1,720,962 research outputs found
Combining Thermal Desorption GC and TOF-MS for the Determination of Melon VOC Profiles
No full textThe quality and safety of ready-to-eat packaged foods—such as salads—is very difficult for
consumers and suppliers to judge, and improving this situation is the focus of a Europe-wide
research project. Part of the project is devoted to the development of better methods to detect
and analyze the volatile organic compounds released from relevant food types, in an effort to
identify biomarkers for quality and microbial contamination. This article examines one important
food—melon—and shows how a method based on thermal desorption with gas chromatography–
time-of-flight mass spectrometry (GC–TOF-MS) can elucidate how key volatiles vary
with the size of the melon pieces. The article highlights how such analytical information will be
of value in efforts to improve the quality and safety of ready-to-eat foods
Use of TD-GC–TOF-MS to assess volatile composition during post-harvest storage in seven accessions of rocket salad (Eruca sativa). BELL L, SPADAFORA D.N. contributed equally to the work
No full textAn important step in breeding for nutritionally enhanced varieties is determining the effects of the postharvest
supply chain on phytochemicals and the changes in VOCs produced over time. TD-GC–TOF-MS
was used and a technique for the extraction of VOCs from the headspace using portable tubes is
described. Forty-two compounds were detected; 39 were identified by comparison to NIST libraries.
Thirty-five compounds had not been previously reported in Eruca sativa. Seven accessions were assessed
for changes in headspace VOCs over 7 days. Relative amounts of VOCs across 3 time points were significantly
different – isothiocyanate-containing molecules being abundant on ‘Day 0’. Each accession
showed differences in proportions/types of volatiles produced on each day. PCA revealed a separation
of VOC profiles according to the day of sampling. Changes in VOC profiles over time could provide a tool
for assessment of shelf life
Multitrait analysis of fresh-cut cantaloupe melon enables discrimination between storage times and temperatures and identifies potential markers for quality assessments
No full textFresh-cut cantaloupe melon is valued for its aroma but is highly perishable. Temperature of storage (typically
0–5 °C) is critical for maintaining fresh-cut melon quality, but often reaches 10 °C during transportation and in
retail outlets. A comparison amongst 0, 5 and 10 °C storage temperatures for fresh-cut melon over 14 days
reveals that storage at 0 °C is optimal for avoiding increases in microbial load and loss of vitamin C especially at
later time points. However, higher temperatures maintain better the balance of esters (acetate versus nonacetate)
and phenolic content. The whole volatile organic compound (VOC) profile can be used to discriminate
both time and temperature effects especially at earlier time points. Potential VOC markers for changes in vitamin
C from day 0 to day 6 of storage (3-methyl butane nitrile) and temperature (limonene) are identified through a
multi-trait analysis
Floral scent evaluation of segregating lines of A. caryophyllaea
No full textFloral scent plays an important role in attracting and guiding pollinators and is composed of a bouquetof volatile organic compounds (VOCs). Alstroemeria is a commercially important cut flower, howeverbreeding efforts have focussed on flower colour and size rather than scent. Recently analysis of twoscented cultivars derived from the scented Alstroemeria caryophyllaea revealed a surprising divergencein VOC profiles. Here 13 scented lines of A. caryophyllaea derived from selfing were characterized includingmorphology, evaluation of the floral scent through GC–MS and sensorial analysis. Leaf shape, stem length,flower size, shape, colouration and productivity all varied between lines. Sensorial analyses indicatedthat two lines (C013 and C017) were most highly rated for their appearance and C017 was also scoredhighest for its scent contrasting with C004 which scored lowest. Analyses of scent bouquets from sixof the lines revealed 23 terpenoid compounds. All lines showed the same most abundant compoundputatively identified as -trans-ocimene, and three further compounds were discriminatory amongstthe lines following PCA. Genomic organization of AlstroTPS, a previously identified myrcene synthase,showed substantial polymorphism between lines. The multifactorial characterization performed in thisstudy showed differences among the lines confirming parental heterozygosity
Gene expression analysis of rocket salad under pre-harvest and postharvest stresses: a transcriptomic resource for Diplotaxis tenuifolia
