Browsing by Author "Skurtys, Olivier"

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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.
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    Grading of potato chips according to their sensory quality determined by color
    (2011) Pedreschi Plasencia, Franco; Bunger, Andrea; Skurtys, Olivier; Allen, Paula; Rojas, Ximena
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    Mechanical properties of calcium alginate fibers produced with a microfluidic device
    (ELSEVIER SCI LTD, 2012) Cuadros, Teresa R.; Skurtys, Olivier; Aguilera, Jose M.
    Fibers are important microstructural elements in many foods. The main objective of this research was to produce calcium alginate fibers with uniform diameters (about 300 and 550 mu m) using a microfluidic device (MFD) and to study the effect of concentration of sodium alginate [Alg] and calcium chloride [CaCl2] on their mechanical properties (MP). Moisture content (MO) and MP as maximum tensile stress (sigma(max)), tensile strain at break (Delta L/L-0) and apparent Young's modulus (E) of fibers were determined and a statistical model and surface responses were developed as a function of [Alg] and [CaCl2]. As [CaCl2] increased first a strengthening and then a weakening of fibers were observed. Furthermore, sigma(max) increased with the addition of Ca2+ and a maximum of sigma(max) was obtained for a [CaCl2] around 1.4% (exceeding several times the stoichiometric requirements of the carboxylate groups of the polymer). Such behavior prompted a molecular explanation of what happens during gelation based on the "egg-box model" and this model is tried to complete. Moreover, fibers with [Alg] >= 1.8% showed high extensibility (Delta L/L-0 around 100%) and low values of MO. High values of E (similar to 0.5 MPa) were obtained for [CaCl2] close to 1.4%. A greater understanding is needed of the interaction between cation-polysaccharide-water, taking into account [Alg] and [CaCl2] to predict the mechanical behavior of fibers. Calcium alginate fibers are important in food engineering as texture and microencapsulation agents. (C) 2012 Elsevier Ltd. All rights reserved.
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    Using RGB Image Processing for Designing an Alginate Edible Film
    (2012) Acevedo, Cristian A.; Lopez, Dario A.; Tapia, Maria J.; Enrione, Javier; Skurtys, Olivier; Pedreschi, Franco; Brown, Donald I.; Creixell, Werner; Osorio, Fernando
    The use of edible films to coat food products is a technique that allows for an extended shelf-life. One of the most widely used polymers is calcium alginate. However, this polymer can modify the original food color and the perception by consumers. The objective was to design an alginate film based principally on color changes using a RGB color model. Edible films were prepared with sodium alginate and glycerol as plasticizer, cross-linking the polymer with calcium. Dry and hydrated states of the edible films were studied. Film thickness was directly proportional to surface concentration and increased with hydration. There is a zone in which the color does not change with alginate surface concentration and another where the color is directly proportional to it. This latter scenario is not a consequence of structural changes or the degree of hydration. Results showed a range where the color was not modified by the alginate concentration; hence, an optimal surface concentration was determined as a design parameter. Edible films made using the optimal surface concentration would not mask microbial contamination and have good physical properties (water vapor transmission and swelling) compared with other surface concentrations. In addition, it was possible to model alginate surface concentration as a function of surface color using mathematical tools (clustering, linear regression, and support vector machine), allowing one to study the optimal use of the edible films.