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

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 of LAL in protein) and the limit of quantitation (95 mg kg of LAL in protein), linearity (r = 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 of protein and from 0 to 8434.21 mg kgof protein during the alkaline pickling period, and then gradually raised to 17481.44 mg kg and 8956.16 mg kg of protein after 18 days of aging, respectively.