1,721,191 research outputs found
Analysis of forced convection heat transfer to supercritical carbon dioxide inside tubes using neural networks.
No full textPreliminary study on the reduced pressure cold plasma processing of fresh cut salads: rheological assessment of modifications in the plant tissue structure
Full text linkCold plasma is a novel nonthermal food processing technology that uses energetic, reactive gases to inactivate contaminating microbes and to achieve an enzymatic depletion on foods. The primary modes of action are due to UV light and reactive chemical products of the cold plasma ionization process. A wide array of cold plasma systems that operate at atmospheric pressures or in low-pressure treatment chambers are under development. Optimization and scale up to commercial treatment levels require a more complete understanding of plasma interaction modes with food. In particular, little attention to date has been paid to structural and textural modification induced by plasma in food matrices. Results that are presented in this paper refer to the study of low pressure cold plasma treatment of fresh vegetable, precisely fresh cut salad leaves (Valerianella locusta Laterr). Throughout dynamic rheology tests, it has been evaluated the impact of the non-thermal plasma treatment on the structural modifications occurring in the salad tissue at a mesoscopic scale-length where cell wall materials (CWM) account for the perceived texture of the salad. The rheological behaviour of CWM water dispersions in steady-state regime proved that plasma treatment is able to induce an immediate modification in flow behaviour, which persists during the shelf-life period. CWM dispersions behave as weak gels. Specifically, cold plasma treatment of salad leaves generates CWM gels with higher coordination of the gel polymers network, as quantified by means of the Bohlin's theory on week gels. Moreover, it has been proved that the relaxation time distribution spectrum may provide useful information on understanding the underlying stress relaxation mechanisms in gels. An in-depth investigation of physical events could be of help in view of the optimization of the cold plasma technology application in plant foods preservation
Supramolecular assemblies from plant cell polysaccharides: self-healing and aging behaviour
No full textChanges in minimally processed apple tissue with storage time and temperature : mechanical-acoustic analysis and rheological investigation
No full textTexture and mesostructure of packaged fresh-cut ‘Fuji’ apple slices were studied during 30 days storage at 4, 10 and 20 °C. Instrumental mechanical–acoustic texture evaluations were carried out, and cell wall materials were isolated from the flesh tissue by means of an ethanol and methanol–chloroform solvents extraction procedure. The emphasis was on relating the macroscopic loss of fresh texture characteristics to the changes in the rheological properties occurring to the structuring elements of the cell wall materials (CWMs). The rheology of the reconstituted CWM water dispersion was evaluated by means of oscillatory dynamic testing, and viscoelastic data were interpreted according to the ‘weak-gel model’ theory. The dynamics of the flowing components at the mesoscale structural level was related to the texture softening, which yields decrease in firmness and rigidity parameters, and an attenuation of the acoustic emission (fewer acoustic peaks and lower sound pressure level), as it was measured in the combined acoustic–mechanical test. The kinetic reaction rate values are presented. Softening of apple flesh is accompanied by slight cleavage of molecular assemblies and a loss in cell adhesion, mediated by the increase in assemblies’ water uptake. The ability to handle the relationship between the sounds produced during flesh crushing and the structure of the cellular tissue would assist breeders and geneticists in the selection and control of the apple crispness, or would support technologists in preventing postharvest softening during storage and retail
Correlation between fracture of semisweet hard biscuits and dough viscoelastic properties
No full textSemi-sweet hard dough biscuits were considered in the present work which aims at assessing whether biscuit failure mode and dough viscoelastic properties, which depend on the resting time after mixing, can be correlated to one another. Uniaxial compressions were performed on rested biscuit doughs to determine biaxial extensional viscosities. The experimental data seemed strongly dependent on the compression rate in the 1-20 mm/min range of crosshead speed. The stress growth trend observed for doughs of different resting time showed that the extent of structural recovery increased with resting. The rheological behaviour of dough under higher extensional deformation was evaluated by means of tensile and tensile-relaxation tests, the result of which can be directly related to the sheeting extensional deformation. These data confirmed the picture of dough structural recovery. Rheological investigations were coupled with DSC determinations of the glass transition temperature, T-g. The higher T-g found for rested doughs was tentatively attributed to gluten protein polymerisation. It was finally shown that the failure mode of biscuits changes with the resting time after mixing: the longer the rest, the less the biscuit strength
COST Action FA1001“The application of innovative fundamental food-structure-property relationships to the design of foods for health, wellness and pleasure”
No full textInstrumental acoustic-mechanical measures of crispness in apples
No full textTexture is a quality attribute closely related to the structural properties of the apple cellular tissue and is claimed to be the most important aspect affecting consumer acceptability apart from taste. Instrumental and humanbased assessment of apples crispness are presented in this paper. A commercially available acoustic AED detector, interfaced with a TA.XT.plus Texture Analyzer, was used to collect both the acoustic emissions recorded during the instrumental mechanical penetration test, and the acoustic emissions resulting from the first bite of an apple flash, which were accomplished by 10 subjects with random dental state. Seven commercial cultivars of
apples with different textural characteristics (Fuji, Golden Delicious, Granny Smith, Pink Lady, Renetta Canada, Royal Gala, and Stark) were analyzed. In order to measure the apple juice content, the expressible fluid released from the apple flash during compression was also quantified.
