Thermal Degradation Of Ascorbic Acid Research Articles

Cinética de degradación del ácido ascórbico en néctar de durazno durante el tratamiento térmico

Ascorbic acid is a beneficial component for health, but it is degraded during the thermal pasteurization of food products. The aim of this research was to determine the influence of temperature on the thermal degradation of ascorbic acid in peach nectar at 75, 85 and 95 °C, evaluating this effect at 0, 30, 60, 90 and 120 minutes. The degradation of ascorbic acid follows a first order reaction model with rate constants that vary between 5.5 to 10.9 x 10-3 min-1. D-Values ranged from 211.28 to 418.73 min, while Z value was 69.4 oC. The values of the free energy of inactivation ranged between 112.63 and 117.17 kJ.mol-1, while for the activation enthalpy the values varied between 25.37 and 25.54 kJ.mol-1 and the range for the activation entropy was from -249.36 to -250.15 J.mol-1.K-1.It can be concluding that the reaction is endothermic and does not occur spontaneously. The knowledge of these values is important not only to explain the loss of ascorbic acid, but also to design and optimize thermal processes aimed at preserving the nutritional quality of peach nectar.

Kinetic changes of antioxidant parameters, ascorbic acid loss, and hydroxymethyl furfural formation during apple chips production

In this study, the kinetic change of the antioxidant properties were determined during apple chips production using three different cultivars. Using a rotary forced-air dryer, apple slices were dried at three different temperatures (65, 70, and 75°C). The ascorbic acid content, total phenolic content (TPC), total flavonoid content (TFC), Oxygen Radical Absorbance Capacity (ORAC) and Trolox Equivalent Antioxidant Capacity (TEAC), and hydroxymethylfurfural content were analyzed. Phenolic compounds of apple chips were also identified by chromatographic separation. Thermal degradation of ascorbic acid was fitted to first-order reaction kinetics. TPC, TFC, ORAC, and TEAC values, and hydroxymethylfurfural content increased with drying time and temperature where the data were fitted to first-order and zero-order reaction kinetics. Reaction rate constants were influenced by temperature, based on the Arrhenius model. The primary phenolic compounds of apple chips were gallic acid, chlorogenic acid, catechin, caffeic acid, epicatechin, and rutin. Practical applications Dietary antioxidants with health benefits have increased attention on fruit and vegetable products. The processing of fruits and vegetables affects their antioxidant properties as well as their quality. Apple chips are dehydrated, ready to eat, fruit-based snacks with desirable sensory properties. The results of this article will contribute to an understanding of the thermal kinetics of antioxidant properties and phenolic content during apple chip production. The kinetic results may be useful for the design of dryers and optimization of the drying conditions.

Kinetics of ascorbic acid thermal degradation in Valencia orange juices and evaluation of its shelf life

Ascorbic acid is a well-known natural antioxidant which is widely distributed in nature, especially in green plants. Its traditionally known sources are citrus fruits like orange. This vitamin acts as an efficient radical inhibitor and it has been used as a food additive. Moreover, it presents antioxidant activity and contributes for the prevention of certain types of cancer. Ascorbic acid is also used as an index of nutritional quality of fruits and vegetables, due to its sensibility to different kinds of degradation in food processing and subsequent storage. Thus, the study of ascorbic acid degradation kinetics is important to raise information that allows estimating the quality changes that occur during the storage of food products. The purpose of this research was to evaluate the thermal degradation kinetics of ascorbic acid in Valencia orange juices and to quantify the effect of water activity on its rate of loss upon storage. Ascorbic acid content was determined by titration with 2,6 dichlorophenol indophenol. Its degradation as a function of storage time was studied at different temperatures during a period of 14 days of storage. Reaction constant rates (k) and the order of reaction (n) were determined through regression analysis of experimental data. Higher coefficient of determination (R2) indicated that a first-order reaction model fits closely well to data obtained in this study. In general, it was observed that increasing temperature and water activity led to increasing losses of ascorbic acid. A direct equation for the estimation of the shelf life of the juice with respect to ascorbic acid losses at any specified temperature and degradation rate has been derived.

