Changes In Volatile Production Research Articles

Development and application of a new low cost electronic nose for the ripeness monitoring of banana using computational techniques (PCA, LDA, SIMCA and SVM)

Potential application of a metal oxide semiconductor based electronic nose (e-nose) as a non-destructive instrument for monitoring the change in volatile production of banana during the ripening process was studied. The proposed e-nose does not need any advanced or expensive laboratory equipment and proved to be reliable in recording meaningful differences between ripening stages. Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), Soft Independent Modelling of Class Analogy (SIMCA) and Support Vector Machines (SVM) techniques were used for this purpose. Results showed that the proposed e-nose can distinguish between different ripening stages. The e-nose was able to detect a clear difference in the aroma fingerprint of banana when using SVM analysis compared with PCA and LDA, SIMCA analysis. Using SVM analysis, it was possible to differentiate and to classify the different banana ripening stages, and this method was able to classify 98.66% of the total samples in each respective group. Sensor array capabilities in the classification of ripening stages using loading analysis and SVM and SIMCA were also investigated, which leads to develop the application of a specific e-nose system by applying the most effective sensors or ignoring the redundant sensors.  

Volatile production changes in the interspecific interaction between endophyte Nodulisporium Sp. and Pythium aphanidermatum

Volatile production changes in the interspecific interaction between endophyte Nodulisporium Sp. and Pythium aphanidermatum

Changes in volatile production and sensory quality of kiwifruit during fruit maturation in Actinidia deliciosa ‘Hayward’ and A. chinensis ‘Hort16A’

Although volatiles have been previously studied in kiwifruit ( Actinidia spp.), there has been no co-ordinated study of volatile release and softening through the full edible period. In this report, the two most important commercial cultivars A. deliciosa ‘Hayward’ and A. chinensis ‘Hort16A’ were evaluated for volatiles released at different ripening stages corresponding to their typical commercial shelf life, and compared to the sensory quality assessed by a trained taste panel. Gas chromatography–mass spectrometry data indicated that large amounts of straight-chain aldehydes and esters were the dominant volatiles in the two cultivars. In particular, butanoates, the main fruity esters in both fruit, significantly increased during ripening and an extremely high level of butanoates was found in the over-ripe fruit. Sensory results indicated that with fruit softening, some of the changes in volatile content could explain changes in fruit flavor detected by a trained panel, and differences in characteristic flavor of the two cultivars. The results have implications for fruit sample handling and volatile assessment.

Changes in volatile production during interspecific interactions between four wood rotting fungi growing in artificial media

Effects of volatile organic compounds (VOCs) produced during interspecific mycelial interactions were examined by measuring extension rate of ‘target’ fungi growing in agar plates taped above two interacting mycelia – Bjerkandera adusta, Hypholoma fasciculare, Stereum gausapatum and Trametes versicolor in all combinations. Extension rates of T. versicolor, S. gausapatum and H. fasciculare above self-pairings were not significantly different (P > 0.05) to growth above agar controls, but the extension rate of B. adusta was significantly (P ≤ 0.05) greater. Extension rates of T. versicolor and B. adusta were often significantly greater above inter-specific interactions and above other species compared with growth above self or agar controls. VOC production was quantified and qualified, by gas chromatography–mass spectrometry (GC/MS), over the course of interactions with T. versicolor replacing S. gausapatum, deadlocking with B. adusta and replaced by H. fasciculare. VOC production was species- and interaction-specific. It varied over the time course of interactions, and changes in production were correlated with production of pigments in interactions involving S. gausapatum. VOCs included 3 monoterpenes, benzoic acid, alkenols of different chain lengths, two long-chain hydrocarbons and a quinolinium-like compound. Their possible roles are discussed.

Changes in Volatile Production During the Course of Fungal Mycelial Interactions Between Hypholoma fasciculare and Resinicium bicolor

The mycelia of two wood decay basidiomycete fungi were grown opposing each other across a 1-microm pore membrane supported on the surface of malt broth, contained within a sealable reaction vessel. Production of volatiles during the time course of interaction was followed by collecting head space samples by solid phase microextraction (100 microm polydimethylsiloxane fiber) on five occasions over 25 d following coinoculation of the fungi: 1, 3 (i.e., immediately prior to mycelial contact), 9 (1-2 d after initiation of pigment production by Resinicium bicolor), 17, and 25 d. Ten volatiles were produced during interactions that were not detected in single species controls. In general, most (18) fungal volatiles were sesquiterpenes eluted between 12.5 and 21 min, with a further two eluted at 29.1 and 33.9 min; a benzoic acid methyl ester, a benzyl alcohol, and a quinolinium type compound with a distinctive fragmentation pattern at m/z 203, 204, 206, and 207 were also identified; three volatiles with m/z maxima of 163, 159, and 206-208, respectively, remained unidentified. The results are discussed in relation to possible ecological roles of volatiles.

