Study On Combination Drying Of Myrica Rubra Powder And Its Neuroproptective Effect

Myrica rubra is a subtropical fruit in southern China. It has a–distinct flavor,sour taste, and a variety of functional nutrients, which lends itself to be a natural,green, health food ingredient. Myrica rubra is fast to reach maturity, strong inpostharvest respiration, and rapid on its aging process. Moreover, the anthocyanin andother polyphenols that Myrica rubra contains are highly volatile. They are liable to belost during processing, transport and storage. The ever-increasing production, coupledby the still limited marketing and sales, results in surplus of the raw material.Therefore, development of a viable processing technology for Myrica rubra hasbecome urgently needed. In this thesis, a powder product was made using a newlydeveloped method, and the processing effects on the bioactivity of the functionalingredients was studied:1. A combined dehydration method for making Myrica rubra powderIn this study, a novel drying technology by combining freeze-drying and vacuumadsorption drying was applied. The sublimation of freeze-drying under vacuumremoved most of the moisture in raw materials at low temperatures. This was followedby using, silica gel desiccant, instead of the conventional desorption with hightemperatures, to adsorb remaining bound water under vacuum at low-temperature (i.e.,40~80Pa, room temperature). The effects on the quality of Myrica rubra powder weredetermined by varying the conditions of the drying process including heating platetemperature, material thickness and vacuumization. Thereby, the optimizedfreeze-drying process was found to be at a heating temperature of40°C, with a materialthickness of8mm and under vacuum of70Pa. On the other hand, the moisture contentof the material at transfer point in the combined drying with silica gel and vacuum was30±2%, the adsorption temperature was40°C, and the adsorption vacuum was70Pa.Based the single factor experiments using the moisture and anthocyanin contents asindices, the optimum parameters for the combined process obtained from the quadraticorthogonal rotation combination and data model were identified to be:29%moisture at the drying transition points,40°C for the adsorption and under70Pa vaccum. Themoisture content of final product using this method was4.91%, the functional factorssuch as the anthocyanins, flavonoids, phenols compounds of product using this combinedfreeze-drying method were26.23mg/g,31.92mg/g, and56.11mg/g, respectively. Compared thedata of reconstituted juice with that of the fresh juice, there were no significant differences on thefunctional components, which elucidated that the non-thermal processing technology couldmaximize the retention of the functional nutrients.2. Effect of Myrica rubra powder on Neuro-2a cellsBrain stroke is the third leading cause of death in the developed countries.Patient's central nerve system is damaged as a consequence of the occurrence ofischemic condition in the brain. The oxygen and glucose deprivation (OGD) ofNeuro-2a cells is a recognized model in screening materials for protecting brain fromischemic damage. The present study was to elucidate the neuroprotective effect ofMyrica rubra powder in the OGD model of Neuro-2a cells. A sample of the Myricarubra powder was reconstituted to9°Brix, pH3.2, conditions equivalent to theoriginal juice, for testing. MTT assays showed no significant change in cell viabilityafter24hr pre-incubation with Myrica rubra juice at the concentration of0.27,0.55,1.09,2.19,4.39mg/mL, indicating an absence of cytotoxicity. Whereas, the Neuro-2acell viability decreased to53.61%in the OGD test of the control sample. The cellsunderwent substantial changes in shape, becoming heterogeneous with thedisappearance of axons and dendrites. With the addition of Myrica rubra juice, thecell viability increased in a concentration-dependent manner up to the increment of86.7%. The results showed neuroprotective effect of Myrica rubra powder, made bycombined drying method, suggesting a potential application of Myrica rubra powderas a dietary supplement for protecting brain from ischemic damage.