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Browsing by Author "del Valle, JM"

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Antioxidant activity of crude extract, alkaloid fraction, and flavonoid fraction from boldo (Peumus boldus Molina) leaves
(2004) Quezada, N; Asencio, M; del Valle, JM; Aguilera, JM; Gómez, B
Boldo is an endemic plant from Chile widely used in folk medicine, whose biological (mainly antioxidant) activity has been attributed to the presence of the alkaloid boldine. The aim of this study was to determine the contribution of the flavonoid and other crude fractions from boldo leaves to the antioxidant activity of extracts. The main constituent in the flavonoid fraction was also isolated. The antioxidant activity and reducing power of crude boldo extract and fractions were measured and compared with natural and synthetic antioxidants. The antioxidant activity of boldo leaf extracts came mainly from the flavonoid fraction (44.1%) followed by the alkaloid fraction (15.6%), with catechin and boldine being the main contributors of the antioxidant activity of these 2 fractions (60.9% and 35.6% of the total activity, respectively). On the basis of these results, we propose to use catechin and boldline as markers for the antioxidant activity of boldo leaves. Tailor-made antioxidants to be used in foods can be prepared by enriching these 2 fractions.
Comparision of conventional and supercritical CO2-extracted rosehip oil
(BRAZILIAN SOC CHEMICAL ENG, 2000) del Valle, JM; Bello, S; Thiel, J; Allen, A; Chordia, L
Supercritical CO2 (SCO2) can be utilized to extract oils from a number of plant materials as a nontoxic alternative to hexane, and there is industrial interest in using SCO2 extraction to obtain high-quality oils for cosmetics and other high-value applications, A possible substrate is rosehip (Rosa aff. rubiginosa) seed. The scope of our work was to select SCO2 extraction conditions and to compare cold-pressed, hexane-extracted and SCO2-extracted rosehip oil. We used a fractional factorial experimental design with extraction temperature (T, 40-60 degrees C), extraction pressure (p, 300-500 bar) and dynamic extraction time (t, 90-270 min) as independent variables and yield and color as response variables. Samples of 100 g flaked rosehip seeds were extracted with 21 g CO2/min, following a static extraction (15 min adjustment) period. Resulting data were analyzed using response surface methodology. Extracted oil (4.7-7.1% in our experimental region) increased slightly with p and more pronouncedly with T and specially t. On the other hand, the photometric color index was independent of t but worsened (increased) as a result of an increase in either p or specially T. We extracted five batches of 250 g seeds with 21 g CO2/min at 40 degrees C and 300 bar for 270 min and compared the oil with samples obtained by solvent extraction (a batch of 2.5 kg of laminated seeds was treated with 10 L hexane and rotaevaporated until there was virtually no residual hexane) and cold pressing, by determining color, fatty acid composition, iodine index and saponification index. It was concluded that SCO2 allows an almost complete recovery of rosehip oil (6.5% yield), which is of a better quality than the oil extracted with hexane. Yield was higher than it was when using a cold-pressing process (5.0% yield).
Differential scanning calorimetry of low-moisture apple products
(1998) Aguilera, JM; Cuadros, TR; del Valle, JM
Differential scanning calorimetry (DSC) was used to detect thermal phase transitions in low-moisture apple products, cell walls and related materials. Freeze-dried (FD) apple tissue equilibrated over P2O5 exhibited a T-g around 11 degrees C, similar to that of FD apple juice and slightly higher than the predicted value for the sugar mixture in juice (7 degrees C). Samples also showed an endothermic peak around 50-70 degrees C. Cell wall (CW) material from apple prepared by five different methods and dried over P2O5 showed an endothermic peak (onset around 120 degrees C and peak between 130-160 degrees C) caused by water evaporation. No glass transition was detected in CW preparations for any water activity. The same behavior was observed for microcrystalline cellulose, apple pectin, pine wood and walnut leaves equilibrated over P2O5 Low-moisture CW exhibited a more hydrophobic behavior than apple tissue as revealed by adsorption isotherms. (C) 1998 Elsevier Science Ltd. All rights reserved.
