Development of a new simple estimating method for protein, fat, and carbohydrate in cooked foods.

Evaluations of daily nutrient intakes with practical accuracy contribute not only to public but also to personal health. To obtain accurate estimations of nutrient intake, chemical analyses of a duplicate sample of all foods consumed are recommended. But these analytical methods are expensive, time consuming, and not practically applicable for field surveys dealing with numerous food samples. To solve this problem, a new rapid and simple method of estimating nutrients is developed here. Elemental compositions of cooked foods were examined using a high speed and high performance carbon, hydrogen, and nitrogen autoanalyzer, and the results showed good reproducibility. A significant correlation between Kjeldahl's and the autoanalyzer methods was observed in the nitrogen measurement (n=20; r =0.999; p< 0.001), and very good agreement was observed between the methods. Therefore, the nitrogen amount obtained by the autoanalyzer was used for the estimation of the protein proportion in the cooked foods. The fat and carbohydrate proportions estimated by the new method correlated with the values obtained by the chemical method (p< 0.001 each). There were also good agreements of fat and carbohydrate proportions between the chemical and the new estimation methods. According to these results, the new, rapid and simple estimation method established in this study should be applicable to nutritional research.