1,721,019 research outputs found
The combined effects of carbon dioxide and ethanol vapours on the preservation of sliced bread stored at low oxygen partial pressure
No full textThe experimental design proposed in this work aims at statistically estimating the simultaneous effects of carbon dioxide and ethanol vapours on storage of sliced bread; in particular, it is important to find the best combination of variables assuring to sliced bread a longer shelf-life than the present one (10 days).
In our experiments, the bread was inoculated with a spore suspension of Aspergillus niger and pouched with different combinations of carbon dioxide and ethanol vapours; the ethanol was released by an ethanol emitter obtained with ethanol-saturated silical gel. Results show that Aspergillus niger grew in presence of high levels of carbon dioxide, even if oxygen was present at low concentration; moreover, ethanol alone was not sufficient to inhibit mould grow
Electroanalytical determination of benzidine by differential pulse voltammetry on different electrodes
No full textBenzidine is a solid organic compound which evaporates slowly, especially from
water and soil. It was used in the synthesis of azo-dyes widely employed in textile,
printing, leather, paper making, drug and food companies around the world.
However, in 1973 benzidine was identified as a carcinogenic agent for human
urinary bladder because its oxidation by human enzymes can permit its binding
with DNA. For these reasons, it belongs to the list of the Priority Pollutants [1-2].
Although benzidine production and use was forbidden in many countries since
1970s, benzidine based azo-dyes are still used in many research laboratories and
industries, and its detection and determination is a primarily concern.
Various methods for detection of benzidine are proposed in the literature, such as
colorimetric, spectroscopic, electrochemical [3] and chromatographic ones. In
particular, liquid, high performance liquid and gas chromatography are the most
used techniques, frequently associated with mass spectrometry.
Electroanalytical techniques and particularly those based on pulsed voltammetry,
which are suitable for trace analysis, constitute an interesting alternative in terms of
very high sensitivity, low response time, small dimensions and low costs.
In this presentation a new method for quantitative detection of benzidine based on
differential pulse voltammetry on Glassy Carbon (GC) and Platinum wire bare
electrodes is proposed. The use of carbon-based or platinum-based screen printed
electrodes (SPE) is also investigated
Study of cellulose-lysozyme interactions aimed to a controlled release system for bioactives
Full text linkThe potential use of cellulose based
materials for active food packaging applications was explored. For this purpose, the sorption of lysozyme in
a cellulose based paper pulp was optimized using the experimental design methodology. A Face-Centered Composite design was applied to investigate the effect of short/long fibers ratio and carboxymethyl cellulose concentration on linking lysozyme to the fibers surface and to optimize the cellulosic matrix composition. The related polynomial model showed good fitting ability (R2[0.9) as well as good prediction ability (Q2[0.8). The best combination of factors was 50 % short fibers, 50 % long fibers and at least 4 % carboxymethyl cellulose. Afterwards the lysozyme release was investigated using a mathematical model based on Fick’s second law. It was able to describe the release kinetics of lysozyme from the paper sheets made with the optimized cellulosic matrix into water at different temperatures (between 4 and 23 C), pH (from 4 to 7) and NaCl concentrations (from 0.2 to 2 M). The apparent diffusion coefficients for the
lysozyme were in the range of 3.1 X 10-16 6.6x10-14 and the Ea value was 22.1 kJ/mol at pH 5 and NaCl concentration of 0.5 M
Valutazione dell’interazione tra polifenoli della propoli e componenti della carta per alimenti per la realizzazione di un imballaggio attivo
No full textLa propoli è un composto di origine naturale, prodotto dalle api, che possiede diverse proprietà fra cui elevato potere antiossidante, antivirale e antimicrobico, grazie alla presenza d'innumerevole polifenoli. In questo lavoro si è voluto analizzare la stabilità dei polifenoli della propoli a contatto con carta per alimenti in un sistema di packaging attivo. La carta, infatti, è costituita da materiali cellulosici e da additivi chimici che potrebbero influire sulla stabilità dei polifenoli della propoli. In particolare, si sono effettuate laccature (coatings) di un preparato a base di propoli su due carte commerciali, una resistente ad umido ed una politenata, e per confronto su di un film di polietilentereftalato (PET). I campioni sono