Effects of blanching and calcium infiltration on PPO activity, texture, microstructure and kinetics of osmotic dehydration of apple tissue
(ELSEVIER SCIENCE BV, 1998) del Valle, JM; Aranguiz, V; Leon, H
HTST blanching of apple pieces caused PPO inactivation and sample softening. PPO inactivation was minimal during immersion in water at 40 degrees C, but it increased with temperature after 15 min exposure at 55 to 65 degrees C. Associated softening decreased when adding 0.6% CaCl2 to the blanching medium. Samples blanched at 40 degrees C were softer than those heated at 55 degrees C in calcium solution, thus suggesting PME activation after 15 min at 55 degrees C. Vacuum infiltration of apple pieces caused cellular damage that increased as the applied pressure increased from 59.9 to 9.3 kPa, and was unaffected by the speed of restoration of ambient pressure. Texture improved when using aqueous CaCl2 solutions instead of distilled water, but no positive effect was observed for HTST blanched apples by vacuum infiltration of calcium. As a result of osmotic dehydration (OD) with aqueous sucrose solutions apple pieces lost water and texture and gained sucrose. HTST-blanched apple pieces suffered extensive material losses during OD and had poor final textures. Untreated apples and samples treated with 0.6% CaCl2 at 40 degrees C (Ih) behaved similarly. Samples treated with 0.6% CaCl2 at 55 degrees C (15 min) and vacuum (9.3 kPa) infiltrated with 2% CaCl2 had the largest sucrose gains and best final textures. Improved texture was generally associated with improved maintenance of sample microstructure. (C) 1999 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology. All rights reserved.
Extraction kinetics of pre-pelletized Jalapeno peppers with supercritical CO2
(ELSEVIER SCIENCE BV, 2003) del Valle, JM; Jimenez, M; de la Fuente, JC
The aim of this work was to assess and model supercritical carbon dioxide (ScCO2) extraction kinetics of pre-pelletized Jalapeno peppers (Capsicum annuum L.). Pepper flakes were conditioned to low moisture, ground finely and pelletized at high pressure, and pellets were subsequently ground and size classified. The effects of average sample particle size (D-p = 0.28-3.19 mm) and superficial solvent velocity (U-s = 0.14-2.62 mm s(-1)) were evaluated at 40 degreesC and 120 or 320 bar. Extraction rate increased as a result of a decrease in D-p. It also increased as a result of an increase in US at 120 bar, but the effect was almost negligible at 320 bar. Integral extraction yields of capsicum oleoresin and capsaicinoids were approximate to0.102 g g(-1) and approximate to240 mg kg(-1), respectively, independent of extraction conditions. External mass transfer coefficients (kr) increased with U-s, but this effect was less pronounced than commonly reported in the literature. Values of kr increased as D-p or process pressure decreased, due respectively to increments in specific area and improvements in transport properties. Internal mass transfer coefficients, on the other hand, were 5.3 x 10(-8) m s(-1) at 40 degreesC and 120 bar, and 34.7 x 10(-8) m s(-1) at 40 degreesC and 320 bar. Solutes were effectively liberated from the original matrix with our multistage pretreatment, so that the fraction of free solute did not depend on D-p (alpha = 0.46). Pseudosolubilities for capsicum oleoresin in ScCO2 ( approximate to 2100 mg l(-1) at 40 degreesC and 120 bar; approximate to13,700 mg l(-1) solute/CO2 at 40 C and 320 bar) were of the same order of magnitude as corresponding true solubilities of capsaicin (5600 and 11,800 mg l(-1) respectively). Estimated true solubilities of chlorophyll-a in ScCO2 (2 mg l(-1) at 40 degreesC and 120 bar; 18 mg l(-1) at 40 degreesC and 320 bar), on the other hand, were orders of magnitude smaller, which justifies a much slower extraction rate for green pigments than pungent compounds. Thus, oleoresin obtained after 4 h at 40 degreesC and 120 bar had a very attractive light yellow tinge. (C) 2002 Elsevier Science B.V. All rights reserved.
Extraction of boldo (Peumus boldus M.) leaves with supercritical CO2 and hot pressurized water
(ELSEVIER, 2005) del Valle, JM; Rogalinski, T; Zetzl, C; Brunner, G
High-activity fractions in boldo leaves were extracted with supercritical CO2 (SC-CO2) and hot pressurized water (HPW). Total yield after 3 h of extraction (0.6-3.5%) in low-pressure SC-CO2 experiments increased with process pressure (60-150 bar) and decreased with temperature (30-60 degreesC), as expected. The extract obtained with SC-CO2 at 50 degreesC and 90 bar contained approximately 50% of essential oil components. In higher pressure experiments with solvent mixtures. the yield increased with pressure (300-450 bar) and modifier concentration (2-10% ethanol), ranging 0.14-1.95 ppm for the alkaloid boldine and 1.8-4.81%. for total solids following 1.5 h treatment at 50 degreesC. Boldine recovery was solubility-controlled, reaching 7.4 ppm after 7-h extraction at 450 bar and 50 degreesC using an ethanol-SC-CO2 mixture (5% co-solvent). Boldine solubility and yield decreased when using pure CO2 at higher pressure (600 bar, 50 degreesC). The extract yield after 3 h batch-wise HPW extraction increased from 36.9% at 100 degreesC to 53.2% at 125 degreesC. and then decreased as temperature was increased to 175 degreesC. Boldine yield decreased from 26.8 ppm at 100 degreesC to 0-7 ppm at 125 degreesC. and was negligible at greater than or equal to 150 degreesC. The essential oil yield increased to a maximum at 110 degreesC and was negligible at greater than or equal to 150 degreesC also. The ranking of antioxidant potency of various extracts was as follows: HPW at 110 degreesC > methanol (soxhlet extraction) much greater than high-pressure SC-CO2 with or without polar co-solvent > low-pressure SC-CO2. (C) 2004 Elsevier Ltd. All rights reserved.
