Fruit Aroma Research Articles

Combined ultrasound and low temperature pretreatment improve the content of anthocyanins, phenols and volatile substance of Merlot red wine

Ultrasound combined with low temperature treatment is a new food processing technology. In this study, low temperature, three ultrasound power levels, and their combinations were adopted in the must before fermentation to study their effects on Merlot red wine. The results showed that ultrasound combined with low temperature pretreatment increased the total and monomer contents of anthocyanins and phenols, affected the color of the wine, and significantly increased its antioxidant capacity. In particular, 240 W of ultrasound combined with low temperature pretreatment reduced the bad odors (caprylic acid, benzaldehyde, and 1-ethanol content) and improved the flower and fruit aroma (1-octanol and phenethyl acetate), as well as the aftertaste, thus improving the quality of the wine. Ultrasound combined with low temperature pretreatment positively affected the quality of Merlot red wine.

Introduced resistant grape variety Frontenac Blanc

Th e paper presents a variety trial and technological evaluation of the wine material from Frontenac Blanc grape, isolated as a color mutation in Canada plantations of the Frontenac Gris variety in 2006. Th e study was carried out in 2020–2022 in compliance with vitiviniculture recognized methodology in soil and climatic conditions of Potapenko All-Russian Research Institute of Viticulture and Winemaking, a branch of Federal Rostov Agrarian Scientifi c Centre, Novocherkassk, Rostov Oblast, Russia. Vineyards are open-earth, rainfed, graft ed, with Kober 5BB rootstock, 3.0×1.5 m planting scheme, shaping: double-shouldered low (40 cm) horizontal cordon, short pruning on knots. Agricultural technology is standard, generally recognized. Frontenac Blanc is found to obtain high winter hardiness, promising for open-earth cultivation. Th e variety has good resistance to infections: to mildew (2.0 score), oidium (2.5 score); grey rot has not been observed. Th erefore, frequent use of pesticides is not required and vineyard maintenance is simplifi ed. Th e high level of sugars (248 g/dm3) and t itratable acids (10.4 g/dm3) in t h e juice ensures a harmonious wine with well-balanced acidity. Due to such characteristics, the variety is considered to be promising for the production of diff erent wine styles, including dry still, semi-dry, as well as sparkling and liqueur wines. Th e wine material from Frontenac Blanc presents a distinguishing character, bright fruit aromas, rich structured fl avor, and lingering fi nish. Th e average tasting score of the wine material comprises 8.6 points (on a 1–10 scale). Th e variety has a high yield (16 tonnes/ha), which does not adversely aff ect the quality of products. Frontenac Blanc is resistant to cold and early ripening period (120 days) and can be eff ectively grown in regions with previously limited production due to extreme climatic conditions. Considering that, an innovative development of the wine industry in areas with cool and uncertain climate possesses a high potential.

Comprehensive evaluation of aroma and taste properties of different parts from the wampee fruit.

Wampee is a tropical fruit having high medicinal value. To fully realize the fruit's potential, it is essential to reveal the flavor characteristics. In this study, a comprehensive analysis of the aroma and taste profiles of different parts from the wampee fruit was conducted. The aroma profile was analyzed by E-nose, and 67 volatile components were identified through HS-SPME-GC-MS. Among them, 11 were considered as crucial compounds. Additionally, 42 volatile components were identified by HS-GC-IMS, with 22 compounds showing a variable importance in projection scores greater than 1.0. Moreover, the taste profile and representative compounds were analyzed by E-tongue and HPLC, and 12 compounds were considered as important taste contributors based on taste activity value. These findings shed light on the various compounds responsible for the unique aroma and taste of the wampee fruit, providing theoretical foundation for exploring ways for its comprehensive utilization and development.

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.

Understanding the relationship between tropical fruit aroma, acceptance, and emotional response in chardonnay wines

