DSpace Angular :: Browsing by Author "Pedreschi, Franco"

Browsing by Author "Pedreschi, Franco"

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A non-destructive digital imaging method to predict immobilized yeast-biomass
(ELSEVIER, 2009) Acevedo, Cristian A.; Skurtys, Olivier; Young, Manuel E.; Enrione, Javier; Pedreschi, Franco; Osorio, Fernando
In food fermentation, many types of immobilization systems are used, such as hydrogel entrapment, where alginate is the main biopolymer. one of the important problems in industrial processes is the quantifications of biomass, since the traditional system of direct cell counting cannot be used. In this study, a simple digital imaging method to determine the biomass of yeasts immobilized into alginate capsules was developed. Important evidence of the yeasts growing inside the alginate was the change in the surface color of the capsule. Digital images were taken with different biomass concentration, and the RGB-analysis showed significant differences in the blue field. The histogram of the blue channel was used to develop a PLS multivariate calibration to predict biomass concentration. The method was validated in primary beer fermentation with good efficiency. (C) 2009 Elsevier Ltd. All rights reserved.
Acrylamide reduction in potato chips by using commercial asparaginase in combination with conventional blanching
(ELSEVIER SCIENCE BV, 2011) Pedreschi, Franco; Mariotti, Salome; Granby, Kit; Risum, Jorgen
In this research acrylamide reduction in potato chips was investigated in relation to blanching and asparaginase immersion treatments before final frying. Potatoes slices (Verdi variety, diameter: 40 mm, thickness: 2.0 mm) were fried at 170 degrees C for 5 min (final moisture content of similar to 2.0 g/100 g). Prior to frying, potato slices were treated in one of the following ways: (i) Rinsing in distilled water (control I); (ii) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min; (iii) Rinsing in distilled water plus immersion in an asparaginase solution (10000 ASNU/L) at 50 degrees C for 20 min; (iv) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min plus immersion in an asparaginase solution (10000 ASNU/L) at 50 degrees C for 20 min; (v) Rinsing in distilled water plus blanching in hot water at 85 degrees C for 3.5 min plus immersion in distilled water at 50 degrees C for 20 min (control II). Blanching in hot water (ii) was almost as effective as asparaginase potato immersion (iii) in order to diminish acrylamide formation in potato chips (acrylamide reduction was similar to 17% of the initial acrylamide concentration). When potato slices were blanched before asparaginase immersion, the acrylamide content of the resultant potato chips was reduced considerably by almost 90%. We have demonstrated that blanching of potato slices plus asparaginase treatment is an effective combination for acrylamide mitigation during frying. It seems to be that blanching provokes changes in the microstructure of potato tissue leading to an easier and more effective diffusion of asparaginase. (C) 2011 Elsevier Ltd. All rights reserved.
Automated Design of a Computer Vision System for Visual Food Quality Evaluation
(2013) Mery Quiroz, Domingo Arturo; Pedreschi, Franco; Soto, Alvaro
Color development and acrylamide content of pre-dried potato chips
(ELSEVIER SCI LTD, 2007) Pedreschi, Franco; Leon, Jorge; Mery, Domingo; Moyano, Pedro; Pedreschi, Romina; Kaack, Karl; Granby, Kit
The objective of this work was to study the development of color formation in pre-dried potato slices during frying and acrylamide formation in the final potato chips. Color measurement was done by using an inexpensive computer vision technique which allowed quantifying representatively and precisely the color of complex surfaces such as those of potato chips in L*a*b* units from RGB images. Prior to frying, potato slices (Desiree variety, diameter: 37 mm, width: 2.2 mm) were blanched in hot water at 85 degrees C for 3.5 min. Unblanched slices were considered as the control. Slices of the same dimensions were blanched as in the previous step, and then air-dried until reaching a moisture content of 60% (wet basis). These samples were called pre-dried potato slices. Potato slices were fried at 120 degrees C, 140 degrees C, 160 degrees C and 180 degrees C until reaching moisture contents of similar to 1.8% (total basis) for color quantification. Acrylamide concentration was determined only in final chips fried at 120 degrees C, 150 degrees C and 180 degrees C and compared with that of two brands of commercial chips produced in Chile (Moms and Frito Lay). Color values in L*a*b* units were recorded at different sampling times during frying at the four mentioned temperatures using the total color difference parameter (Delta E). Pre-drying did not affect the color of potato chips considerably when compared against blanched chips; however when fried at 180 degrees C, pre-dried potato chips present 44%, 22%, 44% lower acrylamide content than that of the control, Moms and Frito Lay chips, respectively. (c) 2006 Elsevier Ltd. All rights reserved.
