Kinetics Of Color Changes Research Articles

Thermal degradation kinetics of monomeric anthocyanins, colour changes and storage effect in elderberry juices

Fil: Busso Casati, Carolina Ines. Pontificia Universidad Catolica Argentina Santa Maria de los Buenos Aires. Facultad de Ciencias Agrarias; Argentina

Photometric Characteristics of Aqueous Solutions and Polymer Films Containing Bromothymol Blue/Diphenyliodonium Salts Applied for UV Monitoring

We examined the photometric characteristics of ultraviolet light (UV) measurements of aqueous solution and polyvinyl alcohol (PVA) film containing bromothymol blue (BTB) and diphenyliodonium salts (chloride, nitrate and trifluoromethane sulfonate). The solution and film were initially green (neutral), but were changed to yellow (acidic) by irradiation with 254 nm UV from a mercury lamp. A solution and film containing only BTB did not show the color change, which we concluded was solely induced by the acid generation from the diphenyliodonium salts. Photochemical kinetics of the UV-induced color change are discussed on the basis of experimental results; the color change proceeded obviously according to pseudo-first-order kinetics. This BTB/diphenyliodonium salt system could be used as a low-cost, mobile UV dosimeter. [DOI: 10.1380/ejssnt.2015.15]

Milled industrial beet color kinetics and total soluble solid contents by image analysis

Industrial beets are an emerging feedstock for biofuel and bioproducts industry in the US. Milling of industrial beets is the primary step in front end processing for ethanol production. Milled beets undergo color change during juice extraction. A custom designed computer vision system for measurement of milled beet color kinetics, consisting of a digital camera, custom-designed non-reflective enclosure, and color calibration method was developed in the present study. Beet samples of five different total soluble solids (TSS) contents were prepared by washing with cold water for color kinetics measurement. An artificial neural network model was used for converting the red, green, and blue (RGB) values of the acquired sample images to L*a*b* values. Seven color parameters (L*, a*, b*, hue, chroma, browning index (BI), and total color change (ΔE)) were analyzed. Page, user-defined polynomial, and fractional conversion models gave better fits for the experimental data with color parameters than the zeroth order, first order, exponential, and Peleg kinetic models. Of the color parameters studied, L* (Page R2>0.99, user-defined polynomial R2>0.97, and fractional R2>0.93) and ΔE (Page R2>0.98, user-defined polynomial R2>0.94, and fractional R2>0.85) gave the best description for the color change kinetics of milled beets. Developed TSS prediction models from the color measurements based on Page model constant, kp with color parameter, L* gave good prediction (R2=0.99), also did the simple linear model based on direct color values (R2=0.98). Measurement and mathematical modeling of milled industrial beets color kinetics will serve as important quality assessment tool in processing the beets for various renewable fuel and products applications.

Colour change and proteolysis of skim milk during high pressure thermal–processing

The effect of high pressure–thermal processing (HPTP), in the range of 0.1–600MPa and 100–140°C for up to 60min, on colour change and proteolysis of reconstituted skim milk (10% w/w) was investigated. The kinetic results showed that colour change (ΔEab) and proteolysis (determined by chromatography) increased with both increasing temperature and pressure. The apparent reduction of free amino groups in skim milk, indicating sugar conjugation to milk proteins/peptides, was accelerated with increasing temperature, but decelerated with increasing pressure (at constant temperature) at higher temperature. The milk’s colour changed drastically at 400MPa where most of the milk proteins formed coagulates and left the solutions nearly translucent. Mathematical models describing the kinetics of colour change, proteolysis, and free amino acids reduction as a function of pressure and temperature are proposed.

