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KMID : 1025520040460010091
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Journal of Animal Science and Technology
2004 Volume.46 No. 1 p.91 ~ p.96
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Production of Free D-amino Acids in Raw Milk Related to Psychrotrophic Bacterial Contamination
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Abstract
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It is generally believed that amino acids occurring naturally in mammals are of the L-configuration. D-amino acid(DAA) are common in nature as constituents of bacterial of bacterial cell walls and several antibiotics. Recent reports have demonstrated the presence of small amounts of free DAA in milk. The presence of free DAA may affect the food quality by decreasing the nutritional value. Our objective was to examine whether the free DAA came from psychrotrophic bacteria. Free DAA was produced by treating raw milk with Pseudomonas spp. The samples were extracted with sulphosalicylic acid and derivatized with AccQ-Tag^(TM) reagent when the analysis was carried out by reverse-phase HPLC. We tested correlations of the content of free DAA with bacterial growth. Significant amounts of free D-alanine and D-proline have been found in the raw milk inoculated with Pseudomonas spp. The increase of D-alanine and D-proline appeared to be mainly related to the presence of Pseudomonas fluorescens. There results suggest that free DAA may be considered as an indicator of psychrotrophic bacterial milk contamination.
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