Concentrations Of Total Volatile Compounds Research Articles

Effect of epigallocatechin gallate/transglutaminase synergistic cross-linking on the flavor of surimi gels

Epigallocatechin gallate (EGCG) and transglutaminase (TGase) can improve the structure of surimi gels, and have a significant impact on their texture and flavor quality. The formation and release of volatile odors due to EGCG, TGase and EGCG/TGase synergistic cross-linking of surimi gels were investigated. The characteristic flavor components of the surimi gels were aldehydes. Compared with the blank group, the total content of volatile compounds in EGCG, TGase, and EGCG/TGase groups decreased by 14.43, 11.69, and 20.07 %, indicating that the flavor of EGCG/TGase group was more affected by EGCG than by TGase. The free fatty acid content in these groups decreased by 17.28, 1.30, and 43.98 mg/100 g, indicating that the degree of fatty acid degradation in the EGCG/TGase group was lower during a two-stage heating process, which may be ascribed to EGCG's inhibition of oxidative degradation of fatty acids, thereby reducing the production of flavor substances.

Comparative study of different commercial enzymes on release of glycosylated volatile compounds in white grapes using SPE/GC–MS

Glycosides represent a large source of potential flavor in grape must. Commercial preparations enzymes with glycosidase activity are commonly employed to enhance wine aroma. In this study, we conducted an evaluation of twelve commercial enzymes to assess their effectiveness in releasing volatile compounds from their conjugated forms in a white grape must under laboratory conditions by solid-liquid extraction (SPE) and gas chromatography–mass spectrometry (GC–MS). In this laboratory-level experiment, regardless of the enzymes used, the total concentration of volatile compounds was not statistically affected by the treatments. While the total concentration of volatile compounds remained largely unchanged, four specific volatile groups were significantly affected by the enzyme treatments: acids, alcohols, C13-norisoprenoids, and terpenes. The results also revealed a significant effect of commercial enzymes on individual compounds, which led to a notable increase in the concentration of twenty-one aroma compounds, mainly terpenes. Rapidase Revelation Aroma and Enozym Extra Aroma emerged as the most powerful ones on the must's volatile composition with important ability to release higher concentrations of essential varietal aroma compounds, particularly terpenes and C13-norisoprenoids.

Study on ultrasound-assisted extraction of cold brew coffee using physicochemical, flavor, and sensory evaluation

Cold brew coffee is popular with consumers due to its simple preparation and unique taste. However, traditional cold brew coffee extraction is time consuming and inefficient, which can be improved by ultrasound-assisted extraction to enhance the product market potential. In this study, the flavor profiles and sensory differences of coffee prepared at three different ultrasonic temperatures, as well as traditional cold brew and hot brew coffee, were evaluated by consumer-based sensory evaluation, Rate-All-That-Apply, combined with the determination of the content of volatile and non-volatile components. The results showed that ultrasound assisted cold brew coffee prepared at 25 °C had a good extraction effect, with chlorogenic acid (CGA) and organic acid contents of 1.05 mg/mL and 0.97 mg/mL, respectively, which were higher than the traditional cold brew coffee obtained after 12 h of preparation, with contents of 0.53 mg/mL and 0.85 mg/mL, respectively. And the total content of volatile compounds can almost reach the results of traditional cold brew for 12 h, which were 1.25 mg/kg and 1.42 mg/kg, respectively. Sensory evaluation indicated that ultrasonic treatment enhanced the sensory attributes such as nutty and cocoa flavors in the coffee. Consumers preferred the cold brew coffee obtained via ultrasound-assisted extraction. These samples presented higher levels of sweetness, floral, and fruity flavors, which were associated with 2,5-Dimethyl-3-(2-methylpropyl)pyrazine, 2,3-Dimethyl-5-(3-methylbutyl)pyrazine, (S)-(+)-4-sec-Butylpyrazole, and styrene. In this study, we demonstrated that ultrasound-assisted extraction can help reduce the time to prepare cold brew coffee and make it possible to commercialize ultrasound-assisted cold brew coffee.