Evaluation of the Browning Kinetics for Bananas and Pears Submitted to Convective Drying

The aim of this work was to evaluate the kinetics of colour change for bananas and pears dried in hot air at different temperatures, and also to test different kinetic models to verify which describe best the experimental data. Banana fruits from Madeira island and Costa Rica were and pears from cultivar D. Joaquina were peeled, cut and dried with hot air at 0.5 m/s and temperatures ranging from 50 to 70 oC, until reaching a final moisture content lower than 10% (wet basis). Along drying colour measurements were done using a tristimulus colorimeter measuring the CIELab coordinates, L*, a* and b*. The experimental data was then fit to different kinetic models found in literature (first order, second order and exponential rise functional). The results obtained showed that bananas undergo a more intense color change than pears. It was further observed that the increase in drying temperature lead in general to an increase in the colour degradation, being this effect more pronounced in the pears. As to the kinetics of color change, the exponential rise function showed the best fitting, and the values of the kinetic constant found with this model varied from 5.7023x10 to 1.0086 h.

Color Degradation Kinetics of Carrot (D aucus carota L.) Slices during Hot Air Drying

The effect of temperature on color change kinetics of carrot slices was investigated during hot air drying. The color parameters for the color change of the foods were quantified by Hunter L (whiteness/darkness), a (redness/greenness) and b (yellowness/blueness) values. These values were also used for calculation of the total color change (ΔE). The color values (L, a and b) decreased, while ΔE increased during drying. Zero- and first-order kinetic models were applied to describe color change. Mathematical modeling color change kinetics indicated that both models were found to describe the L, a and b values adequately. However, ΔE followed zero-order kinetics. PRACTICAL APPLICATIONS In this study, a hot air dryer was used. The effect of air temperatures (45, 55 and 65C) on color change kinetics of carrot slices was investigated. The color of carrot slices was measured during hot air drying. Zero- and first-order kinetic models were applied color change. The first-order kinetic model adequately described evolution of L, a and b values derived for carrot slices during drying. Dried carrots are used as an ingredient in instant soups or meals and an excellent candidate for developing oil-free, healthy snack food if the nutritional value can be well preserved.

Effect of Antioxidants on the Colour Stability of Fermented Sausage “Sucuk” Type

Abstract: Purpose - The aim of this study was to investigate effect of some antioxidants on the cross section color stability of dry-fermented beef sausage “sucuk” type, during 120 minute exposure of sausage slices to air, at the temperature of 20°C and 4°C. Design/methodology/approach - Samples were produced in industrial conditions, seven experimental model samples with selected antioxidants added separately to each (sodium ascorbate, rosemary extract, green tea extract, ascorbic acid, ascorbyl palmitate, tocopherols and butylatedhydroxyanisole) and control sample, without antioxidants. Colour parameters, expressed as CIE L*, a* and b* values, total colour difference (∆E), the kinetics of colour change, chemical composition and pH value were determined. Findings - The cross section colour of all samples significantly changed (p<0.05), due to exposition of sausage cuts to air, but significantly smaller changes in colour (p<0.05) were observed in the samples kept at lower temperature. Dry-fermented beef sausage “sucuk” type, produced with selected antioxidants, can be sliced 120 minutes before serving and stored at the temperature of 4°C, and cross section colour changes are unrecognisable, but at the temperature of 20ºC colour changes are significantly greater. Addition of natural antioxidant, rosemary extract and green tea extract, have a positive effect on colour stability of tested sausage “sucuk” type. Originality/value - This paper provides information on colour changes during exposition of dry sausage cuts to air and the findings may be interesting for entrepreneurs whose activity is connected with serving these products in restaurants, catering services or the households.

Thermal Kinetics of Colour Degradation of Yellow Sweet Pepper (Capsicum Annum L.) Undergoing Microwave Assisted Convective Drying

Experiments were conducted to study the kinetics of colour change of yellow sweet pepper during microwave-assisted convective drying at power levels of 280, 210, 140, and 70 W; temperatures of 60, 45, and 30°C; and a constant air velocity of 1.5 m/s. Colour change kinetics were determined using Hunter’s primary L, a, b values, chroma, hue, total colour change (ΔE), and browning index (BI) values. The results indicated that the degradation of a, ΔE, and hue followed zero order kinetics and L, b, chroma, and browning index followed first order kinetics. The rate constant was assumed to have Arrhenius-type dependence on temperature. Again, based on activation energy, b and hue parameters proved to be the most sensitive measures of color change, which could be taken into account during thermal processing of capsicum for getting a quality product.

