绿原酸对糖酸反应体系中5-羟甲基糠醛形成的影响

Effect of Chlorogenic Acid on Formation of 5-Hydroxymethylfurfural in Fructose-acid Reaction Systems

根据李子果实成分和干制温度条件,设置果糖、柠檬酸-柠檬酸钠缓冲液反应体系,探讨不同浓度绿原酸在不同pH环境下对5-羟甲基糠醛（HMF）及其中间产物3-脱氧奥苏糖（3-DG）形成的影响。结果表明,绿原酸影响HMF和3-DG形成,且受pH的影响。当pH为2.80、3.70时,添加绿原酸抑制HMF和3-DG的形成,pH越低,抑制率越高。当pH为4.70、5.70时,添加绿原酸显著促进HMF的形成,pH越高,促进率越高,产生的3-DG越多,但在同一pH下绿原酸对3-DG的促进作用不显著。当pH为6.0时,高剂量（42μmol/mL）的绿原酸显著增加HMF的形成速率,在90℃下反应48 h后,HMF的产生量增加了1.14倍。可以得出结论：在低pH值下,果糖倾向通过果糖呋喃阳离子途径形成HMF,绿原酸的作用机理可能是抑制3-DG的形成而降低HMF含量;在高pH值下,果糖主要通过3-DG途径生成HMF,绿原酸的作用机理可能是促进3-DG转化为HMF而提高HMF含量。

In this study, a reaction system consisting of fructose, citric acid, and sodium citrate buffer solution was developed to investigate the effect of chlorogenic acid on the formation of 5-hydroxymethylfurfural（HMF） and the intermediate product 3-deoxyglucosulose（3-DG） under different pH environments, to mimic drying of plum fruit under high temperature conditions. The results showed that chlorogenic acid could influence the formation of HMF and 3-DG, which was also affected by pH conditions. At pH values of 2.80 and 3.70, the addition of chlorogenic acid inhibited the formation of HMF and 3-DG; the lower the pH value, the higher the inhibition rate. At pH values of 4.70 and 5.70, the addition of chlorogenic acid significantly promoted the formation of HMF; with increasing pH, an increased production of HMF as well as 3-DG was observed. However, at the same pH, chlorogenic acid did not have a significant promoting effect on the formation of 3-DG. At pH 6.0, a high dose（42 μmol/mL） of chlorogenic acid could significantly increase the rate of HMF formation. When the reaction was carried out at 90 ℃ for 48 h, HMF yield was increased by 1.14-fold. Thus, at lower pH, fructose tended to form HMF via the fructofuranosyl cation pathway and chlorogenic acid could inhibit the formation of 3-DG to decrease the HMF content. At higher pH, fructose was more likely to form HMF via the 3-DG pathway and chlorogenic acid could increase the HMF content by promoting the conversion of 3-DG to HMF.