Effect of puffing treatment on volatile components of green tea explored by gas chromatography–mass spectrometry and gas chromatography-olfactometry

The effect of puffing treatment on the volatile components of green tea has been studied. A total of 155 volatile compounds were identified by using HS-SPME and SPE extraction methods, combined with gas chromatography–mass spectrometry (GC–MS). The total concentration of volatile compounds in puffed green tea increased by 2.25 times compared to that in before puffing. 12 key volatile compounds in green tea were identified before and after puffing using a combination of multivariate statistical analysis, GC-O, AEDA dilution analysis, and relative odor activity value (rOAV). The puffing process generates the Maillard reaction, where sugars react with amino acids to produce Maillard reaction products (such as pyrazine, pyrrole, furan, and their derivatives), giving them a unique baking aroma. The proportion of these compounds in the total volatile matter increased. The research results provided guidance and a theoretical basis for improving the aroma processing of green tea.

Comparison of Flavor Profiles of Honey Peach Cultivars by Gas Chromatography–Mass Spectrometry (GC–MS) with Odor Activity Values (OAVs), E-Tongue, and Sensory Evaluation Combined with Chemometrics

The honey peach is popular due to its unique flavor. However, the flavor characteristics of honey peaches cultivated in Yangzhou and Wuxi remain unclear. In this study, the flavor profiles in five famous honey peaches, Yangzhou Baifeng (YBF), Yangzhou Zhonghujing (YZHJ), Yangzhou Wanhujing (YWHJ), Wuxi Baifeng (WBF), and Wuxi Wanhujing (WWHJ), were investigated using gas chromatography-mass spectrometry (GC–MS) combined with odor activity values (OAVs), electronic tongue (E-tongue) and sensory evaluation. A total of 84 flavor substances were identified by GC–MS and 17 odor-active compounds were detected with OAVs more than 1. WBF samples had the highest concentration of total volatile compounds, and relatively higher OAVs of γ-decalactone and γ-dodecalactone contributed to peach-like aroma. Principal component analysis (PCA) and heatmap analysis indicated that the honey peach cultivars from different origins and varieties had distinct aroma and taste profiles. Sensory evaluation demonstrated that WBF samples had the highest scores of peach-like, fruity aroma, sweetness, juiciness and overall acceptability. Partial least squares regression (PLSR) was performed to investigate the correlation between physicochemical properties, odor-active compounds, E-tongue measurements and sensory attributes. Results indicated that linalool and umami had significant contribution to honey peach sensory attributes, and further confirmed that YBF was characterized by floral aroma and WBF was similar with peach-like and green attributes. The results of this study provide a comprehensive understanding of flavor characteristics and differences of the honey peaches, which could contribute to the further development and production of these products.

GC-IMS-Based Volatile Characteristic Analysis of Hypsizygus marmoreus Dried by Different Methods.

