Study On Extraction And Purification Of Mulberry Anthocyanins And Its Stability In Functional Beverages

Medicinal mulberry is the only domestic mulberry with 22 ploidy of flower sex chromosome and dual use of medicine and food.It matures from June to September and is planted in southern Xinjiang.It is not easy to transport and store,and its shelf life is short.Studies have shown that medicinal mulberry is rich in anthocyanins,and has biological activities such as protecting blood vessels,vision,anti-cancer and anti-tumor.It has great application prospects in food,daily necessities and pharmaceutical raw materials.In this paper,the subcritical water extraction and ultrasonic-assisted extraction of anthocyanins from medicinal mulberry were optimized,and the antioxidant activity and anthocyanin components were determined under the optimal process.The crude anthocyanin extract was separated and purified by ultrafiltration membrane step by step,and the functional beverage was prepared.The stability of anthocyanin during storage was preliminarily studied,and the following results were obtained :Orthogonal combined with response surface test design was used to optimize the extraction process of mulberry anthocyanins,and the antioxidant activity and cyanidin content of crude extract were determined.The results showed that the optimum conditions for the extraction of anthocyanins by subcritical water were as follows : extraction temperature 102°C,solid-liquid ratio 1:31(g/m L),and extraction time 10 min.Under these conditions,the yield of anthocyanins was 4.453 mg/g;the optimum conditions for ultrasonic-assisted extraction of anthocyanins were as follows : ultrasonic temperature 55 °C,solid-liquid ratio 1:34(g/m L),ultrasonic time 15 min.Under these conditions,the yield of anthocyanins was 5.248mg/g.The results showed that the efficiency of ultrasound-assisted extraction was higher than that of subcritical water extraction.The content of cyanidin and the ability of scavenging free radicals in the crude anthocyanin extract of subcritical water extraction were significantly higher than those of ultrasound-assisted extraction.The ultrafiltration membranes with different molecular weight cut-offs were used to separate and purify the crude extract of mulberry anthocyanins step by step.It was found that the smaller the molecular weight cut-off of the membrane,the greater the retention rate of macromolecular substances such as protein and total sugar,and the higher the color value of anthocyanins.After the separation and purification of anthocyanin crude extract by 1 KDa ultrafiltration membrane,the product color of vacuum freeze-dried product was bright red,which was 15 times higher than that before purification.The optimum formula of functional beverage was determined by sensory evaluation as anthocyanin powder 1.3 %,white sugar 4.5 %,citric acid 0.09 % and salt 0.08 %.The functional beverage prepared by compound taurine and other components had a rose red color,bright and uniform color,moderate sour and sweet,no odor,and certain antioxidant activity.The ABTS + free radical scavenging rate was 86.43 %,and the DPPH free radical scavenging rate was 79.57 %.The soluble solids content was 4.6 %,the p H value was 3.15,and the microbial indicators met the national standards.During the storage of functional beverages,affected by factors such as time and temperature,after storage at 4 °C,25 °C and 37 °C for a period of time,the anthocyanin preservation rate decreased the least at 4 °C,the total number of colonies grew the slowest,and the beverage quality remained stable.Therefore,low temperature storage can make the beverage maintain good color,flavor and tissue morphology.