The calibration factor 98.2 of method 4 is improperly
used, because original papers of Fuleki and Francis
(1968a,b) report a value of 982 (not 98.2) as absorbance
at 535 nm of a solution containing 1% (w/v) of cranberry
anthocyanins. Moreover, cranberry anthocyanins are an
unsuitable standard because these are different from
those of blood orange juice (Zapsalis and Francis, 1965).
Finally, the data of method 5 result from the application
of the factor 402.3, i.e., the absorbance at 532 nm of a
solution containing 1% (w/v) of blood orange juice
anthocyanins, but such a value is not supported by any
experimental evidence.