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30 Crude Fat Methods​

30-10.01 Crude Fat in Flour, Bread, and Baked Cereal Products Not Containing Fruit

Crude fat is determined by acid hydrolysis of the sample with HCl (25 + 11) followed by extraction of hydrolyzed lipid materials with mixed ethers. Ethers are evaporated, and lipid residue is heated to constant weight at 100°. Residue is expressed as % crude fat. This method is applicable to cereal products, particularly heat-treated products, but not to cereal products containing fruit.

30-12.02 Crude Fat in Cocoa

Crude fat is determined by hydrolysis of a sample with HCl and subsequent extraction. The sample is weighed and dispersed in boiling water to gelatinize starches and aid in subsequent hydrolysis of starches and lipid materials in boiling HCl. The hydrolysate is filtered. The lipid residue on filter paper is dried and extracted by Soxhlet with petroleum ether. The solvent is removed, and residue is dried to constant weight at 100°C. Results are expressed as % crude fat. This method is applicable to cocoa products containing less than 22% fat (breakfast and regular cocoa).

30-14.01 Crude Fat in Baked Pet Food

Crude fat is determined by acid hydrolysis with HCl (25 + 11) followed by extraction of hydrolyzed lipid materials with mixed ethers. The solvent mixture is evaporated, and the residue is re-extracted and filtered with four, 10-ml portions of ethyl ether. The ether is then evaporated, and the residue is heated to constant weight and expressed as % crude fat. This method is applicable to baked pet foods.

30-16.01 Crude Fat in Dry Milk Products

Weighed sample is dissolved in water and treated with concentrated aqueous ammonia. Alkaline solution is extracted with mixed ethers and evaporated on a steam bath. Residue is dried under vacuum, weighed indirectly, and corrected by reagent blank determination. This method is applicable to regular and instant full-fat and nonfat dry milk products.

30-18.01 Crude Fat in Egg Yolk by Acid Hydrolysis

This method determines amount of crude fat in egg yolk and dried whole egg by acid hydrolysis.

30-20.01 Crude Fat in Grain and Stock Feeds

Feedstuffs high in water-soluble materials such as sugars, corn-syrup solids, molasses, urea, lactic acid, or glycerol are weighed, extracted first with water, and dried prior to exhaustive extraction with Soxhlet or continuous (Goldfisch) extraction utilizing dry ethyl ether as solvent. Solvent is evaporated, and residue is dried to constant weight at 100°. Weight is corrected by reagent blank and expressed as % crude fat or ether extract. This method is applicable to mixed feeds that have not been heat-treated, baked, or expanded. It is not applicable to dried milk products or feeds containing high levels of urea.

30-25.01 Crude Fat in Wheat, Corn, and Soy Flour, Feeds, and Mixed Feeds

Dried sample is exhaustively extracted by Soxhlet or continuous (Goldfisch) extraction, utilizing petroleum ether as solvent. Solvent is evaporated, and residue is dried to constant weight at 100°. Residue is expressed as % crude fat or ether extract. This method is applicable to flours of grains (wheat, corn, soybean, etc.) and mixed feeds that have not been heat-treated, baked, or expanded.

30-40.01 Unsaponifiable Matter

Macaroni products are hydrolyzed in concentrated HCl (1 + 1) and saponified by the addition of KOH pellets. Aqueous layer containing soaps is separated, and ether layer is washed several times with dilute KOH. Ether is slightly acidified, filtered, and dried, and residue weight is corrected by reagent blank. Residue is reported as % unsaponifiable matter. This method is applicable to macaroni and other extruded pasta products.