Peach Aroma Research Articles

Sensory Determination of Peach and Nectarine Germplasms with Instrumental Analysis.

The flavour and mouthfeel of peaches are crucial qualities of peach germplasm resources that significantly influence consumer preferences. In this study, we utilized 212 peach germplasm resources from the Nanjing Peach Resource Repository, National Fruit Germplasm facility, Jiangsu Academy of Agricultural Sciences as materials for sensory analysis, electronic nose analysis, and composition analysis via high-performance liquid chromatography (HPLC). In the sensory analysis, we divided 212 peach germplasms into three clusters based on hierarchical cluster analysis (d = 5). No.27, No.151, and No.46 emerged as the most representative of these clusters. The electronic nose was used to conduct an evaluation of the aroma profiles of the 212 peach germplasms, revealing that the primary distinguishing factors of peach aroma can be attributed to three sensors: W1S (methane), W1W (terpenes and organosulfur compounds), and W5S (hydrocarbons and aromatic compounds). The primary differences in the aromatic substances were characterized by sensors W2W (aromatic compounds, sulphur, and chlorine compounds) and W1C (aromatic benzene). The HPLC analysis indicated that the persistence of peach sensory characteristics was positively correlated with acids and sourness and negatively correlated with sweetness and the ratio of sugar to acids. The overall impression of the 212 peach germplasms revealed a negative correlation with acids, while a positive correlation was observed between the overall impression and the ratio of sugar to acids. Therefore, this study substantially contributes to the preliminary screening of the analysed specific characteristics of peach germplasms such as No.27, No.46, No.151, and No.211. These selections may provide valuable information for the potential creation of superior germplasm resources.

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.

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.

Effects of gamma irradiation on the sensory and metabolic profiles of two peach cultivars.

The suitability of commercial peaches for minimal processing (MP) is limited, mainly due to shortened shelf-life. Gamma irradiation has emerged in MP fruits as a promising technology. This study aimed to investigate the effects of gamma irradiation on the sensory and metabolic profiles of MP peaches from two cultivars - 'Forastero' (FT) and 'Ruby Prince' (RP) - and evaluate the relationship between both profiles. MP peaches were packaged and divided into two groups: one without additional treatment (K) and the other subjected to gamma irradiation (1.0 kGy, I- irradiation treatment), making a total of four samples (FTK, FTI, RPK and RPI). The sensory profile was carried out by an assessor panel. Metabolite analysis was accomplished by gas chromatography-mass spectrometry. Irradiation significantly affected color, homogeneity, peach aroma, total flavor intensity, peach flavor, sweetness and juiciness in FT, increasing their intensities. In the RP cultivar, irradiation increased brightness, total aroma intensity, peach aroma, and flavor and texture descriptors. Regarding metabolites, only malic acid and sucrose increased their concentrations in the irradiated samples. Partial least squares showed that sucrose was mainly correlated with sweet, total aroma intensity and peach flavors, and linked with FTI sample. Bitter along with peach aroma and total intensity flavor were associated with RPI sample. The applied dose accelerated the ripening process of the peach. The study highlights the importance of complementing sensory analysis with metabolomics tools to optimize fruit quality in minimally processed peaches. © 2023 Society of Chemical Industry.

Using Conjoint-based Experimental Design to Assess Willingness to Purchase Florida Peaches

Although consumers are not very familiar with peach production in Florida, Florida peaches are the first domestic peaches produced in the United States, being available from mid-March through early May. Moreover, Florida peach acreage has increased 8.5-fold in the past 10 years. Using a conjoint-based experimental design and analysis, we measured U.S. consumer reactions to diverse groups of ideas describing peaches, including production regions, and identified attributes that positively and negatively influence consumer preference. The main objective of this research was to identify external and internal attributes that make the “ideal peach.” Are consumers willing to pay more for a locally grown peach? Will consumers prefer a Florida peach instead of a Georgia or California peach? The top three peach attributes identified were “juicy and fully ripe,” “strong peach aroma and sweet peach taste,” and “grown in Georgia.” Cluster analysis revealed two segments of consumers: consumers in the first segment focused on physical aspects of the peach, and consumers in the second segment were concerned with peach production regions and health benefits. The findings from this research will be helpful in developing marketing programs for Florida peaches as an item that is perfect for snacking because of their small size and desirable texture and flavor.

