Analysis of Volatile Flavor Compounds in Sea Duck Egg White during Salting by Gas Chromatography-Ion Mobility Spectrometry

Sensory evaluation, gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate statistical methods such as principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to analyze the changes of volatile flavor compounds in sea duck egg white during salting. A total of 43 volatile organic compounds (VOCs) were identified, including esters, ketones, aldehydes, acids and alcohols, ranked in decreasing order of their numbers. A total of 20 characteristic compounds were identified throughout the salting process, including ethyl acetate, 3-hydroxy-2-butanone, n-propanol, isobutyric acid, isopropyl acetate, 2,3-butanedione, propionic acid, 3-methyl-3-butene-1-alcohol, 2-methylbutyraldehyde, propyl acetate, n-butyraldehyde, 2-butanone, isopropanol, isovaleraldehyde, ethyl isobutyrate, tetrahydrofuran, 2-pentanone, n-butanol isoamyl alcohol and trans-2-pentenoaldehyde. Isobutyric acid and propionic acid were the major fishy odor compounds of salted egg white. The content of 2-butanone in fresh duck eggs was the highest. After five days of salting, ethyl acetate became the most abundant volatile compound. After 25 days of salting, the relative proportions of isobutyric acid and propionic acid gradually increased. The relative contents of n-butyraldehyde and isovaleraldehyde increased gradually during salting. The characteristic flavor substances clearly differed among salting stages. GC-IMS identification of flavor substances in sea duck egg white can provide a theoretical basis for identifying the unique flavor and judging the quality change of sea duck eggs during salting.