Effect of Drying Methods on Volatile Compounds of Burdock (Arctium lappa L.) Root Tea as Revealed by Gas Chromatography Mass Spectrometry-Based Metabolomics

A Comparison of the Impacts of Different Drying Methods on the Volatile Organic Compounds in Ginseng

Ginseng (Panax ginseng C. A. Meyer) is a valuable plant resource which has been used for centuries as both food and traditional Chinese medicine. It is popular in health research and markets globally. Fresh ginseng has a high moisture content and is prone to mold and rot, reducing its nutritional value without proper preservation. Drying treatments are effective for maintaining the beneficial properties of ginseng post-harvest. In this study, we investigated the effects of natural air drying (ND), hot-air drying (HAD), vacuum drying (VD), microwave vacuum drying (MVD), and vacuum freeze drying (VFD) on volatile organic compounds (VOCs) in ginseng. The results showed that the MVD time was the shortest, followed by the VFD, VD, and HAD times, whereas the ND time was the longest, but the VFD is the most beneficial to the appearance and color retention of ginseng. A total of 72 VOCs were obtained and 68 VOCs were identified using the five drying methods based on gas chromatography-ion mobility spectrometry (GC-IMS) technology, including 23 aldehydes, 19 alkenes, 10 alcohols, 10 ketones, 4 esters, 1 furan, and 1 pyrazine, and the ND method was the best for retaining VOCs. GC-IMS fingerprints, principal component analysis (PCA), Euclidean distance analysis, partial least squares discriminant analysis (PLS-DA), and cluster analysis (CA) can distinguish ginseng from different drying methods. A total of 29 VOCs can be used as the main characteristic markers of different drying methods in ginseng. Overall, our findings provide scientific theoretical guidance for optimizing ginseng's drying methods, aromatic health effects, and flavor quality research.

Loss of Volatile Metabolites during Concentration of Metabolomic Extracts

Volatile metabolites can be lost during the preanalytical stage of metabolomic analysis. This work is aimed at the experimental and theoretical study of mechanisms of volatile substance evaporation and retention in the residues during the drying of extract solutions. We demonstrate that solvent evaporation leads to the unavoidable loss of nondissociating volatile metabolites with low boiling points and high vapor pressures (such as acetone and ethanol). The retention of dissociating volatile compounds (primarily organic acids RH) during the evaporation depends on the presence of buffer salts in solution, which are responsible for maintaining the neutral pH. An acid remains in the solution as long as it is present predominantly in the dissociated R- state. At the very last stage of solvent evaporation, buffer salts precipitate, forming a solid matrix for metabolite trapping in the residue. At the same time, buffer precipitation leads to a decrease of the solution pH, increase of the portion of RH in associated state, and acceleration of RH volatilization. The RH recovery is thus determined by the competition between the solute volatilization in the associated RH form and metabolite trapping in the solid matrix. The retention of volatile acids in the residue after extract drying can be improved either by adding buffer salts to maintain high pH or by incomplete sample drying.

Comparison of Metabolic Profiles of Fruits of Arctium lappa, Arctium minus, and Arctium tomentosum

Metabolites of the edible and medicinal plant Arctium have been shown to possess beneficial activities. The phytochemical profile of Arctium lappa is well-explored and its fruits are known to contain mainly lignans, fatty acids, and sterols. But the fruits of other Arctium species have not been thoroughly investigated. Therefore, this study compares the metabolic profiles of the fruits of A. lappa, Arctium tomentosum, and Arctium minus. Targeted metabolomics led to the putative identification of 53 metabolites in the fruit extracts, the majority of these being lignans and fatty acids. Quantification of the major lignans showed that the year of collection had a significant effect on the lignan content. Furthermore, A. lappa fruits contained lesser amounts of arctigenin but greater amounts of arctigenin glycoside than A. minus fruits. Regarding the profile of fatty acids, A. minus fruits differed from the others in the presence of linolelaidic acid.