Understanding the interactive effects of volatile compounds contributing to ‘stone fruit’ aroma nuances in white wines

Background and Aims The sensory experience of wine aroma is challenging to study. Given the presence of numerous and trace level volatiles, the subtle aroma nuances involved, as well as the complexity of human odour processing, the contribution of individual compounds and mixtures can be difficult to determine. In white wines, the volatile compounds eliciting stone fruit aromas are not well understood. Methods and Results Factorial designs were used with odorants added to model wine and assessed using sensory quantitative descriptive analysis. In model Viognier-like wines, several monoterpenes were confirmed to convey stone fruit attributes Apricot and Peach, which were strongly suppressed by aldehydes which imparted Cardboard-like odours. Importantly, lactones increased Apricot aroma when combined with the monoterpenes. For model unoaked Australian Chardonnay wine, sensory-directed screening followed by factorial studies showed that aliphatic ethyl esters, in particular ethyl octanoate, directed Peach aroma. Fatty acids were strong suppressors of the Peach attribute and gave Cheesy odours. Conclusions Apricot and peach aromas in Viognier and Chardonnay, although perceptually similar, were caused by different chemical compound families: grape-derived monoterpenes with lactones and yeast-derived fatty acid ethyl esters, respectively. Significance of the Study Having confirmed the compounds responsible for apricot and peach white wine aromas, there is potential to modify their concentration through established viticultural and winemaking practices.

Volatile Profile Characterization of Commercial Peach (Prunus persica) Cultivars Grown in Georgia, USA

Peach production in Georgia, USA, extends from mid-May to mid-August. Multiple cultivars are commercially grown in the U.S., and each cultivar has unique fruit quality characteristics, which could influence consumer perception and acceptability. Among those, peach flavor has been minimally characterized among cultivars. Headspace-solid phase microextraction (HS–SPME) combined with gas chromatography–mass spectrometry (GC–MS) was used to characterize the volatile profile of 42 peach cultivars commercially grown in 2016. The goal of this research was to understand the aroma composition and content of peach cultivars grown in Georgia, USA. Thirty-six volatile compounds were identified. Significant differences (p ≤ 0.0001) were observed for all the flavor volatiles across all cultivars being evaluated. Esters were the major compounds isolated from the 42 peach cultivars, followed by lactones, alcohols, aldehydes, and terpenoids, in that order. Lactones, benzaldehyde, and linalool, which are known to be peach aroma compounds, exhibited the highest mean concentrations among the cultivars with ɣ- and δ-decalactones having a concentration of approximately 180 ng·g−1 and 60 ng·g−1, respectively. Among the cultivars, “Majestic” had the highest mean concentration of ɣ-decalactone, followed by “Southern Pearl” with approximately 503 ng·g−1 and 443 ng·g−1, respectively. “Southern Pearl” and “Fairtime” also exhibited the highest average concentration of δ-decalactone. The results obtained will help provide an understanding of the distribution of the various volatile organic compounds found in Georgia-grown peach cultivars.

Genetic Variability and Structure of Fragaria nilgerrensis Schlecht. Germplasm in Sichuan Province