Color kinetics and acrylamide formation in NaCl soaked potato chips
(ELSEVIER SCI LTD, 2007) Pedreschi, Franco; Bustos, Oscar; Mery, Domingo; Moyano, Pedro; Kaack, Karl; Granby, Kit
The objective of this work was to study the kinetics of color development in blanched and blanched-NaCl impregnated potato slices during frying by using the dynamic method and also to evaluate the effect of NaCl in reducing acrylamide formation in potato chips. The measurement of color was done by using an inexpensive computer vision technique which allowed quantifying in a more precise and representative way the color in L*a*b* units of complex surfaces such as those of potato slices during frying. The effect of potato slice soaking in NaCl was evaluated not only for color change but also for acrylamide formation. Prior to frying, potato slices (Desiree variety, diameter: 37 mm, width: 2.2 min) were blanched in hot water at 85 degrees C for 3.5 min; these slices were considered as the control. Slices of the same dimensions were blanched as in the previous step, and soaked at 25 degrees C in a NaCl solution of 0.02 g/l 5 min at 200 rpm of agitation. These samples were considered as NaCl soaked potato chips.
Color measurement in L*a*b* units from RGB digital images
(ELSEVIER, 2006) Leon, Katherine; Mery, Domingo; Pedreschi, Franco; Leon, Jorge
The superficial appearance and color of food are the first parameters of quality evaluated by consumers, and are thus critical factors for acceptance of the food item by the consumer. Although there are different color spaces, the most used of these in the measuring of color in food is the L*a*b* color space due to the uniform distribution of colors, and because it is very close to human perception of color. In order to carry out a digital image analysis in food, it is necessary to know the color measure of each pixel on the surface of the food item. However, there are at present no commercial L*17*b* color measures in pixels available because the existing commercial colorimeters generally measure small, non-representative areas of a few square centimeters. Given that RGB digital cameras obtain information in pixels, this article presents a computational solution that allows the obtaining of digital images in L*a*b* color units for each pixel of the digital RGB image. This investigation presents five models for the RGB -> L*a*b* conversion and these are: linear, quadratic, gamma, direct, and neural network. Additionally, a method is suggested for estimating the parameters of the models based on a minimization of the mean absolute error between the color measurements obtained by the models, and by a commercial colorimeter for uniform and homogenous surfaces. In the evaluation of the performance of the models, the neural network model stands out with an error of only 0.93%. On the basis of the construction of these models, it is possible to find a L*a*b* color measuring system that is appropriate for an accurate, exacting and detailed characterization of a food item, thus improving quality control and providing a highly useful tool for the food industry based on a color digital camera. (c) 2006 Elsevier Ltd. All rights reserved.
Description of the kinetic enzymatic browning in banana (Musa cavendish) slices using non-uniform color information from digital images
(ELSEVIER, 2009) Quevedo, Roberto; Diaz, Oscar; Ronceros, Betty; Pedreschi, Franco; Miguel Aguilera, Jose
A novel methodology "fractal browning indicator" (FBI) is presented, that describes the enzymatic browning kinetic based on the use of irregular color patterns from banana slice images. It uses the fractal Fourier texture image value in a selected area, to calculate a fractal dimension (FD), which represents the complexity of color distribution. During the procedure, colors from digital images were first transformed to L*a*b* space color using a transformation function (quadratic model), in order to derivate three color channels, lightness (L*), redness (a*), and yellowness (b*). In the results, lightness and yellowness parameters decreased during the browning kinetic, when their respective FD values increased, indicating major color distribution complexity in a selected area analyzed during the kinetic. The redness color (a*) did not show any statistical variation. The empirical power law model was suitable to correlate enzymatic browning kinetic data both for FBI and for the traditional method (when an L* mean was used). However, enzymatic browning rates using the FBI method, were between 8.5 and 35 times higher than rates calculated with the traditional method. (C) 2009 Elsevier Ltd. All rights reserved.
Development of a computer vision system to measure the color of potato chips
(ELSEVIER, 2006) Pedreschi, Franco; Leon, Jorge; Mery, Domingo; Moyano, Pedro
The objective of this research was to design and implement an inexpensive computer vision system for measuring the color of a highly heterogeneous food material not only in shape as well in color such as potato chips in L*a*b* units from RGB images. The system was composed of (i) a digital color camera for acquiring the images in a digital format, (ii) a computer for storage the images, (c) image analysis routines integrated into a software programmed in Matlab that converts the color RGB of the food image into L*a*b* units. In this way the color of potato chips can be calculated in L*a*b* units over representative areas and in a reproducible way. The kinetics of color changes in potato slices during frying at four temperatures was followed using the implemented computer vision system (CVS). Color values in L*a*b* units were recorded at different sampling times during frying at the four oil temperatures using the total color change parameter (AE). Chips fried at higher temperatures get darker as expected and showed by the CVS. The implemented computer vision system can be used to study as well foods different from potato chips by selecting their proper settings for image acquisition and digital image processing. (c) 2006 Elsevier Ltd. All rights reserved.
