Hi christine,

We use the following method for measuring the total anthocyanin content in fresh strawberry fruit by pH differential assay.

* two 2 ml of strawberry juice are added into two flasks.

* Each 2 ml of juice is diluted to 25 ml with pH 1 or pH 4.5 buffer as follows:

125 ml of KCl (0.2 N) + 385 ml of HCl (0.2 N) are mixed for preparing pH 1 buffer. Whereas, 400 ml of 1M (CH3 COONa) + 240 ml of 1 N HCl + 360 ml of H2O are mixed for preparing pH 4.5 buffer.

* The absorbance of the mixture is measured at 510 nm .

* The total anthocyanin content is measured according to the following equation:

C (cyanidin-3-glucoside equivalents, mg/L)=(Abs at pH 1 - Abs at pH 4.5) × 449.2 × DF × 1000⁄26900 × m

Where, DF is the dilution factor, m is the weight of the sample, 449.2 is the molecular mass of cyanidine-3-glucoside, 1000 to convert g to mg, and 26900 is the molar extinction coefficient at pH 1 and 510 nm.

Note: the juice must be clear, if not centrifuge.

Please refer to the following reference:

Dear Duried,

Thanks for your answer. However, I am still i not sure how to calculate the m in the equation - do you have any suggestion since it is a powder that i dissolve in liquid after which I extract it in liquid and in the end only use a small part for the final assay?

I agreed with Duried answer he mentioned an easy protocol to determine the anthocyanins conc.

Dear Christine,

Please do not mind about the initial weight of your sample. The DF already includes your initial weight. As well as I understand from your explanation, you've already solved your issue. When you include the DF value (40*0.05g/0.002 L) in the formula, the resultant unit of anthocyanin content will be W/W.

Best.