Evaluation of tomato maturity by electronic nose

Over the past years, electronic nose (E-nose) technology opened has enhanced the possibility of exploiting information on behavior aroma to assess fruit ripening stage. The objective in this study was to evaluate the capacity of electronic nose to monitor the change in volatile production of ripeness states for tomato, using a specific electronic nose device with 10 different metal oxide sensors (portable E-nose, PEN 2). Principal component analysis (PCA) and linear discriminant analysis (LDA) were used to investigate whether the electronic nose was able to distinguishing among different ripeness states (unripe, half-ripe, full-ripe and over-ripe). The loadings analysis was used to identify the sensors responsible for discrimination in the current pattern file. The results prove that the electronic nose PEN 2 could differentiate among the ripeness states of tomato. The electronic nose was able to detect a clearer difference in volatile profile of tomato when using LDA analysis than when using PCA analysis. Using LDA analysis, it was possible to differentiate and to classify the different tomato maturity states, and this method was able to classify 100% of the total samples in each respective group. Some sensors in E-nose have the highest influence in the current pattern file for electronic nose PEN 2. A subset of a few sensors in E-nose can be chosen to explain all the variance. This result could be used in further studies to optimize the number of sensors.

Discrimination of storage shelf-life for mandarin by electronic nose technique

Over the past years, electronic nose technology opened the possibility to exploit information on aroma attribute to assess fruit ripening stage during storage. The objective in this study was to evaluate the capacity of electronic nose in monitoring the change in volatile production of mandarin during different storage treatments, and storage shelf-life of mandarin was evaluated by measuring the change in volatile production of mandarin using electronic nose device (PEN 2). By comparing, storage shelf-life of mandarin was better distinguished using Linear Discriminant Analysis (LDA) than Principal Component Analysis (PCA). PCA and LDA analysis were efficient to classify mandarin with the same storage time in its respective groups; but the methods are not efficient to separate the mandarins by different storage times. The correlation between the measured and predicted values of fruit quality attribute (such as soluble solid content, acidity and compression force) shows poor to reasonable prediction performance by means of electronic nose signals. The results prove that sensors 2, 7 and 9 in the electronic nose PEN 2 for mandarin have a higher influence in the current pattern file. Hence, nearly a subset of few sensors can be chosen to explain all the variance. This result could be used in further studies to optimize the number of sensors and find better performance.

Electronic nose technique potential monitoring mandarin maturity

Over the past years, electronic nose technology opened the possibility to exploit information on behavior aroma to assess fruit ripening stage. The objective in this study was to evaluate the capacity of electronic nose to monitoring the change in volatile production of mandarin during different picking-date, using a specific electronic nose device (PEN 2). Principal component analysis (PCA) and linear discriminant analysis (LDA) were used in order to investigate whether the electronic nose was able to distinguish among different picking-date (ripeness states). The loadings analysis was used to identify the sensors responsible for discrimination in the current pattern file. The results obtained prove that the electronic nose PEN 2 can discriminate successfully different picking-date on mandarin using LDA analysis. But, electronic nose was not able to detect a clear difference in volatile profile on mandarin using PCA analysis. During external validation using LDA was obtained to classified 92% of the total samples properly. Some sensors have the highest influence in the current pattern file for electronic nose PEN 2. A subset of few sensors can be chosen to explain all the variance. This result could be used in further studies to optimize the number of sensors.

Production of volatile compounds by Fuji apples following exposure to high CO2 or low O2.

