Identification and source analysis of volatile flavor compounds in paper packaged yogurt by headspace solid-phase microextraction-gas chromatography-mass spectrometry

Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze volatile flavor compounds of yogurt packaged in carton. Volatile flavor compounds of off-flavor yogurt were compared with that of fresh milk, unpackaged yogurt, non-off-flavor yogurt, and its packaging materials. Furthermore, volatile flavor substances from paper packaging materials were analyzed by migration assay. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to describe the changes of volatile compounds in different kinds of yogurt and to identify the potential markers associated with the off-flavor of yogurt. A total of 30 volatile flavor compounds were identified in two kinds of off-flavor yogurt. Importantly, three flavor compounds: Nonanal, 2-ethyl-1-hexanol, and d-limonene were not only detected in off-flavor yogurt, but also in paper packaging materials, which indicated that these substances from paper packaging materials have a certain contribution to off-flavor yogurt. Migration assay combined with VIP values showed that ethanol and ethyl acetate contributed can be considered as the other indicators for the monitoring of yogurt quality.