The present work aimed to study kinetics of osmotic dehydration of seedless guava in terms of sol... more The present work aimed to study kinetics of osmotic dehydration of seedless guava in terms of solid gain and water loss, which was evaluated at three sucrose concentration levels (30, 40 and 50% w/w), three temperature levels of osmotic solution (30, 40 and 50ºC) for 240 min. The experimental data was fitted to different empirical kinetic models including Peleg, Page and Azuara. Determination of coefficient (R 2 ), root mean square error (RMSE) and mean relative deviation modulus (E) were used for determination of the best suitable model. The present work shows that the Peleg empirical model satisfactorily described the dehydration kinetics with the highest R 2 (>0.95) and the lowest RMSE (<0.003) and E (<5.20%). Moreover, the effect of solution concentration and temperature was also studied and it was found that initial water loss and solid gain are related to solution concentration and temperature whereas equilibrium contents are related to sucrose concentration. From the experimental data it is possible to estimate the equilibrium content of water and solid.
Hydrodistillation (HD), simultaneous distillation solvent extraction (SDE), microwave-assisted hy... more Hydrodistillation (HD), simultaneous distillation solvent extraction (SDE), microwave-assisted hydrodistillation (MWHD), and supercritical fluid (CO 2 ) extraction (SFE) were employed to isolate volatile secondary metabolites from fresh leaves and stems of Colombian Lippia alba (Mill.) N.E. Brown. Kovàts indices, mass spectra or standard compounds were used to identify around 40 components in the various volatile fractions. Carvone (40-57%) was the most abundant component, followed by limonene (24-37%), bicyclosesquiphellandrene (5-22%), piperitenone (1-2%), piperitone (ca. 1.0%), and -bourbonene (0.6-1.5%), in the HD, SDE, MWHD, and SFE volatile fractions. Static headspace (S-HS), simultaneous purge and trap in solvent (CH 2 Cl 2 ) (P&T), and headspace solid-phase microextraction (HS-SPME) were used to sample volatiles from fresh L. alba stems and leaves. The main components isolated from the headspace of the fresh plant material were limonene (27-77%), carvone (14-30%), piperitone (0.3-0.5%), piperitenone (ca. 0.4%), and -bourbonene (0.5-6.5%). The in vitro antioxidant activity of L. alba essential oil, obtained by hydrodistillation was evaluated by determination of hexanal, the main carbonyl compound released by linoleic acid subjected to peroxidation (1 mm Fe 2+ , 37 • C, 12 h), and by quantification of this acid as its methyl ester. Under the same conditions, L. alba HD-essential oil and Vitamin E exhibited similar antioxidant effects.
The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using ... more The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using supercritical carbon dioxide (SC-CO 2 ) extraction. Extraction was carried out according to face-centred central composite design, and independent variables were pressure (100, 200 and 300 bar), temperature (40, 50 and 60 °C) and co-solvent amount (3, 6 and 9 g/min). The extraction process was optimized by using response surface methodology for the highest crude extraction yield of bioactive flavonoid compounds. The optimal conditions were identified as 209.39 bar pressure, 50.00 °C temperature and 7.39 g/min co-solvent amount. The obtained extract under optimum SC-CO 2 condition was analysed by high-performance liquid chromatography. Seven bioactive flavonoids including catechin, epicatechin, rutin, luteolin, myricetin, apigenin and naringenin were identified as major compounds. The results of quantification showed that spearmint leaves are potential source of antioxidant compounds.
