Metabolite profiling of the ripening of Mangoes Mangifera indica L. cv. 'Tommy Atkins' by real-time measurement of volatile organic compounds

Advances in Physiological, Transcriptomic, Proteomic, Metabolomic, and Molecular Genetic Approaches for Enhancing Mango Fruit Quality

Mango (Mangifera indica L.) is a nutritionally important fruit of high nutritive value, delicious in taste with an attractive aroma. Due to their antioxidant and therapeutic potential, mango fruits are receiving special attention in biochemical and pharmacognosy-based studies. Fruit quality determines consumer's acceptance, and hence, understanding the physiological, biochemical, and molecular basis of fruit development, maturity, ripening, and storage is essential. Transcriptomic, metabolomic, proteomic, and molecular genetic approaches have led to the identification of key genes, metabolites, protein candidates, and quantitative trait loci that are associated with enhanced mango fruit quality. The major pathways that determine the fruit quality include amino acid metabolism, plant hormone signaling, carbohydrate metabolism and transport, cell wall biosynthesis and degradation, flavonoid and anthocyanin biosynthesis, and carotenoid metabolism. Expression of the polygalacturonase, cutin synthase, pectin methyl esterase, pectate lyase, β-galactosidase, and ethylene biosynthesis enzymes are related to mango fruit ripening, flavor, firmness, softening, and other quality processes, while genes involved in the MAPK signaling pathway, heat shock proteins, hormone signaling, and phenylpropanoid biosynthesis are associated with diseases. Metabolomics identified volatiles, organic acids, amino acids, and various other compounds that determine the characteristic flavor and aroma of the mango fruit. Molecular markers differentiate the mango cultivars based on their geographical origins. Genetic linkage maps and quantitative trait loci studies identified regions in the genome that are associated with economically important traits. The review summarizes the applications of omics techniques and their potential applications toward understanding mango fruit physiology and their usefulness in future mango breeding.

Bioactive Compounds in Extracts from the Agro-Industrial Waste of Mango

Mango by-products are important sources of bioactive compounds generated by agro-industrial process. During mango processing, 35-60% of the fruit is discarded, in many cases without treatment, generating environmental problems and economic losses. These wastes are constituted by peels and seeds (tegument and kernel). The aim of this review was to describe the extraction, identification, and quantification of bioactive compounds, as well as their potential applications, published in the last ten years. The main bioactive compounds in mango by-products are polyphenols and carotenoids, among others. Polyphenols are known for their high antioxidant and antimicrobial activities. Carotenoids show provitamin A and antioxidant activity. Among the mango by-products, the kernel has been studied more than tegument and peels because of the proportion and composition. The kernel represents 45-85% of the seed. The main bioactive components reported for the kernel are gallic, caffeic, cinnamic, tannic, and chlorogenic acids; methyl and ethyl gallates; mangiferin, rutin, hesperidin, and gallotannins; and penta-O-galloyl-glucoside and rhamnetin-3-[6-2-butenoil-hexoside]. Meanwhile, gallic acid, ferulic acid, and catechin are reported for mango peel. Although most of the reports are at the laboratory level, they include potential applications in the fields of food, active packaging, oil and fat, and pharmaceutics. At the market level, two trends will stimulate the industrial production of bioactive compounds from mango by-products: the increasing demand for industrialized fruit products (that will increase the by-products) and the increase in the consumption of bioactive ingredients.

