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dc.contributor.author Donner, Horst en_US
dc.date.accessioned 2007-05-15T15:29:46Z
dc.date.available 2007-05-15T15:29:46Z
dc.date.issued 1998-11-01T00:00:00Z en_US
dc.identifier.uri http://hdl.handle.net/1993/1129
dc.description.abstract Using high performance liquid chromatography (HPLC) with a reverse phase column and a photodiode array detector, the chromatographic profiles of the four red onion varieties 'Mambo', 'Red Bone', 'Red Granex' and 'Red Jumbo' were determined. A total of four major and four minor anthocyanins were present in red onions. The anthocyanins and colourless phenolics were identified using a rapid identification procedure based on spectrophotometric, and liquid and gas chromatographic techniques. The major anthocyanins were identified as cyanidin 3-glucoside, cyanidin 3-laminaribioside, cyanidin 3-(6$\sp{\prime\prime}$-malonylglucoside), and cyanidin 3-(6$\sp{\prime\prime}$-malonyllaminaribioside). The four minor anthocyanins were identified as cyanidin 3-(3$\sp{\prime\prime}$-malonylglucoside), peonidin 3-glucoside, pe nidin 3-malonylglucoside and cyanidin 3-dimalonyllaminaribioside. Using the same technique, the colourless phenolic compounds were identified as protocatechuic acid 4-glucoside, quercetin 7,4$\sp\prime$-diglucoside, quercetin 3,4$\sp\prime$-diglucoside, quercetin 3-glucoside, quercetin 4$\sp\prime$-glucoside, and a 5,7-dihydroxy flavanone glucoside or a 5,7-dihydroxy dihydroflavanol glucoside. The copigmentation effect was studied using cyanidin 3-glucoside, cyanidin 3-malonylglucoside, cyanidin 3-malonyllaminaribioside, chlorogenic acid, protocatechuic acid and caffeine in aqueous buffers at pH 3.7, 4.7 and 5.7. It was observed that copigment structure and concentration, and pH have a dramatic influence on the copigmentation phenomenon. Colour stability studies using cyanidin 3-glucoside solutions at pH 3.7, 4.7, and 5.7 without and with added chlorogenic acid, protocatechuic acid and caffeine in the presence and absence of light, demonstrated that intense exposure to fluorescent and incandescent light was detrimental to the photostability of copigmented cyanidin 3-glucoside solutions at any pH. (Abstract shortened by UMI.) en_US
dc.format.extent 11131774 bytes
dc.format.extent 184 bytes
dc.format.mimetype application/pdf
dc.format.mimetype text/plain
dc.language en en_US
dc.language.iso en_US
dc.title The anthocyanins of red onions, Allium cepa L, extraction, characterization, complexation and stabilization. en_US
dc.degree.discipline Food Science en_US
dc.degree.level Master of Science (M.Sc.) en_US


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