Fragaria nilgerrensis Schlecht. (wild strawberry) is widely distributed in Southwest China, characterized by stress tolerance and the fruits of a notable peach aroma. So far there is only limited knowledge of variability and genetic structure in this species. Using AFLP markers, we investigated the genetic variability of 37 plants of F. nilgerrensis sampled in six main mountain areas of Sichuan Province and analyzed their genetic structure. Genetic similarity according to Nei and Li was used for cluster analysis based on UPGMA method and Agglomerative Hierarchical Clustering. Stratification of plants into more distinctive genetic groups was determined using Bayesian structure analysis. Six primer combinations produced a total of 1302 fragments of which 818 (62.8%) were polymorphic. Bayesian analysis showed the 37 plants of F. nilgerrensis grouped into five distinctive genetic groups. Most of the plants from the same mountain area clustered into the same genetic group, indicating each area as an area with the unique genetic profile. The genetic parameters analyzed here indicate a huge genetic variability of F. nilgerrensis in Sichuan Province. Our results provide reference data for surveying and protecting the germplasm resources of F. nilgerrensis that could be used in strawberry breeding programs.

Different Roles of the Five Alcohol Acyltransferases in Peach Fruit Aroma Development

Peach (Prunus persica) fruit emit more than 100 volatile organic compounds. Among these volatiles, γ-decalactone is the key compound that contributes to peach aroma. The final step in lactones biosynthesis is catalyzed by alcohol acyltransferases (AATs). In this study, five AAT genes were isolated in the peach genome, and the ways that these genes contribute toward the peach aroma were studied. The sequence analysis of the five AATs showed PpAAT4 and PpAAT5 are truncated genes, missing important residues such as HXXXD. The expressions of PpAATs were investigated to identify the roles in creating the peach aroma. The results indicated that only PpAAT1 is highly expressed during γ-decalactone formation. A functional survey of the five PpAATs, using the oleaginous yeast expression system, suggested that only PpAAT1 significantly increased the γ-decalactone content, whereas the other four PpAATs did not significantly alter the γ-decalactone content. Enzyme assays on PpAATs heterologously expressed and purified from Escherichia coli indicated that only PpAAT1 could catalyze the formation of γ-decalactone. All results indicated that PpAAT1 is a more efficient enzyme than the other four PpAATs during the γ-decalactone biosynthesis process in peach fruit. The results from this study should help improve peach fruit aroma.

Fruit volatilome profiling through GC\u2009\xd7\u2009GC-ToF-MS and gene expression analyses reveal differences amongst peach cultivars in their response to cold storage

Peaches have a short shelf life and require chilling during storage and transport. Peach aroma is important for consumer preference and determined by underlying metabolic pathways and gene expression. Differences in aroma (profiles of volatile organic compounds, VOCs) have been widely reported across cultivars and in response to cold storage. However, few studies used intact peaches, or used equilibrium sampling methods subject to saturation. We analysed VOC profiles using TD-GC × GC-ToF-MS and expression of 12 key VOC pathway genes of intact fruit from six cultivars (three peaches, three nectarines) before and after storage at 1 °C for 7 days including 36 h shelf life storage at 20 °C. Two dimensional GC (GC × GC) significantly enhances discrimination of thermal desorption gas chromatography time-of-flight mass spectrometry (TD-GC-ToF-MS) and detected a total of 115 VOCs. A subset of 15 VOCs from analysis with Random Forest discriminated between cultivars. Another 16 VOCs correlated strongly with expression profiles of eleven key genes in the lipoxygenase pathway, and both expression profiles and VOCs discriminated amongst cultivars, peach versus nectarines and between treatments. The cultivar-specific response to cold storage underlines the need to understand more fully the genetic basis for VOC changes across cultivars.

The alleviation of methyl jasmonate on loss of aroma lactones correlated with ethylene biosynthesis in peaches

