Study On Enzyme Inactivation-Drying Methods And Triterpenic Acid Extraction Of Loquat Flower

Buds and Infloresences of loquat flowers contain various elements, phenols, triterpenoids and amino acids. In the course of loquat cultivation, almost 60%-80% loquat flowers on each tree are thinned out in order to maximize the needs of high quality loquat fruit in market. In fact, most of the loquat flowers have been thrown out instead of being fully utilized and this result in a waste of resources. This paper investigated the activity of peroxidase (POD), polyphenol oxidase (PPO) in loquat folwer. The loquat flowers with its enzymes are inactivated were used to make into loquat flower tea during different drying treatments. This paper also studied the extraction method of oleanolic acid and ursolic acid in loquat flowers tea. Rusults were as follows.(1) The activities of POD and PPO in loquat flower at diffetent temperatures were studied, and the two kinds of enzyme avtivities in different tissue and developmental stage of loquat flower were investigated. Two kinds of enzyme inactivity methods, i.e hot-steam and microwave, were compared. The result showed that the optimum temperature of POD and PPO were 25℃and 30℃ respectively. POD and PPO activities in petal were significantly (p<0.05) higher than those in other tissues; POD and PPO activities in full-bloom stage were significantly (p<0.05) higher than those in other developmental stage. After 75 s treatment of hot-steam or microwave in 420 W, the residual activities of POD and PPO were both less than 5%. Vacuum freeze drying needs the longest time to make the mosiure of loquat flower bellow 10%, so its effency was the lowest. On the contrary, microwave treatment had the highest drying effiency and needed the shortest time.(2)The sensory and soup color of loquat flower tea were compared among the four drying methods:hot-air, vacuum, microwave and vacuum freeze drying. Effects of extracting conditions on the water-soluble bioactive ingredients content of loquat flower tea soup were studied; and the influence of different tissues, developmental stages, drying methods and storage temperatures on water-soluble bioactive ingredients, and free radical scavenging ability of loquat flower tea soup were investigated. The result indicated that the loquat flower tea obtained by vacuum freeze, microwave 140,280,420 W achieved in higher sensory score; all the tea soups had a high brightness and had the color of light yellow. The optimum extraction conditions are extraction temperature 80℃, liquid/solid ratio 150(V/W), extracting time 45 min. Among different tissues of loquat flower tea, the petal contained the most of phenols, flavonoid and has the stongest ability of scavenging free radical; the stamen contained the most of amino acids; while the calyx contained the most of caffeine. Among different stages of loquat flower, the full-bloom stage contained the most of phenols, flavonoids, amino acids and had the stongest ability of scavenging free radical; the bud stage contained the most of caffeine. The loquat flower tea obtained through vacuum freeze-drying method followed by microwave 420 W drying methods contained the highest bioactive ingredients and had the strongest ability of scavenging free radical. Under 5℃ storage, loquat flower tea could preserve its bioactive ingredients and remain the ability of scavenging free radical.(3) The conditions for microwave-assisted extraction of oleanolic acid (OA) and ursolic acid (UA) in loquat flower tea using single-factor and orthogonal experiments were optimized. The OA, UA content in different tissues and developmental stages of loquat flower were analysed, and the influence of drying method and hot-water extraction on OA, UA content of loquat flower tea were studied. The result showed that the optimum conditions of microwave-assisted extraction were ethanol concentration 80%, liquid/solid ratio 40 (V/W), extraction time 40 min, microwave power 100 W and extraction temperature 50℃. The extraction yields of OA and UA were both significant (p<0.01) higher than those using ultrasonic-wave assisted extraction and thermo-refluxing extraction. Different drying method had no significant (p<0.05) effect on OA, UA content in loquat flower tea. OA,UA content in calyx were significantly (p<0.05) higher those in other tissues. The difference of OA, UA content among different developmental stage was not significant (p>0.05). The retention rate of OA, UA in the flower tea dregs were 69.92% and 49.56% respectively after hot-water extraction.