苹果酸酰化对黑果枸杞花青素稳定性改善的研究

由于黑枸杞花青素的稳定性较差,在食品及药品中的应用受到限制。为了提高其稳定性,对黑枸杞花青素进行苹果酸酰基化改性。酰化后在p H3.5体系下以90℃水浴下酰化花青素提高保留率为指标,通过单因素实验探讨苹果酸与花青素的质量比、搅拌时间和反应温度对酰化效果的影响,采用正交实验优化酰化反应工艺条件,并用紫外可见和傅里叶红外吸收光谱法验证。研究了酰基化花青素的光、热稳定性,同时建立并验证酰基化花青素热降解动力学模型。结果表明,当黑枸杞花青素与苹果酸的质量比为1∶3.5,搅拌5 h,反应温度50℃时,花青素的酰化提高保留率可达26.39%,与非酰化花青素相比,光稳定性增加17%。未酰化花青素预测模型:t=（lnρ₀-lnρ₁）/（0.3765exp（-742.7/T））;酰化花青素预测模型:t=（lnρ₀-lnρ₁）/（0.2640exp（-685.8/T））。在80℃条件下应用热降解模型分别预测未酰化和酰化黑果枸杞花青素的半衰期,其结果分别为15.09和18.32 h,测定其保留率分别为53.2%和48.7%,接近初始值的一半,热降解动力学模型有效。实验表明苹果酸酰化花青素方法切实可行,产物酰化花青素的稳定性得到提升。 

Study of improvement on stability of anthocyanin modified by malic acid acylation from Lycium ruthenicum

Due to the poor stability of natural anthocyanins from lycium ruthenicum, its application in the food and medical industry is limited.In order to improve its stability, the anthocyanins of lycium ruthenicum were modified by malic acid.In the p H3.5 system, improving retention rate of acylated anthocyanin under 90℃water bath was as the effect of indicators.The single factor experiment designs were used in order to investigate the effect of mass ratio of malic acid to anthocyanins, the stirring time and reaction temperature on acylation.The orthogonal experiment was used to optimize the acylation reaction conditions, and the results of acylation were proved by FT-IR spectrum and ultraviolet absorption spectroscopy.The photochemical and thermal stability of acylated anthocyanins were studied.Finally, the kinetic model of thermal degradation about the anthocyanin was constructed and verified.The optimization reaction conditions were gotten as follows.It is showed that the ratio of malic acid to anthocyanins was 1∶3.5, and stirring time was 5 h under 50℃.The retention rate of lycium ruthenicum anthocyanin was increased by 26.39%.The light stability of acylated anthocyanins was increased by 17%comparing to anthocyanins.Prediction model of thermal degradation is t= (lnρ₀-lnρ₁) / (0.3765exp (-742.7/T) ) for anthocyanins.Prediction model of thermal degradation of acylated anthocyanin is t= (lnρ₀-lnρ₁) / (0.2640exp (-685.8/T) ) .The half-lives of anthocyanin and acylated anthocyanin were 15.09 and 18.32 h, respectively, predicted by thermal degradation kinetics model at 80℃.The retention rates of anthocyanins were 53.2%and 48.7%, respectively, close to the half of prediction value predicted thermal degradation kinetics model.Experiments show that acylation by malic acid is practicable for improving stability of anthocyanin from lycium ruthenicum.