Kinetics modelling of color deterioration during thermal processing
of tomato paste with the use of response surface methodology
Seid Mahdi Jafari
Received: 17 November 2017 /Accepted: 28 May 2018
Springer-Verlag GmbH Germany, part of Springer Nature 2018
To study the kinetics of color degradation, the tomato paste was designed to be processed at three different temperatures including
60, 70 and 80 °C for 25, 50, 75 and 100 min. a/b ratio, total color difference, saturation index and hue angle were calculated with
the use of three main color parameters including L (lightness), a (redness-greenness) and b (yellowness-blueness) values.
Kinetics of color degradation was developed by Arrhenius equation and the alterations were modelled with the use of response
surface methodology (RSM). It was detected that all of the studied responses followed a first order reaction kinetics with an
exception in TCD parameter (zeroth order). TCD and a/b respectively with the highest and lowest activation energy presented the
highest sensitivity to the temperature alterations. The maximum and minimum rates of alterations were observed by TCD and b
parameters, respectively. It was obviously determined that all of the studied parameters (responses) were affected by the selected
Color is one of the most substantial and widely used factors in
food industries that is directly related to the quality of the
obtained products. This parameter is highly affected by ther-
mal processing. Thermal processing influences on the prod-
ucts’ color including pigments decomposition particularly ca-
rotenoids (lycopene, xanthophyll etc.) and chlorophylls and/or
accelerate the reactions such as browning including Maillard
and ascorbic acid oxidation in food products and as a result
makes alterations in processed products’ colour parameters.
The reaction conditions including pH and acidity values as
well as processing time were also detected effective on the
deterioration reactions .
Destruction of lycopene pigment and its conversion to cis
isomerization and structure is the most noticeable color deg-
radation reaction occurs commonly in concentrated tomato
products [2, 3]. Chlorophylls existing in immature tomatoes
may enter in the production lines and produce green
pheophytin pigment due to thermal processing. Reynolds
(1965) introduced phenolic compounds polymerization as
one of the factors participating in color alterations of food
materials. Tomato due to containing lycopene compounds
may present several potential health benefits [4, 5].
The color characteristics of food products such as tomato
paste with high color values is usually estimated by L, a and b
values. This method is not appropriate in term of light colored
products. L indicates the lightness of the samples graded from
100 for pure white to zero for pure black. Positive values of
Ba^ express the redness and its negative values present the
greenness of the studied samples’ colour. Positive values of
Bb^ indicate the yellowness and its negative values represent
the blueness of the studied sample . Total color difference
(TCD), saturation index or Chroma (SI) (representing the sat-
uration index and intensity of the color), a/b ratio and hue
angle (HU) are the other derivations of L, a and b values
studied in the present study .
a/b ratio indicates the color quality of tomato products.
Values ≥2 on this parameter indicate the best quality and
values ≤1.8 are considered for rejection in different industries.
Hue angle is other parameter used frequently in color evalua-
tion of food products. The values equal to zero and 360 °
represent red hue, but the values equal to 90, 180 and 270 °
express yellow, green and blue hue respectively.
Arrhenius equation presents the mathematical influence of
temperature on the studied chemical reaction rates and may be
considered as the base of the predictions of the reaction rates.
* Seid Mahdi Jafari
Department of Food Materials and Process Design Engineering,
Gorgan University of Agricultural Sciences and Natural Resources,
Heat and Mass Transfer