Frying of Potatoes: Physical, Chemical, and Microstructural Changes
(TAYLOR & FRANCIS INC, 2012) Pedreschi, Franco
Frying is one of the oldest unit operations and is used not only in industry but also at home. The most commonly fried vegetable is potato, for important commercial products such as potato chips, par-fried potatoes, and french fries. Quality parameters of interest for fried potatoes include physical and chemical properties such as color, mechanical properties (e. g., crispness, hardness, etc.), structural properties (e. g., porosity and roughness), oil content, and water content, among others. Some chemical contaminants such as acrylamide and furan are heat-generated during the frying of potato slices or strips, leading to final fried pieces with considerable amounts of these contaminants. The controllable variables in industrial frying processes are generally potato variety, oil type, frying time, and frying temperature. Therefore, the study of the quality changes during frying is critical because knowledge regarding kinetics parameters will enable prediction of the final quality in fried potatoes and improvements in the final product value by selecting properly the processing conditions. Finally, modern techniques such as computer vision provide valuable tools to quantify and predict physical and chemical properties of potato pieces during frying in a fast and noninvasive way. In addition, computer vision can allow us to classify fried potatoes in different quality classes previously determined by sensorial panels.
Furan Occurrence in Starchy Food Model Systems Processed at High Temperatures: Effect of Ascorbic Acid and Heating Conditions
(AMER CHEMICAL SOC, 2012) Mariotti, Maria; Granby, Kit; Fromberg, Arvid; Risum, Jorgen; Agosin, Eduardo; Pedreschi, Franco
Furan, a potential carcinogen, has been detected in highly consumed starchy foods, such as bread and snacks; however, research on furan generation in these food matrixes has not been undertaken, thus far. The present study explored the effect of ascorbic acid addition and cooking methods (frying and baking) over furan occurrence and its relation with the non-enzymatic browning in a wheat flour starchy food model system. Results showed that furan generation significantly increased in the presence of ascorbic acid after 7 mm of heating (p < 0.05). The strongest effect was observed for baked products. Additionally, the furan content in fried products increased with the increase of the oil uptake levels. As for Mallard reactions, in general, the furan level in all samples linearly correlated with their degree of non-enzymatic browning, represented by L* and a* color parameters (e.g., wheat flour baked samples showed a R-2 of 0.88 and 0.87 for L* and a*, respectively), when the sample moisture content decreased during heating.
Grading of Potatoes
(2008) Pedreschi, Franco; Mery Quiroz, Domingo Arturo; Marique, Thierry
Prediction of Mechanical Properties of Corn and Tortilla Chips by Using Computer Vision
(2012) Matiacevich, Silvia B.; Mery Quiroz, Domingo Arturo; Pedreschi, Franco
Quantification of enzymatic browning in apple slices applying the fractal texture Fourier image
(ELSEVIER SCI LTD, 2009) Quevedo, Roberto; Jaramillo, Marcela; Diaz, Oscar; Pedreschi, Franco; Miguel Aguilera, Jose
A new approach (FBI) describing the enzymatic browning kinetics for three apple cultivars, is presented. It is based on quantification of the irregular color patterns that emerge from the apple surface during enzymatic browning, rather than using the color average in the same area analyzed. In the experiments, three apple cultivars slices were placed under a computer vision system and color digital images were captured. The images were transformed to Lab space color using a quadratic transformation function and the Fourier fractal texture image was used to calculate a fractal dimension value (FD), in order to represent the complexity of lightness intensity distribution (L) over the surface. FD (proposed method) and the mean L value (traditional method) were used indistinctly (as a fractional conversion) to model the enzymatic kinetic using the power-law model. The results showed that the fractal theory can be used to describe the browning kinetic and to distinguish apple cultivars, based on their browning sensitivity under the same experimental conditions. Enzymatic browning rates derived using the fractal kinetic method, were between 14.3 and 23.2 times (in absolute value) higher than the rates calculated with the traditional method. The fractional first-order model was established only for kinetics calculated using the traditional method. (c) 2009 Elsevier Ltd. All rights reserved.
Soaking in a NaCl solution produce paler potato chips
(ELSEVIER, 2007) Santis, Nathalie; Mendoza, Fernando; Moyano, Pedro; Pedreschi, Franco; Dejmek, Petr
Pairs of potato slices were blanched, soaked in a NaCl solution or water and fried. The originally adjoining faces of the chips were analysed for average L*a*b* color by digital photography and image analysis.

Browsing by Author "Pedreschi, Franco"

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