Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
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Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

capacity4dev.ec.europa.eu
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30.10.2014 Views

9 SOLID PHASE MICRO-EXTRACTION AND HEADSPACE TRAPPING EXTRACTION However, static headspace samples are normally too small to quantify odorants that are present only at low concentrations in the vapor phase. In other words, one can smell them, but in many cases it is not possible to obtain a signal in a mass spectrometer. 9.7.2 Dynamic Headspace Trapping To overcome the disadvantages of headspace trapping method, dynamic headspace trapping can be used (Figure 6). Again, the food sample is placed in a heated vessel but the evaporating compounds are continuously swept by a stream of inert gas into a trap containing a porous polymer, which adsorbs more or less the organic constituents. This method yields a much higher amount of trapped volatiles so that, after desorption, it is no longer problematic to obtain an MS signal. Figure 6: Dynamic headspace trapping technique However, the disadvantage of this procedure is the strong dependence on the yield of the odorants, on the velocity of the carrier gas and on the selectivity of the adsorption and desorption process for different compounds. It is very diffi cult to control these parameters precisely and therefore, the results of such quantitative measurements might be inaccurate. 9.7.3 Recovering the Adsorbed Volatiles by Thermal or Liquid Solvent Desorption Several studies have reported methods of desorption using organic solvents. Drawbacks of the use of solvent desorption include the loss of volatile compounds during removal of excess solvent before GC analysis, solvent selectivity and solvent impurities. We recently developed a sensitive and highly reproducible dynamic headspace (DHS) protocol with thermal 164

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS desorption (using injector glass liners packed with Tenax-TA as adsorbent traps for aroma collection at ambient room temperature) and desorption at the interior of a GC injector. This DHS-type protocol was used to characterize fresh tomato fl avor compounds; the results were compared with published data from a static headspace method (Table 1). Table 1: Concentration of selected tomato aromas from heat-processed tomato juice by static headspace trapping (SHT) and dynamic headspace trapping (DHT), expressed in parts per billion (ppb) Compound SHT, ppb DHT, ppb (E)-2-hexanal 5 340 1-Penten-3-one 61 100 2-Isobutylthiazole 2 450 2-Methylfuran 97 1,060 2-Pentylfuran 26 700 3-Methybutanal 17 750 3-Methylfuran 717 3,200 6-Methyl-5-hepten-2-one 21 1,330 Acetone 325 - Benzaldehyde 3 30 Dimethyl disulfi de 16 630 Dimethyl sulfi de 5,205 2,974 Ethanol 311 - Geranial 2 130 Hexanal 188 6,210 Pentanal 48 470 In the present study, this DHT-type protocol was used to characterize fresh tomato fl avour compounds for comparison with related literature methods. 9.7.4 Some Practical Examples of Headspace Technique Use 9.7.4.1 Tomato Juice Fresh tomato juice was made from vine-ripe fruit by Campbell Soup Company’s R&D centre in Davis, USA. Chemicals were reagent grade, supplied from reliable sources. 165

EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS<br />

desorption (using injector glass liners packed with Tenax-TA as adsorbent<br />

traps <strong>for</strong> aroma collection at ambient room temperature) <strong>and</strong> desorption at<br />

the interior of a GC injector. This DHS-type protocol was used to characterize<br />

fresh tomato fl avor compounds; the results were compared with published<br />

data from a static headspace method (Table 1).<br />

Table 1: Concentration of selected tomato aromas from heat-processed tomato<br />

juice by static headspace trapping (SHT) <strong>and</strong> dynamic headspace trapping (DHT),<br />

expressed in parts per billion (ppb)<br />

Compound SHT, ppb DHT, ppb<br />

(E)-2-hexanal 5 340<br />

1-Penten-3-one 61 100<br />

2-Isobutylthiazole 2 450<br />

2-Methylfuran 97 1,060<br />

2-Pentylfuran 26 700<br />

3-Methybutanal 17 750<br />

3-Methylfuran 717 3,200<br />

6-Methyl-5-hepten-2-one 21 1,330<br />

Acetone 325 -<br />

Benzaldehyde 3 30<br />

Dimethyl disulfi de 16 630<br />

Dimethyl sulfi de 5,205 2,974<br />

Ethanol 311 -<br />

Geranial 2 130<br />

Hexanal 188 6,210<br />

Pentanal 48 470<br />

In the present study, this DHT-type protocol was used to characterize<br />

fresh tomato fl avour compounds <strong>for</strong> comparison with related literature<br />

methods.<br />

9.7.4 Some Practical Examples of Headspace Technique<br />

Use<br />

9.7.4.1 Tomato Juice<br />

Fresh tomato juice was made from vine-ripe fruit by Campbell<br />

Soup Company’s R&D centre in Davis, USA. Chemicals were reagent grade,<br />

supplied from reliable sources.<br />

165

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