Abstract: 【Objective】‘Zihong NO.1’ red-fleshed apple is cultivated widely in Xinjiang Autonomous Region of China. Through investigating copigmentation of phenolic acids on anthocyanins in red-fleshed apple and their stability, this paper aims at providing a theoretical basis and reference for industrial utilization of red-fleshed apple anthocyanins. 【Method】 Ultrasonic-assisted method was used to extract anthocyanins, and pH differential method was adopted to determine the total content of red-fleshed apple anthocyanins. Besides, the constituents of red-fleshed apple anthocyanins and content of monomeric anthocyanins were also analyzed by HPLC. In phosphate buffer (pH 3.0) of red-fleshed apple anthocyanins, the copigmentation effect of these four acids was evaluated. The absorption spectra and absorbance at λ_max of all treatment groups as well as the contrast groups were measured before and after the treatments of heating, light exposure, oxidation and adding metal ions (Fe³⁺).【Result】The content of total anthocyanins in red-fleshed apple is 268.6 mg·kg^-1 and mainly consist of cyanidin-3-galactoside, cyanidin-3-arabinoside and cyanidin-3-glucoside, and cyanidin-3-galactoside accounts for the largest proportion of 75.34%. The wavelength of maximum absorption of red-fleshed apple anthocyanins in water system is at 515 nm, and the color and A_515mn of red-fleshed apple anthocyanins change due to different pH values. At the concentration of 0.01 mol·L^-1, caffeic acid, ferulic acid, chlorogenic acid and gallic acid all showed evident copigmentation, which led to the phenomena of hyperchromic effect and the bathochromic shift in varying degrees. Especially, ferulic acid caused the greatest extent of redshift (11nm) in anthocyanins solution. After anthocyanins was heated in water-bath at 60℃, 80℃, and 100℃ for one hour, respectively, chlorogenic acid and gallic acid showed the best protection effect, which is better than caffeic acid and ferulic acid. Under the natural lighting, the half-life of anthocyanins solution without copigments was less than 7 days, while the stabilities of anthocyanins with phenolic acids as copigments increased evidently (P＜0.05). The half-life of anthocyanins with chlorogenic acid, caffeic acid, gallic acid, and ferulic acid increased by 170.87%, 142.68%, 39.56% and 23.05%, respectively. When the concentration of H₂O₂ in anthocyanins solution was at a range of 0.1%-0.6%, anthocyanins was oxidized rapidly, but phenolic acids can protect anthocyanins from oxidation apparently. After being oxidized by 0.1% H₂O₂ for one hour, the content of anthocyanins in contrast group decreased to 38.39%, however, the retention rate of treatment groups with caffeic acid, ferulic acid, chlorogenic acid and gallic acid were 57.95%, 63.10%, 59.95% and 48.81%, respectively. The solution of Fe³⁺ with concentration of 2.5×10^-4—1×10^-3 mol·L^-1 had an adverse effect on anthocyanins color. In the solution containing Fe³⁺, the stability of anthocyanins with gallic acid as copigment was the highest. Additionally, the A_515nm of treatment groups were higher than contrast group (P＜0.05). 【Conclusion】The color of red-fleshed apple anthocyanins depends on pH value of solutions obviously. The property of anthocyanins remained stable and the color kept bright red when pH＜3.0. Caffeic acid, ferulic acid, chlorogenic acid and gallic acid showed varying degrees of hyperchromic effect and the bathochromic shift on red-fleshed apple anthocyanins and evidently improved the stability of anthocyanins (P＜0.05) under various conditions of heating, light exposure, oxidation and adding metal ion of Fe³⁺.

Key words: red-fleshed apple, anthocyanins, phenolic acids, caffeic acid, ferulic acid, chlorogenic acid, gallic acid, copigmentation; stability