Effect of thermal processing on the quality loss of pineapple juice

Three indexes, namely colorimetric Hunter parameters (L, a, b and DeltaE), hydroxymethylfurfural (HMF) and brown pigment formation, were monitored to determine the quality loss of pineapple juice at temperatures ranging from 55 to 95 degreesC. The changes in a and b values followed first order kinetics while DeltaE fitted well to a combined model which described both non-enzymatic browning reaction and destruction of carotenoid pigment. For browning indexes, HMF and brown pigment formation increased linearly with heating time and could be explained using zero order reaction kinetics. The results suggested that processing temperature had a significant effect on the color change of pineapple juice. The dependence of the rate constant on temperature was represented by an Arrhenius equation. (C) 2004 Elsevier Ltd. All rights reserved.