Gas chromatography-ion mobility spectroscopy (GC-IMS) was used to analyze the volatile components in dried Hypsizygus marmoreus of different drying methods, including hot air drying (HAD), heat pump drying (HPD), heated freeze-drying (HFD), and unheated freeze-drying (UFD). A total of 116 signal peaks corresponding to 96 volatile compounds were identified, including 25 esters, 24 aldehydes, 23 alcohols, 13 ketones, 10 heterocyclic compounds, 8 carboxylic acids, 7 terpenes, 3 sulfur-containing compounds, 2 nitrogen-containing compounds, and 1 aromatic hydrocarbon. The total content of volatile compounds in H. marmoreus dried by the four methods, from highest to lowest, was as follows: HAD, HPD, HFD, and UFD. The main volatile compounds included carboxylic acids, alcohols, esters, and aldehydes. Comparing the peak intensities of volatile compounds in dried H. marmoreus using different drying methods, it was found that the synthesis of esters, aldehydes, and terpenes increased under hot drying methods such as HAD and HPD, while the synthesis of compounds containing sulfur and nitrogen increased under freeze-drying methods such as HFD and UFD. Nine common key characteristic flavor compounds of dried H. marmoreus were screened using relative odor activity values (ROAV > 1), including ethyl 3-methylbutanoate, acetic acid, 2-methylbutanal, propanal, methyl 2-propenyl sulfate, trimethylamine, 3-octanone, acetaldehide, and thiophene. In the odor description of volatile compounds with ROAV > 0.1, it was found that important flavor components such as trimethylamine, 3-octanone, (E)-2-octenal, and dimethyl disulfide are related to the aroma of seafood. Their ROAV order is HFD > UFD > HPD > HAD, indicating that H. marmoreus using the HFD method have the strongest seafood flavor. The research findings provide theoretical guidance for selecting drying methods and refining the processing of H. marmoreus.

Dynamic changes in metabolomics and flavoromics during industrial scale fermentation of Chinese traditional soy sauce

Flavor substances are crucial to the quality of soy sauce and closely related to the intermediate metabolites. This study systematically explored the dynamic changes in physicochemical characteristics, metabolomics and flavoromics during traditional Chinese soy sauce fermentation. The results indicated that the amino acid nitrogen gradually increased to 0.95 g/100 mL on the 13th day and then stabilized, and the changes of reducing sugars increased to 66.40 mg/mL on the 7th day and then slowly decreased. A total of 90 volatile compounds and 1172 non-volatile metabolites were detected. In the early fermentation period (1–7 day), alcohols, aldehydes and ketones were the main volatile compounds, but as fermentation proceeded, phenols and esters gradually accumulated. The total content of volatile compounds, mainly alcohols and phenols, reached the highest value on the 23rd day. Non-volatile metabolites were mainly amino acids, organic acids, lipids and carbohydrates, and the content and types of varied with fermentation time. KEGG analysis indicates there were significant changes in the proline and arginine metabolism in the middle and late periods (7–28 day) compared to the early fermentation period. Correlation analysis indicating a delicate balance between the transformation of metabolites and the formation of volatile compounds in traditional Chinese soy sauce.

Characterization and comparison of flavors in fresh and aged fermented peppers: Impact of different varieties

The flavor profiles of fresh and aged fermented peppers obtained from four varieties were thoroughly compared in this study. A total of 385 volatile compounds in fermented pepper samples were detected by flavoromics (two-dimensional gas chromatography–time-of-flight mass spectrometry). As fermentation progressed, both the number and the total concentration of volatile compounds changed, with esters, alcohols, acids, terpenoids, sulfur compounds, and funans increasing, whereas hydrocarbons and benzenes decreased. In contrast to the fresh fermented peppers, the aged fermented samples exhibited lower values of pH, total sugars, and capsaicinoids but higher contents of organic acids and free amino acids. Furthermore, the specific differences and characteristic aroma substances among aged fermented peppers were unveiled by multivariate statistical analysis. Overall, 64 volatiles were screened as differential compounds. In addition, Huanggongjiao samples possessed the most abundant differential volatiles and compounds with odor activity values > 1, which were flavored with fruity, floral, and slightly phenolic odors. Correlation analysis demonstrated that the levels of 23 key aroma compounds (e.g., ethyl 2-methylbutyrate, 1-butanol, and ethyl valerate) showed a significantly positive correlation with Asp, Glu and 5 organic acids. By contrast, there is a negative association between the pH value and total sugar. Overall, aging contributed significantly to the flavor attributes of fermented peppers.

