Superatmospheric oxygen storage enhances nutraceutical properties in blood oranges

Red-fleshed varieties of sweet oranges known as 'blood oranges' have been listed as one of the promising new "superfoods" due to their health properties. The blood oranges are distinguished from blond varieties by high accumulation of anthocyanins and superior antioxidant activity of the juice. The blood oranges are predominantly grown in Sicily (Italy) and among them Tarocco, Moro and Sanguinello are most important commercially.

Italian scientists have investigated the chemical changes in the composition of "Sanguinello Comune" caused by the superatmospheric oxygen storage.

For the study, the oranges were kept for 40 days at 10°C in hermetically closed chambers continuously ventilated with atmospheric air (control) or with oxygen-enriched air containing 76 kPa O2 (EnrO2).

Results in table 1 show that superatmospheric oxygen enhanced anthocyanin accumulation in the fruit juice. By the end of storage, total anthocyanin content in the juice of the EnrO2 oranges increased almost tenfold compared with the initial level, while only a threefold increase was observed in the control.


Click here to enlarge the table.

The important increase of anthocyanin accumulation was accompanied by significant increase in total content of phenolic compounds and in total antioxidant activity in the EnrO2 oranges, while in the control these parameters did not change significantly.


Fig. 1. Color difference in "Sanguinello Comune" orange after 40 days of storage at 10°C and 90% RH between Xontrol (to the left) and oxygen-enriched (76 kPa O2) air (to the right). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article).

These phenomena might be related to protective response of the fruit toward oxidative stress caused by the oxygen-enriched atmosphere. Moreover, superatmospheric oxygen storage caused a significant decline in acidity, total content of soluble solids, contents of sucrose, glucose, fructose and ascorbic acid in the juice of blood oranges, however these changes were relatively minor compared to the enhancement of anthocyanin accumulation.

Scientists conclude that the study has demonstrated a strategy for obtaining blood oranges with a higher content of antioxidant anthocyanins by postharvest stimulation of their synthesis under oxidative stress conditions. Even if oxygen-enriched atmosphere enhanced losses of sugars, vitamin C and acids, these losses were relatively minor compared with the dramatic increase in anthocyanin content, thus the overall effect on nutraceutical juice value was positive and could be further improved by blending the juice from EnrO2-stored oranges with one from non-stored or normal air-stored fruit.

Ultimately, the results of this study may have implications for the processing industry reducing its dependence on potentially allergenic antioxidant additives and food colorants such as carminic acid.

The full study is available online (since October 2015):
http://www.sciencedirect.com/science/article/pii/S0925521415301423

Source: Maria Giovanna Molinu, Antonio Dore, Amedeo Palma, Salvatore D'Aquino, Emanuela Azara, Victor Rodov, Guy D'hallewin, 'Effect of superatmospheric oxygen storage on the content of phytonutrients in 'Sanguinello Comune' blood orange', February 2016, Postharvest Biology and Technology, Vol. 112, pages 24–30.

Contacts:

Maria Giovanna Molinu
Consiglio Nazionale delle Ricerche
Istituto di Scienze delle Produzioni Alimentari
Traversa La Crucca, 3
Loc. Baldinca
07040 Li Punti, Sassari, Italy
Email: mariagiovanna.molinu@ispa.cnr.it

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