Glass transitions and shrinkage during drying and storage of osmosed apple pieces
(ELSEVIER SCIENCE BV, 1998) del Valle, JM; Cuadros, TRM; Aguilera, JM
The relationship between shrinkage during drying and 'glass'-'rubber' transitions of apple tissue was studied. Our results did not indicate that structural collapse of apple pieces can be reduced by diminishing the difference Delta T between drying temperature and glass transition temperature (T-g) of the fruit matrix. Apple shrinkage was not consistently depressed by reducing drying temperature, infusing larger amounts of T-g-depressing agents (sucrose, maltose, lactose) or infusing similar amounts of solutes with higher anhydrous T(g)s. However, sugars added during osmotic dehydration pretreatments help decreasing structural collapse during subsequent air drying, which was reflected by a 20-65% increase in final volume of samples treated with 50% sucrose and maltose solutions as compared to an air-dried, control sample. Dried samples remained in the "rubbery" state after drying and shrunk during subsequent storage. (C) 1999 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology. All rights reserved.
Microstructural effects on internal mass transfer of lipids in prepressed and flaked vegetable substrates
(ELSEVIER, 2006) del Valle, JM; Germain, JC; Uquiche, E; Zetzl, C; Brunner, G
Predictive models that describe supercritical fluid extraction (SCFE) processes would be welcomed to support its industrial application, particularly for the supercritical carbon dioxide (SC-CO2) extraction of vegetable oil from seeds subjected to common high-shear pretreatments. This work explores the application of microstructure-extractability relationships for modeling the SCFE of lipids from vegetable substrates. We measured the extraction kinetics of prepressed rapeseeds, olive husks, and flaked rosehip seeds, with SC-CO2 at 313 K and 30 MPa, and simulated the extractions using a shrinking-core model. Model parameters included the oil solubility and film mass transfer coefficient from literature correlations, and an effective diffusivity (D-e) inside the porous particles. We determined that D, could be calculated as D-12 x F, where D-12 is the diffusivity of oil in CO2, and F is a microstructural correction factor, estimated as the ratio between the final porosity (epsilon(p) from Hg porosimetry) and pore-network tortuosity (tau, from fractal-texture analysis of binary light-microscopy irnages) of the substrates. Simulations adjusted the experimental data reasonably well (5.4% < mean percent error < 15%). Additionally, best-fit estimates of D, were obtained for literature data on SC-CO2 extraction of lipids from prepressed and flaked seeds. Resulting values of F did not depend on particle size and spanned a narrow range - one order of magnitude (0.030-0.29) - as it would be expected when comparing similar systems. Although further work will be required to refine the relationship between tau and fractal parameters, or between tau and the hysteresis of Hg infiltration, this work demonstrates that is possible to develop predictive models for SCFE of solid substrates subjected to high-shear pretreatments. (c) 2005 Published by Elsevier B.V.
Natural convection retards supercritical CO(2) extraction of essential oils and lipids from vegetable substrates
(AMER CHEMICAL SOC, 2005) Germain, JC; del Valle, JM; de la Fuente, JC
External mass-transfer coefficients (k(f)) during supercritical fluid extraction (SCFE) of high-solubility solutes, under solvent upflow conditions and low superficial velocities, can be small because of the negative influence of natural convection phenomena. A shrinking-core model for mass transfer was used to estimate best-fit values of k(f) for data on SCFE of lipids from prepressed rapeseeds. Values of k(f) at a high Reynolds number (Re = 14.1) were similar when using solvent upflow or downflow, but k(f) at lower Re (1.57) was 3.6 times smaller when using solvent upflow than that predicted from a literature correlation for downflow conditions. These k(f)'s are consistent with values estimated by fitting literature data, or gathered from various sources under similar, nonadequate conditions (solvent upflow under low Re) for the extraction of both fatty and essential oils. Care is advisable when employing best-fit values of k(f) from laboratory data for process design purposes, especially when sizing of the solvent pumps for the experiments is questionable.