Extraction, structure and bioactivities of polysaccharide from root of Arctium lappa L.: A review

Arctium lappa L. root is a well-known Chinese medicine with high medicinal and food values. Arctium lappa L. root polysaccharide (ALP), as the main component and bioactive substance, has a variety of biological activities, including anti-inflammatory, antioxidant, hypoglycemic, hypolipidemic, antithrombotic, immunomodulatory activity and improvement of intestinal flora. The biological activities of polysaccharides are closely related to their structures, and different extraction and purification methods will yield different polysaccharide structures. As a kind of natural polysaccharide, ALP has a broad application prospect in drug carrier. In this paper, we reviewed the research progress on the extraction, purification, structural characterization, biological activities, structure-activity relationship and drug carrier application of ALP, in order to provide basic reference for the development and application of medical and health care value. At the same time, the shortcomings of ALP research are discussed in depth, and the potential development prospect and future research direction are prospected.

A Network of Processes for Biorefining Burdock Seeds and Roots

In this work, a novel sustainable approach was proposed for the integral valorisation of Arctium lappa (burdock) seeds and roots. Firstly, a preliminary recovery of bioactive compounds, including unsaturated fatty acids, was performed. Then, simple sugars (i.e., fructose and sucrose) and phenolic compounds were extracted by using compressed fluids (supercritical CO2 and propane). Consequently, a complete characterisation of raw biomass and extraction residues was carried out to determine the starting chemical composition in terms of residual lipids, proteins, hemicellulose, cellulose, lignin, and ash content. Subsequently, three alternative ways to utilise extraction residues were proposed and successfully tested: (i) enzymatic hydrolysis operated by Cellulases (Thricoderma resei) of raw and residual biomass to glucose, (ii) direct ethanolysis to produce ethyl levulinate; and (iii) pyrolysis to obtain biochar to be used as supports for the synthesis of sulfonated magnetic iron-carbon catalysts (Fe-SMCC) to be applied in the dehydration of fructose for the synthesis of 5-hydroxymethylfurfural (5-HMF). The development of these advanced approaches enabled the full utilisation of this resource through the production of fine chemicals and value-added compounds in line with the principles of the circular economy.

Comparison of the volatile organic compounds in Citrus reticulata 'Chachi' peel with different drying methods using E-nose, GC-IMS and HS-SPME-GC-MS

Introduction

Citrus reticulata 'Chachi' peel (CRCP), which is named "Guangchenpi" in China, is a geographical indication product with unique flavor properties. CRCP has been used for centuries as a traditional genuine herb because of its excellent therapeutic effects. In addition, owing to its unique odor and high nutrition, it is widely used in various food preparations. Volatile organic compounds (VOCs) are regarded as an important quality marker for CRCP and are highly susceptible to effects in the drying process due to their thermal instability.

Methods

In the current study, the main VOCs in CRCP were processed using different drying methods, including sun-drying, hot air drying, and vacuum-freeze drying. The VOCs were identified by the electronic nose (E-nose), gas chromatography-ion mobility spectrometry (GC-IMS), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS).

Results

The results showed that the CRCP dried by vacuum-freeze exhibited the highest VOCs contents and retained the richest compounds compared to those dried by other methods, which indicated that vacuum-freeze drying is the most suitable for CRCP production. Furthermore, the chemometrics analysis revealed that the primary differential metabolites of the samples generated using different drying methods were terpenes and esters.

Discussion

Overall, our study would help better understand the VOCs present in CRCP with different drying methods. The outcomes of the current study would guide the drying and processing of CRCP, which is beneficial for large-scale storage and industrial production of CRCP.

