Characterization of the key-aroma compounds in egg yolk powder and the changes of aroma profile during the storage

The aroma compounds in different shelf-lives egg yolk powder were extracted by solid-phase microextraction(SPME)and analyzed by gas chromagraphy-olfactometry-mass spectrometry. A principal component analysis(PCA)was adopted to explore the difference of key-aroma active compounds among five different shelf-lives egg yolk powder. The results indicated that 31 aroma compounds were identified.Totally 10 kinds of substances such as,2-methylbutanal(cocoa),3-methylbutanal(malty),hexanal(grass),1-octen-3-one(mushroom),2-nonanone(hot milk like),3,5-octadien-2-one(fatty),n-propyl acetate(cheesy),2-pentylfuran(green bean),2,5-dimethypyrazine(roasted nut)and 2-ethyl-5-methyl-pyrazine(fruit),were regarded as the key-aroma active compounds in egg yolk powder because of the great attribution to the aroma profile of the egg yolk powder. From the results of PCA analysis,the flavor profile of egg yolk powder was simpler in first two samples. The major categories were pyrazines and aldehydes. With the extension of the shelf-life,the more aroma compounds were generated,such as alcohols and ketones,and enriched the flavor profile of the egg yolk powder. According to the results of the compounds detected by GC-MS,Lipid oxidation and Maillard reaction was the main reason for the overall change of the flavor of egg yolk powder,therefore,in order to improve the shelf-life stability of egg yolk powder,a good way could be taken was that not only inhibit fat oxidation,but also promote the Maillard reaction.