Preparation,Characterization And Application Of Superfine Jujube Powder

Dried jujube are one of the main varieties of jujube planted in Xinjiang,and due to the lack of deep processing technology,dried jujube are still the main marketing method.As a new type of product,jujube powder is easy to eat,has a long storage time,can maintain its original nutritional flavour and can be.The most common method of processing fruit and vegetable powders requires the addition of auxiliary ingredients which directly affect the composition and flavour of the fruit and vegetable powders.Therefore,the search for the preparation of fruit and vegetable powders without the addition of excipients and the improvement of the quality of fruit and vegetable powders has become an urgent issue.In this work,the dried jujube from Xinjiang was used as the raw material,raw material to prepare superfine powder by dry superfine crushing technology,and the effects of different Pre-processing on the physicochemical properties of the superfine powder were studied;Taking the particle size as the index,the process was optimized;Investigating changes in powder property characterisation after ultra-micronization;The application of the prepared ultrafine powder of jujube was studied.The main research contents and results are as follows:(1)Five pretreatment methods(hot water,alcohol method,ultrasonic,enzyme method and alkali method)are used to find the way of making powder.The soluble sugar content decreased and the amino acid solubility increased after pretreatment in 5 compared to the control group.Powder colour from bright to dark: alcohol > ultrasonic > hot water > enzymatic > alkaline.The particle size from smallest to largest is: alcohol < ultrasonic < hot water < alkaline < enzymatic.A total of 91 volatile organic compounds,consisting mainly of 31 esters,19 acids,10 alcohols,10 aldehydes,6 ketones,11 alkanes and 4 carbohydrates,were detected by gas chromatography-mass spectrometry in the five processes compared to the untreated group of jujube and municipal jujube powder,orthogonal partial least squares discriminant analysis(OPLS-DA)and displacement tests combined with variable importance analysis in the projection method show that specific processes influence the type and content of VOCs in powders,which can be identified using specific organic compounds.In addition,according to the results of OPLS-DA and VIP,the differences between ultrasonic and alkaline processes were insignificant,while the differences between the other five groups were significant(P< 0.05).The pretreated powders were observed by SEM to have severely broken cell walls,smaller particle size and more uniform particle size.The results showed that the alcohol pretreatment was superior to the other pretreatment groups.(2)According to the conclusions of the previous chapter,the alcohol process was optimized,and the effects of pretreatment time,solid-liquid ratio,pulverizing time and ethanol concentration on the particle size of the powder were studied by single factor and response surface method combined with dry ultra-fine pulverization technology.A response surface test was carried out on the basis of a single-factor test with the particle size as the index,and three factors were selected: material-toliquid ratio,pretreatment time and ethanol concentration.The results showed that the optimum alcohol process conditions were 1:3,53 h pretreatment time and 60(v/v)% alcohol concentration,and the particle size was 28.47 μm.(3)After comminution,the contents of total sugar,reducing sugar and sucrose decreased by42.22%,39.06% and 74.78% in dried jujube superfine powder,respectively.The contents of amino acid and protein increased significantly.The brightness,angle of repose,slip angle and bulk density were also promoted.Besides,the wetting suspension time was significantly shortened by 41.99%,indicating that the wettability of the powder was improved.The water holding capacity and swelling capacity of the superfine jujube powder decreased by 60.30% and 56.28% respectively,showing that the superfine grinding reduced the hydration capacity of the powder.There were little changes in the functional groups of the superfine jujube powder according to the analyses of scanning electron microscope and Fourier infrared spectroscopy.(4)The performance was improved after ultra-fine grinding,which laid a foundation for the application of jujube ultra-fine powder in ice cream.A single-factor test was conducted with the amount of jujube superfine powder added,the ratio of rosehip paste to jujube e superfine powder,the amount of sugar added and the ratio of milk to milk powder,On the basis of the orthogonal experiments,the optimum process conditions for ice cream preparation were determined as follows:the addition amount of jujube superfine powder was 20%,the ratio of rosehip paste to jujube superfine powder was 3:5,and the ratio of milk to milk powder was 2:3,and the highest sensory evaluation score of 83.32 was obtained under this condition.