| Pueraria lobata has high nutritional value and is rich in flavonoids.It has the effects of producing body fluids and quenching thirst,relieving the surface and reducing fever,and relieving alcohol toxins.It also has good effects in anti-oxidation,liver protection,blood sugar reduction.It can be used as medicine and food,and is a high-quality raw material for the development of functional foods.Although the resources of Pueraria lobata in China are abundant,the degree of comprehensive processing and utilization and the technical level are low.Based on this background,this article used wild Pueraria thomsonii Benth,cultivated Pueraria thomsonii Benth and Pueraria lobata(Willd.)Ohwi grown in Wuling Mountains of Hunan as raw materials,the effects of hot air drying(60?,70?,80?,90?,100?),vacuum drying(60?)and freeze drying on total flavonoids content,antioxidant activity and color of Pueraria lobata were investigated.The optimal ultrasonic extraction technology of Pueraria lobata was studied,and the contents of total flavonoids and antioxidant activity of different extracts were compared and analyzed.The optimal formula of Pueraria lobata beverage was studied,and the effects of light and accelerated test on the color,total flavonoids content and antioxidant activity of Pueraria lobata beverage were investigated,which could provide reference for the comprehensive processing and utilization of Pueraria lobata.The results are as follows:1.The water content of wild Pueraria thomsonii Benth,cultivated Pueraria thomsonii Benth and Pueraria lobata(Willd.)Ohwi produced in Wuling mountainous area of Hunan Province were all exceeded 50%;the total flavonoids and dietary fiber content of wild Pueraria thomsonii Benth and cultivated Pueraria thomsonii Benth were significantly lower than those of Pueraria lobata(Willd.)Ohwi(P<0.05),But the starch content was higher than that of Pueraria lobata(Willd.)Ohwi(P<0.05).The nutrient content of Pueraria lobata(Willd.)Ohwi and wild Pueraria thomsonii Benth and cultivated Pueraria thomsonii Benth were quite different,while the latter two were relatively close.2.The content of total flavonoids of the two kinds of Pueraria thomsonii Benth after being dried by hot air at 100? was not significantly different from that of freeze-drying(P>0.05);the DPPH· scavenge activity,total reducing power and ·OH scavenging activity of the three kinds of kudzu roots after freeze-drying were the highest.There was no significant difference in DPPH· scavenge activity after freeze-drying of cultivated Pueraria thomsonii Benth with hot air drying at 100v(P>0.05).The total reducing power of Pueraria lobata(Willd.)Ohwi and cultivated Pueraria lobata after freeze-drying was not significantly different from that after hot air drying at 100?.The OH scavenging ability of wild Pueraria thomsonii Bent,cultivated Pueraria thomsonii Bent,and Pueraria lobata(Willd.)Ohwi,after freeze-drying was not significantly different from that after hot air drying at 100?(P>0.05).Taken the comprehensive cost and energy consumption into consideration,100? hot air drying was a suitable drying method for Pueraria lobata.Freeze-dried Pueraria lobata had the largest L value and the smallest a value,which was very significantly different from other drying methods of Pueraria lobata(P<0.01),and had the least negative impact on the color of Pueraria lobata,while hot air drying and vacuum drying were both reduced to varying degrees.If Pueraria lobata powder was used as a product to evaluate its color,the freeze-drying method was the best,but if the purpose was to prepare Pueraria lobata beverage,the hot air drying method with low cost and low energy consumption was more suitable.3.Taking the extraction rate of Pueraria lobata total flavonoids as an index,ultrasonic-assisted extraction was adopted,and the optimal extraction process conditions were determined through single factor test combined with response surface method.The optimal extraction process conditions for dry Pueraria lobata were:water to material ratio 30:1(mL/g),ultrasonic power 310 W,ultrasonic time 38 min,the total flavonoids yield was(12.68±0.05)mg/g;the optimal extraction process conditions for fresh Pueraria lobata were:water to material ratio 4.5:1(mL/g),the ultrasonic power 442 W,the ultrasonic time 39 min,and total flavonoids yield was(4.36±0.04)mg/g.4.The dried and fresh extracts of Pueraria lobata obtained under the optimal process conditions(compared after fresh and dried)were compared.For the same kind of Pueraria lobata,total flavonoids content,DPPH·scavenging activity,total reducing ability and ·OH scavenging activity of the extract obtained from dried Pueraria lobata were better than fresh Pueraria lobata(P<0.05);in the comparison of dry or fresh state,total flavonoids content and antioxidant capacity of Pueraria lobata extract were significantly higher than wild Pueraria thomsonii Benth and cultivated Pueraria thomsonii Benth(P<0.01),while total flavonoids content of wild Pueraria thomsonii Benth extract was greater than that of cultivated Pueraria thomsonii Benth(P<0.05),But the difference in antioxidant capacity between the two was not significant(P>0.05).At the same time,the color of fresh Pueraria lobata extract was darker than that of dried Pueraria lobata extract;the color,taste and smell of the wild and cultivated Pueraria thomsonii Benth extracts were similar,and Pueraria lobata(Willd.)Ohwi extract was dark black in color with a strong medicinal flavor.In summary,the preparation of Pueraria lobata beverage should choose dried Pueraria lobata(Willd.)Ohwi and dried wild Pueraria thomsonii Benth as the processing raw materials,and the wild Pueraria thomsonii Benth extract should be used as the main raw material.5.Combining orthogonal test and fuzzy mathematics comprehensive evaluation method,it was determined that the best formula of the drink was:10%Pueraria lobata(Willd.)Ohwi extract,65%wild Pueraria thomsonii Benth extract,0.009%sucralose,The color of Pueraria lobata drink developed under the best conditions was reddish brown,clear and translucent,with a peculiar sweet odor of Pueraria lobata,the sweetness was appropriate,and it met the quality requirements of "National Food Safety Standard Drink".6.At the end of the accelerated test,the L value of the light group was significantly higher than the light-shielded group(P<0.05),and the a and b values were significantly lower than the light-shielded group(P<0.05).Compared with the initial value,the L value and b value of the light group increased by 6.13%and 11.23%(P<0.05),and the a value decreased by 8.42%(P<0.05).At the end of the accelerated test,the total flavonoid content of the light group Pueraria lobata beverage,and the light-shielding group Pueraria lobata beverage decreased by 7.92%and 6.63%respectively;Their DPPH·clearance rate dropped by 38.26%and 30.49%respectively;Their total reducing power dropped by 39.56%and 33.23%respectively;The·OH clearance rate decreased by 7.49%and 6.28%respectively,and the four indicators were significantly different from the initial values(P<0.05).In the accelerated test,the color of the Pueraria lobata drink became lighter.The total flavonoid content,DPPH·scavenging activity,total reducing power and OH scavenging activity of Pueraria lobata beverages all showed a downward trend during the accelerated test;The light-proof treatment could prevent the color of the Pueraria lobata beverage from becoming lighter,and it could also inhibit the decrease of the antioxidant activity of the Pueraria lobata beverage. |
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