Gas Chromatography-mass Spectrometry-olfactometry Research Articles

Comparison of the Aroma-Active Compounds and Sensory Characteristics of Different Grades of Light-Flavor Baijiu.

This study comprehensively characterized and compared the aroma differences between four different grades of Fenjiu (FJ, the most representative light-flavor Baijiu). Aroma-active compounds were analyzed by liquid-liquid extraction (LLE) coupled with gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 88 aroma-active compounds were identified, and 70 of them were quantified. The results showed that a majority of aroma compounds in high-grade FJ had higher aroma intensities and concentrations. Among these compounds, there were 28 compounds with odor activity values (OAVs) greater than one in all four wines, which indicated that they might contribute to the characteristic aroma of FJ. Temporal dominance of sensation (TDS) and quantitative descriptive analysis (QDA) were used to characterize the sensory differences. The results suggested that high-grade FJ had a rich, pleasant and lasting retronasal aroma perception and exhibited pleasant orthonasal aroma of floral, fruity, sweet and grassy. Partial least squares regression (PLSR) analysis effectively distinguished four kinds of FJ and revealed associations between the orthonasal aroma attributes and the aroma compounds with OAVs >1. There were 15 compounds with variable importance in projection (VIP) values >1, and they were considered potential aroma markers for quality prediction.

Discovery and Flavor Characterization of High-Grade Markers in Baked Green Tea

Green tea is a popular beverage around the world and possesses a unique flavor. The flavor qualities of green tea are closely related to its grade and this relationship has not yet been studied. Three baked green teas with similar flavor were studied, namely, Huangshan Maofeng, Taiping Houkui, and Shucheng Xiaolanhua. A total of 34 odor compounds were identified by solid phase microextraction (SPME) combined with two-dimensional comprehensive gas chromatography-olfactometry-mass spectrometry analysis (GC×GC-O-MS). The results of the clustering analysis showed that the content of D-limonene and linalool in the high-grade (Grade A) tea was much higher than the content in other grades, so they were identified as odor markers of Grade A baked green tea. The taste components of different grades of green tea infusion were analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and HPLC. A combination of clustering analysis, principal component analysis (PCA), and orthogonal partial least squares discrimination analysis (OPLS-DA) indicated that galloylglucose, digalloylglucose, trigalloyglucose, strictinin, and gallic acid could be used as taste markers of Grade A baked green tea. Therefore, the results in this paper reveal the substances responsible for the odor and taste markers of high-grade baked green tea.

Decoding the evolution of aromatic volatile compounds and key odorants in Suancai (a Chinese traditional fermented vegetable) during fermentation using stir bar sorptive extraction–gas chromatography–olfactometry–mass spectrometry

This study aimed to reveal the evolution of volatile compounds and key odorants in Suancai during two-stage fermentation using stir bar sorptive extraction–gas chromatography–olfactometry–mass spectrometry (SBSE–GC–O/MS). In total, 138 volatile compounds were identified, and 53 aroma-active compounds were detected. The ester composition and alkane and alcohol contents were different in fresh leaf mustard and Suancai in various fermentation stages. During pre-salting, the aroma profile transformed from pungent to salty as the isothiocyanate level decreased. During secondary fermentation, isothiocyanate levels were further reduced, and esters and alcohols with mild aroma were produced, causing the rich and mild aroma of Suancai. Based on the reduced isothiocyanate content and transformed aroma, isothiocyanate may be a key marker for estimating the maturity degree of Suancai. This study provides a theoretical basis for improving the aromatic quality of fermented vegetables.

Comparison of Commercial Fish Proteins' Chemical and Sensory Properties for Human Consumption.

To stop overfishing and meet the protein needs of a growing population, more information is needed on how to use marine by-catches, by-products, and undervalued fish species for human consumption. Turning them into protein powder is a sustainable and marketable way to add value. However, more knowledge of the chemical and sensory properties of commercial fish proteins is needed to identify the challenges in developing fish derivatives. This study aimed to characterize the sensory and chemical properties of commercial fish proteins to compare their suitability for human consumption. Proximate composition, protein, polypeptide and lipid profiles, lipid oxidation, and functional properties were analyzed. The sensory profile was compiled using generic descriptive analysis, and odor-active compounds were identified with gas-chromatography-mass spectrometry-olfactometry (GC-MS/O). Results indicated significant differences in chemical and sensory properties between processing methods but not between fish species. However, the raw material had some influence in the proteins' proximate composition. Bitterness and fishiness were the main perceived off-flavors. All samples, apart from hydrolyzed collagen, had intense flavor and odor. Differences in odor-active compounds supported the sensory evaluation results. The chemical properties revealed that the lipid oxidation, peptide profile, and raw material degradation are likely affecting the sensory properties of commercial fish proteins. Limiting lipid oxidation during processing is crucial for the development of mild-tasting and -smelling products for human consumption.

