红皮云杉球果原花青素在液体状态下稳定性
Stability of proanthocyanidins from Picea koraiensis Nakai in solution
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摘要: 以红皮云杉球果为研究对象,以原花青素残留率为指标衡量含量变化情况,研究在不同的pH值、温度、浓度条件下原花青素稳定性及降解动力学。结果表明,原花青素稳定性随温度和pH值的升高而降低,低温与酸性条件下更适宜原花青素储存;原花青素浓度为4 mg/mL时残留率最高,降解反应遵循一级反应动力学,反应活化能Ea<33 kJ/mol,降解速率较大。仅在低浓度(2 mg/mL)、低pH值(pH 3.0)时添加剂1%蔗糖可起到延缓反应速率,提高原花青素稳定性的作用。原花青素在无添加剂条件下反应活化能Ea值均小于42 kJ/mol,可说明此条件下的反应速率非常大,极易发生降解反应。而在2 mg/mL、pH 3.0时蔗糖,活化能Ea值提高19%,降解反应速率降低,说明添加剂的加入显著增强了原花青素稳定性,且在添加蔗糖后,半衰期明显增加。原花青素在2 mg/mL,pH 3.0,4 ℃条件下,降解速率较慢,反应所需活化能较大,半衰期较长,有利于原花青素的贮藏稳定性。加入蔗糖可以在某种条件下提高原花青素稳定性,因为加入蔗糖等糖类物质,原花青素与蔗糖能够结合形成大分子物质,使得原花青素稳定性增强。Abstract: The aim of this study was to investigate the stability and degradation kinetics of proanthocyanidins from Picea koraiensis Nakai in solution at different pH values, temperatures and concentrations, and the residual rate was used as an index to measure the change of proanthocyanidins content. The results showed that the stability decreased with increasing temperature and pH value, the residual rate was the highest at the concentration of 4 mg/mL and the degradation reaction followed first-order kinetics with the activation energy Ea33 kJ/mol. Adding 1% sucrose and may contribute to delaying reaction rate and improving the stability of the proanthocyanidins only at low concentrations and low pH values. The Ea value in the test measured in the absence of additives was less than 42 kJ/mol, suggesting that the reaction rate under these conditions was high, and degradation reaction was mostly likely to happen. Under the conditions of 2 mg/mL concentration and pH 3.0, the activation energy Ea value could be increased by 19% if adding sucrose, and degradation reaction rate decreased, indicating that the additives significantly enhanced the stability of proanthocyanidins. Under the conditions of 2 mg/mL concentration, pH 3.0, and temperature 4 ℃, degradation rate was slow, and higher activation energy was required for the reaction and half-life period was longer, which was conducive to the storage stability of proanthocyanidins. Sugar could be added to improve the stability of proanthocyanidins under certain conditions, because the addition of sugar and other carbohydrates could enable proanthocyanidins and sucrose to form macromolecules which enhance the stability of proanthocyanidins.