APPLICATION OF A COLORIMETRIC METHOD TO THE DETERMINATION OF THE PROTEIN-CONTENT OF COMMERCIAL FOODS, MIXED HUMAN DIETS AND NITROGEN LOSSESIN INFANTILE DIARRHEA

Recently we reported on the application of a method for protein determ ination which measures nitrogen in Kjeldahl digests colorimetrically. This procedure has the advantage of eliminating the distillation and t itration steps of the Kjeldahl method and it is ideal for nutritional studies, since many samples can be run in a single day. Accordingly, t he purpose of the present report was to extend the application of this method to the determination of the protein content of commercially av ailable foods such as dairy products, dry cereals or cereal based prod ucts and legumes and also to evaluate this method in the determination of the protein content of the mixtures of cooked foods served during lunch at the cafeteria of the Universidad Simon Bolivar, Caracas, In b oth cases the results of the colorimetric nitrogen agreed very well wi th those obtained by the macro Kjeldahl, indicating that the colorimet ric method may be used in monitoring the protein content of commercial foods and in evaluating the protein offered in institutional food ser vices. Finally, to further demonstrate the value of this method in cli nical trials, we used it to monitor the daily nitrogen intake and nitr ogen losses in 43 male young children with acute diarrhoea, and 15 wit h persistent diarrhoea fed liquid formulae, and showed that protein di gestibility and retention were higher in persistent than in acute diar rhoea. The severity of acute diarrhoea affected negatively (r = -0.62) the percentage of protein absorbed, whereas the protein absorbed (r = 0.70) and retained (r = 0.55) correlated positively with protein cons umption. In general, the results of these studies indicate that the co lorimetric methods may be useful in studying many aspects of protein n utrition, as it measures the protein content of raw materials, cooked foods and nitrogen intake and excretion in clinical and nutritional st udies.