1,721,223 research outputs found
Evaluation of the Effects of Different Fermentation Methods on Dough Characteristics
No full textDough characteristics as affected by different preferment types and fermentation times were evaluated. A dough type was obtained with yeasted stiff preferment (60% water), fermented for a long period (biga-type dough - B) and another one made with a semiliquid preferment (100% water), obtained with sourdough and fermented for a short period (poolish-type dough - P). The doughs obtained were compared with a standard dough (direct dough - D). During the first 60min of fermentation, pH, titratable acidity, volume, empirical and fundamental rheological properties and gas cells number were evaluated. During fermentation time, all doughs underwent structural changes related mainly to an increase of resistance to the extension and a decrease of area and extensibility, with a noticeable change in volume and pH. Between all samples, B dough was the stiffest reaching the lowest volume (44.3mL), the highest storage modulus (G′=10,982Pa) and resistance to extension (31.78g)
Microstructural and Rheological Properties of White Chocolate During Processing
No full textThe relationship between the microstructural and rheological properties of white chocolate was studied during the main steps (mixing, pre-refining, refining, conching and tempering) of the manufacturing process. Laser light diffraction and light microscope techniques were used to study the particle size distribution (PSD) and the modifications of the network structure of the samples. Rheological parameters in terms of yield stress, apparent viscosity and thixotropy were evaluated by using a stress-strain controlled rheometer. The Casson and Windhab rheological models, which are widely used for dark and milk chocolate matrices, were used in order to explain better the rheological values obtained from the flow curves. Particle analysis revealed significant changes in the network structure during process. In particular, from the mixed sample to the refined one, a reduction in particle size was found; Sauter (D[3.2]) and Feret diameters decreased, the former from 18.6 to 6.67 μm and the latter from 320 to 33 μm. Consequently, an increase in the matrix aggregation was observed. The white chocolate samples obtained from the conching and tempering steps were characterized by the statistically lowest values of yield stress and apparent viscosity and by the weak structure. Moreover, the samples were well discriminated by both rheological models applied
Microstructural and rheological characteristics of dark, milk and white chocolate: A comparative study
Full text linkThree different chocolate types: dark, milk and white were characterized and compared for the microstructural and rheological (fundamental and empirical) characteristics. A light microscope coupled to an image analysis system was employed in order to evaluate the particle size, the network structure and the distance between particles of each matrix. Rheological parameters (yield stress, viscosity, thixotropy) were evaluated by using a stress-strain rheometer, while mechanical properties (consistency and cohesiveness) were analysed using a texture analyzer. The Power law, Casson and Windhab rheological models were used in order to better explain the rheological behaviour of chocolate samples. Results showed that white chocolate, with the highest amount of fat in formulation, had the smallest sized particles, the less aggregate structure and the lowest yield stress, viscosity and thixotropic values. Dark chocolate samples instead presented the highest aggregate structure, with less void spaces between particles that involved the highest rheological parameter values. Milk chocolate matrix exhibited intermediate microstructural and rheological characteristics compared to dark and white chocolate ones
Moisture adsorption behaviour of biscuit during storage investigated by using a new Dynamic Dewpoint method
No full textThe changes in moisture adsorption isotherms of commercial biscuits during storage were investigated by means of a rapid Dynamic Dewpoint Isotherms (DDIs) method. Moreover, the relationships between the changes in moisture content and some quality characteristics of biscuits (moisture, aw, peroxide value - PV and texture) were studied during 92 days of storage at 35°C. GAB model was used to fit the experimental sorption behaviours. During storage, moisture content and aw of biscuits increased and the obtained isotherms showed modifications in behaviour and shape. Significant changes were observed in PV values and texture, particularly during the first 40 days of storage. The monolayer moisture content, obtained by the BET equation, significantly increased during storage from 1.473 to 2.080 g water 100 g db-1, probably because of the increase in the active sites for water binding due to the chemical and physical changes of the main components, induced by product ageing
Qualità “in tazza” del caffè espresso: dati relativi ad oltre dieci anni di indagini
No full textIn questo lavoro vengono discussi i risultati di una ricerca decennale sulla “qualità in tazza”
del caffè espresso, condotta presso 688 esercizi di vendita di 6 aree geografiche del Centro-
Nord Italia. Nella ricerca sono state prese in considerazione variabili di processo quali:
impianto di torrefazione, macina-dosatore, macchina di estrazione, miscela, pressione e
temperatura dell’acqua, peso del macinato e grado di pressione all’interno del filtro. Per la
“qualità in tazza” sono stati valutati: consistenza e altezza della crema, pH, gradi Brix e
volume dell’estratto. Oltre 9.000 dati sono stati elaborati mediante l’Anova, il Mann-Whitney
test e il Levene test. L’Analisi delle Componenti Principali (PCA) è stata applicata ai dati
relativi ai campioni raccolti in aree diverse e per discriminare gli anni di indagine. Tipo di
macchina di estrazione, tipo di macina-dosatore e formazione dell’operatore sono risultati gli
elementi più significativi che influenzano la qualità del caffè espresso
Cold plasma treatment for fresh-cut melon stabilization