Differential responses of Bactrocera dorsalis and its parasitoids to headspaces of different varieties of tree-attached mango fruits and the associated chemical profiles

Bactrocera dorsalis (Hendel) is a major pest of fruits and vegetables worldwide with documented losses of up to 100%. Various management techniques including the use of parasitoids, such as Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) within the context of the Integrated Pest Management (IPM) approach have been deployed for its control. The effectiveness of parasitoids is well understood, but knowledge of the semiochemicals that mediate their behavior, as well as that of the host fruit fly to tree-attached mangoes, is lacking. Here, we first compared the attractiveness of the above-mentioned fruit fly and its parasitoids to volatiles of different treatments (non-infested physiologically mature unripe and ripe mangoes, mangoes newly exposed to ovipositing B. dorsalis, and mangoes on day 7 and day 9 post-oviposition) of tree-attached Kent, Apple, and Haden mango varieties relative to control (clean air). The fruit fly was significantly more attracted to the mango volatiles (up to 93% of responsive insects) compared to the control (clean air). Fopius arisanus was significantly more attracted to mangoes with ovipositing fruit flies (68–76%) while D. longicaudata was significantly more attracted to day 9 post-oviposited mangoes (64–72%) compared to the control. Secondly, we elucidated the headspace volatile profiles of the non-infested and infested tree-attached mangoes using gas chromatography linked to mass spectrometry (GC-MS). The volatiles revealed various types of organic compounds with qualitative and quantitative differences. The majority of the compounds were esters making 33.8% of the total number, followed by sesquiterpenes-16.4%, and monoterpenes-15.4% among others. Most compounds had higher release rates in headspace volatiles of fruit fly-infested mangoes. Lastly, we harvested the infested mangoes and incubated them for puparia recovery. The number of puparia recovered varied according to the mango variety with Apple mango registering 81.7% of the total, while none was recovered from Kent. These results represent the first report of the changes in the headspace components of non-infested and infested tree-attached mangoes and the associated differential responses of the mentioned insects. A follow-up study can reveal whether there is a convergence in olfactomes which is significant when developing baits that selectively attract the fruit fly and not its natural enemies and fill the knowledge gap from an evolutionary ecological perspective.

HS-SPME-GC/MS Analysis for Revealing Carob's Ripening

Carob's recognized nutritional and medicinal value next to its unique agriculture importance is associated with an array of social, economic, and cultural activities. The carob fruit is popular for its intense aroma due to the emitted volatile organic compounds (VOCs). The composition of VOCs released from carob fruits changes during ripening, rendering it a non-invasive tool for the determination of the ripening period and freshness of the fruit. Therefore, headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS) was applied to reveal the respective gaseous signal molecules related to fruit maturity. The sampling was implemented during weeks 26-36 from five different locations in Cyprus. Additionally, the gaseous emissions of total VOCs (TVOCs) and carbon dioxide (CO₂) were recorded next to the moisture content of the fruit. The major chemical classes in the ripening are acids, followed by esters, and ketones. More specifically, the most abundant VOCs during ripening are propanoic acid, 2-methyl-(isobutyric acid), 2-heptanone, propanoic acid, 2-methyl-, 2-methylbutyl ester, acetic acid, methyl isobutyrate, propanoic acid, 2-methyl-, 3-methylbutyl ester, 2-pentanone, butanoic acid and propanoic acid, 2-methyl-ethyl ester. Finally, CO₂ emissions and moisture content showed a rapid decline until the 31st week and then stabilized for all examined areas. The methodology revealed variations in VOCs' profile during the ripening process.

Fruit quality parameters and volatile compounds from 'Palmer' mangoes with internal breakdown

The internal breakdown (IB) is a premature and uneven mango pulp ripening physiological disorder that is noticed only when the fruit is sliced for consumption. Thus, there is a demand for analytical methods to detect IB in mangoes to avoid consumer dissatisfaction and reduce postharvest waste. In this work, physicochemical and volatile compounds were determined to evaluate the ability to predict pulp IB. Principal components analysis (PCA) and partial least squares discriminant analysis (PLS-DA) of the data show that color, firmness, and volatiles compounds are important to give some information about the physiological changes caused by IB. The volatile compounds methacrylic acid, ethyl ester, isopentyl ethanoate, limonene oxide, (E)-2-pentenal, tetradecane, and γ-elemene were identified as chemical markers of IB. Therefore, mango physical and chemical characteristics combined with PCA and PLS-DA were successfully employed for the identification of IB in mangoes, showing significant differences between healthy and IB fruits.

