Browsing by Author "Pedreschi, F."

Now showing 1 - 8 of 8
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    Comparative study of physical and sensory properties of pre-treated potato slices during vacuum and atmospheric frying
    (ELSEVIER, 2009) Troncoso, E.; Pedreschi, F.; Zuniga, R. N.
    The objective of this research was to study the effect of different processing conditions on physical and sensory properties of potato chips. Potato slices of Desiree and Panda varieties (diameter: 30 mm; thickness: 3 mm) were pre-treated in the following ways: (i) control or unblanched slices without pre-drying; (ii) blanched slices in hot water at 85 degrees C for 3.5 min and air-dried at 60 degrees C until a final moisture content of similar to 0.6 kg water/kg dry solid; (iii) control slices soaked in a 3.5 kg/m(3) sodium metabisulphite solution at 20 degrees C for 3 min and pH adjusted to 3. Pre-treated slices were fried at 120 and 140 degrees C under vacuum conditions (5.37 kPa, absolute pressure) and under atmospheric pressure until they reached a final moisture content of similar to 1.8 kg water/100 kg (wet basis). An experimental design (3 x 2(3)) was used to analyze the effect of pre-treatment, potato variety, type of frying and frying temperature over the following responses: oil content, instrumental color and texture and sensory evaluation. Vacuum frying increased significantly (p < 0.05) oil content and decreased instrumental color and textural parameters. Sensory attributes, flavor quality and overall quality, were significantly improved using vacuum frying. The higher frying temperature (140 degrees C) increased Delta E, maximum breaking force, hardness and crispness and decreased L* and b* values. On the other hand, Panda potato variety improved the color of the product. A great improvement on color parameters was obtained using sulphited potato slices instead of the other pre-treatments. Although, the better flavor was obtained for control potato chips, no significant differences were found for overall quality between control and sulphited potato chips. Significant correlations (p < 0.01) between sensory and instrumental responses were found. (C) 2008 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.
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    Enzymatic browning in sliced and pureed avocado: A fractal kinetic study
    (ELSEVIER SCI LTD, 2011) Quevedo, R.; Ronceros, B.; Garcia, K.; Lopez, P.; Pedreschi, F.
    Modelling of browning is essential to evaluate the effectiveness of the processes applied to obtain fresh-appearance foods and also to determine their shelf life. Computer vision and the fractal kinetic method were used to quantify browning in three avocado cultivars. Samples (avocado slices and pur e) were stored at 4 degrees C and surface images were captured in the tiff format. Browning kinetic was derived from images using the L* mean method and the fractal method. In another experiment, inhibitor kinetic was also quantified, using the polyphenol oxidase activity method (in puree samples) with 0.1%, 0.5% and 1% of sodium bisulfite. In the results for avocado slices, kinetic rate derived by the fractal kinetic method was higher than that obtained with the L* mean method, but the opposite was observed when the avocado was pulping (avocado puree). Kinetic quantified by the fractal method was similarly inhibited by bisulfite, when compared with the L* mean value or PPO activity value methods. In general, the fractal method can be used to record browning kinetic and to discriminate between avocado cultivars, initial structural state of the sample (slice or puree), or in experiments using browning inhibitors. (C) 2011 Elsevier Ltd. All rights reserved.
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    On-line monitoring of fat, dry matter and acrylamide contents in potato chips using near infrared interactance and visual reflectance imaging
    (ELSEVIER SCI LTD, 2010) Pedreschi, F.; Segtnan, V. H.; Knutsen, S. H.
    The contents of dry matter, oil and acrylamide are some of the most relevant parameters in the quality control of potato chips. Near infrared spectroscopy (NIR) is a common technique for routine analysis of bulk chemistry in different raw materials and products because it allows a fast and non-destructive analysis of samples. The objective of this research was to investigate the possibilities of using on-line NIR monitoring of acrylamide, moisture and oil content in potato chips. Sixty samples of potato chips from individual frying runs were measured on-line using a VIS/NIR interactance line scanner. The same samples were analysed in the laboratory to determine their corresponding moisture, acrylamide and oil contents. The mean VIS and NIR spectra for the 60 samples were modelled against the reference values for acrylamide, fat and dry matter using partial least squares regression (PLSR), and the regression models were validated using full cross-validation. On-line NIR interactance was found to predict fat and dry matter of potato chips with high accuracy, i.e. prediction errors of 0.99 and 0.86% (w/w), respectively. The corresponding correlations between predicted values and reference values were 0.99 and 0.97 for fat and dry matter. For acrylamide an average prediction error of 266 mu g/kg was achieved using NIR and VIS signals in combination. The correlation between predicted values and reference values was 0.83 for this model. The system may be used to separate samples with very high acrylamide contents from samples with average to low contents. (C) 2010 Elsevier Ltd. All rights reserved.
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    Physical properties of emulsion-based hydroxypropyl methylcellulose films: Effect of their microstructure
    (ELSEVIER SCI LTD, 2012) Zuniga, R. N.; Skurtys, O.; Osorio, F.; Aguilera, J. M.; Pedreschi, F.
    The initial characteristics of emulsions and the rearrangement of the oil droplets in the film matrix during film drying, which defines its microstructure, has an important role in the physical properties of the emulsion-based films. The objective of this work was to study the effect of the microstructure (two droplet size distributions) and stability (with or without surfactant) of HPMC oil-in-water emulsions over physical properties of HPMC emulsion-based edible films. HPMC was used to prepare sunflower oil-in-water emulsions containing 0.3 or 1.0% (w/w) of oil with or without SOS, as surfactant, using an ultrasonic homogenizer. Microstructure, rheological properties and stability of emulsions (creaming) were measured. In addition, microstructure, coalescence of oil droplets, surface free energy, optical and mechanical properties and water vapor transfer of HPMC films were evaluated. Image analysis did not show differences among droplet size distributions of emulsions prepared at different oil contents: however, by using SOS the droplet size distributions were shifted to lower values. Volume mean diameters were 3.79 and 3.77 mu m for emulsions containing 0.3 and 1.0% without surfactant, respectively, and 2.72 and 2.71 mu m for emulsions with SOS. Emulsions formulated with 1.0% of oil presented higher stability, with almost no change during 5 and 3 days of storage, for emulsions with and without SOS, respectively. Internal and surface microstructure of emulsion-based films was influenced by the degree of coalescence and creaming of the oil droplets. No effect of microstructure over the surface free energy of films was found. The incorporation of oil impaired the optical properties of films due to light scattering of light. Addition of oil and SOS decreased the stress at break of the emulsion-based films. The replace of HPMC by oil and SOS produce a lower "amount" of network structure in the films, leading to a weakening of their structure. The oil content and SDS addition had an effect over the microstructure and physical properties of HPMC-based emulsions which lead to different microstructures during film formation. The way that oil droplets were structured into the film had an enormous influence over the physical properties of HPMC films. (C) 2012 Elsevier Ltd. All rights reserved.
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    Prediction of oil content in tortillas chips using computer vision
    (2009) Matiacevich, S.; Lnostroza, M.; Mery Quiroz, Domingo Arturo; Pedreschi, F.
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    Quality Evaluation and Control of Potato Chips
    (2016) Pedreschi, F.; Mery Quiroz, Domingo Arturo; Marique, T.
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    Quality Evaluation and Control of Potato Chips and French Fries
    (2008) Pedreschi, F.; Mery Quiroz, Domingo Arturo; Marique, T.
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    Segmentation in food images
    (2006) Mery Quiroz, Domingo Arturo; Pedreschi, F.