Study On Extraction Of Polysaccharide From Dendrobium Officinale And Preparation Of Yogurt

Dendrobium officinale polysaccharide is a good immunomodulator.In this paper,Dendrobium officinale was used as the main raw material to study the optimal extraction process of Dendrobium officinale polysaccharide and the preparation of solidified yogurt of Dendrobium officinale,so as to provide reference for the development and utilization of Dendrobium officinale polysaccharide.(1)The effects of twin-screw extrusion pretreatment and superfine grinding pretreatment on the extraction rate of Dendrobium officinale polysaccharide were studied,and the pretreatment process was optimized.The results showed that the optimal parameters of twin-screw extrusion process were as follows:the moisture content of Dendrobium officinale powder was 18%,the feeding capacity was 220 g/min,the screw speed of extruder was 350 r/min,and the extrusion temperature was 180 ?.Under these conditions,the extraction rate of Dendrobium officinale polysaccharide was 6.62%±0.03%.The results showed that the optimal parameters of the pretreatment process were as follows: feeding capacity 800 g/min,mill speed 7000r/min,grinding time 17 min.Under these conditions,the extraction rate of polysaccharides was 7.52%±0.04%.By comparing the coarse powder,superfine powder and extrusion powder,it could be concluded that the extraction rate of polysaccharide from Dendrobium officinale with superfine powder is the largest.(2)The extraction rate of polysaccharide from Dendrobium officinale could be significantly improved by ultrasonic assisted extraction on the basis of superfine grinding pretreatment.Through orthogonal test,the optimal process parameters of extracting polysaccharide from Dendrobium officinale were obtained as follows: grinding particle size 40 ?m.The results showed that the ratio of solid to liquid was 1:20 g/m L,ultrasonic time was 40 min and ultrasonic power was 600 W.Under these conditions,the extraction rate of polysaccharides was 8.73%±0.03%.(3)After extracting polysaccharide from Dendrobium officinale by superfine grinding pretreatment,ultrasonic wave combined with composite enzyme method,the formula and technology of solidified Dendrobium officinale yogurt were optimized by orthogonal test with sensory score as the evaluation index.The optimal formula and technological parameters were obtained as follows: with 20% water extract of Dendrobium officinale,8% sucrose and 2.0% inoculum size,it was fermented at 42 ? for 8 h and then refrigerated at 4 ? for 12 h.