Degradation of colour in beetroot (Beta vulgaris L.): a kinetics study

Abstract

The kinetics of colour (measured as Hunter 'a/b' value) degradation in beetroot puree (Beta vulgaris L.) was studied over a temperature range of 50-120 °C (isothermal process), and also during normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient 'EcoCooker' (non-isothermal heating process). The degradation of visual colour as measured as Hunter 'a/b' value was found to follow a first order kinetics, where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modeled by Arrhenius equation. A mathematical model has been developed using the kinetic parameters obtained from the isothermal experiments to predict the losses of color in the non-isothermal heating/processing method based on the time-temperature data for each of the methods. The results obtained indicate a colour degradation of similar magnitude in all the three modes of cooking used in the study.

Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods

“…Activation energies ranged between 3.2 kJmol −1 (lutein) and 43.7 kJmol −1 (Opuntia betaxanthins), for greater E a the rate of reaction is more sensitive to temperature changes, so a smaller temperature change is sufficient to degrade this colorant more rapidly. These results were consistent with those reported for natural colorants such as red cochineal (3 kJmol −1 , 50-90°C) [16], carotenoids (20 kJmol −1 , 70-105°C) [22], betacyanins (38-53 kJmol −1 , 50-120°C) [15,16], and anthocyanins (59 kJmol −1 , 60-90°C) [23]. …”

“…The CIEL*a*b* system is a versatile and reliable method to appraise precise color modifications and is extensively used for routine quality control measurements by food manufacturers [17]. In agreement with previous studies, thermal processing involved a slight increase in lightness (L*) [15,24], although more profound modifications could be observed in the colorimetric plane. Changes in the red-green parameter (a*) and in the blue-yellow parameter (b*) were much more evident as the heat treatment became more severe, particularly in the case of the most thermosensitive colorants.…”

“…The color loss during the thermal treatment of colorant extracts was assumed to follow first order kinetics [14,15], indicating a logarithmic order of degradation, which is mathematically expressed as:…”

Natural color pigments: oxidative stability and degradation kinetics during storage in thermally pasteurized vegetable purees

“…For beet puree packed in all three different OTR pouches, L* and b* (yellowness) were significantly ( P < 0.05) increased, whereas a* (redness) was not significantly ( P > 0.05) reduced. Chandran et al . also observed a similar trend during thermal degradation kinetics of beet color over a temperature range of 50–120 °C.…”

Betalains rich Rivina humilis L. berry extract as natural colorant in product (fruit spread and RTS beverage) development

“…Loss of betalains colour is justified by the heated aroma (a note typical of fruit juices that undergo thermal processing), which could be due to longer duration of thermal processing, detected in considerable quantity in the beverage unlike in Rivina banana spread. Thermal processing loss of betalains has been reported (Chandran et al 2012). The beverage had low score in terms of banana like aroma, body and sourness (taste elicited by citric acid), whereas sweetness (taste elicited by sugar or sweet taste) was the highest among all the sensory attributes evaluated.…”