Peaches are vulnerable to cold temperature, showing the symptoms of chilling injury (CI). The occurrence of CI results in irreversible aroma loss, especially 'peach-like' lactones loss during cold storage and subsequent shelf life. Methyl jasmonate (MeJA) treatment is effective in alleviating CI symptoms in peach fruit; however, its effect on peach aroma volatiles is still unknown. To explore the effect and mechanism of MeJA treatment on aroma loss of peaches, fruit was treated with 10µmol/L MeJA, then stored at 4°C for 3 weeks, and subsequently transferred to 20°C to simulate shelf life for 3 days. Here, the ability of MeJA to regulate aroma lactones of 'Xiahui 6' peaches was investigated, and the expression of genes responsible for ethylene and lactones biosynthesis was considered. MeJA treatment significantly reduced internal browning index, increased ethylene production, and promoted the emission of aroma-related lactones in peaches during shelf life at room temperature. In addition, MeJA also elevated the expression of PpSAMS, PpACS3, PpACS4, PpACO, and PpACX3 during or after cold storage. These results suggested that MeJA treatment could enhance chilling tolerance in peaches and induce the recovery of ethylene and aroma lactones, which is closely related to ethylene biosynthesis as revealed by upregulated genes expression of PpSAMS, PpACS3/4, and PpACO. PRACTICAL APPLICATION: This research provides theoretical basis for the application of methyl jasmonate in fruit preservation and the basis for molecular breeding to cultivate aroma-abundant peach fruits.

Differences in PpAAT1 Activity in High- and Low-Aroma Peach Varieties Affect γ-Decalactone Production.

Aroma contributes to the unique flavors of fruits and is important for fruit quality evaluation. Among the many volatiles in peach (Prunus persica) fruits, γ-decalactone has the greatest contribution to the characteristic peach aroma. Some peach cultivars have γ-decalactone contents that are too low to detect. Comparison of the transcriptomes and metabolomes of a high-aroma cultivar, Fenghuayulu, and a low-aroma cultivar, Achutao, suggested that amino acid substitutions in ALCOHOL ACYLTRANSFERASE (PpAAT1) are responsible for the undetectable levels of γ-decalactone in cv Achutao fruit. Modeling and molecular docking analysis of PpAAT1 indicated that the substituted residues might determine substrate recognition or act as control channels to the active site. In vitro enzyme assays on PpAAT1 heterologously expressed and purified from Escherichia coli and in vivo assays using transient PpAAT1 expression in Nicotiana benthamiana or the oleaginous yeast Yarrowia lipolytica indicated that PpAAT1 from high-aroma cultivars was more efficient than PpAAT1 from low-aroma cultivars in catalyzing the conversion of 4-hydroxydecanoyl-coenzyme A into γ-decalactone. Examination of loss-of-function mutations of PpAAT1 generated by CRISPR/Cas9 in cv Fenghuayulu showed that fruits with PpAAT1 mutations had significantly lower γ-decalactone contents. Expression of the version of PpAAT1 from cv Fenghuayulu in cv Achutao restored γ-decalactone levels to those measured in 'Fenghuayulu', confirming the specific contribution of PpAAT1 to the formation of this key aroma compound. These results show how the biosynthesis of the peach aroma compound γ-decalactone is compromised in some low-aroma cultivars and illustrate the physiological role of PpAAT1 in plant lactone biosynthesis.

1-MCP treatment affects peach fruit aroma metabolism as revealed by transcriptomics and metabolite analyses.

1-methylcyclopropene (1-MCP) negatively affects peach aroma but the underlying molecular basis remains elusive. In this study, transcriptomics and metabolite analyses were carried out to investigate the regulatory mechanisms of 1-MCP on peach aroma from different standpoints: fatty acid (FA) metabolism, ethylene signal transduction and lipoxygenase/β-oxidation pathway during 20 °C storage. Results indicate that 1-MCP significantly postponed the ethylene climacteric peak appearance and reduced ethylene production through down-regulation of related biosynthesis and signal transduction genes including PpaSAMS1/2, PpaACS1/2, PpaACO1 together with PpaETR1/2, PpaERS1, PpaEIN4 and PpaCTR1. Decrease in the levels of FAs and PpaFADs was observed in treated fruit, except oleic acid and PpaFAD4/5, before day 5 of storage. In addition, 1-MCP-treated fruit also possessed higher levels of C6 aldehydes and alcohols and delayed the formation of volatile compounds characteristic of peach-like aroma by upregulation of PpaLOX1/2/3 and PpaHPL1 expression and down-regulation of PpaLOX5 expression. Our findings suggest that inhibition of peach-like volatiles and promotion of green-note volatiles by 1-MCP were associated with ethylene production and modulation of FA levels through transcriptional regulation.