Tropical fruit aromas are prominent in many white wines. The purpose of this work was to determine if winemaking practices could impact the tropical fruit aromas in the Chardonnay wines and how those aroma differences influenced wine consumers acceptance and emotional responses. Four treatments were tested at varying fermentation temperature gradients and skin contact times: control fermentation at 13 °C with no skin contact (Control), fermentation at 13 °C with 18 h of skin contact (SC), fermentation temperature gradient by time (20 °C for 4 days then reduced to 13 °C) with no skin contact (FG), fermentation temperature gradient by time with 18 h of skin contact (SCFG). Acceptance, using a 7-point hedonic scale, showed there was not a significant difference between treatments. Emotional response, using a 5-point Rate-All-That-Apply (RATA) scale, showed significant differences for ‘calm’ and ‘disgusted’ emotions. Check-all-that-apply (CATA) for aroma descriptors showed that Control is described using aromas of passionfruit, lychee, and pome fruit; SC had aromas of grapefruit and floral; FG was described as having melon, lychee, and pineapple aromas; and SCFG was described with aromas of lemon/lime, mango, and guava. Positive emotions were associated with fruity aromas in the wines, although no difference in acceptance was found. Winemaking treatments impacted the aroma profile of chardonnay wine, with tropical aromas evoking positive emotions in consumers. The relationship between specific aromas and consumers emotion responses can be an important tool to understand the factors behind a wine’s success or lack thereof. Moreover, it can help with the creation of new wine products.

Identification of volatile organic compounds as markers to detect Monilinia fructicola infection in fresh peaches

Monilinia spp. are among the main fungal pathogen affecting peaches, and they can cause severe pre- and postharvest losses. Development of smart packaging technologies (e.g., volatile indicators), facilitating infection detection and preventing other fruit from being contaminated, is still limited. In this study, we compared for the first time the aroma profile of whole healthy fresh peaches to Monilinia fructicola-artificially inoculated peaches, identifying discriminant volatile organic compounds (VOCs). More than one hundred VOCs were detected by applying head space solid-phase microextraction followed by GC-MS analysis. The level of methyl esters, hydrocarbons, lactones, and acids decreased in infected peaches indicating fruit aroma deterioration, while the concentration of ethyl esters and alcohols increased. In particular, the amount of ethanol and derived ethyl acetate reached a maximum of 24- and 20-fold increase in the infected peaches, respectively. Isobutanol, propyl acetate, and ethyl isovalerate were specifically emitted by M. fructicola-infected peaches. These compounds might serve as markers for the development of smart sensors allowing the detection of fungal infection.

Expression of alcohol acyltransferase is a potential determinant of fruit volatile ester variations in Capsicum.

The transcript level of alcohol acyltransferase 1 (AAT1) may be the main factor influencing the variations in volatile esters that characterizing the fruity/exotic aroma of pepper fruit. Volatile esters are key components for characterizing the fruity/exotic aroma of pepper (Capsicum spp.) fruit. In general, the volatile ester content in the fruit is the consequence of a delicate balance between their synthesis by alcohol acyltransferases (AATs) and degradation by carboxylesterases (CXEs). However, the precise role of these families of enzymes with regard to volatile ester content remains unexplored in Capsicum. In this study, we found that the volatile ester content was relatively low in C. annuum and much higher in C. chinense, particularly in pungent varieties. Additionally, fruits collected from multiple non-pungent C. chinense varieties, which harbor loss-of-function mutations in capsaicinoid biosynthetic genes, acyltransferase (Pun1), putative aminotransferase (pAMT), or putative ketoacyl-ACP reductase (CaKR1) were analyzed. The volatile ester contents of non-pungent C. chinense varieties (pamt/pamt) were equivalent to those of pungent varieties, but their levels were significantly lower in non-pungent NMCA30036 (pun12/pun12) and C. chinense (Cakr1/Cakr1) varieties. Multiple AAT-like sequences were identified from the pepper genome sequences, whereas only one CXE-like sequence was identified. Among these, AAT1, AAT2, and CXE1 were isolated from fruits of C. chinense and C. annuum. Gene expression analysis revealed that the AAT1 transcript level is a potential determinant of fruit volatile ester variations in Capsicum. Furthermore, enzymatic assays demonstrated that AAT1 is responsible for the biosynthesis of volatile esters in pepper fruit. Identification of a key gene for aroma biosynthesis in pepper fruit will provide a theoretical basis for the development of molecular tools for flavor improvement.

Development of a New Method for the Quantitative Analysis of Aroma Compounds Potentially Related to the Fruity Aroma of Red Wines.

