Kinetics Of Color Changes Research Articles

Effect of Microwave Vacuum Drying on the Drying Characteristics, Color, Microstructure, and Antioxidant Activity of Green Coffee Beans

The aim of this study is to investigate the effect of microwave vacuum drying (MVD) on the drying characteristics and quality attributes of green coffee beans. We specifically focused on the effective moisture diffusion coefficient (Deff), surface temperature, glass transition temperature (Tg), water state, and microstructure. The kinetics of color changes during drying, total phenolic content (TPC), and antioxidant activity (DPPH, FRAP, and ABTS) were also characterized. Microwave power during MVD affected the porosity of coffee beans, their color, TPC, and antioxidant activity. The Allometric 1 model was the most suitable for simulating surface temperature rise kinetics. Thermal processing of green coffee beans resulted in increased b*, L*, ΔE, and TPC values, and greater antioxidant capacity. These findings may provide a theoretical reference for the technical improvement, mechanisms of flavor compound formation, and quality control of dried green coffee beans.

Kinetics of peroxidase inactivation, color and temperature changes during pumpkin (Cucurbita moschata) blanching using infrared heating

Fresh Pumpkin is sensitive to microbial or enzymatic spoilage even in refrigeration temperatures, thus; blanching before freezing or canning is a proper way for preservation and commercialization of this product. In this study infrared irradiation was chosen as heating source and peroxidase as an indicator of enzyme inactivation adequacy for pumpkin blanching. Pumpkin purée was treated under 5 levels of temperature and 2 levels of sample thickness. Effect of thermal processing on the kinetic parameters of peroxidase inactivation (k, Ea, D and Z values) and color changes (ΔE) was investigated. Peroxidase inactivation of pumpkin samples followed a first order kinetics model. Calculated activation energies and Z values of enzyme inactivation process for 4 and 8 mm thickness levels were 130.63, 119.46 kJ mol−1 and 18.18, 17.85 °C, respectively. No significant difference was observed between activation energies and Z values of two thickness levels. But, the effect of temperature and thickness on inactivation rate constants (k) and D values was significant (P < 0.05). Investigation on the kinetics of color change was carried out by the calculation of ΔE changes during l log enzyme inactivation period. In this study, sample thickness showed a more significant effect on ΔE variations than temperature.

Indirect forced solar drying of banana slices: phenomenological explanation of non-isotropic shrinkage and color changes kinetics

ABSTRACTSolar drying technology is a noteworthy technique as it uses the renewable solar energy. In this study, thin slices of banana were dried by using an indirect forced solar dryer at air mass flow rates of 0.016, 0.041, and 0.082 kg s−1. In order to assess the kinetics of shrinkage and color changes, image processing technique was applied for determining area, volume, density, total color difference and browning index. Shrinkage factor of the samples was less than 1 during drying indicating non-isotropic shrinkage with contraction of inner voids. Furthermore, product shrinkage showed two descending drying steps in which the volume change was more than the evaporated water volume in the first step and equal to that in the second step. The dimensionless evaporated water volume with respect to the dimensionless volume difference of the product also revealed that two steps of volume change existed during drying separated at critical moisture ratio 0.23. The area and volume changes were only related to the product moisture content and were independent of the air mass flow rate, and hence air temperature. In contrary to the browning index, the total color difference was not influenced by air mass flow rate and the least change in browning index occurred at mass flow rate of 0.041 kg s−1.

Color Change Kinetics of the Inner and Outer Surface of Brussels Sprouts During Microwave Drying Process

The effect of microwave output powers on colour change kinetics of the inner and outer surface of brussels sprouts was investigated during microwave drying process. The colour changes of the materials were quantified by means of the CIELab scale parameters like L*, a*, and b*. The total color change (∆E), chroma (C*), hue angle (h*), and browning index (BI) were also calculated by using these values. As expected, microwave drying process changed the colour parameters at different rates depending on the output power used because of browning. The values of a*, ∆E, and BI on both surfaces of the brussels sprouts increased, other values decreased during drying. The mathematical modeling study of color change kinetics indicated that all colour parameters fitted to a zero-order kinetic model and the 460 W output power occured the lowest change rates of all colour parameters. According to the values of activation energy calculated by colour change kinetic parameters, more colour change on the outer surface of brussels sprouts happened by the increase in microwave output power.