Isolation and Identification of Lactic Acid Bacteria and Their Effects on the Off-odor of Burdocks

Burdocks have diverse nutritional and pharmacological functions, but their unique odor is unwelcome. Here, the effect and mechanism of lactic acid bacteria fermentation on the off-odor of burdocks were investigated. The sensory evaluation showed that burdocks had earthy, musty, grassy, and pepper odors. 2-Isobutyl-3-methoxypyrazine (IBMP) and 2-secbutyl-3-methoxypyrazine (IPMP) mainly contributed to burdock's unique off-odor and were identified by gas chromatography-mass spectrometry combined with headspace-solid phase microextraction (HS-SPME-GC-MS) and relative odor activity value (ROAV) analysis. Weissella cibaria ZJ-5 from screened strains performed with the strongest ability to remove the off-odor and generate a fragrant odor, as determined by sensory evaluation. When incubated aerobically together with IBMP during fermentation, ZJ-5 degraded IBMP directly from 149.56 ± 0.72 to 71.55 ± 1.81 ng/mL. Additionally, linoleic acid content in fermented burdocks was significantly decreased compared with unfermented burdocks. (E,Z)-2,6-Nonadienal, which mainly contributed to fermented burdock's odor, may have been generated from linoleic acid during ZJ-5 fermentation, through the acid catalysis pathway. It indicated that LAB fermentation could improve burdock odor by degrading off-odor compounds and precursors and by generating new aldehydes.

Components research on Tetrastigma hemsleyanum Diels et Gilg: identification and effect of drying methods on the content of ten main constituents by targeting metabolomics method

Tetrastigma hemsleyanum Diels et Gilg (TH) is one of the new eight Genuine Medicinal Materials of Zhejiang. It has extensive biological activities, such as anti-inflammatory, anti-tumor and analgesic activities, etc. In this study, the chemical components of TH were systematically investigated by ultra high-performance liquid chromatography-tandem quadrupole time of flight mass spectrometry (UPLC/Q-TOF-MS). Based on the MS spectrum, 39 compounds in TH extracts including 14 flavonoids, 10 fatty acids, 5 polyphenols and phenolic acids, 4 terpenes and other compounds were detected and tentatively identified. TH samples were treated under different drying methods (vacuum freeze drying, hot air drying, natural drying, light drying and vacuum drying). Besides, the effect of different drying methods on the content of 10 main chemical constituents in TH extracts including catechin, rutin, kaempferol-3-O-rutinoside and so on was also investigated by targeting metabolomics method with ultra high-performance liquid chromatography-tandem triple quadrupole mass spectrometry (UPLC-MS/MS) assisted by multivariate statistical analysis. Large differences were observed between vacuum drying and vacuum freeze drying with remarkable content changes. The contents of rutin, proanthocyanidin B1 and catechin were the most different among the various drying methods. The systematic identification of chemical constituents is helpful for the further medicinal development and application of TH. The effects of drying methods on the content of TH components were studied, which provided experimental data for the processing, storage and quality control of TH.

Arctium lappa (Burdock): Insights from ethnopharmacology potential, chemical constituents, clinical studies, pharmacological utility and nanomedicine

Arctium lappa L. is a medicinal edible homologous plant, commonly known as burdock or bardana, which belongs to the Asteraceae family. It is widely distributed throughout Northern Asia, Europe, and North America and has been utilized for hundreds of years. The roots, fruits, seeds, and leaves of A. lappa have been extensively used in traditional Chinese Medicine (TCM). A. lappa has attracted a great deal of attention due to its possession of highly recognized bioactive metabolites with significant therapeutic potential. Numerous pharmacological effects have been demonstrated in vitro and in vivo by A. lappa and its bioactive metabolites, including antimicrobial, anti-obesity, antioxidant, anticancer, anti-inflammatory, anti-diabetic, anti-allergic, antiviral, gastroprotective, hepatoprotective, and neuroprotective activities. Additionally, A. lappa has demonstrated considerable clinical efficacies and valuable applications in nanomedicine. Collectively, this review covers the properties of A. lappa and its bioactive metabolites, ethnopharmacology aspects, pharmacological effects, clinical trials, and applications in the field of nanomedicine. Hence, a significant attention should be paid to clinical trials and industrial applications of this plant with particular emphasis, on drug discovery and nanotechnology.

