Optimization of headspace solid-phase microextraction for the analysis of specific flavors in enzyme modified and natural Cheddar cheese using factorial design and response surface methodology.

Optimization of headspace solid-phase microextraction for the analysis of specific flavors in enzyme modified and natural Cheddar cheese using factorial design and response surface methodology.

Journal of chromatography. A (2008-05-23)

Julien Januszkiewicz, Hassan Sabik, Sorayya Azarnia, Byong Lee

ABSTRACT

A headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC/MS) method was developed using experimental designs to quantify the flavor of commercial Cheddar cheese and enzyme-modified Cheddar cheese (EMCC). Seven target compounds (dimethyl disulfide, hexanal, hexanol, 2-heptanone, ethyl hexanoate, heptanoic acid, delta-decalactone) representative of different chemical families frequently present in Cheddar cheese were selected for this study. Three types of SPME fibres were tested: Carboxen/polydimethylsiloxane (CAR/PDMS), polyacrylate (PA) and Carbowax/divinylbenzene (CW/DVB). NaCl concentration and temperature, as well as extraction time were tested for their effect on the HS-SPME process. Two series of two-level full factorial designs were carried out for each fibre to determine the factors which best support the extraction of target flavors. Therefore, central composite designs (CCDs) were performed and response surface models were derived. Optimal extraction conditions for all selected compounds, including internal standards, were: 50 min at 55 degrees C in 3M NaCl for CAR/PDMS, 64 min at 62 degrees C in 6M NaCl for PA, and 37 min at 67 degrees C in 6M NaCl for CW/DVB. Given its superior sensitivity, CAR/PDMS fibre was selected to evaluate the target analytes in commercial Cheddar cheese and EMCC. With this fibre, calibration curves were linear for all targeted compounds (from 0.5 to 6 microg g(-1)), except for heptanoic acid which only showed a linear response with PA fibres. Detection limits ranged from 0.3 to 1.6 microg g(-1) and quantification limits from 0.8 to 3.6 microg g(-1). The mean repeatability value for all flavor compounds was 8.8%. The method accuracy is satisfactory with recoveries ranging from 97 to 109%. Six of the targeted flavors were detected in commercial Cheddar cheese and EMCC.

MATERIALS

Product Number

Brand

Product Description

11072-U

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 572, 20-45 mesh, bottle of 10 g

57299-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), needle size 23 ga, StableFlex, for use with manual holder or autosampler, fiber L 2 cm

57912-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), for use with autosampler, needle size 23 ga, metal alloy fiber, fiber L 1 cm

57906-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 85 μm(CAR/PDMS, for use with autosampler, needle size 23 ga, metal alloy fiber

57914-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), for use with autosampler, needle size 23 ga, metal alloy fiber, fiber L 2 cm

W243906

Sigma-Aldrich

Ethyl hexanoate, ≥98%, FCC, FG

57298-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), needle size 23 ga, StableFlex, for use with autosampler

57295-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 85 μm(CAR/PDMS, needle size 23 ga, StableFlex, for use with autosampler

57343-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 75 μm(CAR/PDMS, needle size 23 ga, for use with autosampler

10477-U

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 1000, 40-60 mesh, bottle of 50 g

504831

Supelco

SPME Portable Field Sampler, coating CAR/PDMS

57335-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 85 μm(CAR/PDMS, needle size 24 ga, StableFlex, for use with autosampler

57328-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), needle size 24 ga, for use with manual holder

10478-U

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 1000, 60-80 mesh, bottle of 10 g

25467

Supelco

Carboxen^®-1010 PLOT Capillary GC Column, L × I.D. 30 m × 0.53 mm, average thickness 30 μm

10269

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 569, 20-45 mesh, bottle of 10 g

57348-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), needle size 24 ga, StableFlex

24246

Supelco

Carboxen^®-1010 PLOT Capillary GC Column, L × I.D. 30 m × 0.32 mm, average thickness 15 μm

25461

Supelco

Carboxen^®-1006 PLOT Capillary GC Column, L × I.D. 30 m × 0.53 mm, average thickness 30 μm

11324-U

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 564, 20-45 mesh, pack of 144 × 290 mg

10471

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 1003, 40-60 mesh, bottle of 10 g

57318

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 75 μm(CAR/PDMS, for use with manual holder, needle size 24 ga

57334-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 85 μm(CAR/PDMS, needle size 24 ga, for use with manual holder, StableFlex fiber

57319

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 75 μm(CAR/PDMS, needle size 24 ga, for use with autosampler

57329-U

Supelco

SPME fiber assembly Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS), needle size 24 ga, StableFlex, for use with autosampler

57344-U

Supelco

SPME fiber assembly Carboxen/Polydimethylsiloxane (CAR/PDMS), d_f 75 μm(CAR/PDMS, needle size 23 ga, for use with manual holder

24241-U

Supelco

Carboxen^®-1006 PLOT Capillary GC Column, L × I.D. 30 m × 0.32 mm, average thickness 15 μm

W243914

Sigma-Aldrich

Ethyl hexanoate, natural, ≥98%, FCC, FG

54041-U

Supelco

Carboxen^® 1000 Reversible SPE Tube, 200 mg/mL, pk 30

11048-U

Supelco

Carboxen^® Adsorbent, matrix Carboxen^® 569, 20-45 mesh, bottle of 500 g