The emission of volatile compounds by Fuji apples following short- or long-term exposure to high CO(2) was studied. The production of ethanol, methyl and ethyl esters, octanal, nonanal, and decanal was enhanced while the production of C(3)-C(6) alcohols, propyl, butyl, pentyl, and hexyl esters and butanal decreased in fruit exposed to 10 kPa O(2) + 20 kPa CO(2) at 20 degrees C for up to 12 days. The impact of high CO(2) exposure on volatile production was dependent on fruit maturity at harvest. Apples stored for 8 months in an ultralow O(2)-controlled atmosphere (CA) (0.5 kPa O(2) + 0.05 kPa CO(2)) or high CO(2) CA (1.5 kPa O(2) + 3 kPa CO(2)) at 0.5 degrees C had reduced production of most volatiles, especially butyl and hexyl esters, as compared to fruit stored in air. Two exceptions were ethanol and ethyl acetate for which the production was enhanced by both CA regimes. Treatment with the antioxidant diphenylamine prior to storage prevented most of the high CO(2)-induced and ultralow O(2)-induced changes in volatile production. The results of this study do not indicate that changes in volatile production following the exposure of Fuji apples to high CO(2) are causally related to the development of CO(2) injury.

Changes in volatile production during an infection of potatoes by Erwinia carotovora

The monitoring of volatiles produced by diseased potatoes has been studied as a method of detecting infections in potato storage units. Previous studies attempted to identify pathogen-specific volatiles as markers for the presence of disease, however, consistent results were difficult to obtain. A possible solution is to consider overall qualitative and quantitative changes in the volatile profile over the course of an infection. The objective of this study was to investigate this method of data analysis. The study was done using 1-kg batches of potatoes stored at room temperature in metal canisters fitted with volatile traps containing Chromosorb 105. Either one or all of the potatoes in the batch were inoculated with Erwinia carotovora, the causative agent of soft rot. A canister containing uninoculated healthy potatoes was used as the control. A dynamic headspace sampling method was used to sample periodically the air for volatiles in the experimental and control canisters. The analysis of volatiles was done by gas chromatography. Comparison of the volatile profiles arranged in chronological order showed a progression over time, in the types and amounts of volatiles produced. A wider range of volatiles were produced by infected potatoes than by healthy potatoes. Differences between the volatile profiles of healthy and inoculated potatoes were observed as early as 24 h into the experiment while the total quantity of volatiles produced was initially low and increased exponentially as the infection became well established. The time difference between these two observations was 36–48 h and represented the time in which measures can be taken to contain the infection. The amount of volatile produced was dependent on the initial amount of bacteria, the growth of the bacteria and the detection limits of the Chromosorb and the gas chromatograph.

Volatile Constituents of Bing Sweet Cherry Fruit following Controlled Atmosphere Storage

Volatile constituents of Bing sweet cherry fruit were analyzed by purge and trap sampling from fruit homogenates at harvest and after air or controlled atmosphere storage. Acetic acid and aldehydes were quantitatively the largest volatile compounds present at harvest. Changes during storage in the concentrations of three compounds previously identified as contributors to sweet cherry fruit flavor, benzaldehyde, E-2-hexenal, and hexanal, were independent of storage conditions. Ethanol accumulated in fruit stored in 15 or 20% CO2 with 5% O2 after 6 weeks of storage. Qualitative and quantitative changes in ester production, particularly ethyl acetate, were coincident with the accumulation of ethanol. 2-Propanol concentrations were consistently highest in fruit stored in 5% O2 with 0.1% CO2. Some qualitative changes in volatile production after 4 weeks of storage were unrelated to storage conditions and may reflect metabolic changes occurring during sweet cherry senescence. A number of esters were not detecta...

Influence of Tapeworm Infection on the Production of Aggregation Pheromone and Defensive Compounds in Tribolium castaneum

Recent studies suggest that parasites affect host development, reproduction, and behavior through alterations of host hormones and pheromones, or other hormone-triggered biochemical events. We previously reported that Hymenolepis diminuta infection affects surface-seeking and cannibalism behaviors, and reduces male sperm precedence of Tribolium castaneum beetles. This study examined the quantitative effects of H. diminuta on the production of aggregation pheromone and 3 defensive compounds in male T. castaneum beetles, using 2 wild-caught, geographically distinct T. castaneum strains. For the c-Madison strain, infected beetles exhibited a 2- to 22-fold increase in defensive compounds; conversely, no changes were observed in strain c-Africa. Parasite infection did not significantly influence aggregation pheromone secretion in either strain. Because defensive compounds function as repellents or deterrents to other insects, parasite-induced increases in the secretion of defensive compounds may be a physiologic clue for the behavioral changes in infected T. castaneum beetles. Significant among-strain variation in defensive compound production seen in infected beetles suggests that caution is needed before generalizing about changes in volatile production and in host behavior induced by a parasite.