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

Abstract

The degradation kinetics of colour and individual carotenoids including lutein, α-carotene and β-carotene in pumpkin slices was investigated during microwave-vacuum drying (MVD) at selected microwave powers (4–8 W/g). The contents of lutein, α-carotene and β-carotene significantly decreased, while visual colour parameters such as the Hunter L* value decreased and the total colour difference (ΔE) value increased with the increase of processing time and microwave power. Degradation of lutein, α-carotene, β-carotene and Hunter L* value followed the first-order reaction kinetics; however, zero-order reaction kinetics was found adequate to describe changes in ΔE with R2 ≥ 0.9027. The relationship between individual carotenoid content and Hunter L* value was found to be more consistent through one-dimensional linear regression analysis with R2 ranging from 0.8697 to 0.9701. These results indicated that visual colour might be used to predict the lutein, α-carotene and β-carotene contents during drying pumpkin slices.