Degradation of Carotenoids in Apricot (Prunus armeniaca L.) During Drying Process

Carotenoids are natural compounds whose nutritional importance comes from the provitamin A activity of some of them and their protection against several serious human disorders. The degradation of carotenoids was investigated during apricot drying by microwave and convective hot-air at 60 and 70 A degrees C. Seven carotenoids were identified: antheraxanthin, lutein, zeaxanthin, beta-cryptoxanthin, 13-cis-beta-carotene, all-trans-beta-carotene and 9-cis-beta-carotene; among these, all-trans-beta-carotene was found to be about 50 % of total carotenoids. First-order kinetic models were found to better describe all-trans-beta-carotene reduction during drying, with a degradation rate constant (k(1)) that increased two folds when temperatures increased by 10 A degrees C, in both methods. No differences were found in k(1) between apricots dried by hot air at 70 A degrees C (k(1) = 0.0340 h(-1)) and by microwave at 60 A degrees C. The evolution of total carotenoids (117.1 mg/kg on dry basis) during drying highlighted a wider decrease (about 50 %) when microwave heating was employed, for both set temperatures. Antheraxantin was found to be the carotenoid most susceptible to heat, disappearing at 6 h during both trials with microwave as well as during convective hot-air at 70 A degrees C. For this reason, antheraxanthin could be a useful marker for the evaluation of thermal damage due to the drying process. Also the degree of isomerization of all-trans-beta-carotene could be a useful marker for the evaluation of the drying process.