PHYSICOCHEMICAL PROPERTIES AND ANTIMICROBIAL EFFECTS OF ROSELLE COROLLA, ONION PEELS AND PEANUT SKINS ANTHOCYANINS

Document Type : Original Article

Authors

Biochem. Dept., Fac. Agric., Zagazig Univ., Egypt

Abstract

Anthocyanins would make ideal natural food colourants with additional nutritional
benefits however stability is a hindering factor. The stability, physicochemical properties and the
biological activities of anthocyanins extracted from onion peels, peanut skins or roselle corolla were
achieved. Crude anthocyanins were extracted using two different solvent systems (distilled water and
acidified ethanol with HCl 1.5 N, 85:15, V/V). Roselle corolla pigment extracted by acidified ethanol
was the highest in phenolic and anthocyanin contents compared with water extract content. The
aqueous extract of roselle corolla, onion peels and peanut skin showed activities against Gram+
(Staphylococcus aureus and Bacillus subtilis) and Gram- (Pseudomonas aeruginosa and Escherichia
coli) bacteria. Aqueous extract of roselle corolla and peanut skin inhibited mycelial growth of
Fusarium oxysporum. About 78% of aqueous extract pigments of onion peels were retained when
heated at 75°C. Stability under different light sources showed general decline in pigment retention of
the samples over the time period with all extracts. However, roselle corolla extracted by acidified
ethanol showed more stability under different light treatments compared with distilled water extract.
The extracted pigments were stable against oxidizing agents, whereas it reduced gradually when
treated with cane sugar or salt.

Keywords

Zagazig Journal of Agricultural Research
Volume 46, Issue 3
May and June 2019
Pages 769-781

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