Peels of Some Citrus Fruits As Source of Antioxidants for Use with Different Vegetable Oils

Document Type : Original Article

Authors

Food Science and Technology Faculty of Agriculture - Alexandria University

Abstract

The present study was conducted on peels of three citrus fruits; namely, orange peel (OP), mandarin peel (MP)
and lemon peel (LP) to evaluate their bioactive compounds for use in some vegetable oils as antioxidants. The total
phenolics content in OP, MP and LP were 818.86, 996.8 and 956.86, respectively as mg gallic acid equivalent / 100
g and total flavonoids content in OP, MP and LP were 476.56, 517.38 and 406.23, respectively as mg rutin equivalent
/ 100 g. Two analytical methods were used to determine the antioxidant activity 2, 2- diphenyl-1- picrylhydrazyl
(DPPH) and ferric reducing antioxidant power (FRAP). Separation of phenolic compounds of peel extracts by HPLC
revealed the identification of 24 compounds whose concentrations varied in the three types of peels. The oxidative stability
of palm olein, soybean and sunflower oils containing each of OP, MP and LP and their extracts as novel sources
of antioxidants versus butylated hydroxytoluene (BHT) as a synthetic antioxidant were evaluated by measuring their
induction periods (IPs) using the Rancimat method. The ethanolic extracts of the peels were added at two levels; 1000
and 2000 ppm, individually, while the whole peels (OP, MP and LP) were added in different quantities according to
the extract yield percentage of each. The data revealed that citrus peel extracts, especially orange peels, are considered
as potent antioxidants and thereby can be applied to prolong the storage periods of the three vegetable oils under study
instead of BHT since there is a concern about its use from the safety point of view.

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