Flavor properties of Chinese noodles processed by dielectric drying

Volatile organic compounds (VOCs) significantly impact food flavor. In this work, Electron nose (E-nose), head space solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and head space-gas chromatography-ion mobility spectrometry (HS-GC-IMS) techniques were applied to analyze different drying effects: microwave, hot air, and radio frequency on the aroma of Chinese noodles. E-nose analysis suggests that aromatic differences are mainly from broad range-methane. HS-SPME-GC-MS and HS-GC-IMS identified 47 and 26 VOCs in the fresh and dried noodles, respectively. The VOCs in the dried noodles were mainly aldehydes, alcohols, and esters. Drying significantly reduced the types of VOCs in Chinese dried noodles. Microwave dried noodles exhibited the strongest aroma after the shortest time of treatment, suggesting microwave drying may be the best drying method for noodles. Using aromatic analysis, this paper provides useful information for understanding the flavor of flour products and offers new ideas for drying noodles.

Ultrasound-Assisted Aqueous Extraction of Chlorogenic Acid and Cynarin with the Impact of Inulin from Burdock (Arctium lappa L.) Roots

The ultrasound-assisted aqueous extraction of chlorogenic acid (CGA) and cynarin with the impact of inulin from burdock (Arctium lappa L.) roots was investigated. Three extraction modes, ultrasound at 40 kHz/300 W (U-40), ultrasound at 120 kHz/300 W (U-120), and shaking at 120 rpm (S-120), were compared. The effects of process parameters on the extraction of polyphenols, CGA, cynarin, inulin, and antioxidant activity using U-40 were evaluated. In 10 min, 50 °C, and 1/30 (g/mL-water) of solid-to-liquid ratio, the order of CGA content in the dried burdock root powder (DBR) was U-40 (484.65 μg/g-DBR) > U-120 (369.93 μg/g-DBR) > S-120 (176.99 μg/g-DBR), while the order of cynarin content in DBR was U-120 (376.47 μg/g-DBR) > U-40 (341.54 μg/g-DBR) > S-120 (330.44 μg/g-DBR), showing the selective extraction of CGA and cynarin between using 40 and 120 kHz of ultrasound. The profiles of increase and then decrease in free CGA and cynarin concentrations against time revealed their degradation, including their interactions with the abundant inulin. The kinetic model, considering extraction followed by degradation, was proposed to describe the variations of free CGA and cynarin against time. This study provides an effective method using water to extract CGA, cynarin, and inulin from burdock roots.

Comparison of Different Drying Methods on the Volatile Components of Ginger (Zingiber officinale Roscoe) by HS-GC-MS Coupled with Fast GC E-Nose

Ginger (Zingiber officinale Roscoe) is one of the most popular spices in the world, with its unique odor. Due to its health benefits, ginger is also widely used as a dietary supplement and herbal medicine. In this study, the main flavor components of gingers processed by different drying methods including hot air drying, vacuum drying, sun-drying, and vacuum-freeze drying, were identified on the basis of headspace-gas chromatography coupled with mass spectrometry (HS-GC-MS) and fast gas chromatography electronic-nose (fast GC e-nose) techniques. The results showed that the ginger dried by hot air drying exhibited high contents of volatile compounds and retained the richest odor in comparison with those dried by other methods, which indicated that hot air drying is more suitable for the production of dried ginger. Sensory description by fast GC e-nose exhibited that ginger flavor was mainly concentrated in the spicy, sweet, minty, fruity, and herbaceous odor. The relative content of the zingiberene was significantly higher in the hot air drying sample than those by other methods, suggesting that dried ginger by hot air drying can retain more unique spicy and pungent odorants. Furthermore, the results of chemometrics analyses showed that the main variance components among the samples by different drying methods were α-naginatene, (+)-cyclosativene, and sulcatone in HS-GC-MS analysis, and α-terpinen-7-al, dimethyl sulfide, and citronellal in fast GC e-nose analysis. For comparison of fresh and dried gingers, terpinolene, terpinen-4-ol, 2,4-decadienal, (E, Z)-, and linalool were considered the main variance components. This study generated a better understanding of the flavor characteristics of gingers by different drying methods and could provide a guide for drying and processing of ginger.

