Effect of Varying Freeze-Thaw Cycles on Volatile Compounds in Roast Duck: An Investigation Using Headspace-Gas Chromatography-Ion Mobility Spectrometry Combined with Multivariate Statistical Analysis

To definite the effect of varying freeze-thaw cycles on the aroma characteristics of roast duck, its volatile compounds were analyzed by sensory evaluation, electronic nose, and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with multivariate statistical analysis. The results showed that roast duck prepared from duck carcasses that underwent more than two freeze-thaw cycles exhibited significant differences in aroma profiles, characterized by loose meat texture, faint aroma, and uneven skin color distribution. A total of 19 aldehydes, 4 alcohols, 6 ketones, 1 ester, 1 furan, and 9 unidentified species were detected by HS-GC-IMS, with the most abundant ones being aldehydes, followed by alcohols, ketones, and esters. With increasing number of freeze-thaw cycles, the relative contents of volatile compounds, such as aldehydes and ketones, decreased, while the relative content of alcohols increased in roast duck. Five key odor markers, nonanal, octanal, heptanal, 2-methylbutanal, and (E)-2-pentenal were selected using orthogonal partial least squares-discriminant analysis (OPLS-DA) and relative odor activity values (ROAV). There was a correlation between the five key odor markers and the number of freeze-thaw cycles for raw duck carcasses. This study provides a theoretical basis for retaining and rapidly identifying volatile compounds in roast duck produced from repeatedly frozen-thawed carcasses.