Analysis of volatile compounds, betaine, and antioxidant effect in goji berry (Lycium barbarum L.) powder extracted by various drying methods and extraction solvents

Goji berry (Lycium barbarum L.), a deciduous solanaceous shrub, were subjected to extraction using five solvents (water, 50% and 70% ethanol, and 50% and 70% methanol) and dried using two methods: freeze drying (FD) and spray drying (SD). To investigate the chemical properties of these various goji berry powders, an examination was conducted on the content of volatile compounds, betaine, antioxidant effect, total phenolic content (TPC), and total flavonoid compounds (TFC) (p < 0.05). The total volatile compound content was highest in SD powder with 50% ethanol extract, showing a 66.7% increase over the control. The betaine content was in the range of 9.25–31.9 mg/g dry weight, and it exhibited a significant increase with higher water concentration in the extraction solvent. Betaine, total phenolic compounds and total flavonoid compounds showed a significant increase in the sequence of SD followed by FD (p < 0.05). Overall, the SD sample showed superior benefits when evaluating volatile compounds, betaine, and antioxidant effect. SD was more suitable for drying goji berry, as it retains its appearance and biological activity.

Difference in Aroma Components of Black Teas Processed on Different Dates in the Spring Season.

Tea aroma greatly varies with the production date. This study investigated the aroma differences among black teas processed on different dates (March 23rd, April 8th, April 15th, April 27th, and May 7th) in the spring. A sensory evaluation showed that the black tea produced on April 15th had a strong and lasting sweet aroma and the highest score of 93.5. In total, 71 volatile compounds were identified, and alcohols were the predominant category, accounting for 60.98%. From March 23rd to May 7th, the total content of volatile compounds showed a parabolic change trend and reached its maximum on April 15th (715.27 μg/L); the flavor index first peaked on April 8th (23.25) and then gradually decreased. A multivariate statistical analysis showed that 39 volatile compounds were important, differential aroma components. An odor activity value (OAV) analysis showed that the predominant odorants were β-ionone, β-damascenone, linalool, (E)-β-ocimene, and geraniol, all with values larger than 100. The total OAVs of undesirable odorants decreased and reached their minimum (70.4) on April 27th, while the total OAVs of pleasant odorants and the ratio of pleasant/undesirable odorants showed inverse changes and reached their maximum (2182.1 and 31.0, respectively) on April 27th. Based on the significance of differences and OAVs, linalool, (E)-β-ocimene, geraniol, and (E,E)-2,4-nonadienal were considered as the key differential odorants. Combined with the sensory evaluation and the differences in aroma components, it was proposed that black teas produced around April 15th in the Hunan district are more likely to have a strong and lasting sweet aroma. This study will provide scientific guidance for the production of black tea in the Hunan district, China.

Flavor Quality Analysis of Ten Actinidia arguta Fruits Based on High-Performance Liquid Chromatography and Headspace Gas Chromatography-Ion Mobility Spectrometry.

Actinidia arguta is a fruit crop with high nutritional and economic value. However, its flavor quality depends on various factors, such as variety, environment, and post-harvest handling. We analyzed the composition of total soluble sugars, titratable acids, organic acids, and flavor substances in the fruits of ten A. arguta varieties. The total soluble sugar content ranged from 4.22 g/L to 12.99 g/L, the titratable acid content ranged from 52.55 g/L to 89.9 g/L, and the sugar-acid ratio ranged from 5.39 to 14.17 at the soft ripe stage. High-performance liquid chromatography (HPLC) showed that citric, quinic, and malic acids were the main organic acids in the A. arguta fruits. Headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) detected 81 volatile compounds in 10 A. arguta varieties, including 24 esters, 17 alcohols, 23 aldehydes, 7 ketones, 5 terpenes, 2 acids, 1 Pyrazine, 1 furan, and 1 benzene. Esters and aldehydes had the highest relative content of total volatile compounds. An orthogonal partial least squares discriminant analysis (OPLS-DA) based on the odor activity value (OAV) revealed that myrcene, benzaldehyde, methyl isobutyrate, α-phellandrene, 3-methyl butanal, valeraldehyde, ethyl butyrate, acetoin, (E)-2-octenal, hexyl propanoate, terpinolene, 1-penten-3-one, and methyl butyrate were the main contributors to the differences in the aroma profiles of the fruits of different A. arguta varieties. Ten A. arguta varieties have different flavors. This study can clarify the differences between varieties and provide a reference for the evaluation of A. arguta fruit flavor, variety improvement and new variety selection.

