Spray Drying Of Ginkgo Biloba And Its Effect On Product Properties

Ginkgo biloba (GB) seed is the seed of the relict. It consists of carbohydrate, protein, fat, Ginkgo acid, Ginkgo alcohol, vitamin, Ca, P, and K, etc. They have very high value in edible and medical applications.Both spray drying (SP) and freeze drying (FD) were selected to investigate effects of different drying methods on GB powder properties. The process condition of spray drying was flow rate 120 m3/h,feed concentration 8 %,inlet air temperature 205℃,outlet air temperature 100℃.The condition of freeze drying was that the feed was frozen at -40℃for 4 hours at first, then dehydrated at 300 mt for 48 hours. It was seen that moisture content by FD was greater than that by SP, i.e., FD>SP, mean particle size FD>SP, color difference FD>SP, protein content FD>SP, drying time FD>SP, energy FD>SP. The results showed that spray dried GB powder had lower moisture content and smaller powder, but whiter color and destroyed protein. Freeze dried GB powder had higher moisture content and bigger particle than spray drying,but yellow color and less destroyed protein were obtained.According to the L1(645)orthogonal experimental design, a total of 16 tests were performed in a compact spray dryer. Parameters, i.e., inlet air temperature, air flow rate, outlet air temperature, and feed concentration, were selected as the affecting factors. The dried product was evaluated with respect to residual moisture content, color difference, mean particle size, and protein content. The experimental results showed that the residual moisture and protein content in the dried product were significantly affected by operating air temperature, especially the outlet air temperature. On the other hand, the mean particle size of GB powder was mainly affected by the feed concentration. Furthermore, from the orthogonal experiment, the optimal conditions of GB seed spray drying were inlet air temperature 190℃, air flow rate 120 m3/h, outlet air temperature 110℃and feed concentration 10 %. GB powder properties by spray drying under optimal condition are obtained as moisture content 5.20 %, color difference 19.76, mean particle size 22.0μm and protein content 9.83 %.According to the orthogonal experimental results, multivariable regression was used to find the relationship between powder properties and the affecting factors. In the modeling, the powder properties, i.e., residual moisture content, color difference, mean particle size, and protein content, were selected as dependent variable and four parameters, i.e., inlet air temperature (T1), air flow rate (Q), outlet air temperature (T2), and feed concentration (D) as independent variables. Mathematical formula model for GB seed powder properties with operating parameters were obtained finally. The correlation coefficient R2 for residual moisture content, color difference, mean particle size, and protein content were 0.957 0, 0.982 0, 0.922 0 and 0.948 1, respectively. It showed that the model might predict the product properties in certain accurancy.In this thesis, the dispersibility and flowability of Ginkgo biloba (GB) dried powder was investigated, as well. The additives, i.e., maltodextrin,β-cyclodextrin and Arabic gum, were selected. The effects of ratios of additives to solid contents in seeds, i.e., 1:10, 2:10, 3:10, 4:10, on the dispersibilty and flowability were studied. The optimal conditions of spray drying, i.e., inlet air temperature 190℃, air flow rate 120 m3/h, outlet air temperature 110℃, feed concentration 10 %, were used for experiments. Dispersibility and flowability of improved GB powder under differet conditions, i. e., additives, ratio of additives to solid contents in seeds and atomizer type, were studied. The dispersibility of powder at different water temperature, i.e., 20℃, 40℃, 60℃, 80℃, 100℃, was measured. The results showed that theβ-cyclodextrin was the best one for the dispersibility and flowability of GB dried product among the three addtitives. The best ratio ofβ-cyclodextrin to solid contents in seeds was 2:10. It was found that two-fluid nozzle atomizer produced better dispersiblity and flowability of improved GB seed powder than rotary disk atomizer. On the other hand, water temperature also affected the dispersibility. It was observed that the dispersibility of improved GB powder inceased with temperature increase first and then decreased. The peak of maltodextrin, Arabic gum andβ-cyclodextrin was near 45℃, 60℃, 50℃, respectively.