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J. Dairy Sci. 86:2283-2287
© American Dairy Science Association, 2003.

Lysinoalanine Content of Formulas for Enteral Nutrition

G. Boschin, A. D’Agostina, A. Rinaldi and A. Arnoldi

Department of Agrifood Molecular Sciences, Section of Chemistry, University of Milan, Via Celoria 2, Milano, I-20133, Italy.

Corresponding author:
A. Arnoldi; e-mail:
anna.arnoldi{at}unimi.it.

Casein and caseinates are the main ingredients of formulas for enteral nutrition. Their manufacturing procedure and the thermal treatments necessary to assure microbiological stabilization and satisfactory shelf-life of the end-products are particularly favorable for the formation of lysinoalanine (LAL), a cross-linked amino acid that is considered a useful marker of the thermal damage and reduced digestibility of proteins.

The lysinoalanine content of 18 different kinds of formulas for enteral nutrition was determined by HPLC after derivatization. The liquid formulas have an average value of 528 µg/g protein LAL, ranging from 160 to 800 µg/g protein (average content of formulas for pediatric use 747 µg/g protein). These values are rather high considering that the average value detected in UHT-treated drinkable milk is 117 µg/g protein. In principle, the preparation of caseinates and the thermal stabilization of the end products are the two steps more favorable for the formation of LAL. The fact that the five samples stabilized by an UHT-treatment have an average value of 512 µg/g protein suggests that the LAL content depends more on the quality of the starting ingredients than on the sterilization process. A better selection of the starting ingredients should improve the quality of formulas for enteral nutrition, which is very desirable when formulating foods for consumers with very high nutritional demands.

Key Words: lysinoalanine • thermal damage • cross-linked amino acids • enteral nutrition

Abbreviation key: LAL = lysinoalanine, FMOC = 9-fluorenylmethylformate, SPE = solid phase extraction






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