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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCEMENT OF THE QUALITY AND MICROBIAL STABILITY OF FRESH FRUITS AND VEGETABLES WITH EDIBLE COATINGS AND OTHER SURFACE TREATMENTS

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Title: Toward a facile method to remove ascorbate interference in the Folin-Ciocalteu assay of "total phenolic content"

Authors
item Ford, Bryan
item Bai, Jinhe
item Manthey, John
item Baldwin, Elizabeth

Submitted to: Southern Region of the American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: February 12, 2010
Publication Date: N/A

Technical Abstract: The long-established Folin-Ciocalteu (F-C) assay for total phenolics can have limitations due to interference by ascorbic acid (AsA). For common fruit juices this interference can easily exceed the magnitude of the total phenolic signal itself. Approaches to eliminating the AsA interference are briefly discussed, with particular attention to the use of ascorbate oxidase (AO). AOs isolated from curcubitaceae and from fungi were tested. Both oxidized AsA, although we found the fungal AO has a broader pH range and wider temperature tolerance and functionality. We found that dehydroascorbic acid (DHA), the AO catalyzed product of AsA with oxygen, also acts as an F-C reductant giving an apparent molar strength of 10 to 20% of the parent AsA. Thus AO alone will likely not completely solve the problem of AsA interference in F-C assays. One promising approach to eliminating the DHA is discussed. Any such approach must remove most or all of the DHA while giving products that are not themselves F-C reductants. Further, it must not substantially alter or damage the phenolics present.

Last Modified: 4/18/2014
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