Estimation of crude fiber
Crude fiber consists largely of cellulose and lignin (97%) plus some mineral matter. It represents only 60% to 80% of the cellulose and 4% to 6% of the lignin. The crude fiber content is commonly used as a measure of the nutritive value of poultry and livestock feeds and also in the analysis of various foods and food products to detect adulteration, quality and quantity.
During the acid and subsequent alkali treatment, oxidative hydrolytic degradation of the native cellulose and considerable degradation of lignin occur. The residue obtained after final filteration is weighed, incinerated, cooled and weighed again. The loss in weight gives the crude fiber content.
» Sulphuric acid solution (0.255 ±0.005N) : 1.25g concentrated sulphuric acid diluted to 100mL (concentration must be checked by titration)
» Sodium hydroxide solution (0.313 ±0.005N0 : 1.25g sodium hydroxide in 100mL disyilled water (concentration must be checed by titration with standard acid)
1. Maynard, A J (Ed) (1970) Methods in Food Analysis Academic Press New York p 176.
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