Determination and modelling moisture sorption isotherms of dehydrated butterfly-pea (Clitoria ternatea L.) flower powder

Abstract

Butterfly-pea flower (Clitoria ternatea L.) is one of the edible flowers that is widely processed into dried flowers or powder form. Processed butterfly-pea flower is mostly used as a food colorant or flavonoid and anthocyanin-rich teas which are naturally present in the flower. Some polyphenolic acid, i.e., gallic acid, protocratic acid, and chlorogenic acid are also contained in this flower. During the storage period, color degradation occurs which will reduce the quality of the powder. Therefore, a study on the determination of moisture sorption isotherm from butterfly-pea powder is necessary information to maintain the quality of this product for a longer storage period. The objectives of this research are to evaluate the behavior of moisture sorption isotherm, construct its mathematical modelling and analyze the color changes at different temperatures and aw. 60 mesh of butterfly-pea powder with 28% initial moisture content (db) was stored at aw 0.3 - 0.9 (in a saturated salt solution containing MgCl2, K2CO3, NaC1, KC1, and BaCl2) at 30, 40, and 50°C by static gravimetric method. The results showed that based on the Brunauer classification, the behavior of moisture sorption isotherm of dehydrated butterfly-pea powder is in accordance with the Type II-sigmoid curve, while the Peleg model is the best model in predicting the moisture sorption isotherm. Recommended storage conditions for butterfly-pea flower powder are at 30°C with equilibrium moisture content at 23-30% (db). During storage powder color turns darker over the entire aw range with a color index of L∗ (lightness, 9.97); a∗ (redness, 2.33); b∗ (yellowness, -5.56).