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•Complex coacervation between WPI-KC using a US pretreatment was achieved.•Despite WPI structure change by US treatment, coacervation with carrageenan remains.•Functional properties ...improvement was observed in US pretreated complex coacervates.
The aim of this work was to evaluate the influence of high-intensity ultrasound (HIUS) treatment on whey protein isolate (WPI) molecular structure as a previous step for complex coacervation (CC) with kappa-carrageenan (KC) and its influence on CC functional properties. Protein suspension of WPI (1% w/w) was treated with an ultrasound probe (24 kHz, 2 and 4 min, at 50 and 100% amplitude), non HIUS pretreated WPI was used as a control. Coacervation was achieved by mixing WPI and KC dispersions (10 min). Time and amplitude of the sonication treatment had a direct effect on the molecular structure of the protein, FTIR-ATR analysis detected changes on pretreated WPI secondary structure (1600–1700 cm−1) after sonication. CC electrostatic interactions were detected between WPI positive regions, KC sulfate group (1200–1260 cm−1), and the anhydrous oxygen of the 3,6 anhydro-D-galactose (940–1066 cm−1) with a partial negative charge. After ultrasound treatment, a progressive decrease in WPI particle size (nm) was detected. Rheology results showed pseudoplastic behavior for both, KC and CC, with a significant change on the viscosity level. Further, volume increment, stability, and expansion percentages of CC foams were improved using WPI sonicated. Besides, HIUS treatment had a positive effect on the emulsifying properties of the CC, increasing the time emulsion stability percentage. HIUS proved to be an efficient tool to improve functional properties in WPI-KC CC.
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•Ultrasonic oil bleaching reduces processing time, temperature and bleaching clay use.•Ultrasound oil bleaching showed no modifications in cis fatty acid configuration.•Spectroscopic ...tests on ultrasound-treated samples showed no evidence of oxidation.•Ultrasound-bleaching treatments generated yellow color in canola oil samples.
Canola seeds (Brassica napus L.) are among the most commonly used seeds in Mexico for vegetable oil production. This is based on the high yield and content of polyunsaturated and monounsaturated fatty acids. During oil bleaching, it is important to maintain fatty acids in their cis configuration because of the health concerns associated with trans-fatty acid consumption. In this sense, the industrial processing parameters employed for this purpose present some limitations, such as high temperatures and long times, which may change the cis configuration to trans. In addition, the amount of bleaching clay employed for this process could be a source of contamination because it is disposed of after treatment. Therefore, the aim of this study was to develop a bleaching process for canola oil using high-power ultrasound (US). US processing was applied to nine treatments with different processing times (60, 75, and 90 min), clay percentages (1, 2, and 3%), and temperatures (60 and 80 °C) to determine the concentrations of chlorophyll a and b (µg chlo/100 g oil), carotenes (µg β-carotene/100 g oil), color (L*, a*, b*, C*, and h°), iodine value (g I2/100 g oil), and finally carrying out a spectroscopic analysis (ATR-FTIR and Raman). A conventional bleaching treatment (100 °C for 180 min, 3% bleaching clay) was used as a control. The results revealed that US treatments with 2% clay at 60 °C for 60 and 90 min eliminated most of the chlorophyll compounds (98%). However, in terms of carotenes reduction, these identical treatments exhibited a similar tendency to that of the control (approximately 30% decrease). These findings also affected the sample color, in which US treatments revealed chromatic coordinates that indicated yellow tones with chroma values that were more intense than those in the control samples. In terms of the iodine value, such treatments fulfilled the international standards for vegetable oils (90–100 g I2/100 g oil). Finally, the spectroscopic study revealed no trans configurations or the presence of different chemical compounds after US treatment, because neither of them presented typical peaks for those molecular configurations. In this regard, US can be a useful methodology for bleaching vegetable oils, helping to reduce time, and bleaching clay with similar pigment reduction results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The shrinkage-deformation (SD) behavior and mass transfer characteristics of white mushroom (Agaricus bisporus) pilei during osmotic dehydration (OD) were investigated. The morphometric ...characteristics of the product (including product contours, cross-sectional area and roundness) were obtained from digital images. Moreover, product contours were averaged to extract relevant deformation characteristics of osmodehydrated samples. An unsteady state 2D-diffusion model taking into account both radial and angular mass transfer, where product is shaped as a hemispherical shell was proposed to describe experimental data. Water and solute diffusivities in product were estimated with and without considering product shrinkage, defined as the shortening of radial dimension. Besides, diffusion coefficients were obtained using simplified models for both the proposed hemispherical shell geometry and a simpler sphere-shaped product, in the latter, under different similitude criteria. Estimated water and solute diffusivities reflecting dimensional changes of product were in the ranges of 1.1–4.6 × 10−10 and 1.5–1.8 × 10−10 m2/s, respectively, and are overestimated in about 39–113% for water and in about 24–66% for solute when shrinkage is not included in the OD model. Moreover, diffusion coefficients can also be corrected for geometry using the appropriate similitude criterion.