To determine the concentrations of aroma compounds involved in the fruity aroma of red wines, an analytical method was developed and optimized using liquid-liquid extraction and gas chromatography coupled to mass spectrometry (GC/MS). The aim was to reduce sample preparation and analysis time, with a single sample preparation and a single injection being needed to quantify 43 compounds. 19 esters, 13 monoterpenes, 5 C13-norisoprenoids, and 6 C6-aldehyde and alcohol compounds were quantified in 14 red wines made from different grape varieties grown in the Mediterranean basin. Samples were selected based on typical varietal aroma by a panel of experts, who produced 7 olfactory descriptors linked to desirable or non-desirable wine aromas. The instrumental analysis showed variations in concentrations of the quantified compounds among the wines. The wines described using positive fruity descriptors had higher mean total concentrations of esters, C6-alcohols, monoterpenes, and C13-norisoprenoids. Some non-ester compounds were positively correlated with the fruity descriptors. Sensory profile results obtained by a panel of 16 trained judges revealed that the addition of non-ester compounds (including 2 cyclic esters) to a red wine initially described as having cooked fruit aromas had a positive contribution to some fresh fruity notes. This study opens up new avenues for research on the potential involvement of non-ester compounds in the fruity expression of red wines.

EFFECT OF PLASMA CHEMICAL OXIDATION OF ETHYLENE IMPURITIES ON THE EFFICIENCY OF KIWIFRUIT STORAGE

The effectiveness of plasma chemical technology in reducing the concentration of ethylene impurities in order to extend the shelf life of kiwifruit has been studied. Ethylene and mold were controlled by plasma treatment, which slowed the ripening of kiwifruit and significantly inhibited rotting. When storing kiwifruit using the plasma chemical system, the level of ethylene was twice lower than that measured in the control batch. Also, the level of ethylene practically did not change during the entire period of the experiment, since the ethylene released from the fruit was quickly oxidized by ozone. Air treatment of kiwifruit storage environment resulted in the fact that ripening mechanism was delayed and the loss of fruits during their further transportation and storage was almost completely prevented. Thus, high efficiency of plasma-chemical method for extending kiwifruit shelf life was shown as well as the prospects of its application. Storage period can be doubled while preserving the subtle aroma of fruits. The effectiveness of plasma chemical technology in reducing the concentration of ethylene impurities in order to extend the shelf life of kiwifruit has been studied. High efficiency of plasma-chemical method for extending kiwifruit shelf life was shown as well as the prospects of its application. Storage period can be doubled while preserving the subtle aroma of fruits.

Aroma of peach fruit: a review on aroma volatile compounds and underlying regulatory mechanisms

SummaryPeach is a highly significant economic fruit renowned for its juicy flesh, delectable taste, and pleasant aroma, which has made it a consumer favourite. Improving fruit quality often involves enhancing its aroma, as it is widely acknowledged that the aroma of a fruit plays a crucial role. However, the formation of aroma volatiles is dynamic and varies with fruit development and ripening and is closely linked to genetic background, cultivation management, and post‐harvest treatment. In recent years, many studies have been conducted to investigate the biosynthetic pathways involved in generating fruit aroma. However, the understanding of the underlying regulatory mechanisms remains limited. With the advancement in molecular biology and multi‐omics techniques, researchers have gained fresh insights into the molecular functions of peach genes, which holds significant implications for enhancing fruit flavour and advancing modern breeding programs. This review aims to summarise the most recent findings pertaining to aroma volatile compounds, shed light on the underlying regulatory mechanisms, and dissect the primary fields of peach fruit aroma research. Its purpose is to provide critical information that will facilitate a profound investigation into the specific components responsible for peach aroma and the mechanisms by which they are regulated.

LOX and AAT Genes Affect the Aroma of “Xiaobai” Apricot during Postharvest Storage

“Xiaobai” apricot is one of the most popular fruits in China. However, during postharvest storage, fruit aroma loss occurs easily. In this study, factors affecting the aroma changes in different ripening stages of “Xiaobai” apricot during postharvest storage were searched. Immature and mature “Xiaobai” apricot samples were collected and monitored for sensory changes during postharvest storage. After 25 days of storage, the aromatic ester and alcohol abundance in mature showed a decrease, related to the loss of characteristic aroma. Immature fruit still tasted sour with an indistinct characteristic aroma, as a result of decreased alcohol and increased acid abundance. The ATT, ADH, PDC, and LOX genes were identified, and their expression levels were detected at different ripening stages during storage. The correlation analysis showed that the expression of LOX and ATT was positively correlated with the variation of aromatic ester ( P < 0.05 ), a key factor affecting the apricot aroma during postharvest storage.

Variation in Volatile Organic Compounds in native, synanthropic accessions and cultivars of the musk strawberry (Fragaria moschata Duchesne ex Weston).