Characterization of Key Compounds of Organic Acids and Aroma Volatiles in Fruits of Different Actinidia argute Resources Based on High-Performance Liquid Chromatography (HPLC) and Headspace Gas Chromatography-Ion Mobility Spectrometry (HS-GC-IMS).

Actinidia arguta, known for its distinctive flavor and high nutritional value, has seen an increase in cultivation and variety identification. However, the characterization of its volatile aroma compounds remains limited. This study aimed to understand the flavor quality and key volatile aroma compounds of different A. arguta fruits. We examined 35 A. arguta resource fruits for soluble sugars, titratable acids, and sugar-acid ratios. Their organic acids and volatile aroma compounds were analyzed using high-performance liquid chromatography (HPLC) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The study found that among the 35 samples tested, S12 had a higher sugar-acid ratio due to its higher sugar content despite having a high titratable acid content, making its fruit flavor superior to other sources. The A. arguta resource fruits can be classified into two types: those dominated by citric acid and those dominated by quinic acid. The analysis identified a total of 76 volatile aroma substances in 35 A. arguta resource fruits. These included 18 esters, 14 alcohols, 16 ketones, 12 aldehydes, seven terpenes, three pyrazines, two furans, two acids, and two other compounds. Aldehydes had the highest relative content of total volatile compounds. Using the orthogonal partial least squares discriminant method (OPLS-DA) analysis, with the 76 volatile aroma substances as dependent variables and different soft date kiwifruit resources as independent variables, 33 volatile aroma substances with variable importance in projection (VIP) greater than 1 were identified as the main aroma substances of A. arguta resource fruits. The volatile aroma compounds with VIP values greater than 1 were analyzed for odor activity value (OAV). The OAV values of isoamyl acetate, 3-methyl-1-butanol, 1-hexanol, and butanal were significantly higher than those of the other compounds. This suggests that these four volatile compounds contribute more to the overall aroma of A. arguta. This study is significant for understanding the differences between the fruit aromas of different A. arguta resources and for scientifically recognizing the characteristic compounds of the fruit aromas of different A. arguta resources.

Effect of milling degree on volatile profiles of cooked rice determined by electronic nose and HS‐SPME‐GC‐MS

AbstractBackground and ObjectivesVolatile components are mainly distributed in the rice bran layer; thus, rice with different milling levels exhibit different volatile profiles, which affects the aroma of rice and cooked rice. Seven diverse rice varieties were investigated to explore the effect of milling degree on volatile profiles of cooked rice, odor activity value (OAV) was applied to identify key aroma compounds, and partial least squares discriminant analysis (PLS‐DA) was applied to determine important marker compounds that may affect aroma.FindingsThe volatile profiles of cooked rice with different milling times were different according to the result of electronic nose. A total of 82 volatiles were identified by headspace solid‐phase microextraction‐gas chromatography‐mass spectrometry. The number and total content of volatile compounds in most samples decreased with increasing milling time. The number of key aroma compounds (OAV &gt; 1) in most samples also showed a decreasing trend with increasing milling time. PLS‐DA model successfully discriminated the differential volatile compounds in cooked rice samples with different milling times. Tridecane, 6‐methyl‐5‐heptene‐2‐one, nonanal, decanal, 2‐butyl‐2‐octenal, pentadecanal, 2,4‐decadienal, anethole, geranylacetone, 1‐dodecanol, 2‐pentadecanone, 2‐methoxy‐4‐vinylphenol, and indole were identified as 13 marker aroma‐active compounds.ConclusionsThe effect of milling degree on the volatile profiles of cooked rice was closely related to the rice varieties. Longer milling time was not in favor of the aroma of cooked rice. Milling degree mainly affected the nutty, citrus, fruity, waxy, herbal, fatty, celery, smoky, and floral aromas of cooked rice.Significance and NoveltyThe study provided important information for understanding the impacts of milling degree on volatile compounds and aroma properties of cooked rice. This is of great significance for advocating moderate processing of rice and regulating the aroma quality of cooked rice.

