Fruit Volatile Compounds Research Articles

Advances in Fruit Aroma Volatile Research

Fruits produce a range of volatile compounds that make up their characteristic aromas and contribute to their flavor. Fruit volatile compounds are mainly comprised of esters, alcohols, aldehydes, ketones, lactones, terpenoids and apocarotenoids. Many factors affect volatile composition, including the genetic makeup, degree of maturity, environmental conditions, postharvest handling and storage. There are several pathways involved in volatile biosynthesis starting from lipids, amino acids, terpenoids and carotenoids. Once the basic skeletons are produced via these pathways, the diversity of volatiles is achieved via additional modification reactions such as acylation, methylation, oxidation/reduction and cyclic ring closure. In this paper, we review the composition of fruit aroma, the characteristic aroma compounds of several representative fruits, the factors affecting aroma volatile, and the biosynthetic pathways of volatile aroma compounds. We anticipate that this review would provide some critical information for profound research on fruit aroma components and their manipulation during development and storage.

Application of SIFT-MS in Monitoring Volatile Compounds in Fruits and Vegetables

This review article focuses on volatile formation in tomatoes, tomatillos, strawberries, jalapeño peppers, bell peppers, garlic, cocoa beans and liquors, cashew nuts, almonds, pumpkin seeds, and carrots, as measured by Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The formation of several key volatile compounds occurs due to enzymatic activity, especially by lipoxygenase. (Z)-3-hexenal and hexanal increase after tissue disruption, reach maximum concentration at a similar time and then decrease due to conversion to other compounds, such as (E)-2-hexenal and hexanol. As temperature increases, there is a higher rate of enzyme activity and increased volatility, resulting in an increase in volatile compounds. During frozen storage, (Z)-3-hexenal and hexenol increase initially during storage and then decrease since (Z)-3-hexenal is converted into (E)-2-hexenal while hexenol is degraded into other compounds. In strawberries, damage stimulates the production of LOX-derived volatiles. During the early ripening stage, the concentration of LOX-derived volatiles is high and fruity esters are low, but the concentrations reverse as ripening progresses. During chewing, some volatile compounds in tomatoes and strawberries increase in the mouthspace and nosespace since chewing breaks intact tissue cells and releases LOX enzymes, resulting in the formation of volatile compounds, especially (Z)-3-hexenal and (E)-2-hexenal. Consumption of some foods, such as water, milk, and sodium caseinate solutions, can reduce volatile levels in the mouth, including malodorous garlic breath. The Maillard reaction is responsible for the formation of many volatiles during roasting and increases with temperature and pH. Both roasting and drying promote the formation of furan compounds.

Aroma of Decontaminated Leaf and Fruit Spices

Selected leaf and fruit spices were steam decontaminated by original continuous process. Aroma compounds of spices were analyzed before and after decontamination. A total of identified 24 volatiles were identified in marjoram, 21 volatiles in thyme, 8 volatiles in caraway and 14 in coriander, as it was also mentioned by other authors. The GC/O analysis showed that the primary compounds responsible for aroma in analyzed spices were linalool and cis-sabinene hydrate in marjoram, thymol in thyme, carvone in caraway and linalool in coriander, which received the highest dilution factor values (FD) both before and after decontamination. It was determined that the content of the main odorants may be estimated by a SPME/GC method. On the basis of these compounds it was found that steam decontamination caused considerable losses in leaf spices. No significant changes were found in the content of volatile compounds in fruit spices as a result of decontamination. Also, chiral analysis of key odorants in spices did not show changes in the enantiomeric distributions (linalool in marjoram, carvone in caraway and limonene in coriander) as a result of decontamination.

Evaluation of the volatile profile of 33 Pyrus ussuriensis cultivars by HS-SPME with GC–MS

Evaluation of the volatile compounds in fruit provides useful information for plant breeding for improved fruit aroma. In this study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to assess the volatile profile of 33 cultivars of the Chinese pear Pyrus ussuriensis. In all, 108 volatile compounds were identified and there were significant differences in the composition and concentration of volatiles among cultivars. On the basis of principal components analysis (PCA), the cultivars could be divided into four groups: Group 1 contained Reli, Jinxiang, Hongbalixiang, Baibalixiang and Fuwuxiang, cultivars with a high concentration of esters and a low concentration of hydrocarbons. Group 2 contained Qiuxiang, Fuanjianba, Longxiang, Guanhongxiao, Shanli24 and Wuxiangli, cultivars with high concentrations of hydrocarbons and low concentrations of esters. Group 3 contained Shatangli and Manyuanxiang, cultivars with high concentrations of aldehydes. Group 4 contained the other 25 cultivars.