Production and stability study of a hospital parenteral nutrition solution for neonates

Standard parenteral nutrition solutions are mixtures comprising interacting components that may degrade themselves over time. The objective of this study was to investigate the physicochemical and microbiological stability of a hospital preparation for parenteral nutrition in neonatology. The analyses were performed throughout the storage of the preparations at 2–8 °C (up to 4 months). The extent of stability was based on the determination of amino acids dosage, visual and physicochemical properties (glucose and electrolytes concentrations, pH and osmolality measurements, particle counting) and microbiological analysis (sterility test). A thermal degradation of ascorbic acid was conducted to evaluate the antioxidant properties of the parenteral mixture. Physicochemical and microbiological controls were found to comply with the specifications. Amino acids showed a good stability throughout the 4months storage except for cysteine, which was progressively degraded to cystine, conferring a yellow coloration to parenteral solutions. Parenteral nutrition standards solutions remain stable for 4 months at 2–8 °C, ensuring safe administration in preterm infants.

Kinetic modeling of ascorbic acid degradation of pineapple juice subjected to combined pressure-thermal treatment

A study was conducted to investigate and model kinetic degradation of ascorbic acid in freshly prepared pineapple juice subjected to various pressure (0.1, 300,450 and 600 MPa)-thermal (30, 75, 85 and 95 °C) treatment combinations. Experiments were conducted using a semi-custom made high pressure kinetic tester as well as an aluminum thermal kinetic tester. Thermal degradation of ascorbic acid was described with simple first order kinetics. The thermal rate constants (k75 -95 ◦C, 0.1 MPa) and activation energy (Ea) for ascorbic acid degradation reaction varied in the range of 0.004–0.006 per min and 14.22–29.78 kJ/mol, respectively. Within the experimental conditions of the study (300–600 MPa at 30 °C for holding times up to 15 min) high pressure processing did not alter ascorbic acid content (535.5–564.5 mg/kg). Combined pressure-thermal treatment (300–600 MPa at 75–95 °C) degraded ascorbic acid with increasing thermal intensity and was modeled using first order fractional conversion kinetics model. The lower asymptote value ([A]∞[A]0), rate constants (k75 -95 ◦C, 600 MPa) and Ea were in the range of 77–85%, 0.108 to 0.138 per min and 17.4–43.8 kJ/mol, respectively. Similarly, pressure sensitivity (ΔV≠) was ∼0 and −2.99 cm3/mol at 30 and 95 °C, respectively. Knowledge gained from the study can be useful for food processors to optimize high pressure treatment conditions for pineapple juice products.

Mathematical Modeling of Ascorbic Acid Thermal Degradation in Orange Juice during Industrial Pasteurizations

AbstractOrange juice is submitted to thermal treatment to increase its shelf life, which may result in loss of ascorbic acid. This paper uses mathematical models and simulations to reproduce the experimental data of ascorbic acid thermal degradation kinetics. Two different models were considered, and all kinetic parameters were identified using linear regression on the logarithmic curves of experimental data. A quick analytical method based on ultra high‐performance liquid chromatography with tandem mass spectrometry was developed to quantify ascorbic acid degradation during the process at three different operating temperatures, allowing the determination of Arrhenius' equations. Ascorbic acid losses were simulated in a tubular industrial pasteurization system by developing an appropriate mathematical modeling, and the residence time presents a higher influence on the process than temperature. In addition, some thermodynamic parameters were evaluated, confirming that the process is not spontaneous but irreversible.Practical ApplicationsThe mathematical modeling developed in this research can be used to estimate the ascorbic acid losses during industrial pasteurization processes. The case study of this paper concerns on tubular systems. However, the kinetic parameter estimation and the degradation rate obtained can be used in any industrial situation by an appropriate modeling adaptation, e.g., considering the common plate systems.

