| Jin Yin Hua (Lonicera japonica Thunb.) is one of the commonly used Chinese herbal medicines, both in food and health care products with the biological activities of antipyretic, detoxification, cooling blood and removing blood stasis. Jin Yin Hua contains chlorogenic acid, and other caffeoylquinic acids such as isochlorogenic acid A and isochlorogenic acid C, and flavonoid such as the main active ingredient galteolin. Previous studies have shown that the quality of Jin Yin Hua is unstable and closely related to the cultivation management, harvest processing, storage and other conditions. In order to obtain quality product and improve the production stability of Jin Yin Hua, drying kinetics and quality study have been carried out in this paper from following aspects:1. Jin Yin Hua drying process Research by establishing direct hot-air drying temperature ranging between temperature of 50 ℃-90℃, relative humidity of 40%-60%, sample density of 50-150 g, and drying air velocity of 0.1-0.5 m/s. Drying temperature is the main factor affecting the rate of hot air drying compared with the air relative humidity, sample density, and wind speed. Drying process with two-stage temperature rising was established, in which Jin Yin Hua was first dried at low temperature of 40,45 or 50℃ and fast to 80℃ when 40% -60% loss of the initial fresh weight reached. And Jin Yin Hua would maintain its color when 60% loss of fresh flowers weight was taken away before raising temperature to 80℃.2. Jin Yin Hua flowers were steamed for one minute, and then received hot air drying at different drying temperatures (50-90℃). The drying rate was faster than that of direct hot air drying at the same temperature, and the steamed flower owned green color but narrow short shape, besides, the flower color was not subsequently affected by air temperature. Jin Yin Hua hot air drying was in the falling rate drying stage, by being fitted to ten different thin layer drying models, the semi-empirical formula Midilli model was in good fitness. The activation energy with the direct hot air drying and steam pretreated hot air drying process were 80.08 kJ/mol and 59.28 kJ/mol, respectively.3. Microwave process before hot air drying has better effect to speeding the drying process than steam pretreatment which failed to achieve the effect of dehydration during steam period. Two minutes microwave pretreatment was chosen when compared with the 0.5,1,3, and 4 min process, and the drying character under different temperature range of 40-80℃ was carried out.4. HPLC method was established to determine chlorogenic acid, galuteolin, isochlorogenic acid A, and isochlorogenic acid C content of Jin Yin Hua simutaniously, with the linearity range of chlorogenic acd, galuteolin, isochlorogenic acid A, and isochlorogenic acid C 0.4746-47.46,0.2538-2.0304,1.625-26, and 0.6224-6.224 μg/mL, respectively, Limit of quantition was 1.43,0.76,5.2,1.87 ng respectively, and the detection limit was 4.74,2.54,16.25,6.23 ng respectively. Polyphenol oxidase activity of Jin Yin Hua was determined by UV spectrophotometer with catechol as substrate, the antioxidant capacity was determed by DPPH radical scavenging ability and color change was tracked with a colorimeter. Steaming and microwave could well retain the active ingredient content, with both inactivating polyphenol oxidase of Jin Yin Hua. Under microwave combined two-stage hot-air drying process, when the water content of Jin Yin Hua is between 200%-100% percent of dried flower, the dried flower can guarantee natural appearance with the chlorogenic acid content of 52.74-54.23 mg/g dry flower mass.5. The stability of the active constituents during storage of Jin Yin Hua was researched with the moisture content of 9.13%-19.95%, relative humidity of 11%-93%, and different temperature of 25℃,40 ℃ or 60℃ at different storage time. Temperature has little effect on the stability of the active ingredients, since the active ingredient content with no significantly decrease when Jin Yin Hua stored for 10 days at 60 ℃, or 6 months at 40 ℃. When the moisture content was maintained not higher than 16%, the active ingredient can be maintained. Relative humidity could greatly affect the active constituents of Jin Yin Hua due to the effect of enzymatic activities. Taken the stability of chlorogenic acid for consideration, the flower with enzyme destruction by microwave treatment show a mild decrease at all different relative humidity conditions for non-enzymatic degradation, while the flower without microwave treatment show a slight increase with time going at lower relative humidity catalysed by synthesizing enzyme, but significantly reduced at higher relative humidity conditions due to degradation by the polyphenol oxidase, when cell tissue ruptured. In addition, polyphenol oxidase was with lower resistence to humidity rising and storage time than phenolic acids, since almost no enzymatic activity was detected when stored for 18 months long, thus, chlorogenic acid would not be threatened by enzymatic degradation.6. Drying kinetics of Jin Yin Hua leaf was studied. Temperature is the main factor affecting the drying rate, while the wind speed and sample density can be appropriately adjusted to the maximum of its allowance; the Midilli model could well describe the drying behaviour of Jin Yin Hua leaf, and activation energy of the leaf hot air drying is 90.84 kJ/mol.To sum up, this paper studies the kinetics of hot-air drying characteristics of Jin Yin Hua. Taking the active ingredient contents, antioxidant capacity, polyphenol oxidase activity and color variation into consideration, microwave treatment combined with two-stage temperature rising hot-air drying process can be further overcome the limitations of traditional Jin Yin Hua processing, not only significantly shortening the processing time and rising the active ingredient content but also ensuring the better trade appearance of Jin Yin Hua. Activity of PPO in Jin Yin Hua significantly affected its quality during storage; humidity and moisture content affected the stability of the active constituent. Drying characteristics of Jin Yin Hua leaf was consistent with that of Jin Yin Hua buds, in line with Midilli model, while the activation energy was higher than that of Jin Yin Hua bud. |
PDF Full Text Request