Comparative investigation of key aroma terpenoids of Litsea cubeba essential oil by sensory, chromatographic, spectral and molecular studies

Litsea cubeba essential oil (LcEO) is a natural product extracted form L. cueba fruits. LcEO is widely used for flavoring in Chinese cooking and provides diverse aromas from different chemotypes, but their characteristic flavor and odorants determining the usage remain unknown. In this study, LcEOs were extracted from three chemotypes L. cubeba fruits by hydrodistillation for 4 h, the liquid to material ratio is 20:1 (mL·g−1) and comprehensively investigated at the sensorial, spectral and molecular levels. Twenty-seven crucial odorants in the LcEOs were quantified using gas chromatography-olfactometry/mass spectrometry (GC-O/MS), and ten odorants with odor activity value (OAV) > 1 were further confirmed, particularly geranial (57917.84), neral (41932.79), β-pinene (4041.23), β-myrcene (1936.86), citronellal (2215.11), terpinen-4-ol (233.97) and 1,8-cineole (7573.95) were identified as the potential odor-active markers. The aroma-spectral/gene expression network elucidated the aroma variation by determining the differential expression pattern of the terpene synthase (TPS) gene LcTPS22. And spectrum bands at 1635 nm, 1902 nm, 2125 nm, 2220 nm and 2250 nm contributed to the variation in the LcEOs. Comparative investigation of the characteristic flavor of LcEOs will significantly expand our knowledge of L. cubeba aroma, provide new insights into LcEO utilization and improve the direct breeding of L. cubeba.

Characterization of the aroma profile of quinoa (Chenopodium quinoa Willd.) and assessment of the impact of malting on the odor-active volatile composition.

Quinoa (Chenopodium quinoa Willd.) is a gluten-free pseudocereal, rich in starch and high-quality proteins. It can be used as a cereal. Recently, a variety of nontraditional food products were developed; however, the sharp bitterness and the earthy aroma of unprocessed quinoa interfered with the acceptance of these products. Malting of cereals is known to improve their processing properties and enhance their sensory quality. To evaluate the acceptance and potential of quinoa malt as a raw material for beverage production, malt quality indicators (e.g., soluble protein) and the aroma profiles of different quinoa malts were compared. Initial sensory assessment of quinoa in its native and malted state identified differences in their aroma profiles and revealed that pleasant nutty and caramel aromas were formed by malting. Subsequently, three complementary isolation techniques and gas chromatography-olfactometry/mass spectrometry (GC-O/MS) were used for volatile analysis. Instrumental analysis detected 34 and 62 odor-active regions in native quinoa and quinoa malt, respectively. In the second part, storage and the impact of three malting parameters on volatile formation were examined. By varying the malting parameters, seven additional odor-active malting byproducts were revealed. Three naturally occurring methoxypyrazines were identified as important contributors to the characteristic quinoa aroma. In all fresh quinoa malts a similar number of volatile compounds was perceived but their intensity and composition varied. Higher germination temperature promoted the formation of lipid oxidation products. Fatty smelling compounds and carboxylic acids, formed during storage, were classified as aging indicators of quinoa malt. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Insights into Characteristic Volatiles in Wuyi Rock Teas with Different Cultivars by Chemometrics and Gas Chromatography Olfactometry/Mass Spectrometry.

Wuyi rock tea (WRT) is one of the most famous subcategories of oolong tea, exhibiting distinct aroma characteristics with the application of different cultivars. However, a comprehensive comparison of the characteristic volatiles among WRTs with different cultivars has rarely been carried out. In this study, non-targeted analyses of volatile fragrant compounds (VFCs) and targeted aroma-active compounds in WRTs from four different cultivars were performed using chemometrics and gas chromatography olfactometry/mass spectrometry (GC-O/MS). A total of 166, 169, 166, and 169 VFCs were identified for Dahongpao (DHP), Rougui (RG), Shuixian (SX), and Jinfo (JF), respectively; and 40 components were considered as the key differential VFCs among WRTs by multivariate statistical analysis. Furthermore, 56 aroma-active compounds were recognized with predominant performances in "floral & fruity", "green & fresh", "roasted and caramel", "sweet", and "herbal" attributes. The comprehensive analysis of the chemometrics and GC-O/MS results indicated that methyl salicylate, p-cymene, 2,5-dimethylpyrazine, and 1-furfurylpyrrole in DHP; phenylethyl alcohol, phenethyl acetate, indole, and (E)-β-famesene in RG; linalool, phenethyl butyrate, hexyl hexanoate, and dihydroactinidiolide in JF; and naphthalene in SX were the characteristic volatiles for each type of WRT. The obtained results provide a fundamental basis for distinguishing tea cultivars, recombination, and simulation of the WRT aroma.

