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4.3

Anthocyanins in Foods: Occurrence and Physicochemical Properties
Adriana Z. Mercadante and Florinda O. Bobbio

CONTENTS
4.3.1 4.3.2 4.3.3 Introduction................................................................................................241 Structures and Physicochemical Properties ..............................................242 Occurrence inFoods..................................................................................243 4.3.3.1 Anthocyanidins............................................................................243 4.3.3.2 Glycosides ...................................................................................257 4.3.3.3 Acyl Groups ................................................................................258 4.3.4 Factors AffectingStability of Anthocyanins .............................................260 4.3.4.1 Structure ......................................................................................260 4.3.4.2 Temperature and pH....................................................................261 4.3.4.3 Ascorbic Acid..............................................................................262 4.3.4.4 Sugars..........................................................................................263 4.3.4.5 Other Factors ...............................................................................264 4.3.5 Stabilization ...............................................................................................264 4.3.5.1 Self-Association..........................................................................265 4.3.5.2 Intermolecular Copigmentation...................................................265 4.3.5.3 Effects of Aldehydes ...................................................................266 4.3.6 Final Remarks............................................................................................267 Scientific Names....................................................................................................268 Acknowledgments..................................................................................................268 References..............................................................................................................268

4.3.1 INTRODUCTION
In the past decade, general interest and research activities focusing on anthocyanins haveconsiderably increased. This increased interest is not only based on the common knowledge that these water-soluble pigments can be used as possible alternatives to artificial food colorants, but also it relates to their bioactive properties. When search241
© 2008 by Taylor & Francis Group, LLC

242

Food Colorants: Chemical and Functional Properties

ing the Chemical Abstract Service andMedline for the word anthocyanin, 910 articles were cited in 2005 compared to 305 articles in 1995. The total number of different anthocyanins reported to be isolated from plants was 539.1 However, the number of anthocyanins found in foods is much smaller. Although a large number of papers were published regarding anthocyanin composition in several foods, investigators in most studies used onlychromatographic and chemical behaviors as bases for identification. In this chapter, we considered only papers in which identification was based at least on mass spectrometry (MS). In fact, the use of only MS and UV-visible information can easily lead to misidentification as the following example shows. A minor peak separated from boysenberry was found to have a mass at m/z 757 and was assigned ascyanidin-3-(6″-p-coumaryl-glucoside)-5-glucoside2 and was also considered to be cyanidin-3-(2-glucosyl)-6-(rhamnosyl)glucoside3, consistent with its molecular weight of 757 μ. Nuclear magnetic resonance (NMR) analysis confirmed that cyanidin-3-(2-(glucosyl)-6-(rhamnosyl)glucoside was the correct assignment.3 The assignment of sugar configuration was not properly investigated in most papers. In addition,...
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