•Morphometric changes of white mushroom pilei during OD were evaluated.•Real product shape was approximated by a hemispherical shell geometry.•A 2D unsteady-state diffusion model was proposed to describe mass transfer.•Product suffers a significant shrinkage and deformation during OD.•Shrinkage is of key importance for an accurate estimation of diffusivities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The mathematical modeling of simultaneous shrinkage and shape change (deformation) during drying of gel model systems (GMS) was investigated. Developed theory was applied to estimate water ...diffusivities during drying of GMS (70 °C, air velocity of 2 m/s) shaped as square prisms (9.53 mm × 9.53 mm × 80 mm) and longitudinal sections (quarters and halves) of cylinders (12.7 mm diameter × 140 mm length) by considering the product shrinkage with and without deformation. The contours of transversal product slices, obtained from digital images, were averaged to extract relevant characteristics of the dried samples, whereas compactness and roundness were used to evaluate product deformation. Experimental shape patterns were used to estimate the initial and final mesh matching the real product geometry during simulation via a new algorithm. The obtained results demonstrate that although shrinkage occurs from the beginning of drying, changes in product shape are noticeable only after the free moisture fraction is below 0.3. Water diffusivities estimated considering the shape change of product were in the narrow range of 3.37–3.58 × 10−10 m2/s for studied geometries, and are overestimated in about 6–12% when this phenomenon is not included in drying model. No significant differences were observed in water diffusivity values between studied geometries (p > 0.05).
•Drying of cylinder sections and square prisms made from gel was studied.•Image analysis was used to characterize shrinkage and deformation of samples.•A new algorithm was used to create a mesh matching the real product shape.•Shape change and moisture profiles during drying were simulated.•The effect of geometry and deformation on water diffusivity was appraised.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Water diffusivity behavior in dried foods is estimated by the method of slopes (MoS).•The MoS is generalized to shrinking solids with complex-shaped geometries.•Mushroom pilei drying was analyzed by ...a 2D model in oblate spheroidal coordinates.•Shrinkage characteristics of product were obtained by point set registration method.•MoS surpassed piecewise regression for describing the experimental drying curves.
Water diffusivity is an important parameter for designing convective drying processes, as it is instrumental for determining the rate at which moisture is removed from solid foodstuffs. Most estimation methods for water diffusivity estimation rely in simple geometries and are based on analytical solutions for mass transfer under constant diffusivity in a rigid solid, assumptions that most often leads to unreliable estimations. In this study, the method of slopes is generalized to complex-shaped geometries lacking analytical solutions, allowing the estimation of variable diffusivities in shrinking solids. The method is validated with experimental drying data for fresh and osmodehydrated mushroom pilei and implemented by using the numerical solution to an unsteady state 2D drying model formulated in the oblate spheroidal coordinate system. Shrinkage descriptors of drying product were determined using the point set registration algorithm. Water diffusivities were further compared to those estimated by using a piecewise regression approach. Drying kinetics simulations using diffusivities obtained with the method of slopes showed an excellent agreement with experimental data, achieving moisture-averaged relative deviation values lower than 2.4%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this study was to evaluate a hurdle technology approach (ultraviolet-C light treatment, vanillin or cinnamaldehyde and storage temperature) for preventing the growth of Salmonella ...Typhimurium inoculated into coconut water. Inoculated coconut water was treated with UV-C light at different times (3.5, 7 and 10.5 min); immediately, selected natural antimicrobials (vanillin and cinnamaldehyde) were added at fixed concentrations and stored under refrigeration (5 °C) and room (22 °C) temperatures for 30 days. Beta model was used for describing either growth or death kinetics of S. Typhimurium. By themselves, antimicrobials significantly decreased S. Typhimurium counts achieving a maximum reduction of 1.4 ± 0.3 log CFU mL−1 with cinnamaldehyde (100 μg mL−1). Natural antimicrobials and low temperature significantly affected (p < 0.05) S. Typhimurium growth during storage. A 7-min UV-C light exposure allowed the inhibition of S. Typhimurium growth in coconut water containing natural antimicrobials over a 30-day storage at 5 °C. Moreover, a 10.5-min UV-C light treatment per se prevented S. Typhimurium growth in coconut water, regardless of any other hurdles applied. Beta model satisfactorily fits the experimental data. Results might be used for developing a low-cost preservation method for coconut water.
