The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Reinhold Carle - One of the best experts on this subject based on the ideXlab platform.
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Colour stability of canned strawberries using black carrot and elderberry Juice Concentrates as natural colourants
European Food Research and Technology, 2007Co-Authors: Dietmar R Kammerer, Oliver Maier, Sandra Schillmöller, Andreas Schieber, Reinhold CarleAbstract:Besides texture degradation and aroma loss colour fading and browning of processed fruits, in particular strawberries, displaying comparatively low amounts of non-acylated anthocyanins, still pose a serious problem. Therefore, in the present study the colour of texture-improved canned strawberries was stabilised using commercial Concentrates from black carrots and elderberries as natural colourants. CIE L ^* a ^* b ^* values of the fruit surface and of the brine solutions were monitored over a period of 24 weeks under light exposure. Furthermore, the contents of individual anthocyanins were analysed by HPLC-DAD. The colour of the processed control fruits (without added colourant) was unacceptable even at the beginning of the storage. Their anthocyanin contents were reduced by more than 85% at the end of the storage period. In contrast, the colour of canned strawberries containing black carrot and elderberry anthocyanins was significantly improved. Colour difference values Δ E ^* of black carrot-coloured strawberries were found to be smaller than those of the samples containing elderberry concentrate as a colourant. This could be ascribed to the presence of acylated anthocyanins in the first exhibiting exceptional storage stability, while all non-acylated pigments were degraded. The chill brining process for fruit firming markedly affected pigment stability, which can be attributed to enzymes that are still active at cold storage conditions.
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Colour stability of canned strawberries using black carrot and elderberry Juice Concentrates as natural colourants
European Food Research and Technology, 2007Co-Authors: Dietmar R Kammerer, Oliver Maier, Sandra Schillmöller, Andreas Schieber, Reinhold CarleAbstract:Besides texture degradation and aroma loss colour fading and browning of processed fruits, in particular strawberries, displaying comparatively low amounts of non-acylated anthocyanins, still pose a serious problem. Therefore, in the present study the colour of texture-improved canned strawberries was stabilised using commercial Concentrates from black carrots and elderberries as natural colourants. CIE L * a * b * values of the fruit surface and of the brine solutions were monitored over a period of 24 weeks under light exposure. Furthermore, the contents of individual anthocyanins were analysed by HPLC-DAD. The colour of the processed control fruits (without added colourant) was unacceptable even at the beginning of the storage. Their anthocyanin contents were reduced by more than 85% at the end of the storage period. In contrast, the colour of canned strawberries containing black carrot and elderberry anthocyanins was significantly improved. Colour difference values ΔE * of black carrot-coloured strawberries were found to be smaller than those of the samples containing elderberry concentrate as a colourant. This could be ascribed to the presence of acylated anthocyanins in the first exhibiting exceptional storage stability, while all non-acylated pigments were degraded. The chill brining process for fruit firming markedly affected pigment stability, which can be attributed to enzymes that are still active at cold storage conditions. © Springer-Verlag 2007.
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evaluation of different methods for the production of Juice Concentrates and fruit powders from cactus pear
Innovative Food Science and Emerging Technologies, 2006Co-Authors: Markus R Moshammer, Florian C. Stintzing, Reinhold CarleAbstract:Abstract The present work aimed both at improvement and extension of a previously developed process for the production of cactus pear Juice. The total yield was increased by 10% through processing whole instead of peeled fruits and by further optimisation of pulp enzymation. As an alternative to HTST pasteurisation, cross-flow microfiltration was applied for non-thermal cactus pear Juice preservation. Juice Concentrates and fruit powders were produced by rotary evaporation and freeze drying at laboratory scale and compared to products obtained at pilot plant-scale applying a three-stage column evaporator and spray drying, respectively. To monitor process-related quality changes, the resulting products were characterised in terms of colour and selected quality parameters. For both Juice Concentrates and fruit powders, initial colour characteristics were retained. In addition to betanin isomerisation, C 11 -epimerisation of proline-betaxanthin was demonstrated to be a valuable indicator of the respective heat treatment applied. Whereas no adverse reactions were observed during Juice production, non-enzymatic browning and HMF formation were found after concentration at pilot plant-scale and freeze drying, respectively. Industrial relevance Although cactus pear meets all requirements for food colouring purposes, no attempt has been made so far to exploit this potential. The feasibility of processing cactus pear Juice into Concentrates and fruit powders was demonstrated in this study. In contrast to single-strength Juice, Concentrates and powders are easier to handle during transportation and storage and also open further fields of application that may promote cactus pear fruit processing at industrial scale in the future.