Kinetics of colour changes in pasteurised strawberry juice during storage

Colour changes during storage are an important quality defect of fruit-based products. Therefore, this work investigated the effect of storage time, storage temperature and oxygen availability (through the type of bottle) on changes in CIEL*a*b values, anthocyanin and ascorbic acid content of shelf-stable strawberry juice (produced with a spiral-filter press under vacuum conditions) using kinetic modelling. The colour-related attributes changed significantly during storage at ambient (20 °C) and accelerated temperatures (28–42 °C) in both types of bottles. The change in all attributes was accelerated at higher storage temperatures. A higher oxygen availability resulted in a faster change of all attributes. As oxygen availability was not fully controlling colour changes, they are caused by complex oxidative and non-oxidative reactions. The results of this work demonstrate the applicability of a kinetics-based accelerated shelf-life testing approach to obtain faster insight into colour changes of strawberry juice and to be used for shelf-life investigations.

Green Pea and Garlic Puree Model Food Development for Thermal Pasteurization Process Quality Evaluation.

Development and selection of model foods is a critical part of microwave thermal process development, simulation validation, and optimization. Previously developed model foods for pasteurization process evaluation utilized Maillard reaction products as the time-temperature integrators, which resulted in similar temperature sensitivity among the models. The aim of this research was to develop additional model foods based on different time-temperature integrators, determine their dielectric properties and color change kinetics, and validate the optimal model food in hot water and microwave-assisted pasteurization processes. Color, quantified using a* value, was selected as the time-temperature indicator for green pea and garlic puree model foods. Results showed 915 MHz microwaves had a greater penetration depth into the green pea model food than the garlic. a* value reaction rates for the green pea model were approximately 4 times slower than in the garlic model food; slower reaction rates were preferred for the application of model food in this study, that is quality evaluation for a target process of 90 °C for 10 min at the cold spot. Pasteurization validation used the green pea model food and results showed that there were quantifiable differences between the color of the unheated control, hot water pasteurization, and microwave-assisted thermal pasteurization system. Both model foods developed in this research could be utilized for quality assessment and optimization of various thermal pasteurization processes.

Comparison of the kinetics of monomeric anthocyanins loss and colour changes in thermally treated Blackcurrant, Maqui Berry and Blueberry pulps from Argentina

Comparison of the kinetics of monomeric anthocyanins loss and colour changes in thermally treated Blackcurrant, Maqui Berry and Blueberry pulps from Argentina

Kinetics of color changes of popped rice during microwave popping: Effect of salt and moisture content

AbstractPaddy, coated with a dielectric salt was popped using microwave energy. The kinetics of color changes of the popped rice with the variation of heating time (0–60 s), sample moisture content (12–18% wb), and level of salt coating (0–5% w/w) were studied. The parameters, estimating the change in color of the popped rice, were measured in terms of L*, a*, b* color coordinate system using a Chroma‐meter. The total color change (ΔE*), chroma (C*), hue angle (H*), and browning index (BI*) were estimated from these measured parameters. The shift in color change with microwave popped paddy was found darker side with the increase in heating time and salt content. These color changes showed that, ΔE* was fitted well to zero‐order kinetic model, while BI* followed a first‐order kinetic model. All these color parameters were fitted to a quadratic equation as a function of salt and moisture content. Both ΔE* and BI* increased with the increase in salt:moisture ratio.Practical applicationsThe color development in the product during microwave popping of paddy is an important sensory quality attribute concerning consumer acceptability. The popping characteristics of paddy and simultaneously kinetics of its color changes are closely associated with the factors like moisture content, level of salt (dielectric) coating and heating time adopted in domestic MW oven. Modeling of the kinetics of color changes could be a useful practical tool in predicting the final and acceptable color of the product. Estimation of heating time for desirable color development of the product could be arrived with certain ratio of salt to moisture contents of the paddy.

Kinetics of colour changes in marigold petals during microwave drying

Microwave assisted convective dehydration of marigold species Pusa Narangi petals was carried out at three levels each of microwave power (140, 210 and 280 W), air temperature (30, 45 and 60°C) and a constant air velocity of 0.5 m/s. The experiment was laid out using full factorial CRD with three replications. The colour values L, a, b of the marigold petals was measured with Hunter Lab colourimeter which were found decreasing. There was change in chroma values of marigold is due to drying by using both combinations of microwave power level and temperature. The total colour change has been increased significantly during microwave drying with drying time.