Merging distinctive parameters taken from the mechanical signals and simultaneously recorded acoustic traces allowed apples to be clustered based on their crispness attributes using principal component analysis (PCA), a qualitative approach for multivariate data set.
Results showed that sounds emitted during the human biting could not be assumed as a capable predictor of the sensory attribute of crispness, while apples can be efficiently distinguished for crispness by means of coupled acoustic and mechanical texture analysis. Finally, the inclusion of juiciness in the acoustic-mechanical PCA data set did not significantly increase the efficiency in cluster separation in terms of the texture crispness property
Proprieta’ fisiche di film edibili ottenuti da gel di pectina ad alto metossile
No full textTipicamente le pectine alto grado di metossile gelano mediante formazione di zone di giunzione per mezzo di interazioni idrofobiche. In questo lavoro viene proposto un meccanismo differente di gelazione basato sulla complessazione ionica, meccanismo tipico per le pectine a basso grado di metossile. Dai gel deboli di pectina e dalle soluzioni macromolecolari dello stesso polimero sono stati prodotti film mediante casting. La densificazione della struttura indotta dalla gelazione delle pectine conferisce migliori proprietà meccaniche dei film, ma solo un minimo miglioramento delle proprietà di barriera al vapor d’acqua
Spirulina: ingrediente alimentare e integratore funzionale. Aspetti tecnologici e di mercato = Spirulina: ingredient and functional food : Technological and market considerations
No full textSpirulina is a multicellular filamentous cyanobacteria that has achieved a considerable popularity
in the food industries and in the nutraceutical sector. Spirulina has very high content of macro
and micronutrients, essential amino acids, proteins, vitamins, minerals and anti-oxidants. The
article offers an overview of its potential food applications and marketing opportunities, besides
suggesting a distinctive marker, the antioxidant capacity, to be highlighted on the nutritional
label. Moreover, it reports the outcomes from interwiews to Spirulina producers and from a
consumers’ survey regarding the most common challenges about microalgal biomass cultivation
and production of Spirulina-based foods, and the interest in their consumption, respectively.La Spirulina è un cianobatterio multicellulare filamentoso che ha raggiunto una notevole popo-
larità nelle industrie alimentari e nel settore nutraceutico. Ha un contenuto molto elevato di macro
e micronutrienti, aminoacidi essenziali, proteine, vitamine, minerali e antiossidanti. L’articolo offre
una panoramica sulle sue potenziali applicazioni alimentari e sulle opportunità di commercializ-
zazione oltre a suggerire un indice caratterizzante, il potere antiossidante, da evidenziare nel label nutrizionale. Inoltre, riporta i risultati di interviste ai produttori di Spirulina e di un sondaggio fra i consumatori rispettivamente riguardanti le sfide più comuni relative alla coltivazione della biomassa microalgale e produzione di prodotti a base di Spirulina e l’interesse relativo al loro consumo
Investigation on the rheological properties of agar gels and their role on aroma release in agar/limonene solid emulsions
No full textA lipophilic aroma widely used in the food field, R-(+)-limonene, was entrapped in a solid emulsion in absence of emulsifiers using agar gel as encapsulating medium. The perception of the flavour release was evaluated by means of an electronic nose. The relation between structural organization of the agar gels and flavour release and perception was studied. Different viscoelastic properties of the continuous phase of the solid emulsion were achieved by varying the gelling polysaccharide concentration from 0.2% up to 1% (w/v) and the consequent aroma trapping effect was correlated with the perception of the flavour release from the solid emulsion during aging up to 15 days storage. Release phenomena were finally accelerated by increasing temperature of the gel from 30 to 77 °C. Structure assessment of the gelled phase take place within 24 h from the gel setting time and during this transient period most of the aroma release happens
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