Determination of lysinoalanine formed during alkali-treating and aging of Chinese preserved eggs by gas chromatography

Xu-ying Luo, Yan Zhao, Jian-ke

Abstract

We established a method of gas chromatography with flame ionization detector (GC-FID) using N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) as derivatisation reagent and DL-2,6-diaminopimelic acid (DPA) as internal standard for the determination of lysinoalanine (LAL) in Chinese preserved egg. The derivatisation reaction was under the optimized condition of 75 °C and 30min. Method feasibility was demonstrated by experimental assessments of the limit of detection (32 mg kg-1 of LAL in protein) and the limit of quantitation (95 mg kg-1 of LAL in protein), linearity (r2 = 0.9996), the relative standard deviation values (< 5%) and mean recovery (91.9%-94.0%). The contents of LAL in Chinese preserved egg white and yolk during pickling and aging period were measured. The data revealed a change rule that the LAL content in egg white and yolk was increased from 0 to 17078.62 mg kg-1 of protein and from 0 to 8434.21 mg kg-1of protein during the alkaline pickling period, and then gradually raised to 17481.44 mg kg-1 and 8956.16 mg kg-1 of protein after 18 days of aging, respectively.