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Evaluation of different methods for the production of Juice Concentrates and fruit powders from cactus pear
Innovative Food Science and Emerging Technologies, 2006Co-Authors: Markus R. Moßhammer, Florian C. Stintzing, Reinhold CarleAbstract:The present work aimed both at improvement and extension of a previously developed process for the production of cactus pear Juice. The total yield was increased by 10% through processing whole instead of peeled fruits and by further optimisation of pulp enzymation. As an alternative to HTST pasteurisation, cross-flow microfiltration was applied for non-thermal cactus pear Juice preservation. Juice Concentrates and fruit powders were produced by rotary evaporation and freeze drying at laboratory scale and compared to products obtained at pilot plant-scale applying a three-stage column evaporator and spray drying, respectively. To monitor process-related quality changes, the resulting products were characterised in terms of colour and selected quality parameters. For both Juice Concentrates and fruit powders, initial colour characteristics were retained. In addition to betanin isomerisation, C11-epimerisation of proline-betaxanthin was demonstrated to be a valuable indicator of the respective heat treatment applied. Whereas no adverse reactions were observed during Juice production, non-enzymatic browning and HMF formation were found after concentration at pilot plant-scale and freeze drying, respectively. Industrial relevance: Although cactus pear meets all requirements for food colouring purposes, no attempt has been made so far to exploit this potential. The feasibility of processing cactus pear Juice into Concentrates and fruit powders was demonstrated in this study. In contrast to single-strength Juice, Concentrates and powders are easier to handle during transportation and storage and also open further fields of application that may promote cactus pear fruit processing at industrial scale in the future. © 2006 Elsevier Ltd. All rights reserved.
Yus Aniza Yusof - One of the best experts on this subject based on the ideXlab platform.
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modelling of rheological behaviour of guava pomelo and soursop Juice Concentrates via shear rate temperature concentration superpositioning
Journal of Food Science and Technology-mysore, 2018Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, Norazlin Abdullah, Rosnita A TalibAbstract:The steady-state flow test was conducted on pink-fleshed guava, pink-fleshed pomelo and soursop Juice Concentrates using a rheometer to understand its rheological behaviour. The power law model was used and a master-curve was created using the shear rate-temperature-concentration superposition technique to predict rheological properties from a wide range of temperatures and concentrations. All three Juice Concentrates undergo a double horizontal shift whilst the pink-fleshed guava required an additional vertical shift. The final equations show shear-thinning behaviour of pink-fleshed guava, pink-fleshed pomelo and soursop with flow behaviour index of 0.2217, 0.7507 and 0.6347, respectively. The final master-curve predicts shear stress at wide range of shear rates, i.e. between 10−2 and 106 s−1 for the pink-fleshed guava, 100 and 106 s−1 for the pink-fleshed pomelo and 100 and 107 s−1 for the soursop. The results provide useful information and effective technique to predict fruit Juice Concentrates behaviour affected by heat changes during processing.
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modeling the rheological behavior of thermosonic extracted guava pomelo and soursop Juice Concentrates at different concentration and temperature using a new combination model
Journal of Food Processing and Preservation, 2018Co-Authors: Norazlin Abdullah, Nyuk Ling Chin, Yus Aniza Yusof, Rosnita A TalibAbstract:This study has modeled the rheological behavior of thermosonic extracted pink-fleshed guava, pink-fleshed pomelo, and soursop Juice Concentrates at different concentrations and temperatures. The effects of concentration on consistency coefficient (K) and flow behavior index (n) of the fruit Juice Concentrates was modeled using a master curve which utilized the concentrationtemperature shifting to allow a general prediction of rheological behaviors covering a wide concentration. For modeling the effects of temperature on K and n, the integration of two functions from the Arrhenius and logistic sigmoidal growth equations has provided a new model which gave better description of the properties. It also alleviated the problems of negative region when using the Arrhenius model alone. The fitted regression using this new model has improved coefficient of determination, R2 values above 0.9792 as compared to using the Arrhenius and logistic sigmoidal models alone, which presented minimum R2 of 0.6243 and 0.9440, respectively.
