1,721,055 research outputs found
Antioxidant activity of tomato products as studied by model reactions using xanthine oxidase, myeloperoxidase, and copper-induced lipid peroxidation
No full textThe antioxidant content and activity of commercial tomato products differing in variety and processing were studied. Two procedures for extracting hydrophilic and lipophilic antioxidants, namely, two-step 0.1 M phosphate buffer (pH 3.0 and 7.4) extraction and tetrahydrofuran extraction followed by petroleum ether fractionation, were developed. Carotenoids (lycopene, beta-carotene, and lutein) and ascorbic acid were analyzed by HPLC with spectrophotometric and electrochemical detectors, respectively. Total phenolics were determined by using the Folin-Ciocalteu reagent. The antioxidant activity was studied by the following three model systems: (a) the xanthine oxidase (XOD)/xanthine system, which generates superoxide radical and hydrogen peroxide; (b) the
myeloperoxidase (MPO)/NaCl/H2O2 system, which produces hypochloric acid; and (c) the linoleic acid/CuSO4 system, which promotes lipid peroxidation. Results showed that the hydrophilic and lipophilic fractions of all tomato products were able to affect model reactions, whatever reactive oxygen species and catalysts were used to drive oxidation. In the XOD/xanthine system both the hydrophilic and lipophilic fractions displayed an inhibitory activity. The hydrophilic fractions were
more effective (I50 ranging from 680 to 3200 íg, dry weight) than the lipophilic fractions (I50 ranging from 4000 to 7750 microg, dry weight). In the MPO/NaCl/H2O2 system the hydrophilic fractions inhibited oxidation (I50 ranging from 2300 to 2900 microg, dry weight), whereas the lipophilic fractions had a
lower inhibitory effect at the same concentration. Conversely, in the copper-catalyzed lipid
peroxidation only the lipophilic fractions were effective (I50 ranging from 1030 to 2100 microg, dry weight),
whereas the hydrophilic fractions had a pro-oxidant effect in the same concentration range. The
extent of inhibition varied according to the tomato sample in the superoxide and hydrogen peroxide
generating system and in lipid peroxidation, but was substantially the same in the HClO generating
system. Fresh tomato varieties differed considerably in the antioxidant activities of their hydrophilic
and lipophilic fractions. Processed tomatoes showed a significantly lower antioxidant activity than
fresh tomatoes in their hydrophilic fractions but had a high antioxidant activity in their lipophilic
fractions. Because the oxidative reactions produced by the above-mentioned model systems are also
involved in the pathogenesis of several chronic diseases, the antioxidant activity of tomato fractions
might be related to their in vivo activity. Hence, these measurements may be used for optimizing
tomato technologies
Combined effects of osmo-and air-dehydration treatments on chemical, antioxidant and morphological characteristics of blueberries
No full textOsmo-air dehydration treatments are widely applied to fruits in order to prolong shelf-life, reduce packaging and logistic costs, and to provide ingredients to be used in various food formulations. In this work, osmo-air dehydration was applied to blueberries (Vaccinium corymbosum); blanched blueberries were dipped in 60°Bx sucrose and 48.6°Bx fructose/glucose osmotic solutions (aw = 0.90) for 24 hours, and the osmotic exchanges were determined by mass balances (water loss, solid gain, sugar intake, changes in total phenolics and anthocyanins). Untreated and infused berries were subsequently air-dried at 70°C to final moisture content of 10-14%, and drying kinetics as well as compositional and morphological changes of berries were followed in the course of drying. Data show that the osmotic treatment caused significant losses in the antioxidant components (total phenolics, total and individual anthocyanins) and in the antioxidant activity. Losses in the antioxidant components also occurred in the course of air-drying, with similar kinetics in untreated and infused blueberries. Glucose/fructose infusion gave better results in terms of morphological changes during the subsequent air-drying process, with lower shrinkage and wrinkling of the berries
Effects of blanching pre-treatmnet and sugar composition of the osmotic solution on physico-chemical, morphological and antioxidant characteristics of osmodehydrated blueberries (Vaccinium corymbosum L.)
No full textThe effect of a steam blanching preconditioning step was investigated on the chemical, nutraceutical and morphological characteristics of osmo-dehydrated blueberries (Vaccinium corymbosum L.) in sucrose or glucose/fructose osmotic solutions. Mass transfer phenomena (solid gain, water loss and sugar gain) were monitored into the samples at intervals over a 24-h period of osmodehydration. The antioxidant capacity of untreated and osmo-dehydrated fruits was evaluated by total phenolics, total and individual anthocyanins and antioxidant activity (amperometric method), while colorimetric (luminance) and morphological (area, shape factor, fractal dimension) characteristics of the berries were determined by image-analysis technique. Results showed that the blanching step increased mass transfer phenomena in the course of the osmodehydration treatments (approx + 55% solid gain and + 33% water loss) and reduced the loss of phenolic compounds, improving the retention of antioxidant capacity in the final product (from approx 66.9−56.9 % in not blanched berries to 88.6−95.7% in blanched ones). Blanched berries had also deeper colour and smoother surface. Slight differences in mass balances and in the final composition of berries could be ascribed to the kind of osmotic solution used
Headspace volatile compounds during osmotic dehydration of strawberries (cv Camarosa): Influence of osmotic solution and processing time
No full textThe influence of the type of sugar in the osmotic solution and of the time of processing on the volatile compounds of strawberries was
studied, in order to optimize the technique as a pre-treatment to further processing. Strawberries of cultivar ‘Camarosa’, cut into 1 cm
thick slices, were subjected to osmotic dehydration at 30 1C for 1, 2, 4 and 6 h using either 60% (w/w) sucrose or 60% (w/w) sorbitol
solutions. Volatile compounds of fresh and processed strawberry slices were analyzed by static headspace—gas chromatography.
