Effect of storage and freezing on the phenolic and antioxidant activities of raspberries

Mullen, William C (2002) Effect of storage and freezing on the phenolic and antioxidant activities of raspberries. MSc(R) thesis, University of Glasgow.

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Abstract

A method was developed to analyze anthocyanins in red raspberries (Rubus idaeus L.) cv. Glen Ample. The anthocyanins were extracted from the fruit by homogenizing in acidified methanol. The methanolic extract was centrifuged and the supernatant analyzed by reverse-phase HPLC. The eluent was monitored at 371 and 520 nm before being introduced into a single quadrupole mass spectrometer through an atmospheric pressure chemical ionization probe operating in positive ion mode. This method facilitated the identification of eight anthocyanins in the raspberry matrix. Further analysis of raspberry extracts by gradient, reverse-phase HPLC with diode array detection and tandem mass spectrometry identified eleven anthocyanins, including cyanidin-3-sophoroside, cyanidin-3-(2G-glucosylrutinoside), cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-sophoroside, pelargonidin-3-(2G-glucosylrutinoside) and pelargonidin-3-glucoside. Significant quantities of an ellagitannin, sanguiin H-6, with a Mr of 1870, were detected along with lower levels of a second ellagitannin, lambertianin C which has a Mr of 2804. Other phenolic compounds that were detected included trace levels of ellagic acid and its sugar conjugates along with one kaempferol and four quercetin-based flavonol conjugates. Fractionation by preparative HPLC revealed that sanguiin H-6 was a major contributor to the antioxidant capacity of raspbenies together with vitamin C and the anthocyanins. Vasodilation activity was restricted to fractions containing lambertianin C and sanguiin H-6. The antioxidant capacity of the fresh fruit and the levels of vitamin C and phenolics were not affected by freezing. When fruit were stored at 4

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: Alan Crozier
Keywords: Food science
Date of Award: 2002
Depositing User: Enlighten Team
Unique ID: glathesis:2002-73340
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73340

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