Kinetics Of Color Development Research Articles

Kinetics of Colour Development during Frying of Potato Pre-Treated with Pulsed Electric Fields and Blanching: Effect of Cultivar.

The current research aimed to investigate the effect of pulsed electric fields (1 kV/cm; 50 and 150 kJ/kg) followed by blanching (3 min., 100 °C) on the colour development of potato slices during frying on a kinetic basis. Four potato cultivars ‘Crop77’, ‘Moonlight’, ‘Nadine’, and ‘Russet Burbank’ with different content of glucose and amino acids were used. Lightness (L* values from colorimeter measurement) was used as a parameter to assess the colour development during frying. The implementation of PEF and blanching as sequential pre-treatment prior to frying for all potato cultivars was found effective in improving their lightness in the fried products. PEF pre-treatment did not change the kinetics of L* reduction during frying (between 150 and 190 °C) which followed first-order reaction kinetics. The estimated reaction rate constant (k) and activation energy (Ea based on Arrhenius equation) for non-PEF and PEF-treated samples were cultivar dependent. The estimated Ea values during the frying of PEF-treated ‘Russet Burbank’ and ‘Crop77’ were significantly (p < 0.05) lower (up to 30%) than their non-PEF counterparts, indicating that the change in k value of L* became less temperature dependence during frying. This kinetic study is valuable to aid the optimisation of frying condition in deep-fried potato industries when PEF technology is implemented.

Kinetics of color development in glucose/Amino Acid model systems at different temperatures

This study investigated the influence of temperature on the color development of melanoidins formed from a single combination of glucose with amino acid. The selected amino acid, commonly found in apple juice and highly reactive in the Maillard reaction, were asparagine (Asn), aspartic acid (Asp) and glutamic acid (Glu). For this, the color development was evaluated by measuring browning at 420 nm and color measurements by spectrophotometry and colorimetry methods. The effect of temperature on the color intensity, the absorption of melanoidins were also measured at different wavelengths (280, 325, 405). The value of melanoidins formed from all model systems was located on a dominant wavelength of 325 nm, the ultra violet zone of the diagram. A first-order kinetic model was applied to L* and the evolution of color difference Δ E* . In addition, a*, b* values, significantly differences were found in the glucose/aspartic acid model system in the brown-red zone. Therefore, the color development of the melanoidins was influenced by the type of amino acid and temperature, and it is thought that the a* and b* values can be used to explain the differences among the amino acid in the color development of melanoidins.

Kinetics of colour development in aqueous glucose systems at high temperatures

Non-enzymatic browning was studied in aqueous model systems containing glucose and aspartic acid, glutamic acid or asparagine at three different solid concentrations (15%, 30% and 45% by weight) which were heat treated for different times at four temperatures (85°C, 90°C, 95°C and 100°C). Some indicators were used to evaluate the extent of the Maillard reaction: spectrophotometric measurements at 280 and 420 nm ( A 280 and A 420), formation of 5-(hydroxymethyl)-2-furfural (HMF) and CIE, L ∗,a ∗,b ∗ parameters. The pH and the formol index were also determined. The indicators A 280, A 420 and HMF formation showed that the kinetic constant values increased when increasing the heat-treatment temperature while the influence of solid concentration was not clear. After a short induction period, the data were well correlated to zero-order kinetics. With reference to colourless intermediate formation ( A 280 and HMF), aspartic acid turned out to be the most reactive amino acid while in brown pigment formation, it was asparagine. Glutamic acid was the least reactive amino acid for both processes. The activation energy was found to range from 110 to 180 kJ/mol for both, intermediate and brown pigment formation.

Kinetics of colour development in aqueous fructose systems at high temperatures

Non-enzymatic browning was studied in aqueous model systems containing fructose and aspartic acid, glutamic acid or asparagine at three different soluble solid concentrations (150, 300 and 450 g kg−1), which were heat treated for different times at four temperatures (85, 90, 95 and 100 °C). Various indicators were used to evaluate the extent of the Maillard reaction: spectrophotometric measurements at 280 and 420 nm (A280 and A420) and CIE (Commission Internationale de l'Eclairage) parameters L* (lightness), a* (redness), b* (yellowness) and ΔE* (colour difference, which is expressed as [(Δa*)2 + (Δb*)2 + (ΔL*)2]1/2). The pH and the formol index were also determined. The indicator for colourless intermediate formation, A280, showed that the kinetic constant values increased with increasing heat treatment temperature, while the influence of soluble solid concentration was not clear. After a short induction period the data were well described by assuming zero-order kinetics. Glutamic acid turned out to be the most reactive amino acid, while asparagine was the least reactive. With reference to brown pigment formation, A420 and ΔE*, glutamic acid was the least reactive amino acid. In all the experiments assayed, except for glutamic solutions with fructose concentrations of 150 and 300 g kg−1, the data were best correlated with combined kinetics. © 2000 Society of Chemical Industry

Kinetics of color development in aqueous systems at high temperatures

Kinetics of color development at high temperatures were studied in aqueous solutions containing the color-forming compounds glucose and glycine, as well as a combination of these with ascorbic acid and thiamine. The formed color in test samples sealed in glass ampoules subjected to various time-temperature treatments was evaluated using CIE parameters (luminance factor, Y% and chromaticity coordinates, x and y). The study indicated that the color development could be described by first-order kinetics ( r 2 > 0·92).

Kinetics of color development in the Landolt ("iodine clock") reaction

Kinetics of color development in the Landolt ("iodine clock") reaction