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modelling of rheological behaviour of soursop Juice Concentrates using shear rate temperature concentration superposition
Journal of Food Engineering, 2013Co-Authors: Meei Chien Quek, Nyuk Ling Chin, Yus Aniza YusofAbstract:The effect of temperature and concentration on rheological behaviour of freeze dried soursop Juice Concentrates were investigated using a rheometer over a wide range of temperatures (10–70 °C) and concentrations (10–50 °Brix) at shear rates of 0–400 1/s. The Power law is the best fitted model to the rheological data due to the high value of coefficient of determination (R2 = 0.9989). The soursop Juice Concentrates exhibited shear thinning or pseudoplastic behaviour with n < 1. The consistency coefficients dependency on temperature and concentration were well described by Arrhenius relationship and exponential relationship respectively. The flow activation energy of soursop Juice Concentrates were 8.32–30.48 kJ/mol. The superposition technique with Power law model sufficiently modelled the overall rheological characteristics of soursop Juice Concentrates into a single master curve using shift factors based on double shifting steps with R2 = 0.9184. This technique also showed that the soursop Juice Concentrates increases in viscosity and pseudoplasticity behaviour with concentration.
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Modelling of rheological behaviour of soursop Juice Concentrates using shear rate–temperature–concentration superposition
Journal of Food Engineering, 2013Co-Authors: Meei Chien Quek, Nyuk Ling Chin, Yus Aniza YusofAbstract:The effect of temperature and concentration on rheological behaviour of freeze dried soursop Juice Concentrates were investigated using a rheometer over a wide range of temperatures (10–70 °C) and concentrations (10–50 °Brix) at shear rates of 0–400 1/s. The Power law is the best fitted model to the rheological data due to the high value of coefficient of determination (R2 = 0.9989). The soursop Juice Concentrates exhibited shear thinning or pseudoplastic behaviour with n < 1. The consistency coefficients dependency on temperature and concentration were well described by Arrhenius relationship and exponential relationship respectively. The flow activation energy of soursop Juice Concentrates were 8.32–30.48 kJ/mol. The superposition technique with Power law model sufficiently modelled the overall rheological characteristics of soursop Juice Concentrates into a single master curve using shift factors based on double shifting steps with R2 = 0.9184. This technique also showed that the soursop Juice Concentrates increases in viscosity and pseudoplasticity behaviour with concentration.
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modelling of rheological behaviour of pummelo Juice Concentrates using master curve
Journal of Food Engineering, 2009Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, S M Chan, T G Chuah, Rosnita A TalibAbstract:Abstract The rheological behaviour of freeze-dried-concentrated pummelo Juice was modelled to investigate the effects of temperature and concentration on its fluid type and viscosity using a rotational viscometer at shear rates ranging from 1 to 400 s −1 . The effect of concentration measured by its total soluble solids content resulted in the Juice Concentrates behaving towards shear thinning or pseudoplastic behaviour with flow behaviour index values, n n values at all three investigated concentrations, 20, 30 and 50 °Brix. The consistency coefficient decreases with temperature but increases with total soluble solid contents. Modelling the rheological behaviour of pummelo Juice Concentrates using the master-curve yielded results over a range of temperature to overlap on a single line, which allows generalisation of flow behaviour and characteristics. The master-curve plots confirmed that the Juice viscosity and pseudoplasticity increase with concentration with high regression coefficients, R 2 > 0.98.
Rosnita A Talib - One of the best experts on this subject based on the ideXlab platform.
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modelling of rheological behaviour of guava pomelo and soursop Juice Concentrates via shear rate temperature concentration superpositioning
Journal of Food Science and Technology-mysore, 2018Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, Norazlin Abdullah, Rosnita A TalibAbstract:The steady-state flow test was conducted on pink-fleshed guava, pink-fleshed pomelo and soursop Juice Concentrates using a rheometer to understand its rheological behaviour. The power law model was used and a master-curve was created using the shear rate-temperature-concentration superposition technique to predict rheological properties from a wide range of temperatures and concentrations. All three Juice Concentrates undergo a double horizontal shift whilst the pink-fleshed guava required an additional vertical shift. The final equations show shear-thinning behaviour of pink-fleshed guava, pink-fleshed pomelo and soursop with flow behaviour index of 0.2217, 0.7507 and 0.6347, respectively. The final master-curve predicts shear stress at wide range of shear rates, i.e. between 10−2 and 106 s−1 for the pink-fleshed guava, 100 and 106 s−1 for the pink-fleshed pomelo and 100 and 107 s−1 for the soursop. The results provide useful information and effective technique to predict fruit Juice Concentrates behaviour affected by heat changes during processing.