Color Change Kinetics of American Ginseng (Panax quinquefolium) Slices During Air Impingement Drying

The color change kinetics of American ginseng (Panax quinquefolium) slices were investigated in an air impingement dryer under different drying temperatures (35, 45, 55, and 65°C) using the CIE Lab color parameters (L*, a*, b*) as the assessment indicators. Results illustrated that all three color parameters (L*, a*, b*) increased with drying time. The L* value decreased with increasing drying temperature. However, a* and b* values increased with the increase in drying temperature. Furthermore, at the initial drying stage the change rate of L* increased significantly, while towards the end of drying it reduced significantly. As regards a*, it slowly changed at the initial and final drying stages rather than in the intermediate drying stage. In the case of b*, it increased with increasing drying time and drying temperature during the whole process. The zero-order, first-order, and fractional conversion models were fitted to the experimental data, and the model's parameters were determined using linear regression analysis. By comparing the fitting of kinetic models to the experimental data, the most suitable model was selected to describe the color change kinetics. An Arrhenius equation was used to calculate the activation energy for color change kinetics and it was found that the values were 33.87–38.55, 56.48, and 74.03 kJ/mol for L*, a*, and b*, respectively. The findings of this work contribute to a better understanding of ginseng color changes kinetics during drying, and the established change kinetics models are a good tool for predicting, evaluating, and controlling of color change of American ginseng during its drying process.

Kinetic analysis of color changes in keyaki (Zelkova serrata) and sugi (Cryptomeria japonica) wood during heat treatment

The kinetics of color changes in keyaki (Zelkova serrata Makino) and sugi (Cryptomeria japonica D. Don) wood during heat treatment were examined. The color of wood specimens treated at 90, 120, 150, and 180 °C was measured by an imaging spectrophotometer and expressed using CIELAB color parameters. At any treatment temperature, values for L* and $$ \Updelta E_{ab}^{*} $$ decreased and increased in both wood species, respectively, with increased treatment time. Changes in a* and b* varied depending on wood species and treatment temperature. The color changes were successfully analyzed using the kinetic approach applying time–temperature superposition method. This approach elucidated and accurately predicted color changes during heat treatment.

Study on Kinetics of Color Changes in Thompson Seedless Grapes during Drying Process

The aim of this study was to investigate the characteristic of color changes in Thompson seedless grape during drying at 30°C, 35°C and 40°C air temperatures. The CIE LAB color system was used to measure the surface color of the grapes. It was found that browning began at middle period of drying, where parameters L* and b* decreased and parameter a* increased during drying. Color changes during browning process were described as a first-order kinetic model, where the activation energies for the parameters L*, a*, b*, and total color difference were respectively 40.19, 24.29, 35.43, and 39.46 kJ·mol1.

Effect of natural antioxidants on the colour and lipid stability of paprika salami

The typical red colour of paprika salamis is a very important quality attribute but it is also very susceptible to oxidation. Rosemary extracts and lycopene appear to be efficient antioxidants for dry fermented sausages. The complicated structure of dried sausages with different kinetics of colour changes was evaluated using VIA software NIS-Elements 2.20 and lightness L*, redness a*, yellowness b*, mean red (R), mean green (G), and mean blue (B) were measured; the ratio of red r = R/(R + G + B) and hue h = arctg (a*/b*) were calculated. The addition of rosemary extract has positively affected the colour and suppressed lipid oxidation in both meat and lard particles in the paprika salami. Even more satisfactory results were obtained by adding both the rosemary extract and lycopene. Video image analysis enabled to perform colour measurements of meat and lard particles separately, which could not be done by any available method (reflective spectrophotometry).  