Prior to the world-wide dominance of F. ×ananassa in strawberry production, native species had been cultivated in European gardens for centuries. Especially the musk strawberry (F. moschata) had been highly appreciated due to its fruit size and extraordinary aroma. Detailed studies on the diversity of the species' fruit aroma are lacking, although breeding aims to improve strawberry aroma by complex crossings during recent years. Today a few cultivars, abandoned synanthropic occurrences and native populations of this species exist in Germany. Here we characterised aroma profiles of F. moschata accessions by analysing Volatile Organic Compounds. In particular, differences between native and cultivated accessions as well as the diversity in aroma profiles of native populations were investigated. Profiles of Volatile Organic Compounds were analysed by immersion stir bar sorptive extraction-gas chromatography-quadrupol mass spectrometry (imm-SBSE-GC-qMS). These data were compared with a genetic characterisation of samples based on eight microsatellite loci using univariate and multivariate statistical analyses. High amounts of furanones and the key compound methyl anthranilate were characteristic for the aroma profile of F. moschata. We detected a considerable diversity of Volatile Organic Compounds among accessions of F. moschata, particularly among genetically distinct samples from the same population. Native accessions contained more terpenoids but less esters and were moderately differentiated from cultivated samples. The observed patterns of Volatile Organic Compounds indicate that cultivated accessions had been selected for favourable aroma profiles and thus showing traces of domestication. Moreover, native populations harbour a great diversity of Volatile Organic Compounds, which could be also considered for future breeding efforts.

Role of the transcription factor MdABF2 in abscisic acid-induced volatile compound biosynthesis in ‘Ruixue’ (Malus × domestica) apple during storage

Fruit aroma, which is conferred by an array of volatile compounds, strongly influences both consumer acceptance and market competitiveness. The phytohormone abscisic acid (ABA) regulates volatile compound biosynthesis during fruit ripening. However, the regulatory mechanism by which ABA may alter the production of volatile compounds in apple remains unknown. In this study, ABA treatment accelerated fruit ripening and volatile compound production, whereas treatment with the ABA biosynthesis inhibitor nordihydroguaiaretic acid (NDGA) resulted in the opposite effects. We identified a nuclear-localized ABA-responsive transcription factor (TF), MdABF2, which was upregulated by exogenous ABA. Overexpression of MdABF2 resulted in enhanced production of volatile compounds and biosynthesis gene expression, and these effects were further enhanced by ABA treatment. Moreover, MdABF2 was found to bind directly to the MdLOX1a, MdLOX5a, MdAAT1, and MdAAT2 promoters, activating their expression. The results presented here contribute to our understanding of the mechanism by which ABA regulates volatile compound biosynthesis. Furthermore, these data will be beneficial for the molecular breeding and improvement of apple for better flavor and aroma.

Jasmonate-induced MdMYC2 improves fruit aroma during storage of ‘Ruixue’ apple based on transcriptomic, metabolic and functional analyses

Abundant volatile compounds are predominant contributors to fruit aroma in various species. Plant hormones and transcription factors are pivotal for volatile compound production in fruit. Jasmonate (JA) regulates the biosynthesis of volatiles such as aldehydes and alcohols, but a possible mechanism by which JA-induced MdMYC2 regulates aldehyde and alcohol biosynthesis in apple fruit has not been described. To study the effects of JA on the critical volatiles of ‘Ruixue’ fruit, gas chromatography‒mass spectrometry (GC‒MS) was used to determine the content of volatiles in fruits treated with JA. Our results showed that JA treatment effectively improved fruit quality during storage of ‘Ruixue’ fruit; for instance, sweetness increased and aroma volatiles accumulated. Furthermore, we identified the transcription factor (TF) MdMYC2 (MD16G1274200), whose expression increased 1.5- to 2.0-fold in JA-treated fruits. Subsequently, MdMYC2 overexpression dramatically increased volatile biosynthesis in apple calli (1.6-fold) and tomato calli (2.1-fold). Furthermore, MdMYC2 upregulated MdLOX5a transcription (3-fold) by binding to its promoter according to dual-luciferase and yeast one-hybrid (Y1H) assays. Collectively, these findings provide beneficial information to illustrate the mechanisms by which JA regulates volatile biosynthesis in fruit.