Effect of Yellowing Duration on the Chemical Profile of Yellow Tea and the Associations with Sensory Traits

The yellowing process is the crucial step to form the characteristic sensory and chemical properties of yellow tea. To investigate the chemical changes and the associations with sensory traits during yellowing, yellow teas with different yellowing times (0–13 h) were prepared for sensory evaluation and chemical analysis. The intensities of umami and green-tea aroma were reduced whereas sweet taste, mellow taste and sweet aroma were increased under long-term yellowing treatment. A total of 230 chemical constituents were determined, among which 25 non-volatiles and 42 volatiles were the key chemical contributors to sensory traits based on orthogonal partial least squares discrimination analysis (OPLS-DA), multiple factor analysis (MFA) and multidimensional alignment (MDA) analysis. The decrease in catechins, flavonol glycosides and caffeine and the increase in certain amino acids contributed to the elevated sweet taste and mellow taste. The sweet, woody and herbal odorants and the fermented and fatty odorants were the key contributors to the characteristic sensory feature of yellow tea with sweet aroma and over-oxidation aroma, including 7 ketones, 5 alcohols, 1 aldehyde, 5 acids, 4 esters, 5 hydrocarbons, 1 phenolic compound and 1 sulfocompound. This study reveals the sensory trait-related chemical changes in the yellowing process of tea, which provides a theoretical basis for the optimization of the yellowing process and quality control of yellow tea.

Effect of Freeze-Thaw Cycles on Juice Properties, Volatile Compounds and Hot-Air Drying Kinetics of Blueberry

This paper studied the effects of freeze-thaw (FT) cycles on the juice properties and aroma profiles, and the hot-air drying kinetics of frozen blueberry. After FT treatment, the juice yield increased while pH and total soluble solids of the juice keep unchanged. The total anthocyanins contents and DPPH antioxidant activities of the juice decreased by FT treatments. The electronic nose shows that FT treatments significantly change the aroma profiles of the juice. The four main volatile substances in the fresh juice are (E)-2-hexenal, α-terpineol, hexanal and linalyl formate, which account for 48.5 ± 0.1%, 17.6 ± 0.2%, 14.0 ± 1.5% and 7.8 ± 2.7% of relative proportions based on total ion chromatogram (TIC) peak areas. In the FT-treated samples, the amount of (E)-2-hexenal and hexanal decreased significantly while α-terpineol and linalyl formate remained almost unchanged. Repeated FT cycles increased the ethanol content and destroyed the original green leafy flavor. Finally, the drying kinetics of FT-treated blueberries was tested. One FT treatment can shorten the drying time by about 30% to achieve the same water content. The D_eff values of the FT-treated sample are similar, which are about twice as large as the value of the fresh sample. The results will be beneficial for the processing of frozen blueberry into juice or dried fruits.

Aloe vera Gel Drying by Refractance Window®: Drying Kinetics and High-Quality Retention

In most cases, conventional drying produces inferior quality products and requires higher drying times. A continuous pilot Refractance Window^® equipment was used to dry Aloe vera gel slabs of 5 and 10 mm thick at 60, 70, 80, and 90 °C, seeking a dry product with high-quality retention. Based on five empirical models, drying kinetics, diffusion coefficient, and activation energy were analyzed. Midilli–Kuck was the best predicting model. Short drying times (55–270 min) were needed to reach 0.10 g water/g solid. In addition, the technique yielded samples with high rehydration capacity (24–29 g water/g solid); high retention of color (∆E, 3.74–4.39); relatively low losses of vitamin C (37–59%) and vitamin E (28–37%). Regardless of the condition of temperature and sample thickness, a high-quality dried Aloe vera gel could be obtained. Compared with other methods, Refractance Window^® drying of Aloe vera achieved shorter drying times with higher quality retention in terms of color, vitamins C and E, and rehydration. Finally, the dried Aloe vera gel could be reconstituted to a gel close to its fresh state by rehydration.