Chlorophyll porphyrins are not only a natural pigment but also have pharmacological functions of antipyretic and hemostatic. They are widely used in medicine, food and daily use industries. In China, chlorophyll is extracted mainly from silkworm sand and has been put into industrial production. The sluggish silk industry in recent years has caused restrictions on the sericulture industry and has affected the production of chlorophyll and its derivatives. In recent years, Opuntia Milpa Alta has been rapidly developed in China's planting industry, and it now has a considerable production scale. The cactus bark of deep-processed cactus foods, rich in chlorophyll, is an ideal raw material for the production of chlorophyll. The author uses the bark of Mibanga cactus as the raw material, discusses the optimum technological conditions for extraction of chlorophyll by the orthogonal method, and provides scientific basis for the development and utilization of cactus. The ratio of 2:3 ethanol to acetone was used as extractant. In the process of extracting cactus chlorophyll by heat, the ratio of material to liquid was the main factor affecting the extraction efficiency of cactus chlorophyll. The optimum conditions for chlorophyll extraction were material-liquid ratio 1B10 (M/V), temperature 60°C, and time 4.5 h. Pneumatic Pu Tube,Brass Elbow Pipe Fitting,Adapter Brass Fast Coupling,Brass Liquid Fittings Brando Hardware Co., Ltd. , http://www.nbbrandohydraulic.com
1 Materials and Instruments Mibanga cactus stems are from the Science and Technology Park of Hubei Agricultural College. The skins are taken out, dried and crushed for later use.
The instruments used are: Shimadzu UV-160 UV-vis spectrophotometer, chlorophyll content analyzer, 722 spectrophotometer, HH.S11-6 electric constant-temperature water bath, AE200 electronic analytical balance, SS-300N three-legged centrifuge, rotary evaporation instrument. The reagents used are: absolute ethanol, acetone, copper sulfate, methanol, ether, petroleum ether, sodium hydroxide, sulfuric acid, etc. The above reagents are of analytical grade and supplied by Hubei Chemical Reagent Company.
2 Test methods 2.1 Extracting agent screening Cactus peel 16 g, after crushing were divided into 16 parts, each 1g, placed in a brown reagent bottle. Add 60 ml of ethanol and acetone in different volume ratios to the bottle and soak for 3 days. The absorbance (OD662 nm value) of the extract was measured at 662 nm after filtration. All tests were repeated 3 times and averaged.
2.2 Orthogonal test The solvent with the best extraction efficiency is used as the extraction agent for orthogonal tests. After repeated experiments, three main factors affecting the extraction efficiency of chlorophyll were selected: solid-liquid ratio, extraction temperature and extraction time, and L9 (34) orthogonal design experiments were conducted. All tests were repeated 3 times and averaged.
3 Results and discussion 3.1 Screening results of extracting agent The extracting optical density of the extract at 662 nm was used as an index to evaluate the extraction efficiency, and the extraction agent for extracting chlorophyll was screened. The test uses solvents or solutions of different polarities [petroleum ether, ethyl ether, acetone, acetone B ethanol = 1:1 (V/V) mixture, ethanol, methanol] as extractant, and cactus powder is soaked at room temperature for 3 days. The absorbance of the extracts is compared to their extraction efficiency. The order of their sizes is as follows: Acetone: Ethanol is a 1:1 mixture> methanol> ethanol> acetone> ether> petroleum ether. A mixture of ethanol and acetone was used as the extracting agent, and the volume ratio of the two was changed to determine the extraction efficiency. The results showed that when the volume ratio of ethanol to acetone was 2:3 (ie, the volume ratio of ethanol to acetone was 0.66), the extraction of chlorophyll was performed. The highest efficiency (Figure 1). 
3.2 OPTIMAL SOLUTION To determine the synergistic effect of multiple factors (leaking temperature, extraction time, and material ratio) on chlorophyll extraction efficiency, orthogonal experiments were selected on the basis of repeated investigations of the effects of several single factors on chlorophyll extraction efficiency. The extraction temperature (A) is 45°C, 60°C, 75°C, and the extraction time (B) is 1.5 h, 3.0 h, 4.5 h. The feeding ratio of Cactus bark and extractant (C) is 1:5, 1 : 10, 1:15 (M/V). After the extract has been brought to constant volume, the absorbance at the wavelength of 662 nm is used as an assessment index. The orthogonal experimental data is shown in Table 1. According to the range analysis, the main factors influencing the extraction efficiency of chlorophyll are the solid-liquid ratio, followed by the extraction temperature and extraction time. The order of the factors is C>B>A, and the extraction of chlorophyll from cactus skin is the most important. The optimal solution is A2B3C2, ie, the extraction temperature is 60° C., the extraction time is 4.5 h, and the solid-liquid ratio is 1:10. 
Table 1 Orthogonal Experimental Protocol and Results 4 Conclusions