Impact of harvest date on aroma compound composition of Merlot and Cabernet-Sauvignon must and wine in a context of climate change: a focus on cooked fruit molecular markers

Choice of harvest date can modulate the aroma intensity of herbaceous/vegetal, fresh fruit and cooked fruit nuances, thus helping the winemaker to produce wine of different styles and balance. Relationships between the sensory attributes and aroma compounds of Merlot and Cabernet-Sauvignon grapes that were harvested sequentially and the resulting wines were evaluated for two vintages: 2012 and 2014. The fine-tuning of the harvest date modulated the aromas of the young wine and impacted the intensity of the cooked fruit aromas for both Merlot and Cabernet-Sauvignon. No correlation was observed between the must and wine in terms of the intensity of the cooked fruit aroma. In order to observe an impact on the intensity of the cooked fruit aroma it was necessary to delay the harvest date of Cabernet-Sauvignon by 4 to 12 days in 2012 and 2014 respectively. This value was 7 days for Merlot wines (2014 vintage). Furanones, lactone and ketones were well correlated with the perceived intensity of the cooked fruit aroma in the young wine. In addition, the highest concentrations of γ-nonalactone, 3-methyl-2,4-nonanedione, massoia lactone and furaneol were detected in Merlot wines made using late-harvested grapes. At the measured concentrations, these compounds can explain the aroma of cooked fruit detected in the red wines. Similar results were obtained for the Cabernet-Sauvignon wines made from grapes from a later harvest. The volatile compounds produced from the lipoxygenase pathway in the grapes were putatively involved in the evolution of the aroma of the red wines from sequential harvest dates, opening up the possibility of managing aroma profiles through harvest date decisions. These findings are important, as the identification of measurable key chemical parameters in grapes could provide grape growers and winemakers objective indicators for predicting final wine style and quality.

GC-MS Analysis and Bioactivity Screening of Leaves and Fruits of Zanthoxylum armatum DC.

Zanthoxylum armatum DC. is a plant that has been homologated for medicine and food by the Chinese for three thousand years. In this study, the essential oils of fresh leaves and fruits were extracted by hydrodistillation, the aromas of fresh leaves and fruits were extracted by headspace solid-phase microextraction and their chemical compositions were analyzed by gas chromatography mass spectrometry. The main components of the leaf essential oils were linalool (62.01%), 2-undecanone (9.83%) and 2-tridecanone (5.47%); the fruit essential oils were linalool (72.17%), limonene (8.05%) and sabinene (6.77%); the leaf aromas were limonene (39.15%), β-myrcene (15.8%), sabinene (8.17%) and linalool (5.25%); the fruit aromas were limonene (28.43%), sabinene (13.56%), linalool (11.47%) and β-myrcene (8.64%). By comparison, it was found that the composition of leaf essential oils and fruit essential oils were dominated by oxygenated monoterpenes, while the composition of their aromas were both dominated by monoterpenes; the relative content of non-terpene components in leaf essential oil and leaf aroma is second only to oxygenated monoterpenes, while their content in fruits is low; the chemical composition of leaf aromas and fruit aromas were richer than those of essential oils. In this study, we reported for the first time that the antitumor, tyrosinase inhibition, HMGR inhibition and nitric oxide production inhibition activity of leaf essential oils were stronger than those of fruit essential oils in in vitro tests. The results of the study can provide a reference for the recycling and green low-carbon transformation of the leaves, and also help to deepen the understanding of the value of the volatile chemical constituents of this plant in “forest medicine” or “aromatherapy”, and provide new ideas for the transformation of the value of the plant in the secondary and tertiary industry chain.

Dynamics changes in volatile profile, non-volatile metabolites and antioxidant activities of dark tea infusion during submerged fermentation with Eurotium cristatum

Eurotium cristatum is a dominant fungus in the post-fermentation of Fu brick tea, however, its potential role in affecting the volatile profile and non-volatiles metabolites during the liquid-state fermentation of dark tea is not clear. In this study, dark tea was prepared by liquid-state fermentation with E. cristatum. A total of 51 volatile compounds were identified by HS-SPME-GC-MS, which mainly consisted of ketones, aldehydes, esters, and alcohols. There were 12 volatiles (ROAV >1) contributed to the overall aroma, including linalool, citral, methyl salicylate, etc. The overall flavor of tea infusion had been greatly improved after fermentation. The content of ester-type catechins, total phenols, total flavonoids, theaflavins, thearubigins, soluble sugars, and free amino acids decreased, while the content of theabrownins and soluble proteins increased. Meanwhile, the content of nonester type catechins and gallic acid increased and then decreased. The contents of various volatiles and metabolites change under the action of E. cristatum, coordinating to form a fermented dark tea infusion with mint, flower and fruit aroma and mellow and slightly astringent quality. The antioxidant activities showed a positive correlation with substances such as gallic acid and polyphenols. The results showed that the liquid-state fermentation with E. cristatum can effectively influence the flavor characteristics and antioxidant capacity of dark tea infusion.

