Changes in color and rheological behavior of pineapple concentrate through various evaporation methods

Abstract

The objective of this study was to investigate the effect of various concentration methods namely microwave vacuum evaporation (MVE), microwave heating evaporation (MHE), and rotary vacuum evaporation (RVE) on the concentrate change, the kinetic of color degradation, and the rheological behavior of pineapple juice.  The concentrated behavior of pineapple juice from the experimental data of concentration rate was fitted with three types of exponential models for evaluating a suitable prediction.  The four-parameter exponential model was found to agreeably explain the concentrated change of pineapple juice during each concentration methods.  The Kinetics of color change during concentration processes was evaluated.  The color changing from three different evaporations was measured by lightness values (L^*), redness values (a^*) and yellowness (b^*) values, total color difference (TCD) and brown pigment formation index (A₄₂₀).  The result indicated that the change in Hunter parameters, L^* and b^*, fitted well with the first-order kinetic model while a^*, TCD, and Browning index followed the zero-order kinetic model.  The observed apparent viscosities (μ_a) of pineapple concentrate at 55-85