crude fibre content - Modified Scharrer method.)
Using Online Calculators
Several online tools assist in estimating crude fiber content. These calculators typically require inputting data obtained through laboratory analysis or from existing databases. (A crude fiber calculator is an online tool designed to quickly estimate crude fiber content in feedstuffs and food materials.) However, always remember that these are estimations and laboratory analysis remains the gold standard for accuracy.
