Abstract
As local varieties of citrus fruit in Taiwan, Ponkan (Citrus reticulata Blanco), Tankan (C. tankan Hayata), and Murcott (C. reticulate × C. sinensis) face substantial competition on the market. In this study, we used carbon dioxide supercritical technology to extract oleoresin from the peels of the three citrus varieties, adding alcohol as a solvent assistant to enhance the extraction rate. The supercritical fluid extraction was fractionated with lower terpene compounds in order to improve the oxygenated amounts of the volatile resins. The contents of oleoresin from the three varieties of citrus peels were then analyzed with GC/MS in order to identify 33 volatile compounds. In addition, the analysis results indicated that the non-volatile oleoresin extracted from the samples contains polymethoxyflavones (86.2~259.5 mg/g), limonoids (111.7~406.2 mg/g), and phytosterols (686.1~1316.4 μg/g). The DPPH (1,1-Diphenyl-2-picrylhydrazyl), ABTS [2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] scavenging and inhibition of lipid oxidation, which test the oleoresin from the three kinds of citrus, exhibited significant antioxidant capacity. The component polymethoxyflavones contributed the greatest share of the overall antioxidant capacity, while the limonoid and phytosterol components effectively coordinated with its effects.
Highlights
Citrus trees comprise the most abundant crop of fruit trees in the whole world, providing fruits which have a high commercial value on both the fresh market and the food processing industry [1]
10% ethanol was used as a co-solvent in Supercritical fluid extraction (SFE), and the results showed that the respective oleoresin extraction rates for the Ponkon, Tankan, and Murcott citrus varieties were 1.1%, 2%, and 0.8% (w/w)
Citrus oleoresin extracted via SFE is composed of volatile compounds, a fact which can be applied in identifying specific citrus species when utilizing gas chromatography/mass spectrometry (GC/MS)
Summary
Citrus trees comprise the most abundant crop of fruit trees in the whole world, providing fruits which have a high commercial value on both the fresh market and the food processing industry [1]. The citrus varieties produced in Taiwan are the Ponkon Blanco), Tankan (C. tankan Hayata) and Murcott (C. reticulate × C. sinensis) varieties, with 108,058 tons of Ponkon, 52,023 tons of Tankan, and 24,751 tons of Murcott having been produced in one recent year [2]. The peels and pulps of processed citrus product waste contain high levels of active biological components, including carotenoids, vitamin E, flavonoids, limonoids, phenols, polysaccharides, lignin, cellulose, pectin, and essential oils [3,4,5]. Essential oils and oleoresin are found in citrus peels, the bulk of which are mainly obtained from the byproducts of the juice manufacturing industry, and are extracted for use in beverages and cosmetics with approximately 56,200 tons being used annually [6,7]. According to Molecules 2016, 21, 1735; doi:10.3390/molecules21121735 www.mdpi.com/journal/molecules
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