Image analysis and green tea color change kinetics during thin-layer drying

This study was conducted to investigate the effect of air temperature and air flow velocity on kinetics of color parameter changes during hot-air drying of green tea, to obtain the best model for hot-air drying of green tea, to apply a computer vision system and to study the color changes during drying. In the proposed computer vision system system, at first RGB values of the images were converted into XYZ values and then to Commission International d'Eclairage L*a*b* color coordinates. The obtained color parameters of L*, a* and b* were calibrated with Hunter-Lab colorimeter. These values were also used for calculation of the color difference, chroma, hue angle and browning index. The values of L* and b* decreased, while the values of a* and color difference (ΔE*ab ) increased during hot-air drying. Drying data were fitted to three kinetic models. Zero, first-order and fractional conversion models were utilized to describe the color changes of green tea. The suitability of fitness was determined using the coefficient of determination (R (2)) and root-mean-square error. Results showed that the fraction conversion model had more acceptable fitness than the other two models in most of color parameters.

Kinetics of colour and texture changes of beef during storage

The influence of the packaging films, aerobic and vacuum conditions, and refrigeration storage temperature (0, 4 and 10°C) on colour and texture of raw meat were studied during a 2-week storage period in order to analyze kinetics of colour and texture changes. The rate of redness decrease was most noticeable at the highest storage temperature and aerobic conditions and these changes were well described by the first-order reaction. Texture parameter reflected a progressive softening during storage for both films. Decrease on shear force of raw beef during storage followed a first-order kinetic model. Temperature dependence of colour and texture change was adequately modelled with the Arrhenius equation.

Application of computer vision technique for on-line monitoring of shrimp color changes during drying

The effects of drying temperature and drying medium velocity on color change kinetics of shrimp viz. lightness (L∗), redness (a∗), yellowness (b∗), total color difference (ΔE), chroma (CH), hue angle (H°), and browning index (BI) were on-lineally investigated. Drying experiments were carried out on dryer equipped with computer vision systems using hot air drying (HAD) temperatures of 50–90°C and superheated steam drying (SSD) temperatures of 110–120°C at drying medium velocities of 1–2m/s. Zero-, first-order, and fractional conversion models were utilized to describe the color changes of shrimps and the fractional conversion model successfully tracked the experimental data. The results showed that the color parameters were significantly influenced by the studied parameters. Lightness of the samples decreased, while other color parameters increased as drying proceeded. Generally, increasing drying medium temperature decreased L∗ and H°, whereas increased other color parameters. The color characteristic of the SSD finished products were acceptable than the HAD processed samples. Finally, dimensionless moisture content of shrimps during drying was accurately correlated to the color parameters and drying time using a quadratic regression model. Moisture ratio had strong relationship with the lightness change compared with the redness and yellowness variations.

Physicochemical Properties of Bell Pepper and Kinetics of Its Color Change Influenced by Aloe vera and Gum Tragacanth Coatings during Storage at Different Temperatures

Undesirable storage conditions lead to physicochemical changes in stored vegetables, which affect their consumer acceptability. Studies aimed at quantifying the extent of those changes under different storage conditions are valuable for minimizing the deleterious effect on product quality. The objective of this study was to assess the suitability of Aloe vera and gum tragacanth as edible coatings for bell pepper and to determine their influence on changes in physicochemical properties during storage at 4, 10, 15 and 23C for 30 days. Data on weight loss, shrinkage, hardness and color were collected and subjected to statistical analysis. 4 and 10C showed significantly better physicochemical characteristics than other temperatures and compared with control, A. vera- and gum tragacanth-treated bell peppers were significantly better. Higher temperatures resulted in more rapid changes. The first-order kinetic models showed a good fit to the changes of color parameters. Temperature sensitivity of the rate constants was adequately described by Arrhenius equation. Practical Applications Maintenance of the quality of fresh product is a major challenge for the food industry. Many techniques have been studied in order to extend the shelf life, but most of them are excessively expensive and have some drawbacks. In this study, edible coatings have been used to improve the bell pepper appearance and conservation. They can act as moisture and gas barriers, control microbial growth, preserve the color, texture and moisture, and can effectively extend the shelf life of fruits and vegetables. Evaluation of physicochemical changes of coated fruits and vegetables and study the kinetics of color changes in comparison with the control samples, are the least information for preserving them in industrial scales.

