Microencapsulation Of Flavonoids From Walnut Leaves And Its Application In Functional Beverages

Walnuts is an annual herbal which fruit can be eaten and while roots,stems and leaves are used in the food and drug industry because of its large number of active ingredients.At present,utilization of walnut in China is mostly in its fruit,and there is less research on walnut leaves.Walnut leaves contain a large number of flavonoids,which have good development and utilization value.In the present study,flavonoids were removed from walnut leaves and purified by macroporous resin.Moreover,the flavonoids were encapsulation by different methods.Finally,the functional antioxidant beverage was studied.The main results were as follows:Optimum extraction parameters for flavonoids from walnut leaves were determined.Reflux method and ultrasonic method were utilized to extract the flavonoids in the walnut leaves.The four-factor and three-level experiment was designed by reflux extraction method.The optimum extraction rate was 3.1% when the temperature was 61 ?,the ethanol concentration was 71%,the ratio of material to liquid was 1:26,and the extraction time was 6.2 h.A three-factor and three-level experiment was designed for ultrasonic method.The optimum extraction rate was3.49% when the temperature was 67 ?,the ethanol concentration was 68%,and the extraction time was 31 min.Compared with the two extracted method,the ultrasonic extraction method had the advantage of saving time and have high extraction efficiency,therefore,the method of ultrasonic extraction was chosen for the extraction of walnut leaves flavonoids.The morphological changes before and after purification which was turned out to be dry powder of sticky liquid after AB-8macroporous resin purification and the content ratio significantly increased.The encapsulation yield of complex coacervation,sharp hole-bath method and yeast cells encapsulation methods were determined.On the base of the single factor experiment the optimum results a response surface design of the experiments was generated by the Design-Expert software.The optimum encapsulation yield of the complex coacervation by RSM were as follows: encapsulation p H value of 3.9,temperature 54 ?,core wall ratio 3.5:1 and gelatin/Gum Arabic ratio 1.8:1,which led to a maximum encapsulation yield of 65.5%.The optimum encapsulation yield of the sharp hole-bath method determined by RSM were as follows: the fraction of sodium alginate is 2.1%,the fraction of the chitosan is 2% and the core wall ratio is3.1:1,which led to a maximum encapsulation yield of 86.5%,the optimum encapsulation yield of the yeast cells determined by RSM were as follows:encapsulation time is 4.97 h,the encapsulation temperature is 54.5 ? and the core wall ratio is 2.5:1,under this situation the encapsulation yield is 33.5%.Combined with the comprehensive analysis of three kinds of encapsulation methods,the sharp hole-bath method was used for the next experiment.With flavonoids solution of 44%,orange juice of 10.6%,Chinese wolfberry juice of 19.2%,the optimal DPPH scavenging rate achieved 88.6%,which is the best condition for antioxidant activity.The other additives for beverage was as follows 4% sugar,0.015% citric acid,0.015% honey.Finally,we can get complex walnut leaves beverage that not only with special walnut leaves flavor but also with the orange juice and Chinese wolfberry juice taste which was sweet and sour taste and pleasant.