GC–MS-Olfactometric characterization of key odorants in rainbow trout by the application of aroma extract dilution analysis: Understanding locational and seasonal effects

The effect of seasonal and regional differences of rainbow trout on its aroma and aroma-active profile was investigated. Solvent–assisted flavor evaporation (SAFE) procedure was employed for the aroma extraction while Gas Chromatography–Mass Spectrometry–Olfactometry (GC–MS–O) and aroma extract dilution analysis (AEDA) were utilized to assess the aroma-active substances. The olfactometric analysis indicated seasonal and regional differences in the aroma-active compounds contributing to the characteristic odours of the trout samples and the compounds were more intense in autumn and winter. The strongest aroma-actives were hexanal (green), acetoin (buttery, green), limonene (citrus), 2-hexanol (green, pungent) and 1-octen-3-ol (oily, mushroom). The findings of this study can provide useful information for the selection of rainbow trout based on the seasons and locations in terms of marketing and consumer preference.

Where has all the aroma gone? Identification of aroma compounds in fresh and dried leaves of Melissa officinalis

Melissa officinalis is a popular aromatic plant, renowned for its lemon-like smell and pharmaceutical effects. Drying of Melissa officinalis is important for long-term storage and commercial purposes but can impact the sensory quality of the final product. Here, we aimed to characterize drying-related changes in aroma quality. In a first step, aroma profiles of fresh and dried leaves of Melissa officinalis were established by a trained sensory panel. In a second step, one- and two-dimensional gas chromatography-mass spectrometry/olfactometry (GC-MS/O) was performed to identify odor-active substances from fresh and dried leaves. A hay-like, straw-like and algae-like/fishy off-flavor was evident in dried leaves. GC-MS/O analyses led to the identification of known odor-active substances from Melissa officinalis like neral, geranial, geraniol in both fresh and dried leaves and additionally demonstrated the generation of further odor-active compounds due to drying, amongst others (Z)-4-heptenal and (E,Z)-2,6-nonadienal. Based on these results, further experiments can be designed to further investigate drying-related aroma changes, for instance with regard to quantitative determination of the aroma compounds in the leaves of Melissa officinalis.

Key aroma-active compounds identification of Ziziphus jujuba cv. Huizao: Effect of pilot scale freeze-drying

Aroma profile and key aroma-active of red jujube subjected to pilot scale freeze drying (FD) were investigated based on molecular sensory science. After FD, 41 aroma compounds were identified through gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and quantified through calibration curves. The total aroma compounds content was decreased 26.71% compared with raw red jujube, of which ketones and acids contents were decreased 63.33% and 62.88%, while, the esters, lactones and alcohols contents were increased 34.10%, 8.52% and 480.17%, respectively. Through the GC-O-MS, odor active values combined with recombination and omission tests, 14 key aroma-active compounds were identification in freeze-dried red jujube. In which, 2-ethyl-3,5-dimethyl-pyrazine had the highest OAV (2687.00) and dominated the roast note of aroma profile. In addition, ethyl heptanoate, hexyl acetate, 2,3-butanediol, ethyl dodecanoate and 5-heptyloxolan-2-one were newly identified as the key aroma-active compounds in freeze-dried red jujube.