Harvest Maturity Stage and Cold Storage Length Influence on Flavour Development in Peach Fruit

Peach market is facing a constant decrease due to the poor fruit quality perceived at consumption that might be greatly affected by fruit ripening stage at harvest and by the post-harvest management. The present work aimed at clarifying the influence of maturity at harvest on the evolution of peach aroma and quality during shelf-life after prolonged cold storage. “August Flame” peaches were harvested at three maturity stages, determined based on IAD (index of absorption difference) and ethylene emission. Fruit quality traits (firmness, soluble solids, titratable acidity), ethylene and volatile organic compound (VOC) emission were monitored during for four weeks of cold storage (0 °C). Every week of cold storage was followed by 6 days of shelf-life (18 °C). Ripening segregation at harvest based on IAD was successful since each maturity classes significantly differed based on all quality traits. Cold storage enhanced the aroma development of ‘August Flame’ peach, primarily by increasing the emission of esters and lactones associated with pleasant aroma. Moreover, cold storage also reduced the differences in aroma between the maturity classes. The role of ethylene, which was also influenced by cold storage, in regulating the VOCs emission is discussed.

Multiplex analyses of the changes of aromatic compounds during the development of peach fruit using GC–MS and iTRAQ proteomic techniques

Abstract This study aimed to combine GC–MS and iTRAQ techniques to investigate the changes in aromatic compounds and protein profiles of peach fruit peel (Prunus persica cv. Hujiingmilu) at its different developmental stages. The fruits were collected 50, 90, 95, 100, and 105 days after flowering. GC–MS during development and ripening revealed more than 200 volatile compounds, and 18 of them were aroma-related. Based on the varying amount and pattern, γ-decalactone, δ-decalactone, hexyl acetate, and 1-hexanol were involved in peach aroma. Proteomic analysis with the iTRAQ technique identified 1848 unique proteins, out of which 842 were related to biological processes and 100 related with aromatic compounds and energy transfer during fruit development and ripening. The up-regulated linoleate 9(S)-lipoxygenase plays an important role in the increase of hexanal and benzaldehyde content during ripening. The activity of phosphoglycerate mutase, glyceraldehyde 3-phosphate dehydrogenase, and inorganic pyrophosphatase regulated the terpenoids production for linalool through the 3-phosphoglyceric acid/pyruvic acid pathway but not the mevalonic acid pathway. Caffeoyl-CoA-O-methyltransferase had linear interactions with 4-coumarate-CoA ligase and 3-hydroxyisobutyryl-CoA hydrolase, and it might be the critical pathway of aromatic compounds during the development of peach fruit. Overall, the fatty acid metabolism was the primary pathway for aromatic compound formation in peach fruit and the AOC, AOS, LOX, and OPR were the key functional proteins for the formation of lactones and esters representing the characteristic aroma of honey peach. This study combined the techniques of GC–MS and proteomics to delineate the relationship between the change of aromatic compounds and proteins and their possible biological processes with aroma formation in peach fruit during development and ripening.

Comparative Analysis of Three Types of Peaches: Identification of the Key Individual Characteristic Flavor Compounds by Integrating Consumers' Acceptability with Flavor Quality

In order to recognize the key flavor compounds influencing the consumers' choice for honey peach, nectarine, and flat peach and provide important information for orientation breeding, sugars, organic acids, and aroma volatiles in 3 types of peaches were examined by high performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS) and their key individual characteristic flavor compounds were identified by multivariate analysis integrated with consumers' evaluation. No significant differences in sugar and organic acid were observed between 3 types of peaches. In hierarchical clustering analysis (HCA) and principal component analysis (PCA) models, 3 types of peaches could not be differentiated by sugars or organic acids, but could be identified completely by aroma volatiles or by flavor compounds. A partial least squares regression (PLSR) model revealed that the key individual characteristic volatiles in nectarine, honey peach, and flat peach are C9 compounds and terpenic compounds, norisoprenoids and C6 compounds, and benzaldehyde, γ-decalactone, and δ-dodecalactone, respectively. These results suggest that sugars and organic acids form the background flavor of peach fruit and lactones shape the typical peach aroma. However, the individual aroma volatiles play the decisive role in unique flavor determination of different types of peaches.

