Berries and berry products are generally known to be rich sources of antioxidants which is a result of their high concentrations of anthocyanins, phenolic acids and usually either proanthocyanidins or ellagitannins. For anyone beginning a new project relative to the bioactive components in berries, two databases could be referenced (see ‘Learn More’ section for Web sites) relative to componnets to be expected. Processing of berries into juices or various dried products including freeze dried berry powders can alter some of these components. The source(s) of the anthocyanins can be determined from the anthocyanin profile based upon HPLC separation. Assays of ORAC and total phenolics provide measures of antioxidant capacity and total phenolics in the material. An often unrecognized change that can occur with processing is the formation of polymeric color where monomeric anthocyanins complex with other polyphenolics compounds in the mixture. This process results in the formation of large polymers which are likely not absorbed and but the amount of monomeric anthocyanins is decreased. However, antioxidant capacity may not be altered markedly by this reaction. Juice products in particular are subject to formation of polymeric color. Thus, to adequately characterize a berry or berry product, a number of analyses are needed.
Total Anthocyanin Content
Total Anthocyanin assay in Brunswick Laboratories utilizes a pH differential method. It is based on the fact that anthocyanin pigments reversibly change color with a change in pH; the colored oxonium form exists at pH 1.0, and the colorless hemiketal form predominates at pH 4.5. The difference in the absorbance of the pigments at 520 nm is proportional to the pigment concentration. Results are expressed on a cyanidin-3-glucoside basis. Although determination of total anthocyanin pigment is useful in assessing the quality of food products, it is highly recommended to be used in conjunction with analyses for individual anthocyanins as well as analyses of polymeric anthocyanins.
Individual Anthocyanins – HPLC/MS/MS profile
There are over 600 naturally occurring anthocyanins, and all are O-glycosylated with different sugar substitutes and/or acylated groups. Authentication of the source and relative amounts of the individual anthocyanins is important to the consistency of anthocyanin products. Analytical standards are not available for all anthocyanins, but quantitation is achieved using the glucosides of the 6 common aglycones.
Phenolic acids may be intermediates in the synthesis of flavonoids in plants. Increasing amounts of data are becoming available on possible health effects of phenolic acids. The particular phenolic acids present in different berries varies considerably. Thus, these compounds are important to the characterization of different berries and berry products. Brunswick Laboratories has the capability using HPLC/MS/MS to quantify those phenolic acids for which standards are available, and also to identify new phenolic acids present.
Berries contain some of the highest measures of antioxidant capacity of any of the fruits or vegetables. With the recently developed ORAC5.0™ methods, measures of antioxidant capacity can be determined using 5 different free radical sources (peroxyl, hydroxyl, peroxynitrite, superoxide anion and singlet oxygen).
HPLC profiles of these phytochemicals and validation by MS/MS can be generated upon request, but standards are not available for all of the individual compounds, so quantitation is not possible.