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modeling the rheological behavior of thermosonic extracted guava pomelo and soursop Juice Concentrates at different concentration and temperature using a new combination model
Journal of Food Processing and Preservation, 2018Co-Authors: Norazlin Abdullah, Nyuk Ling Chin, Yus Aniza Yusof, Rosnita A TalibAbstract:This study has modeled the rheological behavior of thermosonic extracted pink-fleshed guava, pink-fleshed pomelo, and soursop Juice Concentrates at different concentrations and temperatures. The effects of concentration on consistency coefficient (K) and flow behavior index (n) of the fruit Juice Concentrates was modeled using a master curve which utilized the concentrationtemperature shifting to allow a general prediction of rheological behaviors covering a wide concentration. For modeling the effects of temperature on K and n, the integration of two functions from the Arrhenius and logistic sigmoidal growth equations has provided a new model which gave better description of the properties. It also alleviated the problems of negative region when using the Arrhenius model alone. The fitted regression using this new model has improved coefficient of determination, R2 values above 0.9792 as compared to using the Arrhenius and logistic sigmoidal models alone, which presented minimum R2 of 0.6243 and 0.9440, respectively.
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modelling of rheological behaviour of pummelo Juice Concentrates using master curve
Journal of Food Engineering, 2009Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, S M Chan, T G Chuah, Rosnita A TalibAbstract:Abstract The rheological behaviour of freeze-dried-concentrated pummelo Juice was modelled to investigate the effects of temperature and concentration on its fluid type and viscosity using a rotational viscometer at shear rates ranging from 1 to 400 s −1 . The effect of concentration measured by its total soluble solids content resulted in the Juice Concentrates behaving towards shear thinning or pseudoplastic behaviour with flow behaviour index values, n n values at all three investigated concentrations, 20, 30 and 50 °Brix. The consistency coefficient decreases with temperature but increases with total soluble solid contents. Modelling the rheological behaviour of pummelo Juice Concentrates using the master-curve yielded results over a range of temperature to overlap on a single line, which allows generalisation of flow behaviour and characteristics. The master-curve plots confirmed that the Juice viscosity and pseudoplasticity increase with concentration with high regression coefficients, R 2 > 0.98.
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prediction of physicochemical properties of pummelo Juice Concentrates as a function of temperature and concentration
International Journal of Food Engineering, 2008Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, S M Chan, T G Chuah, Rosnita A TalibAbstract:The properties of pummelo Juice were studied by measuring its chemical and physical composition. Pummelo fruit Juice was freeze-concentrated to a concentration varying from 10 to 50 °Brix for investigation at temperature ranging from 6 to 75 °C. The fresh pummelo Juice compositions in terms of moisture content, ash, fat, protein, fibre, carbohydrates, and vitamin C are comparable to existing literature. The water activity, pH and acidity were predictable linearly by its concentration measured in °Brix. The density of pummelo Juice was well-predicted using linear regressions with a single parameter (i.e., concentration), giving R2>0.983 and with a temperature at R2>0.921. The density of pummelo Juice showed stronger dependence on its concentration than on the temperature. With multiple linear regressions, the density could be predicted by the equation, with an R2 of 0.9877. As such, these predictions are useful in the Juice processing industry as densities variant by concentration and temperature are important during the pasteurization process.
Nyuk Ling Chin - One of the best experts on this subject based on the ideXlab platform.
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modelling of rheological behaviour of guava pomelo and soursop Juice Concentrates via shear rate temperature concentration superpositioning
Journal of Food Science and Technology-mysore, 2018Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, Norazlin Abdullah, Rosnita A TalibAbstract:The steady-state flow test was conducted on pink-fleshed guava, pink-fleshed pomelo and soursop Juice Concentrates using a rheometer to understand its rheological behaviour. The power law model was used and a master-curve was created using the shear rate-temperature-concentration superposition technique to predict rheological properties from a wide range of temperatures and concentrations. All three Juice Concentrates undergo a double horizontal shift whilst the pink-fleshed guava required an additional vertical shift. The final equations show shear-thinning behaviour of pink-fleshed guava, pink-fleshed pomelo and soursop with flow behaviour index of 0.2217, 0.7507 and 0.6347, respectively. The final master-curve predicts shear stress at wide range of shear rates, i.e. between 10−2 and 106 s−1 for the pink-fleshed guava, 100 and 106 s−1 for the pink-fleshed pomelo and 100 and 107 s−1 for the soursop. The results provide useful information and effective technique to predict fruit Juice Concentrates behaviour affected by heat changes during processing.