PTR-ToF-MS and data mining methods: a new tool for fruit metabolomics

Proton Transfer Reaction-Mass Spectrometry (PTR-MS) in its recently developed implementation based on a time-of-flight mass spectrometer (PTR-ToF-MS) has been evaluated as a possible tool for rapid non-destructive investigation of the volatile compounds present in the metabolome of apple cultivars and clones. Clone characterization is a cutting-edge problem in technical management and royalty application, not only for apple, aiming at unveiling real properties which differentiate the mutated individuals. We show that PTR-ToF-MS coupled with multivariate and data mining methods may successfully be employed to obtain accurate varietal and clonal apple fingerprint. In particular, we studied the VOC emission profile of five different clones belonging to three well known apple cultivars, such as ‘Fuji’, ‘Golden Delicious’ and ‘Gala’. In all three cases it was possible to set classification models which can distinguish all cultivars and some of the clones considered in this study. Furthermore, in the case of ‘Gala’ we also identified estragole and hexyl 2-methyl butanoate contributing to such clone characterization. Beside its applied relevance, no data on the volatile profiling of apple clones are available so far, our study indicates the general viability of a metabolomic approach for volatile compounds in fruit based on rapid PTR-ToF-MS fingerprinting.

Flavour volatile production and regulation in fruit

Consumption of fresh fruits is increasing as consumers become more aware of their nutritional value and role in disease prevention. Improving the flavour properties of fresh fruit reaching the consumer would add value, increase consumption, and create new markets for these commodities. One of the important characteristics of fruit ripening is volatile aroma production. Using apples (Malus domestica), strawberries (Fragaria ananassa Duch.) and melons (Cucumis melo L. var. reticulatus Naud; C. melo L. inodorus; C. melo L. cantalupensis) fruit as examples, this review focuses on recent developments in fruit aroma research. Both sensory studies and instrumental analysis confirm the importance of volatile production in fruit and its contribution to eating quality. Sensory analysis should further define the contribution of individual volatile compounds to total flavour quality. Volatile biosynthesis and its contribution to fruit eating quality is very complex, and is influenced by many factors, such as genome, harvest maturity, and postharvest handling and storage. Application of 1-methylcyclopropene (1-MCP) and transgenic lines suppressing ethylene action and biosynthesis demonstrate ethylene involvement in volatile formation and provide useful research tools to elucidate the volatile production process during fruit ripening. Cloning of genes and characterization of enzymes responsible for volatile production helps us to understand the biochemical pathways and control mechanisms. Despite the exciting developments in flavour research, several challenges still remain to be solved. An understanding of the fundamental mechanisms controlling changes in flavour quality is limited, and most biochemical pathways determining this quality trait are still unknown. As part of secondary metabolism, volatile production in fruit is a complex process with tightly controlled systems involving substrates, enzymes and energy from many pathways. It is our hope that the biochemical pathways regulating the synthesis of volatile compounds in fruit will be determined using integrated approaches, including biochemical, genomic, proteomic and microscopy tools to determine fundamental metabolism and its localization. Combining these efforts with direct measurement of sensory properties will lead us to new methods to optimize and retain fruit flavour in the market place. Key words: aroma, fruit ripening, volatile analysis, sensory, apple, strawberry, muskmelon

Antifungal Activity of Strawberry Fruit Volatile Compounds against Colletotrichum acutatum

Eight volatile products characterizing strawberry aroma, which is generated from the oxidative degradation of linoleic and linolenic acids by a lipoxygenase (LOX) pathway, were examined because of their antifungal activity against Colletotrichum acutatum, one of the causal agents of strawberry anthracnose. In this study, the effects of aldehydes, alcohols, and esters on mycelial growth and conidia development were evaluated. (E)-Hex-2-enal was found to be the best inhibitor of mycelial growth [MID (minimum inhibitory doses)=33.65 microL L(-1)] and of spore germination (MID=6.76 microL L(-1)), while hexyl acetate was the least effective of all volatile compounds tested (MID=6441.89 microL L(-1) for mycelial growth and MID=1351.35 microL L(-1) for spore germination). Furthermore, the antifungal activity of (E)-hex-2-enal on susceptibility of strawberry fruits to C. acutatum was also confirmed. The presence of these molecules in jars containing strawberry fruits inoculated with a suspension of spores inhibited the fungus growth and prevented the appearance of symptoms. Moreover, a study of the effects of (E)-hex-2-enal on conidial cells of C. acutatum was evaluated by transmission electron microscopy. This volatile compound altered the structures of the cell wall and plasma membrane, causing disorganization and lysis of organelles and, eventually, cell death.

