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.