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estimate metabolizable energy, while the modified Atwater method can underestimate energy values. It is important to remember that the differences between the three methods are much smaller than the errors resulting from ignoring the individual differences in digestibility and in measuring food intake.
Analysis of lipids and fatty acid components is dependent on the type of food, the number of samples and the laboratory facilities. The information required on lipids for a nutrient database include the total lipid content for calculation of energy content, as well as comparison between the foods, the fatty acid types and the amount of cholesterol in the food. Cacao-based ingredients are assumed to contain zero cholesterol because they are plant-based components.
Due to their lipid content and makeup, cacao-based ingredients require a complex solvent extraction procedure followed by chromatographic and/or spectrophotometric analysis of all lipid classes. Extraction methods involve denaturing lipoproteins and enzymes in alcohol followed by an extraction into an organic solvent. The type of food will determine the nature of the organic solvent used. Once lipids have been extracted, it is necessary to determine the fatty acid content and composition where gas chromatography methods are preferred. In the USA, standard of identity 21 CFR 163.5 cites the extraction method that must be used to determine fat content of chocolate liquor and cocoa powder (7).
Protein is typically calculated from total nitrogen (N) values as measured by Kjeldahl. This result is a measure of the crude protein and is only an approximation. A true measure of protein is obtained by using the conversion factor of 6.25 x N. Cacao-based ingredients are a challenge in that they contain a large percentage of the nitrogenous compounds theobromine and caffeine. To obtain true protein content, the conversion factor of 6.25 must be employed after removing the theobromine and caffeine components from the total protein content.
Carbohydrates are characterized by digestible portions (i.e. starch and sugars) and indigestible portions (i.e. dietary fiber). The European community defines digestible carbohydrates as 'available' and indigestible carbohydrates as 'unavailable'. Databases typically calculate total carbohydrates by difference the material remaining after subtracting moisture, ash, fat and protein. A major drawback of this method is that calculation by difference accumulates analytical errors from fat, protein, ash and moisture determinations. However, difference methods can and do provide reasonable estimates of total available carbohydrates. It should be noted that carbohydrate values obtained 'by difference' and those obtained by analysis are incompatible and attempts to compare the two should not be made. In foods that do not contain a large amount of non-carbohydrate components, the sum of the individual components will approximate to total carbohydrate 'by difference'.
Dietary fiber can be measured either by a gravimetric method where the non-fiber components are removed and the residue is weighed, or by using enzymatic gravimetric methods that use purified enzymes to measure total dietary fiber or
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