Metabolome Analysis of Banana (Musa acuminata) Treated With Chitosan Coating and Low Temperature Reveals Different Mechanisms Modulating Delayed Ripening

Banana (Musa acuminata) is one of the most important crop plants consumed in many countries. However, the commercial value decreases during storage and transportation. To maintain fruit quality, postharvest technologies have been developed. Storage at low temperature is a common method to prolong the shelf life of food products, especially during transportation and distribution. Another emerging approach is the use of chitosan biopolymer as an edible coating, which can extend the shelf life of fruit by preventing moisture and aroma loss, and inhibiting oxygen penetration into the plant tissue. Gas chromatography-mass spectrometry metabolite profiling of the banana ripening process was performed to clarify the global metabolism changes in banana after chitosan coating or storage at low temperature. Both postharvest treatments were effective in delaying banana ripening. Interestingly, principal component analysis and orthogonal projection to latent structure regression analysis revealed significant differences of both treatments in the metabolite changes, indicating that the mechanism of prolonging the banana shelf life may be different. Chitosan (1.25% w/v) treatment stored for 11 days resulted in a distinct accumulation of 1-aminocyclopropane-1-carboxylic acid metabolite, an important precursor of ethylene that is responsible for the climacteric fruit ripening process. Low temperature (LT, 14 ± 1°C) treatment stored for 9 days resulted in higher levels of putrescine, a polyamine that responds to plant stress, at the end of ripening days. The findings clarify how chitosan delays fruit ripening and provides a deeper understanding of how storage at low temperature affects banana metabolism. The results may aid in more effective development of banana postharvest strategies.

Revealing dynamic changes of the volatile profile of food samples using PTR-MS

Volatile compounds carry valuable information regarding the properties of foodstuffs. Volatiles emitted from food can be used as, for example, indicators of quality, shelf-life, or authenticity. A better understanding of the multitude of transformations which occur during food processing could facilitate the optimisation of production, increase the desirability of food products, and also their wholesomeness. However, as some of these transformations are fast-paced, it is necessary to monitor them using techniques which enable real-time determination of volatiles, such as proton transfer reaction-mass spectrometry (PTR-MS). Recent years have seen a marked increase in its use in food analysis, since it can be used to obtain insight into the dynamics of the monitored processes and can be the basis for precise quality control methods for food processing. This review highlights recent works in which PTR-MS was used in monitoring during foodstuffs production, preparation and storage.

Volatile profiles from over-ripe purée of Thai mango varieties and their physiochemical properties during heat processing

This research investigated volatile profiles of over-ripe Thai mango purée during thermal processing by solid-phase extraction, volatile quantification by XAD-2-solvent extraction, as well as descriptive sensory analysis. Overripe fruits of three varieties were analyzed for the ripening stage using specific gravity as well as firmness and the physiochemical properties were also reported. We found that aromatic profiles could be used as true representative to describe Thai mango identities of each varieties. A simple and straightforward heat treatment had differing effects on aroma characteristics and those effects were dependent with mango varieties. Indeed, the amount of terpene hydrocarbons and oxygenated sesquiterpenoids alternated after heat treatment. All descriptive attributes of heated ‘sam-pee’ purée were intensified while, heat treatment significantly improved only “mango identity” in ‘maha-chanok’ and “fermented” odour in ‘keaw’ purée. With or without heat treatment, the volatile profiles of ‘maha-chanok’ remained quite stable while heating played a significant role on chemical ingredients of ‘keaw’ and ‘sam-pee’. Our study demonstrated that the manufacturing of the over-ripe mango into the products of high market value, selection of varieties is vitally important based upon their specific aroma characteristics before and after processing.