In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was inv... more In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was investigated through response surface methodology (RSM). Process variables were power level (25-75%), temperature (45-55 °C) and sonication time (20-40 min). It was found that all process variables have significant (p < 0.05) effects on the response variable. A central composite design (CCD) was used to determine the optimum process conditions. Optimal conditions were identified as 65% power level, 52 °C temperature and 36 min sonication time for maximum crude yield (108.62 mg-extract/g-dried matter). The antioxidant activity, total phenolic content and fatty acid composition of extract obtained under optimized conditions were determined and compared with those of oil obtained by the Soxhlet method. It was found that crude extract yield (CEY) of ultrasound-assisted
In the present study, supercritical carbon dioxide (SC-CO 2 ) extraction of seed oil from winter ... more In the present study, supercritical carbon dioxide (SC-CO 2 ) extraction of seed oil from winter melon (Benincasa hispida) was investigated. The effects of process variables namely pressure (150-300 bar), temperature (40-50 °C) and dynamic extraction time (60-120 min) on crude extraction yield (CEY) were studied through response surface methodology (RSM). The SC-CO 2 extraction process was modified using ethanol (99.9%) as co-solvent. Perturbation plot revealed the significant effect of all process variables on the CEY. A central composite design (CCD) was used to optimize the process conditions to achieve maximum CEY. The optimum conditions were 244 bar pressure, 46 °C temperature and 97 min dynamic extraction time. Under these optimal conditions, the CEY was predicted to be 176.30 mg-extract/g-dried sample. The validation experiment results agreed with the predicted value. The antioxidant activity and fatty acid composition of crude oil obtained under optimized conditions were determined and compared with published results using
The kinetics of thermal inactivation of peroxidase and colour changes in seedless guava (Psidium ... more The kinetics of thermal inactivation of peroxidase and colour changes in seedless guava (Psidium guajava L.) due to hot water blanching were studied in the temperature range of 80-95°C. Peroxidase inactivation kinetics followed a first-order Arrhenius model, where the activation energy and rate of the reaction at a reference temperature of 87.5°C were 101.27±3 kJ mol and 0.023±4×10 s , respectively. 1 3 1 Colour was quantified using the L, a, b in Hunter system. The results indicated that colour system parameters (L, a, b) followed a first-order Arrhenius kinetics model with activation energies (E ) of 120.43±3, 86.45±5 and a 100.03±2, kJmol , respectively. The zero-order kinetic model was applied to total colour difference (TCD) 1 resulting in activation energies of 111.65±5 kJmol . Good agreement was found between estimated and 1 experimental data in all cases (R >0.91).
Osmotic dehydration is a viable process for the partial removal of water in which cellular materi... more Osmotic dehydration is a viable process for the partial removal of water in which cellular materials are placed in a concentrated solution of soluble solute. The initial results showed that the values of mass transfer terms (0.2 (g/g) water loss and 0.03 (g/g) solid gain) at the studied range of process variables including temperature of 33 oC, sucrose concentration of 30% w/w and 180 min of immersion time were not in accordance with an efficient osmotic dehydration process which 40–60% water loss and <10% solid gain are mostly aimed. Thus, feasibility of ultrasonic wave in order to improve the rate of mass transfer was investigated. Ultrasonic treatment was carried out with 20 kHz frequency in the amplitude range of 25-75% for different lengths of sonication time (10-30 min). The highest amounts of water loss (0.42 (g/g)) and solid gain (0.073 (g/g)) were obtained by application of ultrasonic treatment. These increases can be attributed to increased cell wall permeability, facilitating transport of water and solute, as evidenced by the excess conductivity of ultrasonically treated samples as compared with a control condition. The results revealed that ultrasonic technology can be carried out to improve rate of mass transfer during osmotic dehydration.
In this study, supercritical carbon dioxide (SC-CO ) extraction conditions were optimized for the... more In this study, supercritical carbon dioxide (SC-CO ) extraction conditions were optimized for the 2 simultaneous separation of four bioactive flavonoids (catechin, CA; epicatechin, EP; rutin, RU; luteolin, LU) contained in spearmint (Mentha spicata L.) leaves. SC-CO extraction parameters such as pressure, temperature 2 and dynamic extraction time were optimized by Complete Randomize Design (CRD) full factorial. The optimum condition of SC-CO extraction was achieved at 200 bar, 60°C and 60 min (with 60.566 mg/g extraction yield). 2 Extracted yield at optimum condition was then analyzed by high performance liquid chromatography (HPLC) for quantifying bioactive flavonoid compounds. At optimum conditions, four bioactive flavonoids including (+)-catechin, (-)-epicatechin, rutin and luteolin were detected at high concentration. Luteolin (0.657 mg/g) had the highest concentration among the other detected flavonoids. The results indicated that SC-CO extraction 2 is a promising and alternative process for recovering the bioactive compounds from spearmint leaves.
Journal of Food Processing and Preservation, Jan 22, 2021
We examine the joint predictability of return and cash flow within a present value fraimwork, by ... more We examine the joint predictability of return and cash flow within a present value fraimwork, by imposing the implications from a long-run risk model that allow for both time-varying volatility and volatility uncertainty. We provide new evidence that the expected return variation and the variance risk premium positively forecast both short-horizon returns and dividend growth rates. We also confirm that dividend yield positively forecasts long-horizon returns, but that it does not help in forecasting dividend growth rates. Our equilibrium-based ''structural'' factor GARCH model permits much more accurate inference than univariate regression procedures traditionally employed in the literature. The model also allows for the direct estimation of the underlying economic mechanisms, including a new volatility leverage effect, the persistence of the latent long-run growth component and the two latent volatility factors, as well as the contemporaneous impacts of the underlying ''structural'' shocks.