•Vanillin and cinnamaldehyde reduced S. Typhimurium load in coconut water.•Low UV-C dose induces a stress process that may be repaired by cells.•High UV-C dose inactivates S. Typhimurium and the effect is maintained in storage•Hurdle technology may be useful to enhance coconut water shelf life.•Beta model was able to reproduce experimental data.
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► An analytical model is developed to describe drying kinetics of shrinkable foods. ► The model is based on existing solutions of Fick’s second law of diffusion. ► Solution was obtained by assuming ...both time-varying shrinkage and diffusivities. ► Drying data of chayote were accurately simulated with the proposed methodology. ► Slopes method is demonstrated to be a particular case of the presented solution.
An analytical model based on Fick’s second law of diffusion has been developed to both evaluate mass transfer properties and describe drying kinetics of shrinkable food products. The proposed model was validated with experimental drying data of chayote slices (0.6cm thickness) obtained at air temperatures of 40, 50, 60, and 70°C. In all cases, an excellent agreement was found between experimental drying curves and predicted results (R2>0.9969). As expected, the use of higher drying temperatures increased effective water diffusivities, while no effect was observed on shrinkage evolution of the product (p<0.05). In addition, diffusivity values were found to decrease along with the moisture content of chayote slices (p<0.05). Under the described experimental conditions, mean water diffusivities were in the range of 4.44×10−10–8.60×10−10m2/s. Results demonstrated that the proposed model can be applied for the accurate description of experimental drying curves allowing a reliable estimation of mass transfer properties in shrinkable food products such as chayote.
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•Simultaneous shrinkage and deformation (SD) during food drying is investigated.•SD are analyzed in the dominant mass transfer directions from digital images.•Potato strips were used as model system ...and dried at 50, 60, 70 and 80°C .•Contour shape, perimeter, surface area and specific area were estimated.•SD described as a moisture function were not affected by temperature.
A new methodology based on image analysis was proposed to estimate the simultaneous size reduction (shrinkage) and shape change (deformation) during food drying. Potato strips (9.525mm×9.525mm×80mm) were used as model system and subjected to convective drying at 50, 60, 70 and 80°C with an air velocity of 2m/s. Developed protocol was used to analyze the shrinkage-deformation behavior occurring in minor product dimensions, considered the dominant directions in mass transfer. To this purpose, 2D perpendicular slices were obtained from original 3D product and their digital images were processed to evaluate the changes in contour shape, perimeter, and cross-sectional and specific areas of samples. Product contours were averaged to extract relevant deformation characteristics of dried samples. Drying and shrinkage data were further used to estimate variable water diffusivities in product with a previously reported analytical solution for shrinking solids, which was extended to allow for 2D or 3D mass transfer. Studied responses were successfully described as a function of free moisture fraction (R2>0.84). It was demonstrated that shrinkage-deformation behavior was not affected by drying temperature under the tested conditions (p<0.05). The analysis of averaged contour shapes showed that, although shrinkage occurs from the beginning of drying, deformation appears at the final stages, when the free moisture fraction is below 0.2. Mean water diffusivities were estimated in the range of 3.04–5.36×10−10m2/s for studied drying temperatures.
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•Drying of foods shaped as whole or sections of cylinders is investigated.•A simple method is developed to estimate anisotropic diffusion coefficients.•Diffusivities along axial, radial and angular ...directions can be estimated.•Proposed methodology was tested with two sets of convective drying data of carrot.•Anisotropic behavior of carrot was confirmed.
In this study, a method to estimate water diffusivity in axial, radial and angular directions during drying of anisotropic cylindrical solids is proposed. The method is based on the analytical solution for non-steady state mass transfer equation in products shaped as longitudinal sections of finite anisotropic cylinders. A sequential approach is applied where radial and axial diffusion coefficients are first estimated from drying curves of whole cylinders with increasing height, while angular diffusivity is obtained thereafter from drying experiments carried out with longitudinal sections of fixed-height cylinders varying cut angle. Developed theory was applied to the analysis of two sets of convective drying data of carrot obtained at 80°C with an air velocity of 2m/s. The first experiment set was conducted with carrot cylinders of 2.2cm diameter and heights of 1, 2,…,10cm, while cylinders in the second set were longitudinally cut as halves, quarters, sixths and eighths with a constant height of 10cm. Under such experimental conditions, identified water diffusivities were in the range of 0.53–2.93×10−9m2/s. Differences in water diffusivity for studied mass transfer directions were significant (p<0.05), with SEM images revealing structural differences between longitudinal and transversal product cuts, thus further supporting numerical results. Present findings suggest that, depending on product, anisotropic diffusion should be included in drying modeling in order to obtain an accurate process description.
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