Effect of frozen storage on the untargeted and targeted metabolites of flavored roasted beef using UHPLC-MS/MS and GC-MS.

In this study, we investigated the changes in untargeted metabolites using UHPLC-MS/MS and the flavors of nonflavored (BS1) and flavored (BS2) roasted beef using GC-MS throughout a 6-month frozen period. A total of 509, 659, and 496 metabolites met the conditions for differential screening, and 56, 103, and 47 differential metabolites were recognized between BS1 and BS2 at 0, 3, and 6 months of frozen periods, respectively. The total relative abundance of organic nitrogen compounds, phenylpropanoids, polyketides, organic acids and their derivatives, and benzenoids increased during frozen storage at 3 months and then decreased at 6 months. A total of 16 differential metabolites were identified as markers for prolonged freezing, which belong to organic acids and their derivatives (Asp-Val-Lys, Val-Lys, Met-Phe, Tyr-Leu, N(6)-(octanoyl)lysine, and cis-acetylacrylate), lipids and lipid-like molecules (2,3-dimethyl-3-hydroxyglutaric acid, PC(P-16:0/2:0), (S)-17-hydroxy-9,11,13,15-octadecatetraynoic acid, PC(18:1(9Z)/18:1(11Z)), LysoPC (20:4(8Z,11Z,14Z,17Z)/0:0), PC(20:5/0:0), PE(20:3(8Z,11Z,14Z)/18:4(6Z,9Z,12Z,15Z)), and PS(14:1(9Z)/22:0)), and others (putrescine and phenylacetaldehyde). Sixty-three volatile flavor compounds were detected, and their concentrations were decreased along with frozen storage, except for aldehydes. Positive correlations were observed between volatiles and free amino acids. Therefore, frozen storage has a notable effect on the metabolite profiles of roasted beef.