Protein nutritive utilization in rats fed powder and liquid infant formulas

The effect of food processing involved in the manufacture of infant formula s on protein absorption and metabolic utilization was investigated in rats. Powders (P1 and P2), in-bottle-sterilized (SC1) infant formulas and UHT fo rms (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 rati o and the most intense whey protein denaturation evaluated by SDS-PAGE. Fiv e 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 differe nces were observed in intake, growth and food and protein efficiencies due to the type of infant formula consumed. Fecal nitrogen increased and protei n digestibility decreased in the SC1 group compared with the other groups. Biological value was lower in P1 than in SC1. However, the nitrogen balance and net protein utilization did not show differences among the four test g roups. These results suggest that there are differences among infant formul as, due to the brand and the process, which may affect protein digestibilit y and metabolic utilization.