Comprehensive Evaluation of Ten Actinidia arguta Wines Based on Color, Organic Acids, Volatile Compounds, and Quantitative Descriptive Analysis.

Actinidia arguta wine is a low-alcoholic beverage brewed from A. arguta with a unique flavor and sweet taste. In this study, the basic physicochemical indicators, color, organic acid, and volatile aroma components of wines made from the A. arguta varieties 'Kuilv', 'Fenglv', 'Jialv', 'Wanlv', 'Xinlv', 'Pinglv', 'Lvbao', 'Cuiyu', 'Tianxinbao', and 'Longcheng No.2' were determined, and a sensory evaluation was performed. The findings show that 'Tianxinbao' produced the driest extract (49.59 g/L), 'Kuilv' produced the most Vitamin C (913.46 mg/L) and total phenols (816.10 mg/L), 'Jialv' produced the most total flavonoids (477.12 mg/L), and 'Cuiyu' produced the most tannins (4.63 g/L). We analyzed the color of the A. arguta wines based on CIEL*a*b* parameters and found that the 'Kuilv' and 'Longcheng No.2' wines had the largest L* value (31.65), the 'Pinglv' wines had the greatest a* value (2.88), and the 'Kuilv' wines had the largest b* value (5.08) and C*ab value (5.66) of the ten samples. A total of eight organic acids were tested in ten samples via high-performance liquid chromatography (HPLC), and we found that there were marked differences in the organic acid contents in different samples (p < 0.05). The main organic acids were citric acid, quinic acid, and malic acid. The aroma description of a wine is one of the keys to its quality. A total of 51 volatile compounds were identified and characterized in ten samples with headspace gas chromatography-ion mobility spectrometry, including 24 esters, 12 alcohols, 9 aldehydes, 3 aldehydes, 2 terpenes, and 1 acid, with the highest total volatile compound content in 'Fenglv'. There were no significant differences in the types of volatile compounds, but there were significant differences in the contents (p < 0.05). An orthogonal partial least squares discriminant analysis (OPLS-DA) based on the odor activity value (OAV) showed that ethyl butanoate, ethyl pentanoate, ethyl crotonate, ethyl isobutyrate, butyl butanoate, 2-methylbutanal, ethyl isovalerate, and ethyl hexanoate were the main odorant markers responsible for flavor differences between all the A. arguta wines. Sensory evaluation is the most subjective and effective way for consumers to judge A. arguta wine quality. A quantitative descriptive analysis (QDA) of the aroma profiles of ten grapes revealed that the 'fruity' and 'floral' descriptors are the main and most essential parts of the overall flavor of A. arguta wines. 'Tianxinbao' had the highest total aroma score. The flavor and quality of A. arguta wines greatly depend on the type and quality of the A. arguta raw material. Therefore, high-quality raw materials can improve the quality of A. arguta wines. The results of the study provide a theoretical basis for improving the quality of A. arguta wines and demonstrate the application prospects of HS-GC-IMS in detecting A. arguta wine flavors.

Effect of roasting after sugar-soaking on the level of volatile compounds, total polyphenol, total flavonoid, and isoflavones in black soybean (Glycine max (L.) Merr.)