Color Change Kinetics of Mango at Different Maturity Stages during Air Drying

The objective of the present study was to evaluate color changes for the purpose of gathering data of kinetic parameters (rate constant [k] and activation energy [E a]) of color change in mango slices at different maturity stages during air drying using Hunter color parameter values. Samples of green, half-ripe and ripe stages were dried at air velocities of 1.76, 1.80 and 1.91 m/s and temperatures of 50, 60, 70 and 80C. Colors (total color difference [ΔE], chroma [C] and hue [h]) in slices were monitored at 20 min intervals for 240 min. The changes in ΔE value followed the zero-order kinetics, while C and h values followed the first-order kinetics. Analysis of variance showed that the rate constants (k) for ΔE, C and h differ significantly (P < 0.05) with maturity stage, air temperature, air velocity and their interactions. Dependence of k on temperature followed an Arrhenius relationship, regardless of maturity stage and air velocity. Rate constant as a function of air temperature and velocity was found. Practical Applications To obtain a better understanding of the industrial process applications, it is important to model and quantify the kinetics and process yield. This work was intended to provide models that allow describing the effects of air temperature and velocity on color change kinetics of mango slices at different maturity stages during air drying.

Color Kinetics of Aonla Shreds with Amalgamated Blanching During Drying

Kinetics of color changes of aonla (Emblica officinalis) shreds were investigated using objective colorimetric measurements during drying with different blanching treatments. Kinetic parameters chroma, hue, total color difference, and browning index for the color change were determined using Hunter L, a, b values. The drying process changed all three color parameters (L, a, b), causing a color shift towards the darker region. Parameters L and b decreased and a-value increased during drying. The reaction associated with color change followed zero-order reaction kinetics. The minimum change was observed in the KMS (potassium metabisulphite) blanched shreds.

COLOR CHANGE KINETICS OF CELERY LEAVES UNDERGOING MICROWAVE HEATING

The aim of this study was to investigate the effect of microwave output power and sample amount on color change kinetics of celery leaves (Apium graveolens L.) during microwave heating. The color parameters of the materials were quantified by the Hunter Lab system. These values were also used for calculation of the total color change, chroma, hue angle, and browning index. The microwave heating process changed color parameters of L, a, and b, causing a color shift towards darker region. The mathematical modeling study of color change kinetic showed that L, a, b, and chroma fitted to a first-order kinetic model, while total color change (ΔE), hue angle, and browning index (BI) followed a zero-order kinetic model. For calculation of the activation energy for color change kinetic parameters, the exponential expression based on the Arrhenius equation was used.

Low‐temperature UV irradiation induced the color change kinetics and the corresponding structure development of PVC film

AbstractThe low‐temperature ultraviolet (UV) irradiation equipment, developed in our Lab, was used to study the photo‐aging of poly (vinyl chloride) (PVC) films at low temperature. The color change kinetics and corresponding structure development of PVC film during low‐temperature UV aging were studied through L*a*b* coordinates Commission International d' Eclau‐age (CIE 1976 color space) and Ultraviolet spectrophotometer (UV–vis) and Fourier transform infrared spectroscopy (FTIR). It was found that the yellowness difference (▵b*) and color difference (▵E*) of the PVC film increased almost linearly with the aging time. Their values had a slower change at lower temperature. The kinetic study showed that the relationship between the velocity of coloration of the PVC film and the temperature agreed well with Arrhenius equation at low temperature. The activation energy of coloration of the PVC film was calculated. The FTIR spectra indicated that photo‐dehydrochloration, resulting in the generation of conjugated carbon–carbon double bonds, was the main reaction for PVC during photo‐aging at low temperature. Meanwhile, the photo‐oxidation was also obvious and could not be neglected. It clearly confirmed that the absorption peaks of conjugated carbon–carbon double bond increased and shifted to longer wavelength during photo‐aging in the UV‐abs analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.