Screening of Tropical Fruit Volatile Compounds Using Solid-Phase Microextraction (SPME) Fibers and Internally Cooled SPME Fiber

In this study, the optimization and comparison of an internally cooled fiber [cold fiber with polydimethylsiloxane (PDMS) loading] and several commercial solid-phase microextraction (SPME) fibers for the extraction of volatile compounds from tropical fruits were performed. Automated headspace solid-phase microextraction (HS-SPME) using commercial fibers and an internally cooled SPME fiber device coupled to gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compounds of five tropical fruits. Pulps of yellow passion fruit (Passiflora edulis), cashew (Anacardium occidentale), tamarind (Tamarindus indica L.), acerola (Malphigia glabra L.), and guava (Psidium guajava L.) were sampled. The extraction conditions were optimized using two experimental designs (full factorial design and Doehlert matrix) to analyze the main and secondary effects. The volatile compounds tentatively identified included alcohols, esters, carbonyl compounds, and terpernes. It was found that the cold fiber was the most appropriate fiber for the purpose of extracting volatile compounds from the five fruit pulps studied.

Optimization of the Analysis of Flavor Volatile Compounds by Liquid−Liquid Microextraction (LLME). Application to the Aroma Analysis of Melons, Peaches, Grapes, Strawberries, and Tomatoes

A fast method based on liquid-liquid microextraction (LLME) has been developed for the analysis of volatile compounds in fruit and vegetable juices. The method was tested in an aqueous solution containing 49 common flavor compounds typically found in fruit aroma. Influence on extraction yield of the salts used, their levels, and the time of extraction was investigated. The efficiency of n-propyl gallate to inhibit the formation of secondary compounds from lipids during the crushing of fruit tissues was also tested. The proposed method was then applied to several authentic samples such as melons, peaches, grapes, strawberries, and tomatoes. The advantages and limitations of LLME are discussed.

Effect of cutting and storage on sensory traits of cantaloupe melon cultivars with extended postharvest shelf life

AbstractFresh cut cantaloupe melons (Cucumis melo L var reticulatus) from fruits with extended postharvest shelf life were analysed for changes in their volatile aroma compounds and polygalacturonase activity during storage. The total volatile aroma contents and the number of volatile compounds in fruits with extended shelf life were significantly less than those present in the traditional shelf life cultivar Mission. Esters were the major volatile compounds present in the fruits, and their concentrations decreased considerably with storage of the cut fruit for 24 h at 4 °C. Polygalacturonase activity was detected from measurements of the hydrolytic release of reducing groups after storage of the cut fruit for 3 days. Enzymatic activity decreased thereafter in all fruits. The results indicate a lack of correlation between the postharvest shelf life of whole cantaloupe and that of fresh cut fruit.© 2003 Society of Chemical Industry

Actinidia arguta: volatile compounds in fruit and flowers

More than 240 compounds were detected when the volatile components of the flowers and the fruit from several Actinidia arguta genotypes were investigated. Around 60–70 different compounds were extracted from individual tissues of each genotype. Two different methods of volatile sampling (headspace and solvent) favoured different classes of compounds, dependent upon their volatilities and solubilities in the flower or fruit matrices. The compounds extracted from flowers largely comprised linalool derivatives including the lilac aldehydes ( 12a– d) and alcohols ( 13a– d), 2,6-dimethyl-6-hydroxyocta-2,7-dienal ( 8), 8-hydroxylinalool ( 9), sesquiterpenes, and benzene compounds that are presumed metabolites of phenylalanine and tyrosine. Extracts of fruit samples contained some monoterpenes, but were dominated by esters such as ethyl butanoate, hexanoate, 2-methylbutanoate and 2-methylpropanoate, and by the aldehydes hexanal and hex-E2-enal. A number of unidentified compounds were also detected, including 8 from flowers that are so closely related that they are either isomers of one compound or two or more closely related compounds. This is the first report of the presence of a range of linalool derivatives in Actinidia.