No full textDiplotaxis tenuifolia L. is of important economic value in the fresh-cut industry for its nutraceutical
and sensorial properties. However, information on the molecular mechanisms conferring
tolerance of harvested leaves to pre- and postharvest stresses during processing and shelflife
have never been investigated. Here, we provide the first transcriptomic resource of rocket
by de novo RNA sequencing assembly, functional annotation and stress-induced expression
analysis of 33874 transcripts. Transcriptomic changes in leaves subjected to commerciallyrelevant
pre-harvest (salinity, heat and nitrogen starvation) and postharvest stresses (cold,
dehydration, dark, wounding) known to affect quality and shelf-life were analysed 24h after
stress treatment, a timing relevant to subsequent processing of salad leaves. Transcription
factors and genes involved in plant growth regulator signaling, autophagy, senescence and
glucosinolate metabolism were the most affected by the stresses. Hundreds of genes with
unknown function but uniquely expressed under stress were identified, providing candidates
to investigate stress responses in rocket. Dehydration and wounding had the greatest effect
on the transcriptome and different stresses elicited changes in the expression of genes related
to overlapping groups of hormones. These data will allow development of approaches targeted
at improving stress tolerance, quality and shelf-life of rocket with direct applications in
the fresh-cut industries
Physiological, Metabolite and Volatile Analysis of Cut Size in Melon During Post-Harvest Storage
No full textMelons are an important component of fresh fruit salads, however, they
suffer from limited shelf life. Processing of melon fruit for use in fruit salads induces
a number of changes including alterations in colour and texture. In addition,
respiration rate and ethylene production are affected. Processing also elicits changes
in flavour (sweetness) and aroma (production of volatile organic compounds –
VOCs), of critical importance to the consumer. Several parameters govern shelf life;
temperature is a critical factor. In this study we tested whether cut size is another
parameter that can affect quality indicators. Melon (Cucumis melo ‘Arapaho’) cubes
of three sizes were stored at 4°C and assessed for quality at five time-points over a
15-day period. We assessed a number of parameters including firmness, loss of fresh
weight, respiration rate, antioxidant capacity, phenolic compounds and carotenoid
content. In addition we measured VOC profiles to assess whether there were any
qualitative changes associated with storage period and/or cut size. Fresh weight
(FW) loss and respiration rate increased significantly with storage time and FW loss
was affected by cut size. Total carotenoid levels remained stable during the storage
time as did antioxidant capacity in all cut sizes. However, cinnamic acid levels
tended to decrease in the last stage of the storage period and changes in β-carotene
content correlated with cut size (though not significantly). We were also able to
separate the VOC profiles from the different cut sizes indicating that VOCs may be
useful markers as indicators of the effects of cut size and storage time on quality
Detection of Listeria monocytogenes in cut melon fruit using analysis of volatile organic compounds
No full textReady-to-eat fresh cut fruits and vegetables are increasingly popular, however due to their minimal
processing there is a risk of contamination with human pathogens. Listeria monocytogenes is of particular
concern as it can multiply even at the low temperatures used to store fresh cut products pre-sale. Current
detection methods rely on culturing, which is time consuming and does not provide results in the time
frame required. Growth of bacteria on a substrate alters its chemical composition affecting the profile of
volatile organic compounds (VOCs) emitted. Use of VOCs as a detection method has been hampered by
lack of sensitivity and robust sample collection methods. Here we use thermal desorption gas chromatography
time of flight mass spectrometry (TD-GC-TOF-MS) followed by analysis with PerMANOVA to
analyse VOC profiles. We can discriminate between fresh cut melon cubes inoculated with 6 log CFU/g of
L. monocytogenes and uninoculated controls, as well as melon cubes inoculated with <1 log CFU/g of
L. monocytogenes stored for 7 days at 4 C and following equilibration for 6 h at 37 C. This is a substantial
advance in sensitivity compared to previous studies and additionally the collection method used allows
remote sampling and transport of the VOCs, greatly facilitating analyses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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