Particle size effects on supercritical CO2 extraction of oil-containing seeds
(AMER OIL CHEMISTS SOC A O C S PRESS, 2002) del Valle, JM; Uquiche, EL
Rosehip seeds were milled, sieved, and extracted with 26.3 g/g substrate/h of supercritical carbon dioxide (CO2) at 40degreesC and 300 bar. The extraction kinetics were characterized by an initial solubility-control led period (8.78 g oil/kg CO2 at 40degreesC and 300 bar), followed by a transition period to a final mass transfer-controlled process. The integral yield of oil approached an asymptotic value that was dependent on the particle size of the substrate: 57.1 g oil/kg dry oil-free substrate (large particles), 171.0 g/kg (medium-size particles), or 391.5 g/kg (small particles). Based on gravimetric determinations and microscopic analysis, our size-classification process segregated seed parts having different oil contents. Particles greater than or equal to0.85 mm were mainly composed of tough, lignified testa fragments devoid of oil, whereas particles less than or equal to0.425 mm contained mostly brittle, oil-rich germ fragments. The segregation of seed in fractions with different oil contents may be a common occurrence in supercritical extraction experiments, especially for seeds with thick and/or hard testa and small germ, whose fractions can be separated by sieving.
Recovery of antioxidants from boldo (Peumus boldus M.) by conventional and supercritical CO₂ extraction
(2004) del Valle, JM; Godoy, C; Asencio, M; Aguilera, JM
Boldo (Peumus boldus M.) is a native plant from Chile that has been used is traditional medicine to treat digestive and/or hepatobiliary disorders. An attempt was made in this work to extract antioxidant compounds from boldo using conventional solvents and supercritical carbon dioxide (SCCO2). Yield of soluble solids (SS), boldine, and compounds with antioxidant activity varied depending on part plant, solvent and extraction conditions. Following 24 h extraction, the highest yield was 33.4% (w/w, dry basis) of SS with 70:30 ethanol/water (v/v) mixture at 70 degreesC. Yield of alcoholic extractions increased as the temperature was raised from 20 to 70 degreesC, but the total antioxidant activity (free radical DPPH method) was maximal in boldo leaf extracts with aqueous ethanol at 50 degreesC (1648 TEAC/g dry leaf). Boldine concentration was maximal (12%) in boldo bark extracted with acidulated water, and decreased with extraction time when methanol or ethanol/water mixtures were used. No boldine was detected in boldo leaf extracts. The contribution of boldine to the antioxidant activity of boldo extracts was low, specially when using aqueous ethanol as solvent, and/or boldo leaf instead of boldo bark as substrate. Yield Of SCCO2 extraction was approximate to3% SS. Only non-polar compounds with limited antioxidant activity (0.08 TEAC/g extract) were extracted by SCCO2. (C) 2004 Elsevier Ltd. All rights reserved.
Solubility of boldo leaf antioxidant components (Boldine) in high-pressure carbon dioxide
(ELSEVIER, 2005) de la Fuente, JC; Quezada, N; del Valle, JM
This work contributes to the development of an enrichment process for antioxidant compounds in aqueous alcoholic extracts of boldo (Peumus boldus M.) leaves by using high-pressure CO2 as the solvent. Specifically we measured the high-pressure solubility (y(2), molar fraction) of a selected bioactive compound in boldo leaves (boldine) in CO, as a function of system temperature (298 K <= T <= 333 K) and pressure (8 MPa <= P <= 40 MPa). Experimental data was correlated by using a density-based model which is valid for solvent densities > 607 kg/m(3). Predicted solubility values are low (4 x 10(-7) <= y(2) <= 6 x 10(-5)) but comparable with those of nitrogen-containing organic compounds with similar molecular weight (327.4 Da) and solubility parameter (28.3 MPa (0.5) at 313 K) as boldine. (c) 2005 Elsevier B.V. All rights reserved.
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.
