Distillation/extraction papaya

Figure 6. HRGC comparison of papaya (C.papaya, L.) fruit volatiles obtained after high-vacuum distillation/extraction (pH 5.6) (a) and direct extraction (pH 7.0) (b) (J W DB-Wax, 30 m x 0.32 mm id, df = 0.25 pm). Sta = external standard.

Isomers of 6,7-Epoxy-linalool as Precursors of Linalool Oxides. Previously, the triol (21) had been proposed as a possible precursor of the hydroxy ethers (14) and (15), the so-called linalool oxides(Fig-ure 8). At an acidic pH (<3.5) and/or during heat treatment (e.g., steam distillation/extraction), the triol (21) had been found to be decomposed to (14) and (15) (23,24). In these previous experiments no formation of the corresponding pyranoid linalool oxides (22) and (23) was observed. We evaluated the hypothesis that linalool oxides are formed from triol (21) under natural conditions of papaya pulp (i.e. pH 5.6) and could find no formation of linalool oxides. Even in model experiments carried out at pH 3.5, only traces of linalool oxides were detected after incubation of (21) for three days. As a result of these experiments the isomers of 6,7-epoxy-linalool have to be considered as the natural precursors of linalool oxides (14, 15) as recently suggested by Ohloff et al. (25). The latter s proposal was based on earlier findings obtained in a series of chemical reactions (9). 

Several volatile components of papaya (Solo variety) were recovered by four methods vacuum trapping train (distillation under low temperatures with liquid nitrogen traps), codistillation-extraction (vacuum), vacuum distillation, and codistillation-extraction (1 atm) [17]. In spite of great variations due to the recovery method, the results showed that linalool was always the major compound detected for all the methods. 

Another investigation reported the esters as the predominant volatile components of the Maradol variety (about 41% w/w of the total volatiles) [51]. The major representative compounds in the simultaneous steam distillation-solvent extraction were methyl butanoate and ethyl butanoate. Previous work described the esters as the predominant compounds among the volatiles papayas, for example, from Sri Lanka and Colombia had 52 and 63% of esters in the total volatiles respectively [25,41]. 

When the MS results are expressed as CS2 and compared with the spectrophotometric CS2 results, highly identical values show proof that the MS procedures work well in terms of DTC extractability and accuracy. This was generally the case, with two exemptions, that is, broccoli and papaya, which were free of DTC residues as indicated by both MS methods. Therefore, the CS2 found by the spectrophotometric digestion/ distillation method clearly originates from phytogenic CS2 sources instead of DTC residues [33]. Both plant samples are well known to produce glycosinolates responsible for CS2 formation and, therefore, for falsepositive DTC results. 

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