Abstract:

In order to understand whether phenolic compounds and antioxidant activity of whole citrus fruit powder (WCFP)
decrease after granulation, the impact of granulation on nutritional value of WCFP was evaluated. The phenolic composition
and contents of WCFP from four citrus species were determined by high performance liquid chromatography (HPLC).
The antioxidant activities of all samples were evaluated by ferric reducing/antioxidant power (FRAP), 1,1-diphenyl-2-
picrylhydrazyl (DPPH) free radical scavenging and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical
scavenging methods. The contents of total phenolics and flavonoids did not significantly change after WCFP was granulated
(P < 0.05). Among phenolic compounds detected in the study, only obvious change in naringin content was observed, and
the content of naringin in both Australian orange and grapefruit decreased significantly after granulation. However, the
content of naringin in lemon increased. The antioxidant tests in vitro showed that all values were consistent with each other,
in spite of using ABTS, DPPH and FRAP methods. No significant differences were observed between WCFP powder and
granules (P < 0.05). These results suggested that granulation at 35–40 ℃ did not result in significant reduction in phenolic
compound contents and antioxidant abilities of WCFP, and maintained the nutritional quality of WCFP. Therefore, as a good
micromachining technology, granulation can enable effective utilization of whole citrus fruit.

Key words: granulation, citrus, phenolic compounds, antioxidant activity