Preliminary Study On Improving The Light Stability Of Red Yeast Rice

Monascus has been used as a traditional fermentation product in China for more than one thousand years.It has the effect of both medicine and food and is widely used in food and medicine industry.Monascus pigment,as an edible natural pigment,not only has the physiological activity of lowering blood pressure and lipids,but also has good coloring effect.In this paper,the light stability of Monascus pigment was studied,the stability of Monascus pigment was preliminarily judged,and the orange pigment of Monascus was derivatized by adding amino acids to transform the pigment into stable red pigment.The light stability of Monascus pigment was evaluated.In this experiment,the dynamic changes with time,the absorbance value of various Monascus pigment solutions and the three color difference parameters of L,a,b during illumination were measured,and the retention rate was calculated at a specific time.The results showed that the stability of water-soluble Monascus pigment was higher than that of alcohol-soluble Monascus pigment.It was preliminarily inferred that the orange pigment in Monascus pigment was unstable in ethanol solution,while the red pigment was relatively stable in ethanol solution.It was found that the color saturation of Monascus pigment decreased and the hue angle was almost unchanged during illumination.The orange pigment can be transformed into a red pigment by adding ammonia.The results of HPLC showed that orange pigment rubropunctatin and monascorubrin were transformed into two known red pigments rubropunctamine and monascorubramine,respectively.By measuring the photostability of the two samples,the stability of the transformed sample was higher than that of the control group,and the preservation rate was increased by 14%.Five different amino acids were added to the extract mixture of Monascus pigment to convert orange pigment into different red pigment.The results of HPLC showed that lysine was one of them.Glycine and arginine were converted into two relatively simple red pigments.The stability of Monascus pigment was slightly higher than that of the control group after adding 5 kinds of amino acids to evaluate the photostability of the transformed samples.The conversion of glycine and arginine to two red pigments was higher.Two kinds of red pigments were obtained by preparing amino acid derivatives by preparative high performance liquid chromatography(HPLC).The purity of the two red pigments was detected by analytical liquid chromatography.The purity of both of them was over 95%.The structure of the two red pigments was analyzed by LC-MS-IT-TOF and nuclear magnetic.The synthesis of pigment from Monascus CB-1 by lysine and glycine was studied.The results showed that the color value of lysine added with lmmol/g,5mmol/g and lOmmol/g was reduced by more than 50%compared with the control group,and the lysine pigments added with 5mmol/g and 10mmol/g were transformed.Compared with the control group,the color value of ImM and 5mmol/g glycine was decreased by 30%,and the value of glycine added with 5mmol/g in the early stage of fermentation was increased by 60.Through liquid chromatography analysis,the addition of glycine did not change during fermentation.