Heat processing is necessary to extend the shelf-life of commercially manufactured infant formulas. Heat treatment causes protein denaturation and may thereby affect protein digestibility. Currently, there are several fundamentally different technologies to produce infant formulas such as sterilization which used for production of liquid formulas, and spray-drying which is used for production of powdered formulas. Infant formula (liquid concentrated, powdered, ready-to-feed), prepared according to the manufacturers' instructions were centrifuged at 14,000 g at 4°C for 1 h. Fractions [lipid layer, soluble fraction (whey) and pellet (casein)] were separated. Total N and N in fractions were determined by micro-Kjeldahl analysis and non-protein nitrogen (NPN) after precipitation of proteins. Protein solubility was determined after centrifugation and ranged from 5790%. To simulate the infant gut, in vitro digestion was used. Formulas were adjusted to pH 4.5 with 0.1 N HC1 and pepsin was added (lmg/ml). Pancreatin (0.4 g/100 ml of 0. l M NaHCO3) was added to each sample, which was then incubated at 37°C. Digested formulas were immediately placed in boiling water for 4 min. to inactivate enzymes. True protein content ranged from 12.5-17.5 g/L. Protein digestibility calculated as (NPN after digestionNPN before digestion) x 6.25 x 100/true protein ranged from 49-68%. Protein digestibility was generally highest for powdered formula, while it was slightly higher from liquid concentrate than from ready-to-feed formula. These results suggest that protein utilization by infants may be affected by the type of processing used.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology