Determination of 19 Flavor Esters in Milk Samples of Different Fat Contents Using Modified QuEChERS-gas Chromatography-mass Spectrometry

Abstract:

A modified “quick, easy, cheap, effective, rugged and safe” (QuEChERS)-gas chromatography-mass spectrometry (GC-MS) technique was adopted to determine 19 flavor esters in milk samples having different fat contents, and the relationship between flavor esters and fat content was investigated. The flavor esters were extracted with acetonitrile from the samples and purified using prostate specific antigen (PSA). Subsequently, the extract was filtered through a filter membrane and analyzed using GC-MS. The 19 flavor esters were separated using a DB-FFAP chromatographic column. They were then detected in the single ion monitoring (SIM) mode, and their contents were quantified using the external standard calibration method. The results showed good linear relationships for 19 flavor esters within the range of 5.0~500.0 μg/L, with their correlation coefficients (R2) being higher than 0.999. The average recoveries were in the range of 76.0%~109.2%, and the intra-day precision was 1.9%~8.5% (n=6). The limits of detection (LODs) and limits of quantification (LOQs) are 3.5~14.0 μg/kg and 10.0~40.0 μg/kg, respectively. Real-time sample detection revealed the contents of δ-decalactone, γ-dodecalactone, and δ-dodecalactone to be positively correlated with the fat content, and therefore were higher in whole milk followed by low-fat milk and by skimmed milk. In addition, flavors and fragrances may be added in some milk samples, resulting in significant increases in the contents of γ-nonalactone and γ-undelactone. The proposed method is rapid, simple, and accurate, with good reproducibility and can be used to determine 19 flavor esters in milk samples of different fat contents.