Characterization of odor-contributing volatile in Capsicum chinense ‘JT-1’fruits during development and transcriptome analysis of key fruit-aroma formation periods

Chili pepper (Capsicum spp.) is one of the world's most popular vegetables and spices. C. chinense is a widely consumed domesticated pepper species. Most varieties of this species have distinctive fruity aromas, a trait with high commercial value. Studies have shown that branched-chain esters are the main contributors to the fruity aroma; however, the mechanisms of their accumulation and regulation remain elusive. In this work, we conducted gas chromatography–olfactometry–mass spectrometry analysis of C. chinense pepper ‘JT-1’ fruits harvested from 1 to 7 weeks after flowering (WAF). The main odor-contributing volatile of fruity aroma in ‘JT-1’ fruits was 4-methylpentyl 3-methylbutanoate, the concentration of which dramatically increased at 4 WAF. A shift in the dominant volatile organic compound (VOC) profile from aldehydes and alcohols to esters occurred from 3 to 4 WAF. Transcriptome analysis of fruits at these two stages and qPCR results revealed that the up-regulating of CcBcat4 may play an essential role in accumulating of 4-methylpentyl 3-methylbutanoate in chili pepper. Our findings shed light on the molecular mechanism of aroma biosynthesis in pepper and provide a theoretical basis for the molecular breeding of high-quality pepper fruits.

Characterization of Key Odor-Active Off-Flavor Compounds in Aged Pasteurized Yogurt by Sensory-Directed Flavor Analysis

The purpose of this study was to determine the key odor-active compounds contributing to the off-flavor of aged pasteurized yogurt (APY) using sensory-directed flavor analysis. Additionally, different extraction methods were compared to determine their effects on the volatile compounds, including dynamic headspace sampling (DHS), solid-phase microextraction, and stir bar sorptive extraction, and DHS was found to be suitable for this study. The results showed that comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry analysis (GC × GC-O-MS) had more advantages in separating and identifying the volatile compounds than the traditional GC-O-MS. A total of 17 odor-active compounds were determined in the fresh pasteurized yogurt and APY samples by DHS coupled with GC × GC-O-MS. The dynamic headspace dilution analysis demonstrated that 2-heptanone and hexanal were the most vital components in APY with the highest flavor dilution factor. Furthermore, the spiking and omission experimental results revealed that the odor-active compounds, such as 2-heptanone, butanoic acid, pentanoic acid, hexanal, and (E)-2-heptenal, were the key odor-active off-flavor contributors in APY. Therefore, these compounds could be used as potential indicators to determine the freshness of pasteurized yogurt.

Characterization of hay-like off-odor in basil samples after various processing and strategies for reducing the off-odor

Hay-like off‐odor present in dried basil products results in low consumer acceptance. To understand the hay-like off-odor formation in processing of basil products, identification of hay-like off-odor in thawed, air-dried and spray-dried basil samples was investigated by means of a trained human panel (n = 10) and gas chromatography–mass spectrometry–olfactometry. 3-Methylnonane-2,4-dione (3-MND) was identified in all basil samples to be responsible for the hay-like off-odor. To reduce the hay-like off-odor in dried basil products, the effect of light, oxygen, and temperature on the 3-MND formation was studied during thawing, air drying and spray drying processes. In the thawing process, darkness and nitrogen protection significantly reduced the 3-MND formation. With extending thawing time, no significant increase on the concentration of 3-MND was observed after 60 min in the darkness and under nitrogen. In the designed spray-drying setup, nitrogen protection could further alleviate the 3-MND formation whereas the elevated drying temperature (40–100 °C) boosted the 3-MND formation in air-drying processing. Collectively, these findings indicated that darkness, nitrogen protection and low temperature were considered as critical processing parameters to minimize the generation of hay-like compound 3-MND in dried basil products.

Solvent-assisted stir bar sorptive extraction and gas chromatography–mass spectrometry with simultaneous olfactometry for the characterization of aroma compounds in Japanese Yamahai-brewed sake

Yamahai-brewed sake, a Japanese alcoholic beverage brewed from rice and produced via natural lactic acid fermentation, has a complex and rich flavor compared with Sokujo-brewed sake, brewed with a general method using pure lactic acid. This study aimed to characterize the aroma compounds in Yamahai-brewed sake using solvent-assisted stir bar sorptive extraction (SA-SBSE) with gas chromatography–olfactometry/mass spectrometry (GC-O/MS) and to confirm the enhanced sensitivity of GC-O/MS with SA-SBSE compared with SBSE alone. SA-SBSE with GC-O/MS increased the number of detected odor-active compounds and improved the FD factor sensitivity of Yamahai-brewed sake. SA-SBSE-GC–MS analysis of three pairs of Yamahai-brewed and Sokujo-brewed sake showed higher polar aroma compound content in Yamahai-brewed sake with a low rice polishing ratio. Quantification of 11 characteristic aroma compounds with a wide range of log Kow values revealed that several compounds, including ethyl mandelate, ethyl 2-hydroxy-4-methylvalerate, and the newly identified γ-6-(Z)-dodecenolactone, were more abundant in Yamahai-brewed sake.

