Effect of boiling and roasting on physicochemical and antioxidant properties of dark red kidney bean (Phaseolus vulgaris)

Abstract

The effects of two processing methods (boiling and roasting) on physicochemical qualities of dark red kidney bean (Phaseolus vulgaris) were investigated. Changes in total polyphenol content (TPC) and antioxidant activity due to processing were also analyzed by using Folin–Ciocaltue method and 1,1 diphenyl-2-picrylhydrazyl (DPPH) assay, respectively. Analysis of physicochemical properties exhibited substantial variations (p<0.05) in the levels of moisture, ash, protein, fat, carbohydrate, gross energy and pH of raw and processed beans. Meanwhile, there was no considerable difference (p<0.05) in the fibre content of fresh and processed beans. Investigation of total phenolic content showed the significant (p<0.05) reduction of phenolic compounds in boiled (5.53±0.74 mg GAE/ g) and roasted (8.15±1.60 mg GAE/g) beans than raw samples (12.55±1.42 mg GAE/g). DPPH radical scavenging activity was also decreased significantly (p<0.05) in boiled and roasted samples with IC50 value of 0.0608±0.0765 mg/mL and 0.0523±0.0026 mg/mL, respectively. In the case of household cooking, keeping boiling water would be advised for the preservation of minerals, vitamins and phenolic compounds. The roasting process may be used to develop high-quality health-promoting dark red kidney bean products.