Mathematical Modelling of Thermal Degradation Kinetics of Ascorbic Acid in <i>Brassica Carinata </i>

Ethiopian green collard ( Brassica Carinata ) locally named yeabesha gomen is one of the important vegetable for ascorbic acid source in our society. However, adequate study has not been conducted to exploit the potential of this indigenous vegetable. The kinetics of ascorbic acid thermal degradation in yeabesha gomen as well as in pure ascorbic acid solution over a temperature range of 60–120 o C (isothermal temperature process) for up to 60minutes has been studied. The thermal degradation of ascorbic acid in yeabesha gomen fitted first-order reaction kinetic model where the rate constant increased from 0.0146 to 0.051min -1 with an increase in the temperature from 60 to 120 o C respectively. The temperature dependence of degradation was adequately modeled by the Arrhenius equation with R 2 =0.977 and RMSE=0.0733. Activation energy for ascorbic degeneration kinetics of yeabesha gomen was found to be 21.85kJmol -1 . This lower activation energy value indicates that ascorbic acid in yeabesha gomen is quite susceptible to thermal processes. The outputs this work would be helpful to design and control practical thermal processing situations that minimize the loss of ascorbic acid in Ethiopian green collard as well as other leafy green vegetables contained ascorbic acid compounds.

Kinetics of ascorbic acid loss during hot water blanching of fluted pumpkin (Telfairia occidentalis) leaves

The kinetics of thermal degradation of ascorbic acid in fluted pumpkin leaves were investigated from 60 to 90°C (pH 5.0 to 6.5). Ascorbic acid degradation was modeled as a first order rate reaction with the rate constants increasing with increase in pH of the medium. The pH and temperature dependence of the rates of destruction gave highly significant correlations when analyzed by the thermal resistance and activated complex reaction rate methods. Activation energy (Ea) ranged from 41.2 to 18.2kJ/mol while D-values ranged from 103.3 to 22.4min. The changes in activation energy affected Ko values which ranged from 5.98 × 10(4) to 41.7min(-1).

Diffusion and thermal degradation of ascorbic acid during canned fresh green peas sterilisation

SummaryChanges of ascorbic acid (AA) during canned fresh green peas sterilisation in a rotary retort were predicted. It was considered that AA is thermally degraded in green peas and simultaneously diffuses to brine, where it is also degraded; heat transfer, mass transfer and kinetics equations were simultaneously solved during heating and cooling of the sterilisation process. Kinetic parameters of AA thermal degradation in brine were experimentally determined, while all other parameters needed were taken from bibliography. Simplified assumptions were made to explore diffusion and thermal degradation mechanisms relevance. Experimental runs were performed at different retort temperatures, end‐over‐end rotation speeds and headspaces in a pilot plant rotary retort; experimental data obtained on concentrations of AA in green peas and in brine were used to evaluate predictions goodness. Deviations between experimental and predicted results were 8.44% for AA in green peas and 13.79% in brine.

Ascorbic Acid Thermal Degradation during Hot Air Drying of Camu-Camu (Myrciaria dubia [H.B.K.] McVaugh) Slices at Different Air Temperatures

Air drying of camu-camu slices was performed in order to estimate the effect of air temperature on the kinetics of ascorbic acid thermal degradation. Moisture variation during the air drying process was monitored gravimetrically by weighing the trays at predetermined time intervals. The experimental points were adjusted by Fick's diffusion model and by the Page empirical model. The effective diffusion coefficient (Deff) ranged from 8.48 × 10−10 to 1.34 × 10−9 m2/s.The ascorbic acid content was evaluated in samples taken during the drying process using Iodine titration, and the results modeled by the Weibull equation. Concerning ascorbic acid retention the best drying condition required air at 50°C. The ascorbic acid retention was 78%, when the moisture content of the product reached 10% (wet basis).

Modelling ascorbic acid thermal degradation and browning in orange juice under aerobic conditions

The thermal degradation of ascorbic acid (AA) in orange juice was analysed over in a 20–45 °C temperature range. Dehydroascorbic acid (DA), pH and browning were also monitored. Small amounts of AA degradation could be described by first order kinetics, but when only low amounts of AA were retained sigmoidal kinetics were clearly appropriate. The Weibull model was used to describe this pattern (R2adj > 0.995). The rate constant increased with temperature according to an Arrhenius‐type relationship. The activation energy was 38.6 kJ/mol and at the average temperature of the range tested, 32.5 °C, the rate constant was 64.4 × 10−3 h−1. The shape constant decreased linearly with temperature, from 2.17 to 1.13. Before the time when the maximum degradation rate occurred, pH, DA concentration and browning remained fairly constant, and then increased. It was found that this behaviour, as well as the dependence of the shape constant on temperature, might be explained by (i) the reconversion of DA into AA, following first order kinetics in relation to DA and second order kinetics in relation to AA, and by (ii) different sensitivities of the reaction rate constants to temperature. Browning was also well described by the Weibull model with a temperature independent shape constant.