Kinetics of Reshteh Khoshkar Color Changes During Atmospheric and Vacuum Deep-fat Frying

The effect of frying pressure on the kinetics of color changes during atmospheric and vacuum deep fat frying of Reshteh Khoshkar has been studied. The Hunter color parameters redness, yellowness, lightness and total color difference were used to estimate color changes during frying as a function of process. Lightness (L*) decreased from 85.37 to 75.01 with vacuum frying time, while redness (a*), yellowness (b*) and total color difference increased from -2.09, 4.92 and 0 to 1.22, 37.01 and 31.56, respectively. It was observed that the severity of colour change was higher in atmospheric frying process than the vacuum frying process. The changes in color parameters were modeled by zero-order, first-order and a combined kinetics model. The two first-order and combined kinetics models fitted properly the values of color changes during frying, with good coefficient of determination. The combined model used can describe the experimental colour parameters better than the other studied kinetics models.

A Kinetic Study of Furan Formation in Wheat Flour-Based Model Systems during Frying.

Furan is a possible human carcinogen, which is formed in worldwide highly consumed fried starchy foods. In order to elucidate the mechanisms responsible for its occurrence in this food category and propose techniques for its mitigation, the kinetics of furan formation, oil absorption, lipid oxidation, and color change were studied in wheat flour-based model systems during frying at 160, 170, 180, and 190 °C up to 13min and data were fitted to mathematical models. Additionally, an Arrhenius-type dependency with temperature was evaluated for all studied responses. More drastic frying conditions increased significantly (P ≤ 0.05) the furan content of fried samples. Furan formation followed a sigmoid trend with frying time only for frying temperature of 190 °C (RMS190°C : 7.6%). At lower temperatures, furan generation did not reach the asymptotic concentration level. Color change, lipid oxidation, and oil absorption increased with frying temperature and followed asymptotic relationships with frying time. For all evaluated temperatures, color change (RMS: 4.4% to 12.5%) and polar compound generation (RMS: 2.6% to 7.4%) presented good fit to a first-order kinetic model. Oil absorption was successfully fit to a mass balance-based model (RMS: 10.0% to 19.8%). Under the experimental conditions studied, only color change (EA : 15.47kJ/mol), lipid oxidation (EA : 6.67kJ/mol), and oil absorption (EA : 76.98kJ/mol) presented good fit (RMS: 0.7% to 6.3%) to an Arrhenius-type equation. Based on our results, the keeping of frying temperature below 180 °C and the reduction of the frying time would contribute to reduce not only the final furan occurrence in fried foods but also their oil content.

Modeling the kinetics of peroxidase inactivation, colour and texture changes of Portuguese cabbage (Brassica oleracea L. var. costata DC) during UV-C light and heat blanching

The effects of heat blanching and UV-C light followed by heat on Portuguese cabbage peroxidase (POD), colour and texture were studied in the temperature range of 80-95 °C. POD inactivation, lightness (L) and yellowness (b) colour changes were described by a first-order reaction model. The greenness (a) colour and texture (firmness) changes followed a two fraction kinetic model behaviour. The temperature effect was well described by the Arrhenius law.At lower temperatures the combined treatment showed higher POD inactivation. Colour and texture parameters did not show significant differences between treatments. Long processing times turned the leaves slightly darker, decreased greenness, yellowness and firmness. Short processing times increased the firmness and greenness of the leaves. The treatment at 80 °C for 90 seconds reduced 90% of POD, retaining 98% of lightness and 92% of yellowness and improved the green colour (130%) and firmness (125%). At 80 °C the heat blanching required 7.4 min to inactivate 90% of the enzyme activity, reducing lightness, greenness, yellowness and firmness to 92%, 68%, 62% and 61%, respectively. The present findings will help to optimize the Portuguese cabbage blanching conditions.

