RESUMEN

Aroma is a key criterion in evaluating aromatic coconut water. A comparison regarding key aroma compounds and sensory correlations was made between Thailand Aromatic Green Dwarf (THD) and Cocos nucifera L. cv. Wenye No. 4 coconut water using E-nose and GC × GC-O-TOF-MS combined with chemometrics. Twenty-one volatile components of coconut water were identified by GC × GC-O-TOF-MS, and 5 key aroma compounds were analyzed by relative odor activity value and aroma extract dilution analysis. Moreover, the combination of the E-nose with orthogonal partial least squares was highly effective in discriminating between the two coconut water samples and screened the key sensors responsible for this differentiation. Additionally, the correlation between volatile compounds and sensory properties was established using partial least squares. The key aroma compounds of coconut water exhibited positive correlations with the corresponding sensory properties.

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Three major compounds, 2-acetyl-1-pyrroline (APY), 2-acetyltetrahydropyridine (ATHP) and 2-ethyltetrahydropyridine (ETHP), have been identified as responsible for the mousy off-flavor in wines, although to date quantification data reported in the literature are limited. A simple method for simultaneous quantitation, by SBSE-GC-MS, of these N-heterocyclic compounds was developed. Both previously reported tautomers of ATHP, 2-acetyl-1,4,5,6-tetrahydropyridine and 2-acetyl-3,4,5,6-tetrahydropyridine were identified. The limits of detection and quantification of the method were determined in white, rosé and red wines and are lower than previously published concentrations in spoiled wine. ETHP was detected in almost all wines produced with limited use of SO2. ATHP was detected in almost all wines suspected of mousiness whereas APY was only detected in few cases. This method will provide a support for further studies aimed at understanding the phenomena that influence the occurrence of mousy off-flavor and the oenological parameters that modulate its expression.

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The consumption of soy drink in Western countries is limited due to its green off-flavor. Hence, fermentation of soy drink with Lycoperdon pyriforme to tailor the aroma has been investigated. After 28 h the green off-flavor was not perceived by 60% of the sensory panel (n = 23). Molecular sensory changes of soy drink during fermentation were decoded by means of direct immersion-stir bar sorptive extraction coupled with gas chromatography-mass spectrometry-olfactometry and aroma dilution analysis. The semi-quantification of key odorants revealed a significant decrease of the representative green odorants (i.e., hexanal, (E)-2-nonenal, (E,E)-2,4-decadienal) of soy drink, among of which hexanal even turned below its odor threshold. The quantitative reduction of these odorants correlated with the organoleptic difference. Besides that, nutritionally relevant parameters of soy drink including protein, fat, and polyphenol content kept consistent during the short fermentation process.

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In this work, a total of 35 important aroma compounds with odor activity values (OAVs) greater than 1 were detected by gas chromatography-mass spectrometry (GC-MS) in traditional Chinese-type soy sauce. Of these, fragrant compounds with aromatic rings (20 compounds) accounted for a large proportion, over 57%. Combining principal component analysis and GC-olfactometry-MS (GC-O-MS), 5-methyl-2-furanmethanethiol (OAV: 284-467), 3-methylbutanal (OAV: 409-938), phenylacetaldehyde (OAV: 47.4-566), 2-phenylethanol (OAV: 7.41-14.3), phenylethyl acetate (OAV: 7.00-18.1) and ethyl phenylacetate (OAV: 12.7-21.3) were confirmed as the typical fragrant compounds among all samples. Furthermore, full two-dimensional gas mass spectrometry (GC × GC-TQMS) was applied and 414 aroma compounds were identified, which included another 85 fragrant compounds with aromatic rings.

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Starch in cooked rice affects the volatilization of aroma compounds, due to their interactions. In particular, the linear fraction of starch from various plant sources, i.e. amylose, can form complexes with a wide variety of ligands. In the present work, the capacity of amylose for embedding and controlling the release of five aroma compounds (hexanal, 1-octen-3-ol, γ-decalactone, 2-acetyl-1-pyrroline, 2,3-butanedione), corresponding to the different types of typical aromas in cooked rice, were tested to determine whether they formed complexes with amylose. The results obtained from x-ray diffraction and differential scanning calorimetry showed that the interactions occurred between amylose and aromas, and four of the aromas (except for 2,3-butanedione) could form complexes with V-type crystal. The release behavior of aromas from complexes was further evaluated using gas chromatography, indicating that amylose has effects on aroma release. These findings suggested that interactions between rice amylose and aromas occurred, thus affecting the release of aromas from the amylose matrix.

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2-Acetyl-1-pyrroline (2AP) is a popular yet highly unstable aroma compound, which limits its commercial use as a flavoring ingredient. The stability and application of spray-chilled paraffin-coated microcapsules of 2AP zinc chloride complex (2AP-ZnCl2) were investigated in this study. 2AP-ZnCl2 microcapsules (0.081% (w/w) 2AP loading) and unprotected 2AP-ZnCl2 complex were subjected to ambient storage at four different relative humidities (RH; ∼0%, ∼22.5%, ∼43.2% and ∼100%). The results showed that the microcapsules had significantly greater 2AP stability compared with the unprotected complex under all storage conditions studied. A flavor application study using instant rice was also performed to validate the potential effectiveness of using 2AP-ZnCl2 microcapsules as a flavoring agent. Full 2AP recovery was achieved after the cooking process, where the controlled release function of the microcapsules was clearly exhibited. The results demonstrated that microencapsulation of 2AP-ZnCl2 allows for more flexible handling/storage practices and has potential for application by the flavor industry.

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A moisture-sensitive 2-acetyl-1-pyrroline zinc chloride complex (2AP-ZnCl2) was successfully encapsulated by spray-chilling, using a hydrophobic moisture barrier as a practical way to protect the complex and to help facilitate its general use in food applications. Use of octacosane as wall material provided a flavor retention of 65.3%. The results from scanning electron microscopy (SEM) and X-ray micro-computed tomography (X-ray micro-CT) indicated desirable morphological characteristics of the matrix type microcapsules. Gas chromatography (GC) and absorbance spectroscopy were used for chemical quantitation of 2AP and ZnCl2, respectively, in the microcapsules. Results revealed no degradation of 2AP occurred as a result of the encapsulation process. This study is the first to demonstrate the feasibility of producing high quality microcapsules from labile flavor complexes by spray-chilling. The use of generally recognized as safe (GRAS) substances, including 2AP and ZnCl2, may allow for widespread commercial use of 2AP as a flavor ingredient.

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