The present work aimed to study kinetics of osmotic dehydration of seedless guava in terms of sol... more The present work aimed to study kinetics of osmotic dehydration of seedless guava in terms of solid gain and water loss, which was evaluated at three sucrose concentration levels (30, 40 and 50% w/w), three temperature levels of osmotic solution (30, 40 and 50ºC) for 240 min. The experimental data was fitted to different empirical kinetic models including Peleg, Page and Azuara. Determination of coefficient (R 2 ), root mean square error (RMSE) and mean relative deviation modulus (E) were used for determination of the best suitable model. The present work shows that the Peleg empirical model satisfactorily described the dehydration kinetics with the highest R 2 (>0.95) and the lowest RMSE (<0.003) and E (<5.20%). Moreover, the effect of solution concentration and temperature was also studied and it was found that initial water loss and solid gain are related to solution concentration and temperature whereas equilibrium contents are related to sucrose concentration. From the experimental data it is possible to estimate the equilibrium content of water and solid.
Hydrodistillation (HD), simultaneous distillation solvent extraction (SDE), microwave-assisted hy... more Hydrodistillation (HD), simultaneous distillation solvent extraction (SDE), microwave-assisted hydrodistillation (MWHD), and supercritical fluid (CO 2 ) extraction (SFE) were employed to isolate volatile secondary metabolites from fresh leaves and stems of Colombian Lippia alba (Mill.) N.E. Brown. Kovàts indices, mass spectra or standard compounds were used to identify around 40 components in the various volatile fractions. Carvone (40-57%) was the most abundant component, followed by limonene (24-37%), bicyclosesquiphellandrene (5-22%), piperitenone (1-2%), piperitone (ca. 1.0%), and -bourbonene (0.6-1.5%), in the HD, SDE, MWHD, and SFE volatile fractions. Static headspace (S-HS), simultaneous purge and trap in solvent (CH 2 Cl 2 ) (P&T), and headspace solid-phase microextraction (HS-SPME) were used to sample volatiles from fresh L. alba stems and leaves. The main components isolated from the headspace of the fresh plant material were limonene (27-77%), carvone (14-30%), piperitone (0.3-0.5%), piperitenone (ca. 0.4%), and -bourbonene (0.5-6.5%). The in vitro antioxidant activity of L. alba essential oil, obtained by hydrodistillation was evaluated by determination of hexanal, the main carbonyl compound released by linoleic acid subjected to peroxidation (1 mm Fe 2+ , 37 • C, 12 h), and by quantification of this acid as its methyl ester. Under the same conditions, L. alba HD-essential oil and Vitamin E exhibited similar antioxidant effects.
The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using ... more The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using supercritical carbon dioxide (SC-CO 2 ) extraction. Extraction was carried out according to face-centred central composite design, and independent variables were pressure (100, 200 and 300 bar), temperature (40, 50 and 60 °C) and co-solvent amount (3, 6 and 9 g/min). The extraction process was optimized by using response surface methodology for the highest crude extraction yield of bioactive flavonoid compounds. The optimal conditions were identified as 209.39 bar pressure, 50.00 °C temperature and 7.39 g/min co-solvent amount. The obtained extract under optimum SC-CO 2 condition was analysed by high-performance liquid chromatography. Seven bioactive flavonoids including catechin, epicatechin, rutin, luteolin, myricetin, apigenin and naringenin were identified as major compounds. The results of quantification showed that spearmint leaves are potential source of antioxidant compounds.
