Establishing an ultrasound-assisted water bath system for efficient extraction of natural colorant from <i>Rhus typhina L</i> .

Purpose To expand the range of available natural colorants, a novel colorant was developed from the fruit spikes of Rhus typhina L. The extraction method was optimized, and the colorant’s stability under varying acid-base conditions, light exposure and thermal stress was characterized. Design/methodology/approach The extraction process was optimized through single-factor experiments and orthogonal design, focusing on key parameters such as extraction time, temperature and solid-to-liquid ratio. In addition, the stability of the colorant solution was assessed against acidic, alkaline, light and thermal conditions. The chemical composition, group structures and antioxidant activity of the aqueous extract were analyzed using zeta potential measurements, Fourier transform infrared spectroscopy, liquid chromatography-mass spectrometry (LC-MS) and the 1,1-diphenyl-2-picrylhydrazyl method. Findings The colorant extracted from Rhus typhina L. exhibited a maximum absorption at 520 nm. The optimal conditions for ultrasound-assisted extraction were determined to be an extraction time of 30 min, a temperature of 50 °C and a solid-to-liquid ratio of 1:20. Light exposure for up to 70 min and temperatures below 70 °C had minimal impact on absorbance, with decreases of only 0.4% and 0.1%, respectively. LC-MS analysis revealed a diverse composition of flavonoids, phenolic compounds and their derivatives in the aqueous extract. These components imbued the aqueous extract with an inhibition of 94.1%. In addition, the presence of anthocyanins caused the extract’s color to shift markedly with pH, ranging from red (pH 1–3) to bluish-violet (pH 6–7) and yellow-green (pH 8–10). Originality/value The aurora red colorant extracted from the fruit spikes of Rhus typhina L. demonstrates exceptional light and heat stability. The primary components of this colorant may impart the properties of antibacterial and ultraviolet protection to fabrics and other materials, making the colorant highly suitable for applications in health-focused textiles.