Determinación de vitamina C y carotenoides en zumos de frutas y hortalizas frescos, tratados por calor o por pulsos eléctricos de alta intensidad (PEAI)

Abstract

The general objective of this work is the determination of the vitamin C and carotenoid contents in citric fruits and vegetables and derived products, such as juices and nectars, that are obtained by conventional thermal treatment and by a new non-thermal technology, Pulsed Electric Fields. To achieve it, the following specific objectives are proposed: 1. Final preparation and validation of a chromatographic method for the identification and quantification of carotenoids and their isomeric ones. 2. Final preparation and validation of a polarographic method for the vitamin C determination. 3. Juice characterization of three varieties of mandarins (Citrus reticulata): clemenules, clemenvilla and fortune, and of three varieties of oranges (Citrus sinensis): navel, navelina and navel-lane, of highest production in the Comunidad Valenciana. In addition to this, the modifications that take place during the harvest dates and during the storage. 4. Orange juices and nectars characterization marketed in Spain, squeezed and concentrated. 5. Evaluation of the influence in vitamin C and carotenoids (bioactive compounds) of thermal treatment and Pulsed Electric Fields in an orange-carrot juice. 6. Estimation of useful life of orange-carrot juice pasteurized and treated by Pulsed Electric Fields, stored to 2 and 10ºC during 70 and 60 days, respectively. In this way the citric fruits have been classified in groups of oranges and mandarins, and the diverse varieties have even been predicted with a very high percentage of successes, based on the analyzed parameters. The vitamins content and the carotenoid profile of the different marketed orange juices and nectars has been compared both individually and in groups according to the processing method and storage. It has allowed to compare the orange-carrot juice processing by a thermal treatment and by Pulsed Electric Fields, pointing out the quality of both treated juices and their useful life. And finally, the evolution of the bioactive compounds has also been valued in the fresh orange-carrot juice stored at -40ºC during 132 days. During the study it has been found out that the storage by freezing at this temperature (-40ºC) varies the content in ascorbic acid and modifies the carotenoid profile of the orange-carrot juice.