Effect Of Drying Methods On The Quality Of Jujube Powder

Jujube is peculiar to our country, rich in nutrition, and has unique health care value.Jujube has high TSS, high utilization rate of raw materials, which is suitable for producing date powder; As basic material, the color and flavor of jujube powder can be improved, the health care function is strengthened, which make the species diversity, storage period prolonged, edible convenience, and widely used in all kinds of food, drugs. As a new type of raw products, jujube powder drying technology is not mature, stable product quality is not enough, further study of drying methods on jujube powder’s influence on the function of physics and chemistry, sensory and quality should be studied. To improve quality of jujube powder production, the date of processing and using the theory of degree has practical significance. Based on jujube as raw materials, this study studied the drying methods of jujube powder physical properties, flavonoid glycosides, alkaloids compounds, the influence of vibrating superfine grinding of jujube powder powder properties and the influence of microwave vacuum drying on jujube powder characteristics and dynamic model.Main results and conclusions are as follows:1. The effect of drying method on bulk density, liquidity, solubility, porosity, moisture absorption characteristics, colour and lustre and organizational structure was investigated. Samples were dehydrated with four different drying methods: hot-air drying, spray drying, drum drying and freezing drying. All the properties except substance density were affected by drying method. We used date syrup as raw material. The results showed that the jujube powder of spray drying had small bulk density, high porosity. Its colour and lustre was similar to the original color, and could produce good organizational structure; Jujube powder of freeze drying had good solubility and its colour and lustre was shallow; Jujube powder of hot air drying had large particle size and rough surface; Jujube powder of drum drying had weak hygroscopicity. After comprehensive consideration, this study provides technical support for the jujube powder production and quality control.2.Flavonoid and alkaloid compounds were investigated in date syrup and jujube powder by high performance liquid chromatography equipped with photodiode array detection tandem electro-spray ionization mass spectrometry(HPLC-DAD-ESI-MS(n)). Samples were analyzed by a reversed-phase C18 column using a dual linear gradient elution under gradient conditions. Four flavonoid glyco-sides(Kaempferol-3-diglucose-7-glucoside, 6,4’-dimethoxy-5-hydroxyflavone 7-glucosid, L-Epigallocatechin and 5-Hydroxy-7,2’,6’-trimethoxyflavone) and five alkaloid compounds(Cephalotaxine, Erythroculine, 6-(3-Methyl-2-butenyl)-1,5-dihydroxyxanthonel, Cularine and N-Methylasimilobine) could be separated and detected. The effect of drying method on these compounds could be analysed in the same method. The quality of jujube powder with 4 kinds of drying methods varied from different drying temperature and time. Nutrients lost in high temperature and drying time. With low temperature, freeze drying process saved more of these two kinds of compound; Instantaneous drying, spray drying made these two kinds of material to get a degree of reserves.3. Superfine grinding technology is a new technology, which is a useful tool for making superfine powder with good surface properties. With the aim of providing necessary reference about the micro-powder as ingredients in food and medicine, this study investigated the physical properties of jujube fruit micro-powders, prepared by pulverizing its coarse fruit powder with bailey mill for different periods of time. This study revealed the effect of superfine grinding on the influence of the jujube powder by determining particle size, bulk density and porosity, liquidity, color, solubility and other physical characteristics. The results demonstrated that bailey mill could effectively pulverize coarse powder to different micro-sizes. As milling time increased, the median diameter was significantly decreased and particle size distribution width narrowed, the angle of repose, bulk density and porosity improved to a different extent. The color of superfine powder was whiter and better than coarse powder, which overcome the shortcomings of uneven color material.4. The experiments of microwave vacuum drying of jujube were conducted for study rules of moisture change during drying process. With drying curves and dehydrating rate curves, the effect of relative pressure and specific power on microwave vacuum drying characteristics of jujube was studied, and a drying kinetics model was established. The results showed that, according to the dehydrating rate, the process of microwave vacuum drying for jujube could be divided into two stages-accelerated phase and decelerated phase. As the relative pressure is reduced, the drying time was shortened, but when the relative pressure reduce to- 65 mpa, the moisture content had no significant change; The greater the power, the shorter the drying time; The thinner of jujube paste thickness, the shorter of the drying time. But thickness should not be too thin, otherwise it will be burnt. Page equation was suitable for the kinetic model of microwave vacuum drying progress. Formula as follows, MR = exp(-ktn), for the industrial production.