【作者】 赵倩；

【导师】 熊善柏；

【作者基本信息】 华中农业大学 ， 食品科学， 2009， 硕士

【摘要】 红曲色素（Monascus pigments）是红曲菌发酵生产的天然色素,为红、黄色调的多种单一色素的混合物,在肉品中代替硝酸盐类的应用研究日益受到关注。红曲色素对光照、高温、酸碱、重金属敏感,特别是在肉制品加工中经常因为高温杀菌处理而导致添加红曲色素的产品出现变色现象而影响产品质量。本文以红曲色素为研究对象,研究了光照、温度、pH、金属离子、加热时间以及贮藏方式等对红曲色素保存率和溶液色度的影响,建立了其热降解的动力学模型方程,通过薄层层析对红曲色素的主要组分进行分离,研究了红曲色素中红色组分RP3和黄色组分YP1的热降解特性,并建立了红曲色素热稳定性的评价体系。主要研究结果如下:1、研究了光照、温度、pH值、盐浓度和重金属离子等理化因素对红曲色素的稳定性的影响。在3种光照条件下,连续光照可显著降低红曲色素的保存率,而避光贮藏则可有效保护红曲色素。红曲色素在pH3-10范围内比较稳定,高于或低于该pH值范围其稳定性显著下降。重金属离子对色素溶液的呈色有影响,Cu²⁺、Fe³⁺会使色素溶液由亮红色变为褐色并产生沉淀。随着盐浓度的增大,红曲色素溶液的色度值下降。红曲色素在100℃以下较为稳定,在100℃以上时则随着加热温度的升高、加热时间的延长,色素保存率明显降低。红曲色素的热降解符合一级反应动力学方程。在加热过程中,红曲色素溶液的明度L^*随加热时间的延长而呈现下降趋势,且加热温度越高,下降越明显,而红曲色素溶液的红度则随着加热时间的延长逐渐下降、黄度增加,且加热温度越高这种变化趋势越明显。2、在红曲色素的贮藏过程中,不同温度加热后的红曲色素溶液在不同贮藏方式下的保存率和色度的变化趋势不同,避光组的保存率下降较慢,贮藏90天后保存率都高于85%,而光照组的保存率降低较快,贮藏90天后保存率只有10%左右。色素溶液的亮度随贮藏时间的延长而增大,红度、黄度和彩度随贮藏时间的延长而减小,光照贮藏比避光贮藏变化更快。3、对红曲色素各组分进行分离并研究了纯度较高的红色组分RP3、黄色组分YP1的热降解特性。用薄层层析法,以甲苯:乙酸乙酯:甲酸=7:3:1（v/v）、正己烷:乙酸乙酯:石油醚=30:17:5（v/v）为展开剂,从红曲色素中分离得到4种红色组分和3种黄色组分,经高效液相色谱鉴定,红色组分RP3、黄色组分YP1的纯度较高。经热降解特性研究表明,RP3比YP1的热稳定性差,121℃加热40min后,YP1的色素保存率为71.3%,而RP3的保存率只有45.2%,两种组分的热降解符合一级反应动力学模型,其中红色组分RP3的活化能为77.3826KJ/mol,黄色组分YP1的活化能为87.5049KJ/mol。4、在研究红曲色素浓度、加热温度、加热时间对特征吸收峰和吸光值的影响的基础上,建立了红曲色素热稳定性的评价方法。在热稳定性的测定中,选择初始吸光度为0.45-1.05,加热温度120℃,加热时间40min,可以客观反映出不同红曲色素在热处理过程中的稳定性差别。更多还原

【Abstract】 Monascus pigments are natural pigments fermentated by Monascus spp. They are mixture of kinds of red and yellow single pigment, Application of Monascus pigments to replace nitrates in meat is concerned particularly now. Monascus pigments is sensitive to light, high temperature, acid-base and heavy metal ions, especially in manufacturing of meat products, discoloration of meat products which added to Monascus pigments in heating process have bad effect of the product. Based on studies of the basic physical and chemical effects on the absorbance and chroma of monascus pigments, red pigments and yellow pigments were separated and prepared by TLC. After purity analysis and preliminary structure identification, thermal degradation characteristics were studied between red pigments and yellow pigment. Evaluation method of monascus pigments thermal stability was established, thermal stability of red pigments RP3 and yellow pigments YP1 were determined by this method. The main research results were as follows:1、Effect of light、high temperature、acid-base、salt concentration and heavy metal ions on stability of Monascus pigments were studied. Continuous illumination had significant effects on stability of monascus pigments, preserving rate decreased significantly in continuous illumination. Monascus pigments was stable in avoid light storge. Under the condition of pH 3-10, the stability of the pigment could maintain. Heavy metal ions had ignificant effects on stability of monascus pigments, Precipitation appeared when the monascus pigments were coexistenced with these heavy metal ions such as Cu²⁺, Fe³⁺. Chroma decreased with the increase of salt concentration. monascus pigments had a good stability under 100℃, while above of this temperature, stability of monascus pigments were obviously decreased with the increase of heating temperature and time.Thermal degradation dynamic model of monascus pigments was established. It was proved that it was in accordence with first order reaction kinetics. In heating process, Lightness of monascus pigments was increased with the prolongation of heating time, and the higher the heating temperature was, the lower of the decreasing. At the same time, reddishness of monascus pigments was also decreased with the prolongation of heating time, and the yellowness were increased with the increase of heating temperature.2、Changing trend of monascus pigments chroma in storage after different temperature heating was different. Preserving rate of monascus pigments decreased relatively slow in avoid light storage, the preserving rate was more than 85 percents after 90 days storage while the preserving rate of light storage was no more than 10 percents. Lightness was increased with the prolongation of storage time. Reddishness and yellowness were decreased with the prolongation of storage time. Storage of illumination has a poorer stability than avoid light storage.3、TLC was established to separate four red components and three yellow components from monascus pigments, toluene, ethyl acetate and formic acid（7: 3: 1, v/v）was used to separate red components while n-hexane, ethyl acetate and petroleum ether（30: 17: 5, v/v） was used to separate yellow components from monascus pigments. RP3 of red components and YP1 of yellow components were puritied proved by HPLC. After studied on the thermal degradation characteristics, YP1’s thermal stability was better than that of RP3’ s, after heating 40 minutes of 121℃, preserving rate of YP1 was 71.3%, while that of RP3 was only 45.2%. The thermal degradation kinetics of these two components accord with first order reaction kinetics model, the activation energy of RP3 and YP1 were 77.3826KJ/mol and 87.5049KJ/mol.4、Based on the effect of characteristic absorption peak and absorption value in heating time、heating temperature and concentration of monascus pigments, evaluation method of monascus pigments thermal stability was established. The testing condition was recommended as absorption 0.46-1.05, heating temperature 120℃, heating time 40min, difference of monascus pigments thermal stability could be measured by this method.更多还原