KARAKTERISTIK FISIKOKIMIA DAN PROFIL SENSORI MANGGA GEDONG PADA DUA TINGKAT KEMATANGAN

Mangoes of Gedong variety (Mangifera indica L. var. gedong) is one of the exported commodities from Indonesia. Half mature mangoes of this type are called gedong mangoes, whereas the full ripe mangoes are called gedong gincu mango. This research aimed to determine the physicochemical charac-teristics, sensory attributes and volatile compounds of the above two mango types. The results showed that gedong mangoes had a lower pH value, less total soluble solid, harder texture, and the skin color had a lower intensity of lightness, redness, and yellowness as compared to gedong gincu mango. The sensory analysis using rate-all-that-apply (RATA) method showed that attributes of color, fibrous, aroma (fruity, caramel, cooked, green, fermented, floral, sweet), taste (sweet, sour), melting, firmness, juiciness and astringency were significantly different between gedong and gedong gincu mango. The overall sensory of gedong gincu mangoes was more preferred by the panelists with the hedonic score of 6.20±0.09 (6= like) while that of gedong mango was 5.37±0.09 (5= slightly like). The sensory profiles of both mangoes were supported by the analysis of their volatile compounds. The gedong mango had predominantly green type of volatiles aroma while the gedong gincu was dominated by the fruity sweet ones. The sensory acceptability of gedong gincu mango was significantly higher rather than that of gedong mango.

Volatile organic compounds gas sensor based on quartz crystal microbalance for fruit freshness detection: A review

In this review article, the state of the art of gas sensors based on quartz crystal microbalance (QCM) for fruit freshness detection is overviewed from the aspects of development history, working principle, selection and modification of sensitive materials, and volatile organic compounds detection of fruits. According to the characteristics of respiratory intensity at the stage of fruit ripening, fruits can be divided into respiration climacteric fruits and non-climacteric fruits. In recent years, research has mainly focused on respiration climacteric fruits, such as bananas and mangoes, etc., while related studies on non-climacteric fruits have been rarely reported, except for citrus fruits. The preparation methods and structure design of sensitive materials based on physical/chemical adsorption mechanisms are further discussed according to the odor components that affect the freshness of fruits, namely alkenes, esters, aldehydes and alcohols.

Unraveling dynamic metabolomes underlying different maturation stages of berries harvested from Panax ginseng

BACKGROUND

Ginseng berries (GBs) show temporal metabolic variations among different maturation stages, determining their organoleptic and functional properties.

METHODS

We analyzed metabolic variations concomitant to five different maturation stages of GBs including immature green (IG), mature green (MG), partially red (PR), fully red (FR), and overmature red (OR) using mass spectrometry (MS)-based metabolomic profiling and multivariate analyses.

RESULTS

The partial least squares discriminant analysis score plot based on gas chromatography-MS datasets highlighted metabolic disparity between preharvest (IG and MG) and harvest/postharvest (PR, FR, and OR) GB extracts along PLS1 (34.9%) with MG distinctly segregated across PLS2 (18.2%). Forty-three significantly discriminant primary metabolites were identified encompassing five developmental stages (variable importance in projection > 1.0, p < 0.05). Among them, most amino acids, organic acids, 5-C sugars, ethanolamines, purines, and palmitic acid were detected in preharvest GB extracts, whereas 6-C sugars, phenolic acid, and oleamide levels were distinctly higher during later maturation stages. Similarly, the partial least squares discriminant analysis based on liquid chromatography-MS datasets displayed preharvest and harvest/postharvest stages clustered across PLS1 (11.1 %); however, MG and PR were separated from IG, FR, and OR along PLS2 (5.6 %). Overall, 24 secondary metabolites were observed significantly discriminant (variable importance in projection > 1.0, p < 0.05), with most displaying higher relative abundance during preharvest stages excluding ginsenosides Rg1 and Re. Furthermore, we observed strong positive correlations between total flavonoid and phenolic metabolite contents in GB extracts and antioxidant activity.

CONCLUSION

Comprehending the dynamic metabolic variations associated with GB maturation stages rationalize their optimal harvest time per se the related agroeconomic traits.