Kinetic parameters estimation for ascorbic acid degradation in fruit nectar using the Partial Equivalent Isothermal Exposures (PEIE) method under non-isothermal continuous heating conditions.

With the purpose of testing the Paired Equivalent Isothermal Exposures (PEIE) method to determine reaction kinetic parameters under non-isothermal conditions, continuous pasteurizations were carried out with a tropical fruit nectar [25% cupuaçu (Theobroma grandiflorum) pulp and 15% sugar] to estimate the ascorbic acid thermal degradation kinetic parameters. Fifteen continuous thermal exposures were studied, with seven being cycled. The experimental ascorbic acid thermal degradation kinetic parameters were estimated by the PEIE method (E(a) = 73 +/- 9 kJ/mol, k(8)(0)( degrees )(C) = 0.017 +/- 0.001 min(-)(1)). These values compared very well to the previously determined values for the same product under isothermal conditions (E(a) = 73 +/- 7 kJ/mol, k(8)(0)( degrees )(C) = 0.020 +/- 0.001 min(-)(1)). The predicted extents of reaction presented a good fit to the experimental data, although the cycled thermal treatments presented some deviation. In addition to being easier and faster than the Isothermal method, the PEIE method can be a more reliable method to estimate first-order reaction kinetic parameters when continuous heating is considered.

Kinetic models of ascorbic acid thermal degradation during hot air drying of maltodextrin solutions

The kinetic parameters of models that describe the joint influence of water content and temperature on the thermal degradation of ascorbic acid were estimated from drying experiments using maltodextrin DE 12 as a base material. Two models were used: a first-order decay model with (1) a TDT temperature dependency and a polynomial dependency of the D r and z values with water content, and (2) a WLF dependency of the D value on glass transition temperature, with the Gordon–Taylor equation describing the influence of water content on T g. Experiments were performed in a drying oven with dry bulb temperatures between 100°C and 160°C, with most of the drying occurring with the sample temperature below the oven temperature. Both models provided good fits of the experimental data. Other data from literature for a very different temperature range (4°C–68°C) and for maltodextrin DE 25 were handled in the same way and while the polynomial/TDT model yielded a different moisture dependence structure, the WLF/Gordon–Taylor model yielded similar parameters, thus showing a better predictive power.

Application of D-optimal design for determination of the influence of water content on the thermal degradation kinetics of ascorbic acid at low water contents

The kinetics of thermal degradation of ascorbic acid was studied in a Maltodextrin matrix at different temperatures between 75 and 140 °C. Isothermal experiments were performed with samples earlier equilibrated in environments of known a w at 4 °C, enclosed in hermetically sealed vials, with water contents (w) between 0.17 and 1.68 g water/g solids. Sampling times were selected according to an optimal experimental design in terms of minimum confidence regions of the parameters estimated, using the Bigelow model and estimates from preliminary experiments. The results showed a quadratic dependence of the reference D-value and linear dependence of the z-value with moisture content: D r(140 °C) = 150.07 − 290.73w + 269w 2 (min); z = 12.14 + 22.99w (°C) and showed the applicability of D-optimal designs for determining kinetic parameters in complex situations, with limited experimental requirements. The dependence of the rate constants with water content could not be described by the WLF model in qualitative terms, although in absolute values this model could be used with constants similar to those expected from glass transition theory. The thermodynamic analysis of the results showed a good application of the compensation theory in the whole range of water contents.

Interaction of Ascorbic Acid with Silicic Acid

Interaction of ascorbic acid with silicic acid in the solid state was studied using diffuse reflectance spectroscopic techniques. Surface degradation products from ascorbic acid breakdown were effectively observed using diffuse reflectance spectroscopy, whereas the corresponding transmittance spectral method did not give significant information concerning degradation products. Adsorption of ascorbic acid from methanol solution by silicic acid did not occur, However, after evaporation of the methanol, ascorbic acid did undergo strong interaction with silicic acid, probably through hydrogen bonding. Thermal degradation of ascorbic acid in the adsorbed state was found to be different from that in solution. In acid solution, furfural was a major degradation product; whereas in the adsorbed state, furfural could not be detected.