Fruit juices have come under fire in recent years for a high sugar content, but scientists say the whole picture is not so clear cut.
They found that, although juices reduced the level of carotenoids, vitamin C and flavornoids present, they improved bioaccessibility (how much the body can absorb and use).
Juicy findings
Oranges and their products are rich sources of carotenoids (antioxidants, and a precursor to vitamin A); flavonoids (thought to have antioxidant effects) and vitamin C. They also contain lutein and zeaxanthin, compounds believed to play an important role in preventing age-related macular degeneration (loss of vision) and cognitive impairment in the elderly.
“Consumers perceive orange juice as a healthy and natural source of vitamins and other health promoting nutrients, resulting in an increasing worldwide demand and production,” wrote Ralf Schweiggert, one of the authors. “Additionally, the convenient packaging and long shelf life of juices are advantageous compared to fresh fruit.
“Recent intervention studies demonstrated the health benefits of long-term orange juice consumption, such as an increased total antioxidant status, lower total cholesterol levels, and the prevention of endotoxin increases after meals high in fat and carbohydrate.
“However, greater consumption of orange juice has also been criticized because of its high intrinsic sugar level, being associated with a higher risk of type 2 diabetes and cardiovascular diseases.”
Should we concentrate on juice?
The study analysed five different orange product types: fresh unprocessed orange segments, homogenized segments (puree), freshly squeezed juice, pasteurized juice, and flash-pasteurized juice.
Orange juice (fresh and pasteurized) showed ‘slightly diminished’ carotenoid and vitamin C levels, by 3-18%. Flavonoid and dietary fiber levels were decreased to approximately one-tenth upon dejuicing.
However, carotenoid bioaccessibility – how easily the body can absorb the nutrients - was enhanced from 10.8% in oranges to 28.3% in freshly squeezed orange juice. Flavonoid bioaccessibility was boosted almost five-fold to 96.5%.
The bioflavonoid hesperidin remained similar across all test foods.
“The lower flavonoid levels in orange juices as compared to orange segments might be less relevant regarding their intestinal absorption, because low flavonoid solubility in the digestive fluids is considered to be the limiting factor.”
Researchers add that mashing orange segments did not alter carotenoid bioaccessability, suggesting that processing fiber is more significant.
“In contrast to dejuicing, homogenization of orange segments to a puree did not enhance carotenoid bioaccessability. This indicates a minor role of cell disruption and comminution, compared to the removal of fibers in orange products.”
Title: ‘In Vitro Bioaccessibility of Carotenoids, Flavonoids, and Vitamin C from Differently Processed Oranges and Orange Juices’
Authors: J.K. Aschoff, S. Kaufmann, O. Kalkan, S. Neidhart, R. Carle, R.M. Schweiggert
Source: Journal of Agricultural and Food Chemistry, 2015, 63 (2). DOI: 10.1021/jf505297t
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