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modeling the rheological behavior of thermosonic extracted guava pomelo and soursop Juice Concentrates at different concentration and temperature using a new combination model
Journal of Food Processing and Preservation, 2018Co-Authors: Norazlin Abdullah, Nyuk Ling Chin, Yus Aniza Yusof, Rosnita A TalibAbstract:This study has modeled the rheological behavior of thermosonic extracted pink-fleshed guava, pink-fleshed pomelo, and soursop Juice Concentrates at different concentrations and temperatures. The effects of concentration on consistency coefficient (K) and flow behavior index (n) of the fruit Juice Concentrates was modeled using a master curve which utilized the concentrationtemperature shifting to allow a general prediction of rheological behaviors covering a wide concentration. For modeling the effects of temperature on K and n, the integration of two functions from the Arrhenius and logistic sigmoidal growth equations has provided a new model which gave better description of the properties. It also alleviated the problems of negative region when using the Arrhenius model alone. The fitted regression using this new model has improved coefficient of determination, R2 values above 0.9792 as compared to using the Arrhenius and logistic sigmoidal models alone, which presented minimum R2 of 0.6243 and 0.9440, respectively.
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modelling of rheological behaviour of soursop Juice Concentrates using shear rate temperature concentration superposition
Journal of Food Engineering, 2013Co-Authors: Meei Chien Quek, Nyuk Ling Chin, Yus Aniza YusofAbstract:The effect of temperature and concentration on rheological behaviour of freeze dried soursop Juice Concentrates were investigated using a rheometer over a wide range of temperatures (10–70 °C) and concentrations (10–50 °Brix) at shear rates of 0–400 1/s. The Power law is the best fitted model to the rheological data due to the high value of coefficient of determination (R2 = 0.9989). The soursop Juice Concentrates exhibited shear thinning or pseudoplastic behaviour with n < 1. The consistency coefficients dependency on temperature and concentration were well described by Arrhenius relationship and exponential relationship respectively. The flow activation energy of soursop Juice Concentrates were 8.32–30.48 kJ/mol. The superposition technique with Power law model sufficiently modelled the overall rheological characteristics of soursop Juice Concentrates into a single master curve using shift factors based on double shifting steps with R2 = 0.9184. This technique also showed that the soursop Juice Concentrates increases in viscosity and pseudoplasticity behaviour with concentration.
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Modelling of rheological behaviour of soursop Juice Concentrates using shear rate–temperature–concentration superposition
Journal of Food Engineering, 2013Co-Authors: Meei Chien Quek, Nyuk Ling Chin, Yus Aniza YusofAbstract:The effect of temperature and concentration on rheological behaviour of freeze dried soursop Juice Concentrates were investigated using a rheometer over a wide range of temperatures (10–70 °C) and concentrations (10–50 °Brix) at shear rates of 0–400 1/s. The Power law is the best fitted model to the rheological data due to the high value of coefficient of determination (R2 = 0.9989). The soursop Juice Concentrates exhibited shear thinning or pseudoplastic behaviour with n < 1. The consistency coefficients dependency on temperature and concentration were well described by Arrhenius relationship and exponential relationship respectively. The flow activation energy of soursop Juice Concentrates were 8.32–30.48 kJ/mol. The superposition technique with Power law model sufficiently modelled the overall rheological characteristics of soursop Juice Concentrates into a single master curve using shift factors based on double shifting steps with R2 = 0.9184. This technique also showed that the soursop Juice Concentrates increases in viscosity and pseudoplasticity behaviour with concentration.