Modeling the kinetics of peroxidase inactivation, colour and texture changes of Portuguese cabbage (Brassica oleracea L. var. costata DC) during UV-C light and heat blanching

The effects of heat blanching and UV-C light followed by heat on Portuguese cabbage peroxidase (POD), colour and texture were studied in the temperature range of 80-95 °C. POD inactivation, lightness ( L ) and yellowness ( b ) colour changes were described by a first-order reaction model. The greenness ( a ) colour and texture (firmness) changes followed a two fraction kinetic model behaviour. The temperature effect was well described by the Arrhenius law. At lower temperatures the combined treatment showed higher POD inactivation. Colour and texture parameters did not show significant differences between treatments. Long processing times turned the leaves slightly darker, decreased greenness, yellowness and firmness. Short processing times increased the firmness and greenness of the leaves. The treatment at 80 °C for 90 seconds reduced 90% of POD, retaining 98% of lightness and 92% of yellowness and improved the green colour (130%) and firmness (125%). At 80 °C the heat blanching required 7.4 min to inactivate 90% of the enzyme activity, reducing lightness, greenness, yellowness and firmness to 92%, 68%, 62% and 61%, respectively. The present findings will help to optimize the Portuguese cabbage blanching conditions.

Kinetics of color change of osmotically dehydrated chub mackerel (Scomber japonicus) during storage at different temperatures

The aim of this study was to determine the effect of storage temperature on the kinetics of color change of chub mackerel dehydrated in a ternary solution (water, glycerol and salt) and vacuum packaged in films. The color of processed fish can change because of lipids and protein oxidation during storage. Samples were stored at 7, 25 and 35 °C for seven months and kinetic models of 0, 1 and 2 order were applied to describe the color changes. It was observed that an increase in the storage temperature improved the changes in the CIE color values (L*, a* and b*). First-order reaction had the best statistical parameters for a* at the three temperatures tested. The temperature dependence of parameter a* indicated an Arrhenius relationship and the activation energy (Ea) was 44.33 kJ/mol. The parameter b* fitted to the proposed models only in samples stored at 35 °C. The L* value decreased during storage at 25 and 35 °C (pale to dark). Storage at refrigeration temperature (7 °C) minimized the color changes.

New model for colour kinetics of plum under infrared vacuum condition and microwave drying.

Quality of dried foods is affected by the drying method and physiochemical changes in tissue. The drying method affects properties such as colour. The colour of processed food is one of the most important quality indices and plays a determinant role in consumer acceptability of food materials and the processing method. The colour of food materials can be used as an indirect factor to determine changes in quality, since it is simpler and faster than chemical methods. The study focused on the kinetics of colour changes of plum slices, under infrared vacuum and microwave conditions. Drying the samples was implemented at the absolute pressures of 20 and 60 kPa, drying temperatures of 50 and 60°C and microwave power of 90, 270, 450 and 630 W. Colour changes were quantified by the tri-stimulus L* (whiteness/darkness), a* (redness/greenness) and b* (yellowness/blueness) model, which is an international standard for color measurement developed by the Commission Internationale d'Eclairage (CIE). These values were also used to calculate total colour change (∆E), chroma, hue angle, and browning index (BI). A new model was used for mathematical modelling of colour change kinetics. The drying process changed the colour parameters of L*, a*, and b*, causing a colour shift toward the darker region. The values of L* and hue angle decreased, whereas the values of a*, b*, ∆E, chroma and browning index increased during exposure to infrared vacuum conditions and microwave drying. Comparing the results obtained using the new model with two conventional models of zero-order and first-order kinetics indicated that the new model presented more compatibility with the data of colour kinetics for all colour parameters and drying conditions. All kinetic changes in colour parameters can be explained by the new model presented in this study. The hybrid drying system included infrared vacuum conditions and microwave power for initial slow drying of plum slices and provided the desired results for colour change.

Kinetic of Color Changes in Almond (Akbadem Variety) During Roasting and Storage

In this research, the color change kinetics of the Akbadem variety during roasting and storage processes was investigated. The roasting process was carried out at three different temperatures (150, 160, and 170°C) and four different times 10, 20, 30, and 40 min. Then, roasted samples were separated in two groups and stored for 6 months in 4 and 22°C. All of the color parameters reactions during roasting and storage took place according to first order reaction kinetics. L- and hue angle-values tended to decrease linear significantly during roasting. The L-values of Akbadem samples roasted at 150, 160,and 170°C for 40 min was determined as 52.34 ± 2.53, 47.96 ± 1.35, and 43.17 ± 0.09, respectively. The highest Ea-value was determined on the L-value as 14.80 ± 4.26. The a, b, ΔE, metric chroma (C), and metric saturation (S) values increased during roasting. L-, C-, a-, b-, and S-values tended to decrease linear significantly during storage. The L-, a-, and b-values of Akbadem samples which were roasted at 170°C and stored at 4°C for 6 months were decreased from 43.17 ± 0.09, 14.25 ± 0.026, and 29.53 ± 0.06 to 34.91 ± 0.13, 10.06 ± 0.15, and 15.93 ± 0.12, respectively. According to sensory analysis, the panelists gave low scores as taste (1.9 ± 0.88), color (2.1 ± 0.57), and flavor (2.4 ± 0.7) for Akbadem samples roasted at 170°C for 40 min. ΔE was increased during storage Ea-values were decreased during roasting and storage at 4 and 22°C for 6 months.

