Berries of Vaccinium myrtillus L. Detection of adulterations by other species

Introduction

The dark blue-black color associated with Blueberry berries is directly linked to the presence of flavonoids and more particularly anthocyanins which are its main active ingredients (about 0.5% of dry weight). Organic acids are also contained at approximately 1% (including citric acid), flavonol glycosides, some hydroxycinnamic acids and catechin tannins. Bilberry dry extracts are regularly found in food supplements, particularly for antioxidant and antibacterial activities or for action on microcirculation. For more activity, the dryDry extracts are particularly concentratedusually standardized in anthocyanins, i.e. they have undergone  with value that can reach up to 25% thanks to a purification process and it is common to find extracts titrated at 25%.. Compared to the natural concentration of 0.5% dry weight, 25% anthocyanins represents a significant yield. This is why blueberry extracts often have extraction ratios close to 100/:1 meaning that the quantity of anthocyanins contained in 1g of this dry extract would be equivalent to the quantity of anthocyanins contained in 100g of dried fruit. It is easy to imagine that the price of 100/:1 dry extracts of blueberry berries is high, which makes it a risky material that can present falsifications. These frauds are frequent and you have to knowcommon and let see together how to anticipate them when carrying out an authenticity check.analysis. As the main active ingredients are anthocyanins, falsifications can be made using other sources of these substances and some of these frauds can be complex to identify.

Case study

Adulterations by very different species

The easiest frauds to detect are cases where the anthocyanins come from species very different from the target species. The profile of anthocyanins being generally significantly different, the study of this profile easily allows the detection of many frauds. But to achieve this, it is necessary to analyze the samples after separation of the compounds by chromatography. Thus, an assay by UV spectrophotometer of anthocyanins content alone will not make it possible to separate the compounds. On the other hand, a method by CCM/HPTLC or by HPLC-UV will allow this separation and will allow you to highlight these frauds.

Falsifications of closely related species

If we have seen that some falsifications are relatively easy to detect (provided that the compounds are separated), it is not the same for all frauds. Berries of similar species, moreover all called “Blueberry” are sometimes used for economic reasons. Among the species, we can cite V. corymbosum, V. uliginosum or even V. angustifolium and in these cases, it is much more difficult to apprehend the fraud.

Indeed, we can see in this single example that the profiles of two close species (here V. myrtillus and V. corymbosum) present the same anthocyanins profile but in different proportions. The mere presence of the expected anthocyanins is not sufficient to guarantee the proper authentication of a Bilberry dry extract. A detailed analysis of the anthocyanin composition, such as the UHPLC-UV analysis on the right, is therefore necessary. It alone makes it possible to avoid all types of falsification. With another less exhaustive analysis, all the risks of fraud cannot be spot out.