Protein nutritive utilization in rats fed powder and liquid infant formulas / Utilización nutritiva de la proteína en ratas alimentadas con formulas infantiles en polvo y líquidas

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Abstract
The effect of food processing involved in the manufacture of infant formulas on protein absorption and metabolic utilization was investigated in rats. Powders (P1 and P2), in-bottle-sterilized (SC1) infant formulas and UHT forms (UHT2) from two manufacturers were used. The highest level of furosine was determined in P1. Lactulose was higher in the liquid than in the powder products, especially in SC1, which had the highest lactulose/furosine ratio and the most intense whey protein denaturation evaluated by SDS-PAGE. Five groups of rats were fed during 12 days with a control diet or isocaloric diets containing each of the infant formulas and a standarized diet in the proportion 40:60. The protein content of the diets was 162 g/kg. No differences were observed in intake, growth and food and protein efficiencies due to the type of infant formula consumed. Fecal nitrogen in creased and protein digestibility decreased in the SC1 group compared with the other groups. Bio logical value was lower in P1 than in SC1. However, the nitrogen balance and net protein utilization did not show differences among the four test groups. These results suggest that there are differences among infant formulas, due to the brand and the process, which may affect protein digestibility and metabolic utilization.