Color and total carotenoid concentration changes in the thermal degradation of an aqueous model system of cashew apple juice.

L. Q. ZEPKA; M.A.A.P. DA SILVA; C. D. BORSARELLI; R. JORGE; A. Z. MERCADANTE

UNICAMP, Campinas, Brasil

Simposio; 7o SIMPOSIO LATINO AMERICANO DE CIENCIAS DE ALIMENTOS; 2007

FEA-UNICAMP

The time-dependent changes on color and total carotenoid content (TCC) occurring in a 20% ethanol aqueous solution acidified at pH 3.8 with 0.5 M of citric acid (CA) of cashew apple extracts by heating at 60 and 90 C was studied. Color measurements were done with a Hunter (D65/10 oC) colorimeter and the CIELAB parameters L*, a*, b* were determined and total color variation value DE* = (DL*2 + Da*2 + Db*2)1/2 was calculated. TCC was determined by high performance liquid chromatography (HPLC) with diode array detection. The reduction of TCC was estimated of 43% and 74% after 480 min showing bi-exponential decay kinetics with observed first-order rate constants of k1= 3x10-3 min-1 and 1x10-2 min-1, and k2= 3x10-4 min-1 and 2x10-3 min-1, at 60 and 90 C, respectively. The activation energy related with both decays was estimated as Ea,1 = 9.3 kcal/mol and Ea,2 = 16.7 kcal/mol, yielding a total value of 25 kcal/mol, which is a typical value for thermal degradation of carotenoids. At the same time, the variation of the color parameters L*, a*, b*, and DE* showed first-order kinetic behavior with observed rate constants kobs = 6.4x10-3 min-1 and 4.6x10-2 min-1 at 60 and 90 C, respectively, yielding Ea,obs = 15.9 kcal/mol. In addition, the parameters L*, a*, and b* were reduced and the final DE* was 5.6, confirming a noticeable visual difference after heating. In summary, the kinetic analysis by either color or composition changes could be an interesting tool for monitoring heating processes of natural and modeled fruits juices. Keywords: color, carotenoids, kinetics Acknowledgement: The authors thank FAPESP for financial support.