Browsing by Author "Ortiz, J"

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    Effect of kappa-carrageenan on the gelation of horse mackerel (T-murphyi) raw paste surimi-type
    (SAGE PUBLICATIONS LTD, 2004) Ortiz, J; Aguilera, JM
    Gelation of fresh (unfrozen) raw surimi-type paste (RS paste) from horse mackerel (T murphyi) was studied in the presence Of kappa-carrageenan (0.5, 1, 2% Ckappa) and KCl (0.5-2%) as a substitute for NaCl. Gelation was traced by measuring the storage modulus (G') during heating-cooling cycles. Variations in G' during the heating stage of the mixed system RS-Ckappa characterised the presence of a phase separation in this stage due to Ckappa solubilitation (at about 50degreesC) as well as to RS gelation (35-80degreesC) in the mixture. It was also observed that when Ckappa was added as a single ingredient. it inhibited RS gelation as a function of its concentration (>2%). Nevertheless, during the cooling stage, the final G' value for the RS-2% Ckappa mixed system was greatly increased. This reinforcing would be caused by further (cold) Ckappa gelation in the mixture. It is theorised that Ckappa might act by forming 'packed' microgels within the RS protein gel network, which is favoured upon application of a moderate (40degreesC, 60 min) thermal treatment rather than when an extreme (90degreesC, 20 min) treatment is applied. On the other hand, although KCl enhanced gelation of the 2% Ckappa solution, addition of this salt to the RS-2% Ckappa mixture did not improve its gelation. Rheological information was complemented with observation of the resulting structures by scanning electronic microscopy (SEM).
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    Note. Effect of thermal history on the gelation of horse mackerel (T-murphyi) raw paste surimi-type
    (ASPEN PUBL INC, 2000) Aguilera, JM; Ortiz, J
    Fresh paste from horse mackerel (T. murphyi) surimi-type, was processed during setting using (2%) KCl. The paste was subjected to different heating and cooling cycles. The salt produced an improvement in kamaboko-type gel formation. The heating and cooling cycles enhanced the setting process and improved textural quality of the resulting gel, mainly when the heating before cooling was slow. The setting process was characterized by several physical parameters: storage module (G'), using an oscillatory rheological technique, and apparent Young module (E), by means of mechanical compression tests. The enthalpic changes for gelification of the paste were determined using differential scanning calorimetry.
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    Supercritical carbon dioxide extraction of red pepper (Capsicum annuum L.) oleoresin
    (2004) Uquiche, E; del Valle, JM; Ortiz, J
    The extraction kinetics of red pepper oleoresin with supercritical carbon dioxide (SC-CO2) at 40 degreesC from a pelletized substrate was evaluated as a function of crushed-pellet particle size (D-p = 0.273-3.90 mm), superficial solvent velocity (U-s = 0.57-1.25 mm/s), and extraction pressure (320-540 bar). Batch productivity increased with substrate pelletization, which caused a 4-time increase in apparent density. Microscopy was utilized to characterize the microstructure of the pelletized substrate. Fractal analysis of binary images and mercury porosimetry allowed an estimation of pellet porosity and tortuosity, which in turn allowed an independent estimation of effective diffusivity. Solute partition between the solid matrix and SC-CO2 (K) was estimated from the initial slope of cumulative plots of oleoresin yield versus specific solvent mass, and did not depend on D-p and U-s. Yield of oleoresins and carotenoid pigments increased, and K decreased as the extraction pressure increased. A linear driving force approximation was used to model experimental data, and discrepancies between model predictions and experimental data points with large particles were explained. (C) 2003 Elsevier Ltd. All rights reserved.