Degradation Kinetics of Colour and Total Carotenoids in Jackfruit (Artocarpus heterophyllus) Bulb Slices During Hot Air Drying

Abstract

The kinetics of colour and carotenoids degradation in jackfruit bulb slices was evaluated during hot air drying at 50, 60 and 70°C. Visual colour as well as total carotenoids (TC) content was found to be influenced by the drying process. Tri-stimulus colour parameters such as Hunter L and b values decreased and a value increased during drying. The combination of Hunter L×b value was found to represent the colour change adequately. Degradation of TC and visual colour in terms of Hunter L×b value followed first-order reaction kinetics; however, zero-order reaction kinetics was found adequate to describe changes in total colour difference (TCD) and non-enzymatic browning (NEB). Dependence of the rate constant followed the Arrhenius relationship. The process activation energies (E a ) for Hunter L×b value, TCD, NEB and TC were 29.96, 27.21, 27.48 and 55.61 kJ/mol, respectively. Higher E a for TC content indicated greater temperature sensitivity as compared with other colour parameters. Relationship of TC content and Hunter L×b value was found to be more consistent through regression analysis with R 2 ≥0.979. NomenclatureA Absorbance at 420 nm at drying time t A o Initial absorbance at 420 nm C Value of total carotenoids content at drying time t C o Initial value of total carotenoids content E a Activation energy H Value of visual colour in terms of hunter L×b value or total color difference at drying time t H o

Degradation kinetics of carotenoids and visual colour in pumpkin (Cucurbita maxima L.) slices during microwave-vacuum drying

“…Correlations between visual colour coordinates with carotenoids content have been widely discussed in the literature. Saxena et al [17] found that the degradation of colour parameters Hunter L*×b* value and the total carotenoids of jackfruit bulb slices agreed well with the first-order reaction kinetics during hot air drying. Moreover, there was a certain correlation between total carotenoids and the L*×b* value, and the combination of Hunter L*×b* value could replace carotenoid content for online quality control adequately.…”

“…However, Ahmed et al [39] observed that apart from the Hunter b* value, both L* and a* values also decreased with time at a given temperature as the mango puree turned brown. Chutintrasri and Noomhorm [40] and Saxena et al [17] both found that the Hunter L* and b* values decreased and the a* value increased during heat-treated pineapple puree at 70-110 º C and hot-air drying for jackfruit bulb slices. The different results may be due to the changes in the yellow and red colour of the pumpkin slices, which may be caused not only by the variation of carotenoids content but also by a series of complex Maillard reactions in the drying process.…”

“…In addition, it was found that the degradation of ΔE value followed zero-order reaction kinetics with R 2 values of 0.9027-0.9806, which is in agreement with previous reports. [17,40] Relationship between visual colour and carotenoids content…”

“…Correlation of the Hunter a* × b* values was also reported to agree with the total carotenoids and lycopene contents in heated watermelon juice by Sharma et al [43] . Saxena et al [17] described a good relationship of the total carotenoids content and the Hunter L* × b* value and suggested that the combination of Hunter L* × b* value could represent the colour change adequately. Thus, determination of the L* value can be a good predictor of lutein, α-carotene and β-carotene losses during the drying of pumpkin slices in our study.…”

“…Other reactions such as the Maillard reaction will affect the colour parameters, so it is necessary to examine whether there is a correlation between colour and carotenoid, which may be used as a substitute for the determination of carotenoid content. [17,19] The objective of this study was to determine the kinetic parameters for the degradation of lutein, α-carotene, β-carotene and visual colour of pumpkin slices during MVD at different microwave powers as well as to evaluate the relationship between visual colour parameters and total carotenoids, which contributed to optimize the process through the control of processing parameters during drying and perform simulations using accurate kinetic parameters.…”