Study On The Drying Process And Product Development Of Nymphaea Stellata Willd

Nymphaea stellata Wild.is a kind of tropical flower of herb plant growing on the lake and the river bank.At present,it is mainly applied to the ornamental of fresh-cut viewing flowers while rarely used in other aspects.However,due to easily putrid characteristics,fresh-cut flower has a short shelf life which may cause a serious waste.Traditionally in china,N.stellata is used as herbal medicine and food resource,for it is rich in bioactivity ingredients including a variety of anthocyanins,flavonoids and phenolic acid active substances,as well as a variety of amino acids,vitamins and trace elements,such as iron,selenium,etc..N.stellata has been considered as a potential resource in medicine and food industry due to its utilization for the therapy of dyspepsia,diarrhea,hemorrhoids,fever,apoplexy and encephalitis.In this paper,hot-air and microwave drying processes were used respectively to dehydrate N.stellata materials to investigate drying dynamics and the differences of these two processes were discussed comparedly.Furthermore,we investigated the factors of the N.stellata flower discoloration.Based on this,we employed color preservation ways to treat folwer materials and developed a kind of N.stellata flower beverage.The main research contents and results are showed as followings:1.The drying characteristics and dynamics with two processes(hot-air and microwave drying)treating N.stellata flowers was investigated.The temperature of hot-air drying process possessed a great influence on flesh flower drying.With the increase of temperature,the drying treatment time should be shortened.It was observed that the hot-air drying process of N.stellata could be divided into three stages:acceleration,constant speed,and speed reduction.Both microwave power and load amount of flower materials showed an impact on drying rate of flowers with microwave process.Though The increasing microwave power and decreasing load amount of flower materials could decrease the drying time and the microwave power showed more prominent effects on dehydration time for flowers.Additionally,acceleration and deceleration stages were observed in drying process of N.stellata flowers.To describe the drying process,we gave a Page equation through the kinetics in accordance with hot-air and microwave drying processs.The expressions of the drying model were respectively summed:MR = exp[(0.0986-0.0026T)t(0.6739+0.0136T)]and MR =exp[e(-6.076+131 644P-1057.988p2)t(1.925-26.657P+234.362P2)]; the best process parameters for the microwave drying was the following:continuously dried at 4 kw microwave power for 6-8 min in the early stage to decrease the water content of flower materials to 50%-70%,the microwave drying carrying out at 2 kw microwave power at a later stage with interval of 2 min for each drying treatment until reaching to the safe water content.2.The effect of hot air and microwave drying process was investiagated and two processes were comparatively studied.The results indicated that the microwave-dried method treating flowers possessed higher content of total phenols,flavonoids and anthocyanins and the chromatism value was lower than the hot-air drying method.According to more main aroma components preserved and higher resistant activity for ABTS and DPPH free radical measured through microwave drying method,the new drying process revealed more advantages than traditional hot-air drying process.Furthermore,comparative investigation showed that the average rate of microwave drying process was nearly 42 times as high as that of hot-air process,while the average energy consumption of hot-air drying process was 22 times that of microwave drying process.3.The influence factors of coler fading and color preservation process were investigated during the storage of dried N.stellata flower products.The results indicated that temperature,moisture content and oxygen were the main factors leading to the fading of produts during storage.The light almost had no effects on colver fading during storage.The water content showed a dramatically influence on the fading of products.Based on the research,the flower materials before drying should be treated to preserve product color.Throught the single factor analysis,the optimum of color protection agent formula was obtained by using response surface optimization:gallic acid 0.21wt%,sodium chloride 0.97 wt%,and citric acid 0.05 wt%,and ascorbic acid 0.30 wt%.It was confirmed that the N.stellata treated with the color preservation agent showed better storage effect than the N.stellata with no coler preservation treatments which could prolong the product shelf life in some extent.4.N.stellata flower tea beverage was developed.On the base of single factor analysis,the orthogonal design experiment was used to study the extraction process of N.stellata flower beverage.The optimum parameters of extraction process for flower tea were as follows:extraction temperature 65 ?,extraction time 15 min,solid-liquid ratio 1:300,which could prepare the best quality flower extration.Following above process,the flower extraction was used to develop beverage produt by adding citric acid 0.01 wt%,white granulated sugar 3 wt%,three sucrose 0.006 wt%,sodium citrate 0.01 wt%,CMC-Na 0.1 wt%,EDTA-two sodium 0.0015 wt%and the beverage presented the best stability and taste charactering the flavor of the N.stellata.