Describing Quality and Sensory Attributes of 3 Mango (Mangifera indica L.) Cultivars at 3 Ripeness Stages Based on Firmness.

To determine the ideal ripening stage for consumption of the mango cultivars, "Ataulfo," "Haden," and "Tommy Atkins"; fruits at 3 flesh firmness levels (ripeness stages) were evaluated by a trained panel using descriptive analysis after instrumental measurements were made. After harvest, all fruits were ripened to allow softening and quality and sensory attribute changes. Ripening changes during softening of Ataulfo mangos were expressed by a characteristic increase in the perception of "tropical fruit" and "peach" aromas, an increase in "juiciness," "sweetness," and "tropical fruit" flavor, while "fibrousness," "chewiness," and "sourness" decreased. Similar desirable sensory changes were also detected during softening of Haden mangos; an increase in tropical fruit and peach aromas, sweetness and tropical fruit flavor, and a decrease in chewiness, sourness, and bitterness. Softening of Tommy Atkins mangos was followed by reduced chewiness and sourness and increased peach aroma. Softening of all cultivars was followed by decreased sourness and titratable acidity (TA) and increased soluble solids concentration (SSC) and SSC:TA ratio. The results indicate that mango ripening leads to increased expression of sensory attributes such as tropical fruit and peach aromas, tropical flavor, and sweetness that have been related to improved eating quality and these final changes in sensory quality attributes are specific for each cultivar. For example, Ataulfo and Haden mangos had greater improvement in quality and sensory attributes related to fruit eating quality during ripening-softening than Tommy Atkins. In our consumer test, these quality-sensory attributes expressed during ripening that were perceived by the trained panel were also validated, supporting the need for a controlled ripening protocol in mangos.

Identification of volatile and softening-related genes using digital gene expression profiles in melting peach

To reveal the comprehensive mechanism which is associated with the biosynthesis of volatile compounds and the accompanying texture change, RNA-seq was employed to survey the differentially expressed genes (DEGs), at the transcriptional level, of one cultivar at three stages of ripening and of four melting peach cultivars at harvest stage. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that highly ranked genes are involved in “Ribosome” and “Plant-pathogen interaction,” “Flavonoid biosynthesis,” “Linoleic acid metabolism,” and “Flavone and flavonol biosynthesis” during the fruit-ripening process. The quantitative real-time PCR (qRT-PCR) validation with 15 aroma and softening-related genes showed high correlation with the RNA-seq results. Transcripts of a nonspecific lipid transfer protein (nsLTP, ppa013554) and an ATP-binding cassette transporter (ABC, ppa002351) increased from the early ripening stage to the commercial harvest stage and then declined in the fully ripening stage. The highest transcript abundance was in the aroma-enriched cv. “Hu Jing Mi Lu” (HJ) and lowest in the cv. “Zhong Hua Shou Tao” with slight aroma. Fifty gene families related to the formation of aroma compounds were found. For peach lactone biosynthesis, we inferred that ppa002510 and ppa002282 may be the two important acyl-CoA oxidase genes correlating with the difference in γ-decalactone concentrations among the four cultivars. The expression of one 3-hydroxyacyl-CoA dehydrogenase gene (HCAD, ppa008854) was upregulated during ripening. Thirteen gene families were associated to fruit softening. Four aquaporin (AQP) genes showed cultivar-specificity for HJ, and one of them, ppa009506, reached maximum accumulation of transcripts at harvest stage. The batch of novel genes (nsLTP, ACX, AOC, ABC, HCAD, AQP) found here facilitates understanding of the molecular mechanism of melting peach aroma biosynthesis and fruit softening.

