Investigation of the stability and antioxidant properties of anthocyanins-based purple potato colorants after processing

Abstract

To investigate the effect of processing method on the stability and antioxidant properties of anthocyanins-based colorants, purple potato (Solanum tuberosum L.) was treated by steaming, baking before lyophilization, oven drying and direct lyophilization before extracted by 0.5% HCl-methanol solution twice. The concentration of total anthocyanins in different treated samples ranged from 0.34 to 1.03 mg/g fresh weight. The direct lyophilization treated sample had significant higher content than other processing method. Stability study showed that both light and heat could accelerate the degradation of anthocyanin-based purple potato colorant. The fresh purple potato colorant showed the most stable property, followed by the lyophilization, oven drying, steaming before lyophilization and baking before lyophilization samples. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of purple potato extracts ranged from 0.25 to 0.37 mg/ml. The ability of the extracts to reduce Fe³⁺ to Fe²⁺ ranged from 395.40 to 1320.47 μmol/L equivalent to FeSO₄ at the concentration of 10 mg/ml. Lyophilization treated samples showed the most strongest antioxidant activity, significantly higher than that of other processing methods. Our results suggest that to keep stable and functional anthocyanins-based purple potato colorants, lyophilization was a recommended suitable processing method in food industry.

Key words: Solanum tuberosum L., processing methods, anthocyanin-based colorant, stability, antioxidant.