Abstract Consumer preferences, and potential health risks associated with the consumption of synt... more Abstract Consumer preferences, and potential health risks associated with the consumption of synthetic food colors, explain the commercial interest in alternatives from natural sources. Betaxanthins from cactus fruit have been used to color food products, but sugars are not usually removed from these extracts leading to processing and formulation challenges. In this study, low-sugar betaxanthin preparations were obtained from a crude yellow pitaya Stenocereus pruinosus extract using aqueous two-phase systems (ATPS). This study focuses on the effect of the salts and polymer choice (polyethylene glycol (MW 1000; PEG1000) or polyalkylene glycol copolymer (MW 3930, UCON), tie line length (TLL), phase volume ratio (Vr), and crude extract percentage on the partitioning of betaxanthins and sugars in the crude extract. PEG1000-phosphates were more suitable than UCON-salts for the extraction of betaxanthin. Multivariate analysis of variance (MANOVA, α = 0.05) showed that TLL, Vr and crude extract concentration effects were statistically significant (P
An undesirable crispiness loss occurs when some dry fruits reach a critical moisture content () a... more An undesirable crispiness loss occurs when some dry fruits reach a critical moisture content () and their glass transition temperature () matches the storage temperature. Models for sorption isotherms and onsetvalues for dry mango, apple, and banana were used to estimatevalues at 25 and 32 °C. All models yielded > 0.97 but information theory criteria strongly supported GAB in all but one case (40 °C, mango). The Gordon-Taylormodel (GT) yielded highvalues for apple and banana but resulted in = 0.834 for mango. As moisture approached zero, mangoestimates displayed a downward concavity contrasting with a rapidly increasing trend for apple and banana. The Khalloufi-Maslouhi-Ratti (KMR) model foras a function ofshowed a linear behavior. Although the KMR model fitted data with > 0.996, it requires more parameters and whenapproached 0, estimatedvalues increased at a slower rate than for the GT model. In the case of banana and mango, both models predicted approximately the sameat 25 °...
The growth rate and lag phase of Pseudomonas fluorescens, Brochothrix thermosphacta, Salmonella t... more The growth rate and lag phase of Pseudomonas fluorescens, Brochothrix thermosphacta, Salmonella typhlmurium, Enterococcus faecalis, and Staphylococcus aureus were studied in liquid media as a function of temperature, water activity (aw) and solute type. The lag phase lengthened and the growth rate decreased when the temperature was lowered or the aw reduced, and these variations depended on the aw-controlling solute. In general, the magnitude order of the solute effect on the growth rate parameters was glycerol < NaCl < sucrose. This effect can be related to the ability of the solutes to permeate the cell and can be explained by the osmoregulatory mechanism. The specific growth rate was not as sensitive to the aw-controlling solute as the lag phase. A linear extrapolation method was a reliable and convenient method to estimate the minimum aw for microbial growth.
Soluble proteins from surimi wash water (SWW) can be insolubilized by complexing with chitosan-al... more Soluble proteins from surimi wash water (SWW) can be insolubilized by complexing with chitosan-alginate allowing its recovery and the reduction of the organic matter in the processing water discharged from surimi processing plants. The objective of this work was to evaluate the effect of adding soluble proteins recovered from Pacific whiting SWW on the mechanical and functional properties of commercial
Edible barrier films complement modified atmosphere in preserving food quality and extending shel... more Edible barrier films complement modified atmosphere in preserving food quality and extending shelf life. The effects of plasticizer (stearic acid or propylene glycol), pH (4.4 or 9.4) and degree of hydration (58 or 84% RH) on the water vapor permeability, tensile strength and percent elongation at breakpoint were determined for zein and ethylcellulose films. Zein film hydration increased water permeability
An optical method using a custom-built system was investigated to study heating effects on bovine... more An optical method using a custom-built system was investigated to study heating effects on bovine serum albumin (BSA) as affected by pH and ionic strength (IS). Changes in the optical rotation (OR) and transmitted light (TL) of BSA in 0.01 M phosphate buffer at pH 6.1, 7, and 7.9 with IS maintained at 0.04, 0.08, and 0.16 were monitored while
