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Antonio J. Melendez and Paula Mapelli, authors of the study, working with orange juices. Photo: University of Seville

Researchers, from the Laboratory of Food Color and Quality at the University of Seville, have published a study that shows how certain types of cold treatment, used by the citrus fruits industry in the preparation of juices, have a great impact on the color of orange juice and on the concentration and bio-accessibility of the carotenoids present in the juice.

The bio-accessibility of a compound is the quantity of that compound that is freed from the food and is capable of being absorbed by the intestinal wall. Then, it arrives in the blood and is accumulated in the different organs or tissues where they can affect their potential health benefits.

The cold treatments have two opposite effects: on one hand, they cause the carotenoids to degrade (negative effect). On the other hand, they generate an increase in the bio-accessibility of the carotenoids (positive effect). Taking these two effects into account, it can be concluded that deep-frozen juices, that are defrosted to room temperature or in a microwave, are potentially better at increasing the level of carotenoids in the body.

During this project, testing was done on fresh orange juice, on deep-frozen juice that had been defrosted to room temperature, either in a microwave or in the fridge and on pasteurized juices.

The analysis focused on two colorless carotenoids in particular, phytoene and phytofluene.

"These compounds are increasingly acquiring importance among the scientific community as there are ever more studies that indicate their various benefits for health and cosmetics," Paula Mapelli, a professor at the Univeristy of Seville, said.

Although all the cold treatments analyzed generated carotenoid loss, the deep-frozen juices that were defrosted to room temperature or in a microwave were better sources of bio-accessible carotenoids than fresh juice

"That is to say, despite the fact that the concentration of carotenoids in the deep-frozen juices was less than in the fresh juice, the reduction in the size of the particles and the destruction of the cellular material that these treatment produce mean that the amount of carotenoids that can be absorbed by the intestine is higher," Mapelli said.

According to the results, among the treatments analyzed, pasteurization is the treatment that produces the highest level of carotenoid degradation and the greatest change in the color of the juice.

"Fresh juice is the juice that has the highest concentration of carotenoids, but this does not mean that it is the one that raises the carotenoid level in the blood and tissue the most, as you have to take into account the amount of carotenoids that are actually absorbed," the researchers said.

"Consumers tend to think that treated juices are less healthy than fresh juices. However, in this study, it has been shown how, at least in relation to the content of carotenoids that reaches the blood and tissue to protect us from disease, this is not always correct," Antonio Meléndez, a professor at the University of Seville Faculty of Pharmacy, said.

 

Pinalate Orange and the CITIUS laboratories

This research was carried out using the Pinalate variety of orange. This variety is a spontaneous mutation of the Navelate sweet orange. It is completely natural, not transgenic. The most important characteristic of this variety is that it has a high concentration of the colorless carotenoids phytoene and phytofluene.

To carry out the project, researchers made use of the services of Microscopy, Functional Characterization and Biology situated on the Centres of Research, Technology and Innovation at the University of Seville.

"Our next step, which will complete this research, will be to determine the content of colorless carotenoids in the blood after consuming these and other orange juices. That is to say, an in vivo study that corroborates this and other previous in vitro studies with other orange juices," Carla María Stinco, author of the study and researcher, said.

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