Fresh orange juice has the highest amount of carotenoids, but that doesn't mean that our intestines can absorb them.
Researchers at the Laboratory of Food Colour and Quality at the University of Seville, Spain, set out to investigate the "bioaccessibility" of two carotenoids that can be found in orange juice.
These carotenoids have been gaining more and more attention in the scientific community due to their healthful properties.
The vast majority of carotenoids are "yellow, orange, and red pigments synthesized by plants."
Carotenoids are key for optimum visual health, as the human body converts them into retinol, or vitamin A, which is key for visual acuity.
Other, more rare carotenoids, such as those making up the focus of this new study, are colorless.
Two of them, called phytoene and phytofluene, have been getting a lot of attention lately due to their supposed antioxidant properties. Studies have also suggested that these two compounds may prevent prostate cancer, breast cancer, and atherosclerosis, among other diseases.
Phytoene and phytofluene are also widely available, being present in tomatoes, carrots, and some citrus fruits such as oranges. Finally, researchers think that these carotenoids also have cosmetic benefits, as they protect against ultraviolet damage and maintain skin health.
So, if you like orange juice, you may wish to know what the best way to drink it is to fully reap the benefits that these two carotenoids have to offer.
Paula Mapelli-Brahm, a professor at the University of Seville, and team set out to investigate precisely this question. Their findings are published in the Journal of Functional Foods.
Bioaccessible carotenoids matter most
Using an imaging technique called transmission electron microscopy, Prof. Mapelli-Brahm and her colleagues analyzed the cell structures of fresh and pasteurized orange juices, as well as those of ultra frozen orange juice defrosted either at room temperature, in the microwave oven, or in the fridge.
The researchers found that cold treatments lead to a greater degradation of the carotenoids in the orange juice. However, cold treatments also increased the bioaccessibility of these carotenoids, which means greater benefits for our health.
Of all the cold treatments analyzed, ultra frozen orange juice — which was defrosted to either room temperature or in a microwave — provided the most bioaccessible phytoene and phytofluene.
"That is to say, despite the fact that the concentration of carotenoids in the deep-frozen juices was less than in the fresh juice," explains the lead investigator, "the reduction in the size of the particles and the destruction of the cellular material that [this] treatment produce[s] mean that the amount of carotenoids that can be absorbed by the intestine is higher."
"[F]resh 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," further explain the researchers.
The scientists confirm that, of the treatments, pasteurization is the most damaging to carotenoids. Study co-author Antonio J. Meléndez, a professor at the University of Seville Faculty of Pharmacy, comments on the importance of the findings.
"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."
Prof. Antonio J. Meléndez
"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," concludes study co-author Carla María Stinco.