Thermal process with various sugars on black soybean before roasting process affects the levels of volatile compounds, total polyphenol, total flavonoid, and isoflavones. Black soybeans (Glycine max (L.) Merr.) were pre-soaked in 10, 30, and 50 g/L solutions of five types of monosaccharide (glucose, fructose, arabinose, xylose, ribose) for 2 h, followed by drying (50 °C/20 min) and roasting (200 °C/20 min) to determine the level of volatile compounds and isoflavones, and the antioxidant activity. Volatile compounds and isoflavones were analyzed by GC−MS and HPLC, respectively. Of the 22 volatile compounds identified in black soybean headspace, 2,5-dimethylpyrazine was the most abundant (1790 μg/kg). Pre-soaking in 50 g/L glucose gave the highest content of total volatile compounds (67.9% above control), while 10 g/L arabinose gave the highest content of total isoflavone (18.6% above control). With the increase in glucose, fructose, and ribose concentration, the contents of total volatile compounds, isoflavone, polyphenol, and flavonoid increased (p < 0.05) but decreased for xylose and ribose solutions (p < 0.05), except for the total polyphenol. This study provides practical information on the changes in the volatiles, isoflavones, and antioxidants in roasted black soybeans after soaking in five monosaccharide solutions.

Malolactic fermentation performance of indigenous Oenococcus oeni strains from Shaanxi wine region (China) and their mutants on Pinot Noir and Chardonnay wines

This study investigated the malolactic fermentation (MLF) performance of three indigenous Oenococcus oeni strains isolated from the Shaanxi wine region (China) and mutants of those strains with different acid-tolerant phenotypes on Pinot Noir and Chardonnay wines. The MLF kinetics of these strains, as well as the basic chemical parameters and volatile compounds of wines after MLF, were determined. All strains successfully completed MLF in Pinot Noir wines with a pH of 3.45; however, only the acid-tolerant mutants were able to complete MLF in Chardonnay wines with a pH of 3.2. Compared with other strains, inoculation with the acid-tolerant mutants reduced the MLF duration up to 4.5 days in Pinot Noir wines, and significantly increased the concentrations of total volatile compounds in Pinot Noir wines and Chardonnay wines, with values rising from 324226.38 to 361450.91 μg/L and from 213322.96 to 279848.12 μg/L, respectively. These wines had higher levels of 2,3-butanediol, linalool, α-terpineol and β-damascenone, contributing to more pronounced butter and floral aroma profiles. MLF performance of these strains was positively correlated with their acid tolerance, and indigenous acid-tolerant mutants show great potential to be developed as MLF starters, contributing to the regional characteristics and high quality of wines.

Effects of oak chips on quality and flavor of persimmon brandy: A comprehensive analysis of volatile and non-volatile compounds

A study was conducted to investigate the effects of oak chips on the quality of persimmon brandy. The brandy was prepared from Mopan persimmons through fermentation and distillation, and aged for 30–210 days with 0, 5, 10, and 15 g/L of oak chips. The brandy was analyzed for total phenols, oxidation resistance, color, volatile compounds, and non-volatile compounds. Results showed that the addition of oak chips increased the total phenolic content and DPPH scavenging capacity of the brandy. The brandy achieved a better golden yellow color when aged with 10 and 15 g/L of oak chips. HS-SPME-GC-MS analysis revealed 14, 22, 26, and 21 compounds in the four brandy samples with different amounts of oak chips. The brandy aged with 10 g/L of oak chips had the highest total content of volatile compounds. LC-MS-based metabolomics identified a total of 618 non-volatile metabolites, with 20 having the highest relative expression when aged with 10 g/L of oak chips. These findings suggest that persimmon brandy achieves better quality and flavor when aged with 10 g/L of oak chips for 210 days.

Changes in, and correlation analysis of, volatile compounds, key enzymes, and fatty acids in lemon juice vesicles during freeze drying and hot-air drying.

