Determination and changes of free amino acids in royal jelly during storage

Abstract

Free amino acids (FAAs) in royal jelly (RJ) were determined and their identification was confirmed with mass spectrometric detection (GC-MS). The presence of D-aminoacids was evaluated using GC with a chiral column. The total FAA content was 7.3 mg/g RJ on average; the major FAAs were proline, lysine, glutamate, β-alanine, phenylalanine, aspartate and serine. The concentration of FAAs of the D-series was below the detection limit of the method (0.1 mg/g RJ) in all the samples. The FAA fraction was monitored in RJ frozen immediately after sample collection (control) and in aliquots of the same sample stored at two different temperatures (room temperature and 4°C) for different time intervals (3, 6 and 10 months). The FAA content was constant throughout storage at 4°C. However, at room temperature, proline and lysine increased after three months to 6.8 and 3 mg/g, respectively and then decreased after 6 and 10 months to 3 and 1 mg/g.