Perfect Sample Preparation – is Complete and Holistic

Extraction of Odorants from Foods Possible?

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Introduction

Sample preparation is critical to successfully analyse odorants (odour activevolatile organic compounds). However, there is no one perfect samplepreparation method for the complete, holistic extraction of odorants. Why?

Table 1. Odorants are diverse in; chemical function, physicochemical properties,

odour threshold and reactivity and food matrices are complex.

Is it possible to use a representative test mixture of odorants to measure,

compare and predict the ability of different sample preparation methods?

No. Name BP. (˚C) Kow Odour Threshold (µg / kg)

1 trimethylamine 3 1.10 25 (pH = 7.9)

2 2-methyl-3-furanthiol 58 398 7.0 x 10-3

3 bis(2-methyl-3-furfuryl)disulfide 280 13800 2.0 x 10-5

1Mars Petcare, WALTHAM Centre for Pet Nutrition, Waltham-on-the-Wolds, Leicestershire, UK.

2University of Nottingham, University Park, Nottingham, UK.

3Anatune, Wellbrook Court, Cambridge, Cambridgeshire, UK.

LEWIS L. JONES1, Samuel Wordsworth2, Nathan Hawkins3, Kathy Ridgway3, James B. Addision1.

O

SH

Results

Figure 4. Extraction Efficiency. Neither sample preparation method (SPME orSAFE) extracted completely and holistically across the full physicochemical

landscape assessed. Matrix fat composition has a large effect on extraction

efficiency (mean values shown, n = 8).

Figure 4. Predicting Extraction Efficiency The results can be used to predict the extraction efficiency of odorants from their LogP and Log Vp values, which

are available from on-line databases e.g. Estimation Programs Interface Suite™

Methodology

The extraction efficiencies of a representative test mixture of 23 compounds from

3 model systems were calculated for 2 sample preparation methods. The methods

chosen were complementary:

• extraction based on volatility: headspace extraction by solid phase

microextraction (SPME)

• Extraction based on polarity: liquid extraction – distillation by solvent assisted

flavour evaporation (SAFE).

The model systems for extraction of the test mixture were water, 10% fat in water

and 100% fat.

Extraction efficiency (%) =

Test mixture Extract

Model

Figure 2. Sample preparation by liquid extraction – distillation using solvent assisted flavour evaporation

Peak Area Extract

Peak Area Test Mixturex 100

1.00E-12

1.00E-10

1.00E-08

1.00E-06

1.00E-04

1.00E-02

1.00E+00

1.00E+02

1.00E+04

-10 -5 0 5 10

Odorants Test Mixture

Hydrophobicity (log P)

Vo

lati

lity

(lo

g V

p)

pL

)

Very volatile

Less volatile

Hydrophilic Hydrophobic

Figure 1. A representative test mixture of stable odorants was selected over a broad landscape of physicochemical properties within the area appropriate for GC analysis.

heat

1 2 3

Conclusion

It is possible to measure and compare the extraction efficiency of different

sample preparation methods, using a representative test mixture of stableodorants, selected over a broad landscape of physicochemical properties.

Both methods assessed were unable to extract fully across the physicochemicallandscape occupied by odorants, in any of the 3 matrices. Despite choosingcomplementary methods, areas of the landscape remain inefficiently extractedby both methods. In particular, the very volatile, hydrophilic odorants.

The use of a representative test mixture, the fundamental knowledge producedand subsequent modelling enables:

• Optimisation of sample preparation methods

• Development of new methods to cover a broader landscape or focus onspecific areas e.g., very volatile, hydrophilic compounds

• Estimation of extraction efficiency for targeted analysis – given knowledge of an odorants hydrophobicity (Log P) and volatility (log Vp), which is widely

available online.

Further work is required to: (i) test the model and (ii) investigate odorant stability on extraction efficiency.

References

CAS Number

Properties

Estimated

extraction

efficiency

• Reineccius, G., (2005) In: Flavor chemistry and technology, second edition; CRC Press: p.

33-72.

• Belitz, H.-D., et al. (2000). Food Chemistry. Berlin, Springer.

• Linforth, R (2009) compilation of odorant physicochemical properties, unpublished.

• US EPA. (2016). Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.1, United

States Environmental Protection Agency, Washington, DC, USA

100% Water 10% Fat 100% Fat

SPME

SAFE

Log P

Lo

g V

P

Lo

g V

P

Log P

Lo

g V

P

100

80

60

40

20

0

80

60

40

20

0

60

40

20

0

2

1

0

-1

-2

-3

-4

0-1 1 2 3 4 5 6

2

1

0

-1

-2

-3

-4

0-1 1 2 3 4 5 6

Log P

Lo

g V

P

2

1

0

-1

-2

-3

-4

0-1 1 2 3 4 5 6

2

1

0

-1

-2

-3

-4

Log P0-1 1 2 3 4 5 6

Log P

0-1 1 2 3 4 5 6

Lo

g V

P

2

1

0

-1

-2

-3

-4

Log P

0-1 1 2 3 4 5 6

Lo

g V

P

2

1

0

-1

-2

-3

-4

0.6

0.4

0.2

0

0.6

0.4

0.2

0

0.8

6

4

2

0

8