GC-MS Based Metabolite Profiling to Monitor Ripening-Specific Metabolites in Pineapple (Ananas comosus)

Pineapple is one of the most cultivated tropical, non-climacteric fruits in the world due to its high market value and production volume. Since non-climacteric fruits do not ripen after harvest, the ripening stage at the time of harvest is an important factor that determines sensory quality and shelf life. The objective of this research was to investigate metabolite changes in the pineapple ripening process by metabolite profiling approach. Pineapple (Queen variety) samples from Indonesia were subjected to GC-MS analysis. A total of 56, 47, and 54 metabolites were annotated from the crown, flesh, and peel parts, respectively. From the principal component analysis (PCA) plot, separation of samples based on ripening stages from C0-C2 (early ripening stages) and C3-C4 (late ripening stages) was observed for flesh and peel parts, whereas no clear separation was seen for the crown part. Furthermore, orthogonal projection to latent structures (OPLS) analysis suggested metabolites that were associated with the ripening stages in flesh and peel parts of pineapple. This study indicated potentially important metabolites that are correlated to the ripening of pineapple that would provide a basis for further study on pineapple ripening process.

A metabolomics-based approach for the evaluation of off-tree ripening conditions and different postharvest treatments in mangosteen (Garcinia mangostana)

INTRODUCTION

Metabolomics is an important tool to support postharvest fruit development and ripening studies. Mangosteen (Garcinia mangostana L.) is a tropical fruit with high market value but has short shelf-life during postharvest handling. Several postharvest technologies have been applied to maintain mangosteen fruit quality during storage. However, there is no study to evaluate the metabolite changes that occur in different harvesting and ripening condition. Additionally, the effect of postharvest treatment using a metabolomics approach has never been studied in mangosteen.

OBJECTIVES

The aims of this study were to evaluate the metabolic changes between different harvesting and ripening condition and to evaluate the effect of postharvest treatment in mangosteen.

METHODS

Mangosteen ripening stage were collected with several different conditions ("natural on-tree", "random on-tree" and "off-tree"). The metabolite changes were investigated for each ripening condition. Additionally, mangosteen fruit was harvested in stage 2 and was treated with several different treatments (storage at low temperature (LT; 12.3 ± 1.4 °C) and stress inducer treatment (methyl jasmonate and salicylic acid) in comparison with control treatment (normal temperature storage) and the metabolite changes were monitored over the course of 10 days after treatment. The metabolome data obtained from gas chromatography coupled with mass spectrometry were analyzed by multivariate analysis, including hierarchical clustering analysis, principal component analysis, and partial to latent squares analysis.

RESULTS

"On-tree" ripening condition showed the progression of ripening process in accordance with the accumulation of some aroma precursor metabolites in the flesh part and pectin breakdown in the peel part. Interestingly, similar trend was found in the "off-tree" ripening condition although the progression of ripening process observed through color changes occurred much faster compared to "on-tree" ripening. Additionally, low-temperature treatment is shown as the most effective treatment to prolong mangosteen shelf-life among all postharvest treatments tested in this study compared to control treatment. After postharvest treatment, a total of 71 and 65 metabolites were annotated in peel and flesh part of mangosteen, respectively. Several contributed metabolites (xylose, galactose, galacturonic acid, glucuronate, glycine, and rhamnose) were decreased after treatment in the peel part. However, low-temperature treatment did not show any significant differences compared to a room temperature treatment in the flesh part.

CONCLUSIONS

Our findings clearly indicate that there is a similar trend of metabolic changes between on-tree and off-tree ripening conditions. Additionally, postharvest treatment directly or indirectly influences many metabolic processes (cell-wall degrading process, sweet-acidic taste quality) during postharvest treatment.

