Study On The Debittering Process Of Bletilla Striata Tuber And The Procedures Of Extraction And Purification Of Militarine In The Root Of B.striata

Bletilla striata（Thunb.Reichb.f.）is a perennial herb of Bletilla in Orchidaceae.It has a variety of pharmacological effects such as antibacterial,antitumor and antioxidant.Bletilla striata has been used as the raw material of health food for a long time,but the frequency of use is very low.It is speculated that the bitter taste of Bletilla striata hindrates the acceptability of health food.Bletilla striata root occupies a high proportion in the underground part,but is usually abandoned in the drying process of medicinal materials,and is only used to improve the soil.The fibrous roots of Bletilla striata contain polysaccharides,total phenols,gastroditin and many other components that are the same with tubers,and the content of alcohol extracts and antibacterial effects of fibrous roots are better than those of tubers.Therefore,fibrous roots have potential development and utilization value.In this paper,hot water rinsing method was used to reduce the content of tubers’Militarine content,and ring cutting method was used to obtain different use parts（tissues）of Bletilla striata tubers,in an effort to obtain a simple and easy processing method that can reduce the bitterness of Bletilla striata tubers,and improve the processing and utilization performance and dosage of tubers as health food and functional dietary materials.The extraction technology,separation and purification of Bletilla striata roots were studied in order to explore the extraction and utilization value of active ingredients in Bletilla striata resources.The results are as follows:（1）Response surface experiment was used to study the optimal combination level values of three factors for the hot water rinsing method to reduce the content of Militarine in Bletilla striata slices,which were:rinsing temperature 95.02°C,rinsing time 50 min,p H 6.5.Under the optimized combination level,the content of Militarine in slices decreased from 40.20 mg·g^-1（average value）to 14.65 mg·g^-1 after 5 parallel experiments.After three times of hot water bleaching,the content of Militarine in Bletilla striata slices decreased from 37.85 mg·g^-1 to 14.41 mg·g^-1,9.08 mg·g^-1 and 6.39mg·g^-1,respectively.The decrease ratio was 61.94%,76.02%and 83.10%,respectively.After a hot water rinse,The total phenolic content,polysaccharide content and starch content of rhizome of Bletilla striata decreased from 3.8 mg·g^-1 to 1.9 mg·g^-1,from305.5 mg·g^-1 to 221.1 mg·g^-1 and from 424.1 mg·g^-1 to 197.6 mg·g^-1.According to oral taste evaluation,bitterness of Bletilla striata tubers is definitely related to its Militarine content,and may be the result of Militarine,polyphenols and other potential bitter substances.（2）In Bletilla striata of the same age,with the increase of tuber ring thickness,the content of Militarine in Bletilla striata decreased sharply at first,and then fluctuated to a slight increase.The content of total phenol increased firstly,then decreased,and then stabilized.The polysaccharide content showed a change of"first increased,then continued to decrease".The content of starch increased slowly at first and then decreased rapidly.Correlation analysis showed that there was a significant positive correlation between Militarine content and annular thickness in different parts（tissues）.For the other components,only polysaccharide content had significant positive correlation with peeling thickness in the two ages,while other correlations were not significant.In Bletilla striata of different ages,the contents of Militarine and total phenol in tubers of two ages were higher than those of one age,but the contents of polysaccharide and starch were opposite.（3）The content of Militiarine,which bitter components in Bletilla striata was the highest in November in fibrous roots,October in tubers,September in buds,and only in May,June and November in fasciculate leaves.In the same growing month,the order of Militiarine content is bud>tuber>fibrous root>fasciculate leaf.Total phenol is a potential bitter substance in Bletilla striata,and the highest content in fibrous roots and tubers in October,fasciculate leaves in May and bud in November.The contents in different organs were as follows:fibrous root≥bud>fasciculate leaf>tuber.（4）Using orthogonal design method,the optimal extraction conditions of Bletilla striata roots were as follows:water as extraction reagent,solid-liquid ratio of 1:30,extraction temperature of 100°C,extraction time of 40 min.Based on these conditions,the content of Militarine in the extraction of Bletilla striata roots was 12.67mg·g^-1.Four kinds of macroporous resin were screened to determine that DM130 macroporous resin was suitable for purification of Militarine.The best combination conditions for purification of fibrous root Bletilla striata were:room temperature;adsorption conditions:loading flow rate 2.0 m L·min^-1,loading volume 160 m L.The optimal desorption conditions were as follows:ethanol volume fraction 60%,elution flow rate3.0 m L·min^-1,dosage 150 m L.The results showed that the content of Militarine in the crude extract of Bletilla striata was increased from 0.48 mg·m L^-1 before resin adsorption to 3.19 mg·m L^-1 after separation,and the purity was increased 6.65 times.