DEGRADATION KINETICS OF COLOR IN BUTTERFLY PEA (Clitoria ternatea L.) EXTRACT DRIED WITH SUGAR

Abstract

The Butterfly pea extract dried with sugar is commonly well known as unchan juice powder in Thailand. However, it is subjected to discoloration during storage in laminate pouch at ambient temperature. The objective of this study is aimed at investigation of degradation rate of the extract dried with sugar stored in 3 different packed conditions under accelerated test at the temperature range of 40-55 oC. The degradation of chroma value of the butterfly pea extract dried with sugar was found to follow a first order kinetics and its dependence on temperature was modeled by Arrhenius equation. The visual pigment degraded from azure to maya blue during storage in the conditions of normal atmosphere and partial vacuum for several weeks.
The L*a*b* and hue angle values of the extract dried with sugar increased with longer storage time. The butterfly pea extract dried with sugar was subjected to the slowest discoloration when it was kept in laminated aluminium pouch (PE/Al/PET) under normal atmospheric condition and the activation energy of the reaction was higher than that when it was kept under vacuum condition. The estimated half-life of the reaction was 55 days at 30 oC and the observed shelf-life of the extract dried with sugar kept at the
same condition under ambient temperature (27-33oC) was 64 days.