Differences in the electroantennal responses of apple- and hawthorn-infesting races of Rhagoletis pomonella to host fruit volatile compounds

Domestic apple (Malus pumila)- and hawthorn (Crataegus sp.)-infesting races of Rhagoletis pomonella, Walsh (Diptera: Tephritidae) provide an excellent model to examine the role that host plant specificity plays during sympatric speciation (i.e., divergence in the absence of geographic isolation). Previous work has shown that these races differ in their propensities to accept apple and hawthorn fruits in behavioral choice assays, and that this discrimination translates into "host fidelity" in the field (i.e., apple flies tend to mate on and oviposit into apples and hawthorn flies on hawthorns). ¶We present the results of a study examining possible physiological factors contributing to host choice differences in R. pomonella. We tested whether apple and hawthorn flies differ in their electroantennogram (EAG) responses to biologically relevant volatile compounds emitted from apples and hawthorns. Significant differences were found in the relative EAG responses of apple and hawthorn flies to host fruit compounds at five of six paired study sites across the eastern United States. The geographic pattern of EAG variation was complex, however, with local populations of apple and hawthorn flies tending to be more similar to one another than to flies of the same race at distant sites. This pattern was largely due to EAG responses for several compounds showing longitudinal or latitudinal clines, the latitudinal clines being similar to those observed for allozyme loci in the host races. We also found evidence for sex-related differences, as males tended to have higher mean EAG responses to compounds than females. Host-associated differences were therefore nested within geographic and sex-related differentiation in R. pomonella.¶Further behavioral studies are needed to distinguish whether the EAG differences are responsible for, as opposed to being a consequence of, host-plant fidelity and adaptation. Crosses are also required to establish a genetic basis for the EAG responses, although we did find significant correlations between EAG scores for several compounds and the allozymes NADH-Diaphorase-2 and Hydroxyacid dehydrogenase at one of the study sites. Questions therefore remain concerning the evolutionary significance of the EAG response differences between apple and hawthorn fly races. Nevertheless, these differences raise the possibility that antennal responses to fruit-related volatile compounds contribute to host plant discrimination in R. pomonella. Regardless, the EAG responses represent another set of traits, in addition to diapause/eclosion time phenotypes and allozyme frequencies, differing between apple and hawthorn host races of R. pomonella.

Analysis of volatile fruit components by headspace solid-phase microextraction

A method based on headspace solid-phase microextraction (HS-SPME) has been developed for the analysis of volatile compounds in fruits. Conditions of sampling have been tuned. Repeatability and recoveries obtained with this method have been determined by using a mixture of typical components of fruit aroma. Several fruits, such as raspberries, strawberries, blackberries, banana and mango, have been analysed by the proposed method. The patterns obtained include compounds typically found in fresh fruits and compounds formed during processing or storage. The results showed the use of the technique for fruit characterization and its potential as a routine method for analyzing changes in key flavour compounds during different fruit processing regimes.

273 PRODUCTION OF VOLATILE COMPOUNDS BY `BING' SWEET CHERRIES AFTER CONTROLLED-ATMOSPHERE STORAGE

Sweet cherry ripening is slowed during low oxygen and/or high carbon dioxide controlled atmosphere storage. Cherry flavor can be impacted by prolonged CA storage, therefore ripening after CA and storage was evaluated including production of fruit volatile compounds. `Bing' sweet cherries were harvested at commercial maturity and stored for up to 12 weeks at 1C in air or 5% O2, with 0.1, 10, 15 or 20% CO2. Fruit quality and condition were evaluated after removal from storage plus 1 or 4 days at 20C. Changes in fruit color were slow ed by all atmosphere treatments with differences most notable after longer storage durations. Volatile synthesis changed as storage duration increased, however, treatment differences were not significant. Soluble solids content was maintained at 15 and 20% CO2, but treatment differences were significant only after longer storage durations. High CO, treatments were effective at reducing decay incidence, but residual suppression after removal from storage decreased as storage duration increased. Significant treatment effects were evident for titratable acidity retention after 8 and 12 weeks storage, however, titratable acidity significantly declined in all treatments compared to the initial concentration.