Assessment of the reducing capacity of processed fruit juices with the copper(I)/4,4'-dicarboxy-2,2'-biquinoline complexes.

An alternative method for quantification of the total reducing capacity (TRC) of processed ready-to-drink fruit juices (orange, grape, peach, mango, cashew, strawberry, apple and guava) is suggested. The spectrophotometric procedure is based on the reduction of Cu(II) to Cu(I) by antioxidants (present in the samples) in aqueous buffered solution (pH 7.0), containing 4,4'-dicarboxy-2,2'-biquinoline acid (HBCA), yielding the [Formula: see text] complexes.