Determination of volatile profiles of woodland strawberry (Fragaria vesca) during fruit maturation by HS-SPME GC-MS.

Aroma is an important agronomic trait for strawberries, and the improvement of fruit flavor is a key goal in current strawberry breeding programs. Fragaria vesca (also known as woodland strawberry) has become an excellent model plant with exquisite flavor, a small genome size, and a short life cycle. Thus, the comprehensive identification of fruit volatiles and their accumulation pattern of F. vesca strawberries are very important and necessary to the fruit aroma study. This study examined the volatile profile changes from the fruits of three F. vesca genotypes during maturation using the headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME GC-MS) with multivariate analysis. A total of 191 putative volatile compounds were identified, while 152, 159, and 175 volatiles were detected in 20-30 dap fruits of Hawaii 4 (HW), Reugen (RG), and Yellow Wonder (YW), respectively. Aldehydes and alcohols predominated in the early time point while esters were predominant during the late time point. Ketones were the dominant compounds from F. vesca strawberries fruits at the ripe stage. Certain genotype-characteristic volatiles were identified, including eugenol, γ-octalactone, and δ-decalactone were only detected in YW, and mesifurane was found in HW. RG and YW showed very similar volatile compositions, but YW presented a greater number of volatiles and RG yielded a higher content. Differences in the volatile composition may be primarily due to genetic relationships. The metabolic changes that occurred during fruit ripening and characteristic volatiles will be a useful reference for future strawberry volatile studies. This article is protected by copyright. All rights reserved.

A Systematic Profiling of the Volatile Compounds in 53 Cerasus humilis Genotypes Using Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The fruits of Cerasus humilis have a unique and pleasant aroma. In this study, the volatile compounds of ripe fruits of 53 C. humilis genotypes were extracted via headspace solid-phase microextraction (HS-SPME) and identified via gas chromatography coupled with mass spectrometry (GC-MS). In total, 253 volatile compounds were detected, among which esters and terpenoids were the most dominant volatile components. We also found that the total volatiles contents varied significantly among genotypes with different ripening periods, with middle-ripening periods genotypes having higher total volatile content compared to either early- or late-ripening period genotypes. Moreover, genotypes with yellow fruit peels had higher total volatile contents. Our study revealed the volatile profiles of 53 different C. humilis genotypes and their potential linkages with other fruit parameters. These results should help fruit researchers gain a deeper understanding of the biochemical, physiological, and molecular mechanisms of fruit aroma development for high fruit aroma-targeted breeding of fruit cultivars.

Potential role of fatty acid desaturase 2 in regulating peach aroma formation

Fruit aroma is an important evaluation index for fruit quality. Linoleic acid is an essential precursor pool for the aroma compounds in peach (Prunus persica L.) and is catalyzed by fatty acid desaturase 2 (FAD2). In this study, PpFAD2–1 and PpFAD2–2 were isolated from ‘Jinxiuhuangtao’ peaches. Three typical conserved histidine motifs (HX3or4H, HX2or3HH, and HX2or3HH) were observed in the two PpFAD2 proteins, and 18 candidate amino acid residues potentially involved in fatty acid desaturation were identified in PpFAD2–1. Subcellular localization analysis indicated that PpFAD2s are localized in endoplasmic reticulum membrane. Notably, PpFAD2–1 expression was gradually increased during the fruit ripening stages, whereas PpFAD2–2 changed little. In vitro enzyme assay in both Escherichia coli and yeast revealed that PpFAD2s increased linoleic acid levels, with a larger increment of PpFAD2–1 than that of PpFAD2–2. Furthermore, in vivo enzyme activity assay revealed that levels of two unsaturated fatty acids (linoleic acid and linolenic acid) and peach aroma compounds (including hexyl acetate, γ-dodecalactone, γ-decalactone, γ-octalactone and γ-hexalactone) were increased in PpFAD2–1 transgenic fruit during postharvest storage, especially under recovery storage in room temperature after cold storage (4 ℃), whereas unchanged in PpFAD2–2 transgenic fruit. Favorably, this study provides new insights into the role of PpFAD2s in regulating peach aroma biosynthesis, which contributes to the sustainable fruit storage management and the molecular breading of new peach varieties with more favorable aromas.