Full text linkThe aim of this study was to evaluate the effect of gas plasma treatment on fresh-cut melon stability during controlled storage. Plasma treatments of 15 + 15 and 30 + 30 min were conducted on fresh cut melon using a dielectric barrier discharge (DBD) generator. Samples were packed and stored for 4 days at 10 °C and evaluated for qualitative, metabolic and microbiological indexes. Qualitative parameters of fresh-cut melon (titratable acidity, soluble solid content, dry matter, colour, texture) were only weakly affected by plasma treatment. Peroxidase (POD) and pectin methylesterase (PME) activities were slightly inhibited by the treatment up to respectively about 17 and 7%. Tissue metabolic heat production decreased proportionally to the treatment duration, while a partial conversion to anaerobic metabolism was observed. Microbial results showed that a significant increase in microbial shelf-life was achieved following the 15 + 15 min plasma treatment due to a delayed growth of spoilage mesophilic and psychrotrophic microflora. Industrial relevance: The demand for fresh-cut products characterized by high qualitative and nutritional values and an acceptable shelf-life has promoted the research for non-thermal treatments. Fresh-cut melon is considered to be highly perishable and potentially hazardous food because it can support the growth of spoilage microflora and several pathogens. Cold plasma has shown its potentiality as an antimicrobial treatment and has been tested on different food products, but the impact on product quality and metabolism is still scarcely known. The results obtained in this study contributed to deepen the knowledge on the effect of plasma treatment on microbial, qualitative and metabolic aspects of fresh-cut melon
Effect of freezing on microstructure and degree of syneresis in differently formulated fruit fillings
No full textThis study describes the syneresis and its effect on microstructure in fruit fillings within a wide range of the total soluble solids content and with or without hydrocolloids upon freezing. Linear models showed the relevance of the addition of pectin and gellan gum to fillings to prevent syneresis, increasing the water-holding capacity especially after freezing. Microstructural experiments by means of NMR spin-spin relaxometry combined with fluorescence microscopy allowed to observe that the continuous hydrocolloid gel, containing the dispersed solution of native fruit parts with the addition of inulin and sugars, changed its structure/distribution according to the amount of each ingredient and due to the freezing process. Relaxometry results confirmed that hydrocolloids strength was correlated (R2 > 0.92) with water-holding capacity, due to a relationship between the signal given by the water chemically exchanging with biopolymers, and the changes in the degree of syneresis
Influence of two different cocoa-based coatings on quality characteristics of fresh-cut fruits during storage
No full textThe aim of this work was to evaluate the effect of two different cocoa-based coatings on some quality characteristics
of fresh-cut fruits (grape and apple) during storage. Apples were cut into small pieces before application
of cocoa coatings, while for grapes whole berries were used. Fruit samples were immersed in the cocoa
dipping to obtain a thin layer of coating and then left to solidify. Coated products were packed in polyethylene
terephthalate (PET) trays under atmospheric conditions and stored for 10 days at 6 °C and analysed at 0, 2, 4, 6,
8, 10 days for water activity, moisture, colour, texture, cell viability, microbiological and sensorial quality.
Cocoa coatings provided positive effects on sensory properties of analysed fruit samples during storage. In
general, coated grapes maintained better quality and microbiological characteristics compared to coated apple
samples and uncoated ones showed general better performances mainly in terms of firmness and microbiological
spoilage. All coated samples showed a shelf-life similar to uncoated ones, in particular from a microbiological
point of view, generally until the 3rd day of storage for apples and the 6th day for grapes. Moreover, coating B
showed better performances compared to A in enhancement of the shelf-life of fruits
Optimization of Vacuum Impregnation with Calcium Lactate of Minimally Processed Melon and Shelf-Life Study in Real Storage Conditions
No full textVacuum impregnation (VI) is a processing operation that permits the impregnation of fruit and vegetable porous tissues with a fast and more homogeneous penetration of active compounds compared to the classical diffusion processes. The objective of this research was to investigate the impact on VI treatment with the addition of calcium lactate on qualitative parameters of minimally processed melon during storage. For this aim, this work was divided in 2 parts. Initially, the optimization of process parameters was carried out in order to choose the optimal VI conditions for improving texture characteristics of minimally processed melon that were then used to impregnate melons for a shelf-life study in real storage conditions. On the basis of a 23 factorial design, the effect of Calcium lactate (CaLac) concentration between 0% and 5% and of minimum pressure (P) between 20 and 60 MPa were evaluated on color and texture. Processing parameters corresponding to 5% CaLac concentration and 60 MPa of minimum pressure were chosen for the storage study, during which the modifications of main qualitative parameters were evaluated. Despite of the high variability of the raw material, results showed that VI allowed a better maintenance of texture during storage. Nevertheless, other quality traits were negatively affected by the application of vacuum. Impregnated products showed a darker and more translucent appearance on the account of the alteration of the structural properties. Moreover microbial shelf-life was reduced to 4 d compared to the 7 obtained for control and dipped samples
Effects of different roasting conditions on physical-chemical properties of Polish hazelnuts (Corylus avellana L. var. Katalonski)
Full text linkThe influence of different roasting conditions on the physical-chemical (water activity, moisture, colour, volatile compounds, tocopherols, phenolic content) properties of Polish hazelnuts (cv. Katalonski) was determined. Nuts were roasted at specific temperature/time conditions: 130°C/40 min, 130°C/50 min, 130°C/60 min, 160°C/20 min, 160°C/25 min, 160°C/30 min. Hazelnuts roasted at 160°C showed a darker colour and a lower water activity and moisture than samples roasted at 130°C. Compared to raw hazelnuts, the phenolic content increased in all roasted samples, although with a more concentration in nuts roasted at 160°C (2998.84 mg/100 g, 3429.52 mg/100 g and 2927.81 mg/100 g after 20, 25 and 30 min, respectively). The different roasting conditions led to several aroma modifications, in fact in raw hazelnuts were identified just only 22 compounds, whereas in samples roasted at 130°C and 160°C were found 79 and 102 volatile compounds, respectively
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