Composition of flavonols in red raspberry juice as influenced by cultivar, processing, and environmental factors
1993
Rommel, A. | Wrolstad, R.E.
Flavonols were characterized and measured in experimental (n = 46) and commercial (n = 9) red raspberry juices by HPLC/diode array spectral techniques. Samples were prepared using minicolumns, packed with Polyamide 6. A fraction eluted with methanol contained eight or fewer quercetin glycosides, quercetin, and kaempferol. A second fraction eluted subsequently with 0.5% ammonia in methanol contained three flavonol glucuronides, two flavonol forms, aglycons, ellagic acid, and its derivatives. Quercetin 3-glucuronide was the major flavonol in experimental and commercial juices, respectively (mean of 54 and 51 ppm), and a flavonol presumed to be quercetin 3-sophoroside was the second primary compound means of 29 and 33 ppm). In addition, 36 flavonol forms were measured in trace amounts. The mean total concentrations of quercetin and kaempferol forms, respectively, in experimental juices (n = 45) were 118 and 3.6 ppm and in commercial juices (n = 7) 121 and 3.4 ppm, respectively. The mean total flavonol concentrations in experimental and commercial juices were 122 and 125 ppm, respectively. Influences of cultivar (n = 10), processing method (standard, high-speed centrifugation, depectinization, diffusion extraction, vacuum and osmotic concentration) and environmental factors (geographic origin, maturity, harvesting method, mold contamination) were evaluated.
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