Supercritical CO2 extraction of Chilean hop (Humulus lupulus) ecotypes
(JOHN WILEY & SONS LTD, 2003) del Valle, JM; Rivera, O; Teuber, O; Palma, MT
Hops (Humulus lupulus L) have very stringent requirements of diurnal light hours during flowering. Thus, the beer industry is permanently assessing new agricultural land to grow hops, southern Chile being an excellent candidate for their introduction. Supercritical carbon dioxide extraction procedures were implemented to assess Chilean hop ecotypes. Based on results of a preliminary study with commercial samples (cv Nugget), 200 bar and 40degreesC were selected as extraction conditions. Very limited increases in extraction rate were observed when applying pressures >200 bar; such pressures did not speed up the extraction of alpha-acids (bitter flavor principles), but rather increased the co-extraction of undesirable compounds (hard resins and chlorophyll pigments). On the other hand, the effects of retrograde condensation phenomena were just starting to subside at 200 bar, and thermal damage of samples could increase at >40 degreesC. Ground cone samples of five local hop ecotypes, originating from Osorno, La junta, Coyhaique and Elizalde Lake, were subsequently tested. Osorno exhibited a higher yield (65 g kg(-1) oleoresin/substrate) than other Chilean ecotypes. Moreover, Osorno extract had a light yellowish color, as well as a higher content of bitter flavors (157 g kg(-1) alpha-acid/extract) and 1.5-7.1 times more representative aroma compounds than extracts of the other ecotypes. However, all these indicators were very low compared with the commercial Nugget sample (134 g kg(-1) oleoresin/substrate, 383 g kg(-1) alpha-acid/extract, 14 times more aroma compounds than Osorno ecotype). (C) 2003 Society of Chemical Industry.
Supercritical CO2 processing of pretreated rosehip seeds: effect of process scale on oil extraction kinetics
(ELSEVIER SCIENCE BV, 2004) del Valle, JM; Rivera, O; Mattea, M; Ruetsch, L; Daghero, J; Flores, A
Rosehip oil was extracted from milled seeds with supercritical carbon dioxide (SC-CO2). The effects of sample pretreatment and interstitial solvent velocity (0.40-2.45 mm/s) on kinetics of extraction (oil yield versus time) were evaluated at 40degreesC and 300 bar, and at 50degreesC and 400 bar in a one-pass screening system (laboratory scale). Seeds were grinded in a hammer mill or a roller mill with a gap of adjustable thickness, and samples from the hammer mill were further size-classified. Data was fitted to a two-stage model, with extraction rate controlled by oil solubility initially, and by mass transfer in the solid phase at the end. The mass transfer coefficient and axial dispersion of the solute in the supercritical phase, and the solubility of the oil in SC-CO2 were estimated as a function of the extraction conditions using literature correlations, and the "free" oil content (X-f) and mass transfer coefficient in the solid substrate (k(s)) were used as fitting parameters. Both X-f (0.026-0.030 g oil/g substrate) and k(s) (0.6-0.9 x 10(-9) m/s) depended on sample pretreatment but not on the assayed extraction conditions, as expected. Free oil represented 33-41% of the total content, and effective diffusivities of oil in the solid were 330-710 times smaller than binary diffusivities of oil in SC-CO2. Based on best-fitting parameters for kinetic data at the laboratory-scale, extraction kinetics was simulated for a process development unit with solvent recycle (scale-up factor of 30 for the volume of the extraction vessel). It was observed that extraction was slower at the pilot plant than laboratory scale due probably to flow heterogeneity in the extraction vessel, increased dispersion of solute between the extraction and separation vessels, entrainment of oil droplets in recycled gaseous stream, or a combination of these three effects. (C) 2003 Elsevier B.V. All rights reserved.
Volumetric procedure to assess infiltration kinetics and porosity of fruits by applying a vacuum pulse
(ELSEVIER SCI LTD, 1998) del Valle, JM; Aranguiz, V; Diaz, L
In this work an improved 'volumetric' procedure was developed to assess fruit porosity using a hydrodynamic mechanism, to replace the 'gravimetric' alternative proposed by Fito in 1994 This procedure also facilitated study of the kinetics of liquid infiltration in fruit pieces as a result of the application of a vacuum pulse. It was observed that apparent porosity increased as the absolute pressure of the vacuum pulse decreased, probably as a result of tissue damage or deformation-relaxation phenomena. In the case of apples, porosity increased from an initial value of about 0.20 to about 0.30, and this increase took place in a relatively short period (about 1 min after vacuum rupture). These values did not appear to be significantly (P < 0.01) affected by either apple variety (Granny Smith or Starking Delicious) or sucrose concentration (0 or 16% w/w) in the infiltrated solution, but increased during ambient storage. Porosity values for bananas and peaches are also reported. (C) 1998 Elsevier Science Limited. All rights reserved.

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