An Chao

Abstract： Purple sweet potato is an annual herb of convolvulaceae， which is rich in anthocyanin.Anthocyanin， also known as anthocyanin， is a water-soluble natural pigment.As a new kind of natural pigment， purple sweet potato anthocyanin has the functions of anti-oxidation， anti-aging and protecting eyesight.In this paper， the extraction method， separation and purification of anthocyanin from purple sweet potato and its functional application were mainly described， which provided the theoretical basis for the further development and application of purple sweet potato pigment.

Key words： Purple sweet potato color anthocyanin;Extraction;Separation and purification;Functional applications

CLC number： Q946 ? ? ? ?Document identification code： ?A

1 Introduction

The purple sweet potato pigment contains double indican， pigments anthocyanins were mostly acetoxylation of anthocyanins， including acylation anthocyanin and paeoniflorin derivatives， chemical structure， including a variety of cyanide acyl glucose and methyl anthocyanins [1]， it is because of the sweet potato anthocyanins contains sugar and acyl structure， improve the stability of pigment extraction of sweet potato， to enhance the function of physical health of purple sweet potato [2].Purple sweet potato pigment is a new kind of natural pigment. Research shows that purple sweet potato anthocyanin has many USES and functions， such as coloring， nutrition and health care， etc. It has high development value， and has been widely used in food， medicine， cosmetics and health care products and other fields.

2 Extraction method of anthocyanin from purple sweet potato

The extraction methods of anthocyanin from purple sweet potato include solvent method， microbial fermentation method， ultrasonic extraction method and microwave extraction method.Solvent extraction method includes organic solvent extraction method and aqueous solution extraction method.In the organic solvent extraction method， anthocyanin is mostly extracted by using the properties of anthocyanin dissolved in methanol， ethanol and other organic reagents to soak raw materials in organic solvents.Guan Qingyue et al. [3] used 95% ethanol as the extraction solvent， took purple sweet potato as the test material， and optimized the extraction process by response surface experiment design. The extraction temperature was 77.79 ℃， the extraction time was 20.76 min， and the liquid-solid ratio was 37.25 （mL/g）.The aqueous solution extraction method USES acidified aqueous solvent for extraction. Citric acid or phosphoric acid is commonly used to replace citric acid in the extraction of purple sweet potato pigment， which has the characteristics of low acid concentration and short extraction time， and has certain practical value [4].

With the wide application of microwave and ultrasonic technology， microwave extraction and ultrasonic extraction began to be used in the extraction of anthocyanin from purple sweet potato.A large number of studies have shown that microwave-assisted extraction and ultrasound-assisted extraction can improve the extraction efficiency， which is easy to operate， time-saving and efficient， and has a high extraction advantage.Peng Jie et al. [5] are reviewed in this paper several methods of ultrasonic assisted extraction of purple potato anthocyanin and its latest research progress， the results showed that the extract is ultrasonic assisted enzymatic with better effect， followed by ultrasonic - microwave collaborative method to extract purple potato anthocyanins， is the most commonly used ultrasonic auxiliary solvent method， so as to research in the field of ultrasonic assisted extraction of purple potato anthocyanins work provide theoretical reference.

3 Separation and purification of anthocyanin from purple sweet potato

In the extraction process of anthocyanin from purple sweet potato， a large amount of reducing sugar and other impurities will also be extracted， reducing the purity of pigment.The separation and purification methods of anthocyanins include membrane separation， column chromatography， high performance liquid chromatography， etc.

At present， the main method to separate anthocyanins from purple sweet potato is macroporous adsorption resin.In recent years， a large number of researchers have explored and optimized the purification process of anthocyanin from purple sweet potato by macroporous adsorption resin.

After screening 14 kinds of macroporous adsorption resin， Zan LiFeng et al. [6] studied the static adsorption and analytical performance of macroporous adsorption resin on purple sweet potato pigment， and finally determined that DM-21 resin was the best resin for the separation and purification of purple sweet potato pigment， and based on this， studied the optimal purification conditions.Through the kinetic study of macroporous adsorption resin， Li Danhua et al. [7] found that within a certain temperature range， with the increase of adsorption temperature， the adsorption rate had a tendency to decline， and the adsorption amount reached the highest at 35 ℃， while the adsorption amount decreased at 45 ℃， and the color value of the purified pigment reached 146.31， which was better than the process reported in the existing literature.Macroporous adsorption resin method is characterized by simple operation， low cost and resin reuse， which is widely used at present.

4 Functional application of purple sweet potato pigment

Purple sweet potato pigment is widely used in food， health care products and medicine because of its anti-oxidation， anti-mutation， eyesight protection and other effects.Han Liming et al. [8] investigated the current research status of potato anthocyanin and pointed out that the value of anthocyanin in the prevention and treatment of many diseases has been widely recognized， and anthocyanin preparations have been used as vascular protective agents in France.On food， the purple sweet potato pigment used for coloring， added to the beverage， pasta， milk products.Chen Yali [9] studied purple potato beverage and determined the optimal formula as follows： the addition amount of purple potato pulp is 40%， the addition amount of white sugar is 9%， the addition amount of citric acid is 0.18%， and the addition amount of composite stabilizer （sodium carboxymethyl cellulose： Xanthan gum： AGAR powder =1：1：1） is 0.09%. The purple potato energy beverage has bright color， good taste， rich nutrition and market development value.

In recent years， the microencapsulation of purple sweet potato pigment has attracted extensive attention of researchers.Wang Lishuang [10] of purple sweet potato pigment was optimized by response surface method， the process for the micro capsule， ultimately determine the screening of zein as wall material， get the optimized preparation technology conditions as follows： the embedding time 30 min， embedding temperature 32 ℃， wall material concentration 1%， core material for wall quality than 5：2.2 （w/w）， the purple sweet potato anthocyanins microcapsule embedding rate of 81.55% plus or minus 0.89%， its density is 2.88 g/mL， the moisture content of 4.42%. In addition， purple sweet potato pigment is also used in dyeing. Wu Guohui et al. [11] studied the direct dyeing of purple sweet potato red pigment on cotton fabrics， and the results showed that the dyeing effect was poor， but its antibacterial property could be greatly improved.Purple sweet potato pigment can also be used as a functional indicator ink.

5 Expectation

A large number of studies have shown that purple sweet potato pigment has good antioxidant properties [12]， liver and kidney protection， vision protection， anti-mutation and other health care effects， and is widely used in medicine， food， cosmetics and other aspects.With the further study of pigment properties， extraction and purification technology of purple sweet potato， its application will be more and more extensive.

（責(zé)任編輯：武多多）

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