Voltammetric and spectrophotometric pathways for the determination of total antioxidant capacity in commercial turnip juice

Abstract

In this study, total flavonoid substances, total phenolic substances, and total antioxidant capacity in turnip juice which made from the turnip (Brassica rape), a plant belonging to the family of “Turpgiller” (Brassicaceae), and also a drink specific to the Çukurova, were investigated. The turnip juice samples, taken from the turnip juice (A sample) and hot turnip juice (B) sample in local market, prepared in the laboratory were performed as two different parallel assays. In addition, electrochemical method was used to evaluate total antioxidant capacity (TAC) of turnip juice and hot turnip juice. By the square wave stripping voltammetry (SWSV) method, under the optimized experimental conditions was applied for quercetin determination with a limit of detection (LOD) and limit of quantification (LOQ) of 0.017 and 0.057 µg/L, respectively. These values are satisfactory for application to real food samples for the evaluation of TAC. According to the results carried out by spectrophotometric methods, the highest total phenolic and flavonoid contents and TAC were observed as 13.049±0.40 g GAE/mL, 37.850±0.70 mg QE/mL and 81.831±3,24 mg TE/100 mL, respectively. In addition, the TAC in turnip juice and hot turnip juice were calculated as 573.05±0.43 mg/L and 854.98±9.9 mg/L by SWSV, respectively. The results obtained by voltammetric and spectrophotometric methods for determinations of TAC were in correlation and found to be compatible for the determination of TAC.