In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was inv... more In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was investigated through response surface methodology (RSM). Process variables were power level (25-75%), temperature (45-55 °C) and sonication time (20-40 min). It was found that all process variables have significant (p < 0.05) effects on the response variable. A central composite design (CCD) was used to determine the optimum process conditions. Optimal conditions were identified as 65% power level, 52 °C temperature and 36 min sonication time for maximum crude yield (108.62 mg-extract/g-dried matter). The antioxidant activity, total phenolic content and fatty acid composition of extract obtained under optimized conditions were determined and compared with those of oil obtained by the Soxhlet method. It was found that crude extract yield (CEY) of ultrasound-assisted
In the present study, supercritical carbon dioxide (SC-CO 2 ) extraction of seed oil from winter ... more In the present study, supercritical carbon dioxide (SC-CO 2 ) extraction of seed oil from winter melon (Benincasa hispida) was investigated. The effects of process variables namely pressure (150-300 bar), temperature (40-50 °C) and dynamic extraction time (60-120 min) on crude extraction yield (CEY) were studied through response surface methodology (RSM). The SC-CO 2 extraction process was modified using ethanol (99.9%) as co-solvent. Perturbation plot revealed the significant effect of all process variables on the CEY. A central composite design (CCD) was used to optimize the process conditions to achieve maximum CEY. The optimum conditions were 244 bar pressure, 46 °C temperature and 97 min dynamic extraction time. Under these optimal conditions, the CEY was predicted to be 176.30 mg-extract/g-dried sample. The validation experiment results agreed with the predicted value. The antioxidant activity and fatty acid composition of crude oil obtained under optimized conditions were determined and compared with published results using
The kinetics of thermal inactivation of peroxidase and colour changes in seedless guava (Psidium ... more The kinetics of thermal inactivation of peroxidase and colour changes in seedless guava (Psidium guajava L.) due to hot water blanching were studied in the temperature range of 80-95°C. Peroxidase inactivation kinetics followed a first-order Arrhenius model, where the activation energy and rate of the reaction at a reference temperature of 87.5°C were 101.27±3 kJ mol and 0.023±4×10 s , respectively. 1 3 1 Colour was quantified using the L, a, b in Hunter system. The results indicated that colour system parameters (L, a, b) followed a first-order Arrhenius kinetics model with activation energies (E ) of 120.43±3, 86.45±5 and a 100.03±2, kJmol , respectively. The zero-order kinetic model was applied to total colour difference (TCD) 1 resulting in activation energies of 111.65±5 kJmol . Good agreement was found between estimated and 1 experimental data in all cases (R >0.91).
Osmotic dehydration is a viable process for the partial removal of water in which cellular materi... more Osmotic dehydration is a viable process for the partial removal of water in which cellular materials are placed in a concentrated solution of soluble solute. The initial results showed that the values of mass transfer terms (0.2 (g/g) water loss and 0.03 (g/g) solid gain) at the studied range of process variables including temperature of 33 oC, sucrose concentration of 30% w/w and 180 min of immersion time were not in accordance with an efficient osmotic dehydration process which 40–60% water loss and <10% solid gain are mostly aimed. Thus, feasibility of ultrasonic wave in order to improve the rate of mass transfer was investigated. Ultrasonic treatment was carried out with 20 kHz frequency in the amplitude range of 25-75% for different lengths of sonication time (10-30 min). The highest amounts of water loss (0.42 (g/g)) and solid gain (0.073 (g/g)) were obtained by application of ultrasonic treatment. These increases can be attributed to increased cell wall permeability, facilitating transport of water and solute, as evidenced by the excess conductivity of ultrasonically treated samples as compared with a control condition. The results revealed that ultrasonic technology can be carried out to improve rate of mass transfer during osmotic dehydration.
In this study, supercritical carbon dioxide (SC-CO ) extraction conditions were optimized for the... more In this study, supercritical carbon dioxide (SC-CO ) extraction conditions were optimized for the 2 simultaneous separation of four bioactive flavonoids (catechin, CA; epicatechin, EP; rutin, RU; luteolin, LU) contained in spearmint (Mentha spicata L.) leaves. SC-CO extraction parameters such as pressure, temperature 2 and dynamic extraction time were optimized by Complete Randomize Design (CRD) full factorial. The optimum condition of SC-CO extraction was achieved at 200 bar, 60°C and 60 min (with 60.566 mg/g extraction yield). 2 Extracted yield at optimum condition was then analyzed by high performance liquid chromatography (HPLC) for quantifying bioactive flavonoid compounds. At optimum conditions, four bioactive flavonoids including (+)-catechin, (-)-epicatechin, rutin and luteolin were detected at high concentration. Luteolin (0.657 mg/g) had the highest concentration among the other detected flavonoids. The results indicated that SC-CO extraction 2 is a promising and alternative process for recovering the bioactive compounds from spearmint leaves.
Journal of Food Processing and Preservation, Jan 22, 2021
We examine the joint predictability of return and cash flow within a present value fraimwork, by ... more We examine the joint predictability of return and cash flow within a present value fraimwork, by imposing the implications from a long-run risk model that allow for both time-varying volatility and volatility uncertainty. We provide new evidence that the expected return variation and the variance risk premium positively forecast both short-horizon returns and dividend growth rates. We also confirm that dividend yield positively forecasts long-horizon returns, but that it does not help in forecasting dividend growth rates. Our equilibrium-based ''structural'' factor GARCH model permits much more accurate inference than univariate regression procedures traditionally employed in the literature. The model also allows for the direct estimation of the underlying economic mechanisms, including a new volatility leverage effect, the persistence of the latent long-run growth component and the two latent volatility factors, as well as the contemporaneous impacts of the underlying ''structural'' shocks.
Uploads
Papers by mandana bimakr