Abstract Consumer preferences, and potential health risks associated with the consumption of synt... more Abstract Consumer preferences, and potential health risks associated with the consumption of synthetic food colors, explain the commercial interest in alternatives from natural sources. Betaxanthins from cactus fruit have been used to color food products, but sugars are not usually removed from these extracts leading to processing and formulation challenges. In this study, low-sugar betaxanthin preparations were obtained from a crude yellow pitaya Stenocereus pruinosus extract using aqueous two-phase systems (ATPS). This study focuses on the effect of the salts and polymer choice (polyethylene glycol (MW 1000; PEG1000) or polyalkylene glycol copolymer (MW 3930, UCON), tie line length (TLL), phase volume ratio (Vr), and crude extract percentage on the partitioning of betaxanthins and sugars in the crude extract. PEG1000-phosphates were more suitable than UCON-salts for the extraction of betaxanthin. Multivariate analysis of variance (MANOVA, α = 0.05) showed that TLL, Vr and crude extract concentration effects were statistically significant (P
An undesirable crispiness loss occurs when some dry fruits reach a critical moisture content () a... more An undesirable crispiness loss occurs when some dry fruits reach a critical moisture content () and their glass transition temperature () matches the storage temperature. Models for sorption isotherms and onsetvalues for dry mango, apple, and banana were used to estimatevalues at 25 and 32 °C. All models yielded > 0.97 but information theory criteria strongly supported GAB in all but one case (40 °C, mango). The Gordon-Taylormodel (GT) yielded highvalues for apple and banana but resulted in = 0.834 for mango. As moisture approached zero, mangoestimates displayed a downward concavity contrasting with a rapidly increasing trend for apple and banana. The Khalloufi-Maslouhi-Ratti (KMR) model foras a function ofshowed a linear behavior. Although the KMR model fitted data with > 0.996, it requires more parameters and whenapproached 0, estimatedvalues increased at a slower rate than for the GT model. In the case of banana and mango, both models predicted approximately the sameat 25 °...
The growth rate and lag phase of Pseudomonas fluorescens, Brochothrix thermosphacta, Salmonella t... more The growth rate and lag phase of Pseudomonas fluorescens, Brochothrix thermosphacta, Salmonella typhlmurium, Enterococcus faecalis, and Staphylococcus aureus were studied in liquid media as a function of temperature, water activity (aw) and solute type. The lag phase lengthened and the growth rate decreased when the temperature was lowered or the aw reduced, and these variations depended on the aw-controlling solute. In general, the magnitude order of the solute effect on the growth rate parameters was glycerol < NaCl < sucrose. This effect can be related to the ability of the solutes to permeate the cell and can be explained by the osmoregulatory mechanism. The specific growth rate was not as sensitive to the aw-controlling solute as the lag phase. A linear extrapolation method was a reliable and convenient method to estimate the minimum aw for microbial growth.
Soluble proteins from surimi wash water (SWW) can be insolubilized by complexing with chitosan-al... more Soluble proteins from surimi wash water (SWW) can be insolubilized by complexing with chitosan-alginate allowing its recovery and the reduction of the organic matter in the processing water discharged from surimi processing plants. The objective of this work was to evaluate the effect of adding soluble proteins recovered from Pacific whiting SWW on the mechanical and functional properties of commercial
Edible barrier films complement modified atmosphere in preserving food quality and extending shel... more Edible barrier films complement modified atmosphere in preserving food quality and extending shelf life. The effects of plasticizer (stearic acid or propylene glycol), pH (4.4 or 9.4) and degree of hydration (58 or 84% RH) on the water vapor permeability, tensile strength and percent elongation at breakpoint were determined for zein and ethylcellulose films. Zein film hydration increased water permeability
An optical method using a custom-built system was investigated to study heating effects on bovine... more An optical method using a custom-built system was investigated to study heating effects on bovine serum albumin (BSA) as affected by pH and ionic strength (IS). Changes in the optical rotation (OR) and transmitted light (TL) of BSA in 0.01 M phosphate buffer at pH 6.1, 7, and 7.9 with IS maintained at 0.04, 0.08, and 0.16 were monitored while
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Papers by J. Antonio Torres