Lemon juice vesicles are distinguished by their unique and abundant volatile flavor compounds, which can undergo complex changes during drying. In this study, integrated freeze drying (IFD), conventional freeze drying (CFD), and hot-air drying (AD) were used to dry lemon juice vesicles to investigate the changes in, and correlations among volatile compounds, fatty acids, and key enzyme activity during the drying process. Twenty-two volatile compounds were detected during the drying processes. Compared with fresh samples, seven compounds were lost in the dried samples after IFD, seven after CFS, and six after AD, and the loss rates of the total content of volatile compounds in the dried samples were 82.73% in CFD, more than 71.22% in IFD, and more than 28.78% in AD. In total, 1.015 mg/g of seven fatty acids were detected in the fresh samples; the content loss rates of total fatty acids after drying were 67.68% in AD, more than 53.00% in CFD, and more than 36.95% in IFD, respectively. During the three drying processes, IFD retained relatively higher enzyme activity in the samples. Many positive and negative correlations (P < 0.05) were observed among the key enzyme effects, fatty acids, and volatile compounds, showing close associations. The current work provides information that is important for the selection of suitable drying techniques for lemon juice vesicles and suggests how to control their flavor during the drying process. © 2023 Society of Chemical Industry.

The non-specific lipid transfer protein McLTPII.9 of Mentha canadensis is involved in peltate glandular trichome density and volatile compound metabolism.

Mentha canadensis L. is an important spice crop and medicinal herb with high economic value. The plant is covered with peltate glandular trichomes, which are responsible for the biosynthesis and secretion of volatile oils. Plant non-specific lipid transfer proteins (nsLTPs) belong to a complex multigenic family involved in various plant physiological processes. Here, we cloned and identified a non-specific lipid transfer protein gene (McLTPII.9) from M. canadensis, which may positively regulate peltate glandular trichome density and monoterpene metabolism. McLTPII.9 was expressed in most M. canadensis tissues. The GUS signal driven by the McLTPII.9 promoter in transgenic Nicotiana tabacum was observed in stems, leaves, and roots; it was also expressed in trichomes. McLTPII.9 was associated with the plasma membrane. Overexpression of McLTPII.9 in peppermint (Mentha piperita. L) significantly increased the peltate glandular trichome density and total volatile compound content compared with wild-type peppermint; it also altered the volatile oil composition. In McLTPII.9-overexpressing (OE) peppermint, the expression levels of several monoterpenoid synthase genes and glandular trichome development-related transcription factors-such as limonene synthase (LS), limonene-3-hydroxylase (L3OH), geranyl diphosphate synthase (GPPS), HD-ZIP3, and MIXTA-exhibited varying degrees of alteration. McLTPII.9 overexpression resulted in both a change in expression of genes for terpenoid biosynthetic pathways which corresponded with an altered terpenoid profile in OE plants. In addition, peltate glandular trichome density was altered in the OE plants as well as the expression of genes for transcription factors that were shown to be involved in trichome development in plants.

Effects of dry‐curing salt content on flavour formation in different production steps during the processing of water‐boiled salted duck

SummaryThis study evaluated the effects of dry‐curing salt content [4% low salt (LS), 6% medium salt (MS), 8% high salt (HS)] on volatile compounds, lipid oxidation and lipolysis during the processing of water‐boiled salted duck (WSD). After dry‐curing, the varieties and content of volatile compounds increased significantly. The total content of volatile compounds tended to increase at dry‐curing, brining and early and middle air‐drying stages, and then decrease. The thiobarbituric acid reactive substances (TBARS) values increased during the whole process. The free fatty acids (FFAs) content increased at dry‐curing, brining and early air‐drying stages, and decreased after air‐drying for 1 day. Compared with LS, HS and MS had higher content of characteristic flavour substances and FFAs, especially unsaturated fatty acids (UFA), and higher TBARS during the processing of WSD. It showed that 6% dry‐curing salt content (MS) was applicable to practical production of WSD for flavour formation and salt reduction in dry‐cured meat products.