stati condizionati a temperatura e umidità costante (23°C e 55% UR) ed analizzati dopo 1, 15 e 30 giorni per valutarne la stabilità. E' stato utilizzato metodo DPPH per la valutazione del potere antiossidante.Da queste prime analisi è risultato che la matrice carta composta da fibre di cellulosa e diversi additivi è in grado di diminuire il potere antiossidante della propoli, disattivando parte dei polifenoli in percentuale del 15%. La disattivazione sembra avvenire al momento del contatto delle matrici per mantenersi poi stabile nel tempo (30 giorni). Sono stati eseguiti, quindi, coating su foglietti di carta monoadditivata, prodotti appositamente in laboratorio, per valutare il/i componenti maggiormente responsabili della disattivazione dei polifenoli. Dai risultati ottenuti si evince che la disattivazione di parte dei polifenoli avviene nella prima settimana di stoccaggio del materiale attivo con disattivazione variabile da un minimo di 5% per carte non additivate ad un massimo del 15% per carte additivate con colla a base di colofonia e resina poliamminoepicloridrinica (PAE). Si è proseguito il lavoro quindi applicando dei coating sulla parte politenata delle carte commerciali, in particolare formulando due tipologie di miscele al fine di modulare il rilascio dei polifenoli: la prima costituita da pasta di propoli italiana purificata e decerata e 0.5% di idrossipropilmetilcellulosa (HPMC), mentre la seconda da pasta di propoli e 35% di polivinilpirrolidone (PVP). Entrambe le tipologie di campione sono state poste a contatto con tre terreni colturali: un terreno PCA, un terreno simulate un prodotto carne (beef extract, bacteriological peptone, tryptone, glucosio, agar, pH = 6.9) e un terreno simulante prodotto lattiero caseario (PCA con il 5% di latte intero), sono state quindi effettuate le cinetiche di rilascio dei polifenoli quantificandoli tramite saggio di Folin-Ciocalteu. I risultati ottenuti presentano una percentuale di rilascio di polifenoli intorno al 20% per la formulazione con HPMC, mentre i polifenoli migrati dalla miscela con PVP raggiungono il 40% nel corso delle prime 24 ore, successivamente il rilascio si mantiene costante; il rilascio risulta inoltre modulato della composizione del terreno colturale
The potential of nanocellulose in the packaging field : a review
No full textNanocellulose has potential applications across several industrial sectors and allows the development of innovative materials, as well as the enhancement of conventional materials properties. The nanocellulose particles can be utilized as fillers, in composites manufacture, as coating and as self-standing thin films, achieving always very interesting and promising properties. Very few of the several reviews that recently appeared on this topic in the scientific literature, however, summarized the potential of cellulose in nanoform specifically for the packaging field rather focusing on different aspects, ranging from the chemistry and the morphology of nanocellulose particles to the preparation methods, the industrial applications and the patents released. In the present review, the remarkable chemical and physical properties of nanocellulose are introduced and discussed with specific reference to the packaging needs. First, the cellulose resources and structure are introduced, then the process methods to reach the nanoscale, the corresponding morphologies and nomenclatures are summarized, mentioning also the possible chemical modifications of nanocellulose and, finally, its practical and potential applications for packaging materials, especially food packaging materials, are tentatively proposed and discussed. Although the review might not cover every aspect on nanocellulose, yet the key points, particularly those related to safety and biodegradability issues, are regarded and considered
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
Platinum-Based and Carbon-Based Screen Printed Electrodes for the Determination of Benzidine by Differential Pulse Voltammetry
No full textCarbon- and platinum-based screen-printed electrodes have been tested, in comparison with standard GC and Pt electrodes, for detecting benzidine, an organic carcinogenic synthetic compound mainly used as intermediate in production of azo-dyes. The methodology consists in a DPV in acidic media and offers excellent results in terms of large dynamic concentration ranges, high accuracy and precision and low limits of detection (1.2×10 -9M) and quantification (3.7×10 -9M). The use of disposable electrodes eliminates the problems of fouling and surface regeneration of the device. The use of Nafion membrane to further protect Pt-SPE from fouling is also discussed. The new methodology was also tested on a real water sample
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