Response of pomegranate arils (cv. Wonderful) to low oxygen stress under active modified atmosphere condition

BACKGROUND

Successful characterization of the relationship between respiration rate (RR) and low oxygen (O₂ ) limit is critical for optimizing the modified atmosphere condition. It is well documented that a low O₂ atmosphere reduces the RR of fresh produce, but could also lead to abiotic stress due to the accumulation of glycolysis end products. Therefore, this study investigated the response of pomegranate arils exposed to low O₂ atmosphere (composed of 2 kPa O₂ , 18 kPa carbon dioxide, and 80 kPa nitrogen) and identified the low O₂ limit at 5 °C and 10 °C. The study aim was achieved by using real-time RR and respiration quotient (RQ) data, microbial growth, identifying changes in the fermentative volatile organic compounds profile, and the consumption of respiratory metabolites (organic acids and individual sugars).

RESULTS

The gas concentrations changed significantly respective to the storage temperature and resulted in a significant change in the parameters studied. The response of pomegranate arils to low O₂ stress involves making alterations to the metabolic composition, especially those involved in anaerobiosis, such as the accumulation of ethanol, and an immediate increase on RQ.

CONCLUSION

Pomegranate arils (cv. Wonderful) can tolerate down to 1.9 kPa O₂ and 2.3 kPa O₂ concentrations at 5 °C and 10 °C respectively. © 2018 Society of Chemical Industry.

Volatile compounds profiling by using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS). The case study of dark chocolates organoleptic differences

Direct-injection mass spectrometry (DIMS) techniques have evolved into powerful methods to analyse volatile organic compounds (VOCs) without the need of chromatographic separation. Combined to chemometrics, they have been used in many domains to solve sample categorization issues based on volatilome determination. In this paper, different DIMS methods that have largely outperformed conventional electronic noses (e-noses) in classification tasks are briefly reviewed, with an emphasis on food-related applications. A particular attention is paid to proton transfer reaction mass spectrometry (PTR-MS), and many results obtained using the powerful PTR-time of flight-MS (PTR-ToF-MS) instrument are reviewed. Data analysis and feature selection issues are also summarized and discussed. As a case study, a challenging problem of classification of dark chocolates that has been previously assessed by sensory evaluation in four distinct categories is presented. The VOC profiles of a set of 206 chocolate samples classified in the four sensory categories were analysed by PTR-ToF-MS. A supervised multivariate data analysis based on partial least squares regression-discriminant analysis allowed the construction of a classification model that showed excellent prediction capability: 97% of a test set of 62 samples were correctly predicted in the sensory categories. Tentative identification of ions aided characterisation of chocolate classes. Variable selection using dedicated methods pinpointed some volatile compounds important for the discrimination of the chocolates. Among them, the CovSel method was used for the first time on PTR-MS data resulting in a selection of 10 features that allowed a good prediction to be achieved. Finally, challenges and future needs in the field are discussed.

Metabolic profiling of Garcinia mangostana (mangosteen) based on ripening stages

Metabolomics is an emerging research field based on exhaustive metabolite profiling that have been proven useful to facilitate the study of postharvest fruit development and ripening. Specifically, tracking changes to the metabolome as fruit ripens should provide important clues for understanding ripening mechanisms and identify bio-markers to improve post-harvest technology of fruits. This study conducted a time-course metabolome analysis in mangosteen, an economically important tropical fruit valued for its flavor. Mangosteen is a climacteric fruit that requires an important plant hormone ethylene to regulate ripening processes and rate. We first categorized mangosteen samples in different ripening stages based on color changes, an established indicator of ripening. Using gas chromatography/mass spectrometry, small hydrophilic metabolites were profiled from non-ripened to fully ripened (ripening stages 0-6). These metabolites were then correlated with color changes to verify their involvement mangosteen ripening. Our results suggest that the increase of 2-aminoisobutyric acid, psicose, and several amino acids (phenylalanine, valine, isoleucine, serine, and tyrosine) showed a correlation with the progression of mangosteen ripening. This is the first report of the application of non-targeted metabolomics in mangosteen.