Aroma-active compounds related to Maillard reaction during roasting in Wuyi Rock tea

Maillard reaction could be a breakthrough in standardizing the roasting process, which is a pivotal procedure in refining Wuyi Rock tea (WRT). This study aimed to find indicators to instruct the roasting process scientifically trying to provide theoretical support for actual production. A total of 86 volatile compounds were detected by solid-phase microextraction (SPME) coupled with gas chromatography–olfactometry–mass spectrometry (GC–O–MS) and GC×GC–O–MS in three rough WRTs leaves (RL) Dahonpao, Shuixian, and Rougui and three roasting degrees, light fire (LF), moderate fire (MF), and high fire (HF). Among them, 45 key aroma-active compounds with r-OAV> 1. Significant differences existed between RL/LF and MF/HF. The Maillard reaction primarily strengthened the roasted attributes but eliminated the individual characteristics through 1-ethyl-1H-pyrrole, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-3-methylpyrazine, furfural, and 5-methyl-2-furancarboxaldehyde. If combined with the analysis of amino acids, sugars, and polyphenols, eight aroma-active compounds relating to the Maillard reaction, furfural, 5-methyl-2-furancarboxaldehyde, 1-ethyl-1H-pyrrole-2-carboxaldehyde, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2,5-dimethyl-3-ethylpyrazine, 1-ethyl-1H-pyrrole, and methylpyrazine, could be considered as indicators to monitor the roasting process. The novelty of this result was that it provides the practical knowledge for further deep investigation from the perspective of the Maillard reaction and makes it possible to industrialize WRT manufacturing, rather than only relying on empiricism.

Comparison of Different Volatile Extraction Methods for the Identification of Fishy Off-Odor in Fish By-Products.

This study was conducted to analyze volatile odor compounds and key odor-active compounds in the fish soup using fish scarp and bone. Five extraction methods, including solid-phase microextraction (SPME), dynamic headspace sampling (DHS), solvent-assisted flavor evaporation (SAFE), stir bar sorptive extraction (SBSE), liquid-liquid extraction (LLE), were compared and SPME was finally selected as the best extraction method for further study. The volatile odor compounds were analyzed by gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry (GC × GC-O-MS) techniques, and the key odor-active compounds were identified via aroma extract dilution analysis (AEDA) and relative odor activity value (r-OAV) calculation. A total of 38 volatile compounds were identified by GC-O-MS, among which 10 were declared as odor-active compounds. Whereas 39 volatile compounds were identified by GC × GC-O-MS, among which 12 were declared as odor-active compounds. The study results revealed that 1-octen-3-one, 2-pentylfuran, (E)-2-octenal, 1-octen-3-one, hexanal, 1-octen-3-ol, 6-methylhept-5-en-2-one, (E,Z)-2,6-nondienal and 2-ethyl-3,5-dimethylpyrazine were the key odor-active compounds in the fish soup.

Analysis and Comparison of Aroma Compounds of Brown Sugar in Guangdong, Guangxi and Yunnan Using GC-O-MS.

Guangdong, Guangxi and Yunnan are the three provinces in China that yield the most brown sugar, a brown-red colored solid or powdered sugar product made from sugar cane. In the present study, the differences between odor compounds of brown sugar from Guangdong, Guangxi, and Yunnan provinces in China were compared and analyzed by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 80 odor compounds, including 5 alcohols, 9 aldehydes, 8 phenols, 21 acids, 14 ketones, 5 esters, 12 pyrazines, and 6 other compounds, were detected. The fingerprint analysis of the brown sugar odor compounds showed 90% similarity, indicating a close relationship among the odor properties of brown sugar in each province. Moreover, the orthogonal partial least squares discriminant analysis (OPLS-DA) was performed to identify the compounds contributing to the volatile classification of the brown sugar from three provinces, which confirmed that OPLS-DA could be a potential tool to distinguish the brown sugar of three origins.

