Study On The Detection Method Of Eurotium Cristatum In Fuzhuan Tea

The total viable count of Eurotium Cristatum is a characteristic index to evaluate the quality of Fu zhuan brick-tea.The majority of the testing institutions used the method of GB 4789.15—2016 The national food safety standard-Food microbiology test-moulds and yeasts count to detect the number of E.cristatum.Fuzhuan brick-tea of Jingyang is Geographical Indication Products in Shaanxi,and it belong to compressed tea.E.cristatum growth was not grown on the surface of the brick-tea but in the interior,and it contains cleistothecium,the national standard method could underestimate the real quantity of the microbes.Therefore,optimization of detection method was conducive to the industry development of fuzhuan brick-tea in jingyang.This subject was based on the tracking evaluation of DBS61/0006—2014 Food safety local standard-Jingyang Fuzhuan brick-tea,the detection method of the E.cristatum in fuzhuan brick-tea was discussed in this subject,and the experimental optimization method was applied to the actual test.The main contents and the results were as follows:（1）The tracking evaluation results of DBS61/0006—2014.During this research,27 samples of Fu zhuan brick-tea were collected in Jingyang of Shaanxi,and all indicators were detected.The range of detection results of E.cristatum was35×10⁴-24×10⁵ CFU/g,72.56×10⁴ CFU/g on average,the percent of pass was 96%because one sample was not up to the standard.For the detection method of national standard,it was found that the sampling method was not indicated,the part of the operation procedure was not clear,the culture medium was not the most suitable for the growth of the coronal bursa,etc.The detection method was still to be constructed.（2）Key steps in E.Cristatum detection of Fu zhuan brick-tea.Combined with colony counts of the E.cristatum in Fu zhuan beick-tea as an idex,through changing the sampling methods,the amount of sampling,the homogeneous way and time,the type of dilution,the place culture which to discuss the effects of different conditions on the detection results.Reach results showe that:In the sampling method,crushing method>five point internal≈internal five point method>surface method.Increasing the crush of raw materials can break cleistothecium and release ascospores,so as to significantly（P<0.01）increased the detection rate and reduced standard deviation of detection data from 14.48 to 2.73;The detected results were low and the relative deviation was large when the sampling amount was less than 10 g;In the homogeneous way and time,the test results tend to stabilize after shaking 30min with the thermostat flask cabinet or used the homogenizer to beat 1 min;In the type of diluent,physiological saline>distilled water>phosphate buffer>0.1%peptone water.There were significant differences（P<0.05）between 0.1%peptone water and other diluent results;There were no significant differences between different culture methods.Therefore,the optimal conditions were:all the samples were crushed,the sampling amount was not lesser than 10 g,flapped with homogenization machine for 1 min,the diluent was saline,and the culturing way was spread plate method and upright culture.By applying this treatment condition not only can ensured the accuracy and stability of the test results but also improved the efficiency of detection and the convenience of operation.（3）Optimization of the detection medium of the E.Cristatum in Fu zhuan tea.Combined with growth rate and colony counts of the E.cristatum in Fu zhuan brick-tea as idexes,through changing the concentration of carbon and nitrogen source,inorganic salt（Chloride salt,phosphate,sulfate）and dark tea slurry fluid.Using response surface analysis to determine the optimum ratio of KCl,dark tea slurry fluid and KH₂PO₄.Results showed that the optimal medium compositions and conditions were as follows:42 g/L sucrose,3.6 g/L（NH4）₂SO4,2.4 g/L soya peptone,40 g/L KCl,1 g/L KH₂PO₄,1 g/L MgSO₄,20 g/L agar powder,1%dark tea slurry fluid.Under this conditions,the detection time was reduced from 5 d to3d,and the efficiency was increased by 40%.（4）The test method established in this study was verified and evaluated in the actual sample detection.Using the national standard method and the optimization method to detect the E.Cristatum in parallel 3 times after 6 samples of Fuzhuan brick-tea were collected from different manufacturers and grades.Results showed that in the actual detection by two methods of testing data trend was consistent.And using optimization method to:（1）Improved the accuracy of the detection results:Adding the sampling method can significant increase the detection result,so as to obtain the true quantity of the E.Cristatum.that contained in Fuzhuan brick-tea.（2）Ensured the precision of detection results:By applying this method,the standard deviation of the E.Cristatum testing results decreased by an order of magnitude.（3）Improve the efficiency of detection:This study maked the pretreatment more explicit and convenient,which is conducive to massive detection,meanwhile shorten the incubation time by 40%using the optimized medium.It is suggested that a local standard-detection method of the E.cristatum in Fuzhuan brick-tea should be set up through the conclusion of this study.