Determination of Flavor and Off Flavor Compounds in Dairy Products using Stir Bar Sorptive Extraction (SBSE) and Thermal Desorption GC/MSD/ PFPD

Importance of Topic

The comprehensive profiling of flavor and off-flavor compounds in dairy products is essential for product quality control and development. Conventional extraction methods often involve organic solvents and complex procedures. Stir Bar Sorptive Extraction (SBSE) offers a solvent-free, sensitive, and reproducible alternative capable of capturing a broad range of volatile and semi-volatile analytes.

Objectives and Study Overview

This application note evaluates SBSE combined with thermal desorption GC–MSD and GC–PFPD for the analysis of aroma, flavor, and trace off-flavor compounds in various dairy matrices such as milk, condensed milk, cream cheese, herb-flavored cheese, and fruit-flavored yogurt. The goal was to demonstrate SBSE’s performance versus traditional approaches and to highlight its suitability for routine dairy analysis.

Methodology

Samples were placed in 10 ml headspace vials, stirred with a PDMS-coated stir bar for 60 minutes, then thermally desorbed at 200 °C. Analytes were focused at –150 °C in a cold PTV inlet and transferred to a GC column for analysis. Both splitless and split modes were employed, with detection by MSD for general profiling and PFPD for sulfur compound detection.

Used Instrumentation

• Gerstel Twister stir bars (PDMS, 1 mm film thickness)
• Gerstel Thermal Desorption System TDS 2 with autosampler TDS A
• Gerstel CIS 4 PTV inlet with glass wool liner
• Agilent 6890 GC with 5973 MSD
• O.I. Analytical Pulsed Flame Photometric Detector for sulfur
• 30 m × 0.25 mm × 0.25 μm DB-Wax capillary column

Main Results and Discussion

• Milk (3.5 % fat): Detection of key ketones, fatty acids, and lactones at parts-per-trillion levels. Cooked milk showed elevated hydrogen sulfide and increased lactone formation.
• Condensed milk: Concentration intensified Maillard products and lactones. Styrene contamination from polystyrene packaging was over 100× higher than from polyethylene containers.
• Cream cheese: Profiles dominated by lactones and carbonyls. Herb-flavored variants revealed low-level garlic-type sulfur compounds detectable only by PFPD.
• Yogurt (strawberry): Characteristic esters, alcohols, and lactones responsible for fruit aroma were clearly resolved.

Benefits and Practical Applications

• High sensitivity and reproducibility across diverse dairy matrices
• Solvent-free, environmentally friendly extraction
• Simultaneous profiling of volatile, semi-volatile, and sulfur compounds
• Streamlined sample preparation with minimal matrix interference

Future Trends and Potential Uses

Advances in two-dimensional GC and high-resolution MS coupled with SBSE are expected to improve compound identification in complex food and environmental samples. SBSE may evolve into a rapid screening tool for food authenticity, safety monitoring, and broader industrial applications.

Conclusion

SBSE combined with thermal desorption GC–MSD/PFPD is a robust, sensitive, and green methodology for comprehensive flavor and off-flavor analysis in dairy products. It overcomes limitations of traditional techniques and supports quality assurance and product innovation.

Reference

1. Baltussen E, Sandra P, David F, Cramers C. Journal of Microcolumn Separations 1999;11:737.
2. Belitz HD, Grosch W. Food Chemistry, 2nd Edition. Springer-Verlag, 1999.