Osmotic treatments provoked a loss in volatile compounds due to the migration, mainly of esters, into the osmotic media. The variations
in the volatile pattern depended on both time of treatment and type of osmotic solution. The greater changes occurred after 2 h in
sucrose; with a promotion of fermentative volatiles (acetaldehyde, ethyl acetate), and a decrease in the other volatiles. Using sorbitol as
osmotic agent, the major variations in the volatile pattern occurred after 4 h of osmosis, and the fermentative process was less important
than in sucrose, as sorbitol could be less effective in forming a peripheral layer at the fruit surface and/in reducing tissue porosity
Development of a headspace-solid phase micro extraction method to monitor changes in volatile profile of rose (Rosa hybrida, cv David Austin) petals during processing
No full textIn the present study, headspace solid phase microextraction combined to capillary gas chromatography (HS-SPME-GC) has been applied for the determination of changes in the volatile profile of rose petals (Rosa hybrida, cvs David Austin) following processing (heat treatment and addition as an ingredient to a food product—for example yoghurt). Four SPME fibres at two sampling temperatures (40 and 60 °C) with a sampling time of 30 min were examined. Volatile profiles were detected either by FID or/and by olfactometry (ODP-II, Gerstel). Fibre testing was performed using raw rose petals for sampling temperature selection and an 18 characteristic rose volatile standard mixture in water was used to compare fibre performances at the sampling temperature of 60 °C. Polydimethylsiloxane-divinylbenzene (PDMS-DVB) fibre at the sampling temperature of 60 °C was the most suitable to sample the rose alcohols phenyl ethanol, citronellol, nerol, geraniol and eugenol, as assessed by GC-olfactometry, not only from raw petals, but also from processed rose petals and the food product. PDMS-DVB fibre also showed a desired low affinity to volatiles from yoghurt, which reduces the influence of food matrix on the volatile profile. The method was linear over two orders of magnitude and had satisfactory repeatability, with limits of detection for the rose alcohols ranging from <1 to 10 ng/ml concentration levels
Electronic Nose investigation of strawberry aroma changes during osmotic dehydration
No full textAn electronic nose was used to detect the aroma evolution of strawberry fruits, cultivar “Camarosa,”
during the osmotic dehydration in sorbitol and sucrose solutions. Strawberry sliceswere subjected to osmotic dehydration
at 30 ◦Cfor 1, 2, 4, and 6husing either60%sucrose or60%sorbitol solutions.Volatilecompoundsof fresh and
processed strawberry slices were analyzed by electronic nose and gas chromatography. Electronic nose was able to
reveal changes in the aromaprofile during processing and permitted differentiation between dehydrated strawberry
samples obtained by different osmotic treatments. The electronic nose has the advantage of being simple, rapid,
and nondestructive. Such characteristics and the promising results of this work suggested that this device could be
a useful and innovative tool to monitor strawberry aroma changes during osmotic dehydration, providing real-time
information about the effects of processing conditions and allowing the optimization of technological parameters
Evaluation of fruit aroma quality : comparison between gas chromatography-olfactometry (GC-O) and odour activity value (OAV) aroma patterns of strawberries
No full textGas chromatography-olfactometry (GC-O) is based on the use of human assessors as a sensitive and selective detector to ascertain odour-active volatile compounds in a sample extract, whereas odour intensity value (OAV) determination is widely used to obtain odour patterns starting from quantitative compositions. Whether there is an exact parallelism between odour patterns obtained from GC-O parameters and OAV is not yet well investigated. To this aim, the OAV and GC-O odour patterns of six strawberry genotypes were compared. Esters represented 97.9-99.8% of total volatiles, with methyl butanoate being the main Compound; dimethyl disulfide, dimethyl trisulfide, gamma-heptalactone and delta-decalactone were detected only by GC-O. OAV indicated that 25 volatiles out of 39 could actually contribute to the odour pattern, while the GC-O sensory panel perceived 30 odorous events. The major odour contributors in OAV and the maximum odour intensities of odour events in GC-O were genotype dependent. Comparing OAV with GC-O patterns, the spatial relationships in principal component analysis biplots were comparable: 'VR4' was opposed to 'Alba' and 'CS4', and 'Dora' to 'Darselect' and 'Eva'. GC-O and OAV resulted in comparable strawberry odour patterns, GC-O giving the most detailed qualitative and quantitative description. However, being GC-O, a time-consuming method, it should not be routinely used
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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