Characterization of key odor-active compounds in pure chicken powder and the effect of yeast extract, using instrumental and sensory techniques

Pure chicken powder (PCP) is a reliable source of mellow chicken soup flavor in seasoning, but it has some unstable compounds and is prone to lipid oxidation, which leads to unpleasant odor. Adding yeast extract (YE) can reduce the off-odor intensity of PCP. Based on the results of gas chromatography–olfactometry–mass spectrometry (GC–O-MS), two-dimensional comprehensive gas chromatography–olfactometry–mass spectrometry (GC×GC–O–MS) and combined aroma extract dilution analysis (AEDA), 14 key odor-active compounds were identified. Internal standard curve method was used for quantitative analysis, and the odor activity value (OAV) was calculated. Octanal, 1-octen-3-ol and hexanal were found to be the most vital odor-active compounds in PCP. The odor-active compounds of YE were studied by the same method, and dimethyl trisulfide was identified as the most important odor-active compound of YE. Additionally, recombination and omission experiments were carried out with PCP. Finally, it was found that a low concentration of dimethyl trisulfide had masking effect on the odor of PCP.

An enzymatic tandem reaction to produce odor-active fatty aldehydes

Aldehydes represent a versatile and favored class of flavoring substances. A biocatalytic access to odor-active aldehydes was developed by conversion of fatty acids with two enzymes of the α-dioxygenase pathway. The recombinant enzymes α-dioxygenase (α-DOX) originating from Crocosphaera subtropica and fatty aldehyde dehydrogenase (FALDH) from Vibrio harveyi were heterologously expressed in E. coli, purified, and applied in a coupled (tandem) repetitive reaction. The concept was optimized in terms of number of reaction cycles and production yields. Up to five cycles and aldehyde yields of up to 26% were achieved. Afterward, the approach was applied to sea buckthorn pulp oil as raw material for the enzyme catalyzed production of flavoring/fragrance ingredients based on complex aldehyde mixtures. The most abundant fatty acids in sea buckthorn pulp oil, namely palmitic, palmitoleic, oleic, and linoleic acid, were used as substrates for further biotransformation experiments. Various aldehydes were identified, semi-quantified, and sensorially characterized by means of headspace–solid phase microextraction–gas chromatography–mass spectrometry–olfactometry (HS–SPME–GC–MS–O). Structural validation of unsaturated aldehydes in terms of double-bond positions was performed by multidimensional high-resolution mass spectrometry experiments of their Paternò–Büchi (PB) photoproducts. Retention indices and odor impressions of inter alia (Z,Z)-5,8-tetradecadienal (Z,Z)-6,9-pentadecadienal, (Z)-8-pentadecenal, (Z)-4-tridecenal, (Z)-6-pentadecenal, and (Z)-8-heptadecenal were determined for the first time.Key points• Coupled reaction of Csα-DOX and VhFALDH yields chain-shortened fatty aldehydes.• Odors of several Z-unsaturated fatty aldehydes are described for the first time.• Potential for industrial production of aldehyde-based odorants from natural sources.Graphical abstract

Coffee Leaf Tea from El Salvador: On-Site Production Considering Influences of Processing on Chemical Composition.

The production of coffee leaf tea (Coffea arabica) in El Salvador and the influences of processing steps on non-volatile compounds and volatile aroma-active compounds were investigated. The tea was produced according to the process steps of conventional tea (Camellia sinensis) with the available possibilities on the farm. Influencing factors were the leaf type (old, young, yellow, shoots), processing (blending, cutting, rolling, freezing, steaming), drying (sun drying, oven drying, roasting) and fermentation (wild, yeast, Lactobacillus). Subsequently, the samples were analysed for the maximum levels of caffeine, chlorogenic acid, and epigallocatechin gallate permitted by the European Commission. The caffeine content ranged between 0.37–1.33 g/100 g dry mass (DM), the chlorogenic acid was between not detectable and 9.35 g/100 g DM and epigallocatechin gallate could not be detected at all. Furthermore, water content, essential oil, ash content, total polyphenols, total catechins, organic acids, and trigonelline were determined. Gas chromatography—mass spectrometry—olfactometry and calculation of the odour activity values (OAVs) were carried out to determine the main aroma-active compounds, which are β-ionone (honey-like, OAV 132-927), decanal (citrus-like, floral, OAV 14-301), α-ionone (floral, OAV 30-100), (E,Z)-2,6-nonadienal (cucumber-like, OAV 18-256), 2,4-nonadienal (melon-like, OAV 2-18), octanal (fruity, OAV 7-23), (E)-2 nonenal (citrus-like, OAV 1-11), hexanal (grassy, OAV 1-10), and 4-heptenal (green, OAV 1-9). The data obtained in this study may help to adjust process parameters directly to consumer preferences and allow coffee farmers to earn an extra income from this by-product.