有机肥对肥桃果实品质的影响

[目的]探讨生产中常用有机肥料与“红里肥桃”产量及品质等的相关性，筛选对红里肥桃产量及品质更有效的有机肥。[方法]以红里肥桃为试材，设4个有机肥和3个施肥量，在果实成熟期测定各品质指标，分析比较处理效果。[结果]有机肥对提高果实品质效果明显，与施肥量不相关。贝壳有机肥果实单果重是对照的1.25~1.56倍；豆饼有机肥果实可溶性糖总量较对照高13.56%~39.27%，葡萄糖含量比对照高25.44%~8.38%；海藻有机肥果实糖酸较比对照高102.88%~32.30%，且降酸效果显著，最高可降41.70%，香气成分种类比对照多8种。[结论]豆饼有机肥在提高果实甜度和硬度方面作用明显；海藻有机肥在降低果实酸度、提高果实糖酸比和果实香气效果较好。试验所选肥桃植株在40 kg/株的施肥量时果实品质的各项指标表现较佳，本试验条件下40 kg/株即可满足生产需求。 [Objectives] Aiming at screening effective organic fertilizer on the fruit yield and quality of Feicheng Peach, this study discussed the correlation between frequently used organic fertilizers and the fruit yield and quality of Feicheng Peach, for FeiTao production providing reference basis for Feicheng Peach production. [Methods] This study chose red feicheng peach as experimental material. Four organic fertilizer treatments and three fertilizing amounts were set in this study. In harvest time, many indexes of fruit quality were tested. [Results] Compared with CK, organic fertilizers had increased fruit quality. This test did not find obvious correlation between fruit quality and weight of organic fertilizer. Single fruit weight of sea shell organic fertilizer treatment is 1.25 - 1.56 times of CK. Bean cake organic fertilizer treatment has increased by 13.56% - 39.27% on soluble sugar content and 25.44% - 8.38% on soluble sugar content than CK. It also increased the firmness at harvest time. Sugar-acid ratio of Sea weed organic fertilizer treatment was 102.88% - 32.30% higher than CK. It also has dramatic effect on decrease the organic acid content. Sea weed organic fertilizer treatment had 8 more types of aroma than CK. [Conclusions] Bean cake organic fertilizer had better influence on increase of fruit sweetness and decrease of firmness. Sea weed organic fertilizer had better influence on decrease of fruit acidity, increase of sugar-acid ratio and content and type of aroma. Basis of Feicheng Peach aroma was esters, lactones, aldehydes, alcohols, ethers, ketones, carboxylic acids and hydrocarbons. Esters formed the majority of Feicheng Peach aroma. When weight of organic fertilizer was 40 kg per tree, fruit quality performance is better. 40 kg per tree under this experimental condition could meet the demand of fruit tree production.

Effects of ripening degree and sample preparation on peach aroma profile characterization by headspace solid-phase microextraction

Peaches are consumed worldwide and have great market demand. Compared to apricots, the volatiles defining the typical peach aroma are still poorly analytically characterized. The aim of our study was to determine the impact of the stage of ripening, sample storage conditions, and type of fiber coating and extraction glassware on peach aroma compounds. The peach aroma components were extracted by headspace solid-phase microextraction (HS-SPME) and with the application of a specific fiber (DVB/CAR/PDMS fiber) that retained the main group of volatiles present in peaches. Artisan-made glassware that enabled bigger sample loads was used. It was found that its application provided a 3-fold higher extraction of aromatic compounds on average. Significant differences were also found when the same peach pulp was analyzed fresh or frozen (in liquid nitrogen or in the freezer at -16 °C). In fresh peaches, a higher amount of some alcohols and important esters was determined. Liquid nitrogen had a positive impact on hexanal and (E)-2-hexenal, whereas the storage of samples in the freezer had a major impact on most other aldehydes, as well as limonene. The study revealed the importance of sample preparation and storage on the overall aromatic profile of peaches.