Thermal sensitivity of some plantain micronutrients during deep-fat frying.

The impact of deep-fat frying on the micronutrient content of plantain (Musa AAB"barraganete") was evaluated during processing of plantain chips called "tostones." Water content, micronutrients (potassium, L-ascorbic acid, alpha-carotene, beta-carotene) content, and the temperature within the food were quantified during the course of frying. A nonisothermal kinetics analysis of the 1st-order reaction (micronutrient degradation) induced by deep-fat frying, particularly in terms of the spatial distribution of temperature, was proposed. The kinetic parameters (pre-exponential factor k(0,) activation energy E(a)) were identified by nonlinear optimization, minimizing the residual variance between the experimental and theoretical micronutrient content. Agreement between model and experimental values was checked. During 1st and 2nd frying, potassium was well retained while carotenoid contents decreased significantly. Moreover, L-ascorbic acid contents decreased significantly, just during 2nd frying. k(0) was identified as well as E(a) observed for L-ascorbic acid, alpha-carotene, and beta-carotene as 68.4 to 71.5, 79.6 to 84.9, and 85.9 to 88.6 kJ/mol, respectively. beta-carotene appeared to be more heat-resistant than alpha-carotene and L-ascorbic acid. The behavior of the nutritional markers appears to be the consequence of the thermal and hydric histories of the crust and of the heart of the plantain disk related to heat transfer during preparation of the "tostones."