Color Kinetics During Ripening of Indian Mangoes

During ripening of mangoes, color change kinetics were studied with Alphonso, Banganapalli, and Neelam varieties. The internal and external color change was recorded using CIE-Lab color coordinates. L, a, b, and total color difference (ΔE) values were measured for internal pulp and external peel during the ripening period. Four kinetic models viz. zero order, first order, fractional conversion, and logistic models were used for modeling using MATLAB. Among the explored models, the logistic model was found to be more suitable to predict the changes in all external color coordinates in all the three varieties. Internal color coordinates of different varieties were exhibited contrasting behavior. So different kinetic models were proposed to predict the internal color change for different variety. The fractional conversion model was found to be not suitable in color change kinetics during ripening of mango.

EFFECT OF HOT DRYING ON THE ESSENTIAL OIL CONTENT AND COLOUR CHARACTIRISTICS OF PEPPERMINT (Mentha piperita)

The main objective of this study was to investigate the effect of different temperature of hot air drying on the qualities of dried peppermint included essential oil content, colour parameters, colour sensory quality and modelling the colour change kinetics. The drying experiments were carried out at five air temperature of 40, 50, 60, 70 and 80oC. The colour parameters for colour change of the materials were quantified by the Hunter L (whiteness/darkness), a (redness/greenness) and b (yellowness/blueness) system. These values were also used for calculation of total change (DE) as well as chroma, hue angle and Browning index. A consumer preference test was conducted with 80 consumers to assess the colour quality of 05 dried peppermints. The results showed that the decreasing of essential oils content at high drying temperature is higher than at low temperature. Least Squares regression was used to determine the relationship between colour sensory scores of consumer taster and quantification of three Hunter parameters. In that, variable “L” and “b” could be distributed to decreasing while variable “a” contributory increase the colour quality of dried peppermint products. It was observed that L, a, DE and hue angle values were fitted to the zero-order model, while b and chroma were fitted to the first-order model.

Effect of blanching on enzyme activity, color changes, anthocyanin stability and extractability of mangosteen pericarp: A kinetic study

Mangosteen pericarp is a rich source of anthocyanins. However, the high polyphenol oxidase (PPO) activity challenges potential applications of pericarp as natural colorant. The kinetics of PPO inactivation, anthocyanin loss and color changes were determined over a temperature range of 60–100 °C. First-order kinetic model provided the best prediction of the PPO inactivation (R2 ≥ 0.977), while anthocyanin loss was described by a Weibull kinetic model (R2 ≥ 0.969). The activation energies of PPO inactivation, anthocyanin loss and total color changes were 43.11, 57.66 and 18.86 kJ/mol, respectively. Anthocyanin content was the most sensitive parameter towards temperature changes, suggesting the importance of its monitoring as a quality parameter during thermal processing. Blanching enhanced the efficiency of anthocyanin extraction. Gathering the quantitative information on the changes of PPO activity as well as quality characteristics during blanching of mangosteen pericarp is important in order to design a proper pre-processing condition.

Color Change Kinetics of Tea Leaves During Microwave Drying

Abstract In the present study, the effect of microwave power and sample amount on color change kinetics of tea leaves was investigated during microwave drying. Hunter L, a and b system was used for the color change of the materials; and the total color change (ΔE), chroma, hue angle and browning index (BI) were calculated by using these values. The color of the tea leaves was shifted towards the darker region after the microwave drying process. The mathematical modeling study of color change kinetic showed that a, b, chroma and BI fitted to a first-order kinetic model, while L, total color change (ΔE) and hue angle followed a zero-order kinetic model. For calculation of the activation energy for color change kinetic parameters, the exponential expression based on Arrhenius equation was used.