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modelling of rheological behaviour of pummelo Juice Concentrates using master curve
Journal of Food Engineering, 2009Co-Authors: Nyuk Ling Chin, Yus Aniza Yusof, S M Chan, T G Chuah, Rosnita A TalibAbstract:Abstract The rheological behaviour of freeze-dried-concentrated pummelo Juice was modelled to investigate the effects of temperature and concentration on its fluid type and viscosity using a rotational viscometer at shear rates ranging from 1 to 400 s −1 . The effect of concentration measured by its total soluble solids content resulted in the Juice Concentrates behaving towards shear thinning or pseudoplastic behaviour with flow behaviour index values, n n values at all three investigated concentrations, 20, 30 and 50 °Brix. The consistency coefficient decreases with temperature but increases with total soluble solid contents. Modelling the rheological behaviour of pummelo Juice Concentrates using the master-curve yielded results over a range of temperature to overlap on a single line, which allows generalisation of flow behaviour and characteristics. The master-curve plots confirmed that the Juice viscosity and pseudoplasticity increase with concentration with high regression coefficients, R 2 > 0.98.
Feryal Karadeniz - One of the best experts on this subject based on the ideXlab platform.
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degradation of vitamin c in citrus Juice Concentrates during storage
Journal of Food Engineering, 2006Co-Authors: Hande Selen Burdurlu, Nuray Koca, Feryal KaradenizAbstract:Abstract Kinetics of ascorbic acid degradation in citrus Juice Concentrates (orange, lemon, grapefruit, tangerine) during an eight week storage at 28, 37 and 45 °C were investigated. The loss of ascorbic acid at each temperature followed a first-order kinetic model. Activation energy was determined in the range of 12.77 ± 0.97–25.39 ± 1.98 kcal mol −1 . Ascorbic acid retention after storage at 28, 37 and 45 °C was about 54.5–83.7%, 23.6–27% and 15.1–20.0%, respectively. Since hydroxymethylfurfural (HMF) is one of the decomposition compounds of ascorbic acid degradation, its formation was also investigated. HMF accumulation fitted to a zero-order kinetic model and activation energy ranged from 43.41 ± 0.67 to 80.02 ± 0.07 kcal mol −1 . Significant correlation was obtained between HMF accumulation and ascorbic acid loss at all storage temperatures in all citrus Juice Concentrates.
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effect of storage on nonenzymatic browning of apple Juice Concentrates
Food Chemistry, 2003Co-Authors: Hande Selen Burdurlu, Feryal KaradenizAbstract:Kinetics of nonenzymatic browning in Golden Delicious and Amasya apple Juice Concentrates during 4 months are investigated. Apple Juice Concentrates were at 65, 70, 75 � Bx of Golden Delicious variety, stored at 5, 20, 37 � C and Amasya variety, stored at 37, 50, 65 � C. Colour development was measured by browning index (A420) and the CIE-Lab colour system. Browning level of all apple Juice Concentrates increased according to a zero-order reaction kinetic. Activation energies for 65–75 � Bx of Golden Delicious and Amasya apple Concentrates ranged from 21.4 to 21.0 kcal/mol and 33.7 to 32.5 kcal/mol, respectively. Influence of soluble solids content on browning was negligible. HMF concentration, in Golden Delicious apple Juice Concentrates, was between 0.52 and 963 mg/kg, and between 0.52 and 190 mg/kg in Amasya apple Juice Concentrates. # 2002 Elsevier Science Ltd. All rights reserved.
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kinetics of nonenzymatic browning reaction in citrus Juice Concentrates during storage
Turkish Journal of Agriculture and Forestry, 2003Co-Authors: Nuray Koca, Hande Selen Burdurlu, Feryal KaradenizAbstract:The kinetics of nonenzymatic browning in citrus Juice Concentrates (orange, lemon, grapefruit and tangerine) during 8 weeks of storage at 28, 37 and 45 oC were investigated. Browning development was followed by measuring absorbance at 420 nm (A420) and using CIE-Lab color system. Analysis of kinetic data from A420 values suggested a zero-order reaction for nonenzymatic browning, while changes in L* and b* parameters followed a first-order reaction. Activation energy for nonenzymatic browning determined by A420 values ranged from 17.60 to 35.27 kcal mol-1, while those for L* and b* parameters were 6.67-28.99 kcal mol-1 and 15.38-34.2 kcal mol-1, respectively. Activation energies were higher in orange (28.99-35.27 kcal mol-1) and tangerine (27.84-33.1 kcal mol-1) Juice Concentrates than those in grapefruit (6.74-27.81 kcal mol-1) and lemon (6.67-17.6 kcal mol-1) Juice Concentrates. The lower activation energies determined for grapefruit and lemon Juice Concentrates indicated that nonenzymatic browning reactions are favored in these samples.
