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D‐Amino acids in reconstituted infant formula: A comparison between conventional and microwave heating
Author(s) -
Marchelli R,
Dossena A,
Palla G,
AudhuyPeaudecerf M,
Lefeuvre S,
Carnevali P,
Freddi M
Publication year - 1992
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740590213
Subject(s) - amino acid , proline , hydrolysis , chromatography , chemistry , gas chromatography , microwave oven , enantiomer , microwave , organic chemistry , biochemistry , physics , quantum mechanics
It was recently claimed that microwave heating of reconstituted formulas for infants could induce racemisation of amino acids, in particular, of proline. In the present work we investigated the presence of D‐amino acids in different samples of a reconstituted infant formula heated by a conventional heat‐transfer way (oil bath), in a commercially available domestic microwave oven and in a wave‐guide device. The analyses were carried out both by gas chromatography and by high performance liquid chromatography. The presence of D‐enantiomers was determined both in proteins after hydrolysis (6 M HCl at 100°C for 6 h) and in the free amino acid pool. Regarding protein‐bound amino acids, there is no evidence of racemisation in all samples examined under the different experimental conditions (conventionally and microwave‐treated samples). In particular, D‐proline was not detected at least above 1 mg litre −1 in proteins and above 20 μg litre −1 in free amino acids. Although small percentages (D/D + L %) of D‐glu and D‐asp and higher percentages of D‐ala were detected among free amino acids, in all samples, no significant differences could be found between untreated and treated samples.