Study On Shelf Life Prediction Method Of Fresh Milk And Soy Milk Based On Electronic Tongue Difference Degree Method

Electronic tongue is a modern sensory analysis instruments for evaluating the overall quality of detection solution by analysis the current response signal with multivariate statistical analysis method.At present,the laboratory had successfully developed a multi-frequency large amplitude pulse voltammetric electronic tongue,which consists of a sensor array,signal excitation and acquisition system and data analysis algorithms.Our laboratory has focused on qualitative analysis the differences between the basic material and the actual sample through the electronic tongue and the mechanism of difference degree(spatial distance)methods which were used to characterization the difference between the samples has been explored in the preliminary work,but the research on the application of difference degree was less.In this background,this paper optimized the difference degree algorithms and the best algorithm was applied to shelf life prediction for fresh milk,soy milk based on preliminary studies of laboratory.While the sensory evaluation and microbial detection methods were used to predict the shelf life of these two samples.Finally,the shelf life prediction results of electronic tongue,microorganisms,sensory evaluation methods were combined to establish guidance standard line for the quality of sample.Now the specific work and conclusions were summarized as follows:(1)A study on optimization the applicability of difference degree algorithmDifference degree algorithm such as Dd(separation degree),Dis2,Dis3(Euclidean distance average),Dp(Discrimination Power),DI(Discrimination index)and Ed(Euclidean distance)were optimized by using basic taste substances including citric acid(sour),monosodium glutamate(umami),sodium chloride(salty),quinine sulfate(bitter),glucose(sweet)and the best algorithm Dis3 was obtained with a series of evaluation indexes including the principle of difference degree,standard deviation,CV value,fitting coefficient R2,Ar.(2)A study on shelf life prediction for fresh milk and soy milk sample based on microbial growthTotal bacterial colonies were measured between accelerated deterioration samples at three temperatures of 25,35,45 ? and normal control samples at 4 ?.And based on Arrhenius kinetic equation,the shelf life prediction models of fresh milk and soy milk were established.According to the prediction model,the microbial prediction shelf life of fresh milk and soy milk at 4? was 7.4 days and 5.3 days,respectively.Compared with the actual shelf life,the prediction error of fresh milk reached 5.7%,while the prediction error of soy milk was 6.0%.According to the results,the final time of microbial safety quality for fresh milk and soy milk samples were 7.4 days and 5.3 days,respectively(3)A study on shelf life prediction for fresh milk and soy milk sample based on sensory evaluationThe three-point test of sensory difference test was carried out between accelerated decay samples and normal storage samples.The shelf life prediction models of fresh milk and soy milk were established with the Arrhenius kinetic equation and the shelf life prediction was performed.The results showed that the sensory shelf life of fresh milk and soy milk was 1.2 days and 1.3 days,respectively.According to the results,the best time of sensory quality for fresh milk and soy milk was determined to be 1.2 days and 1.3 days,respectively.(4)A study on shelf life prediction for fresh milk and soy milk sample based on electronic tongue difference degreeThe best algorithm Dis3 was applied to predict the shelf life of fresh milk and soy milk.Shelf life prediction models for fresh milk and soy milk had been developed by combined with Arrhenius kinetic equation.The sensory shelf life and microbial shelf life of fresh milk and soy milk were predicted by combining the sensory critical time point and microbial thresholds with the shelf life prediction model based on electronic tongue difference degree.The results were:(i)The sensory shelf life of fresh milk at 4 ? under normal storage conditions was 4.1 days;The microbial shelf life of fresh milk was 7.7 days.Compared with the actual shelf life on the package,the prediction error reached 9.4%.(ii)The sensory shelf life of soy milk at 4 ? under normal storage conditions was 5.5 days;The microbial shelf life of soy milk was 5.2 days.Compared with the actual shelf life of soy milk,the prediction error was 3.3%.(5)A study on guidance standard line establishment of food quality for fresh milk and soy milkThe guidance standard line of food quality for fresh milk and soy milk were established based on the results of electronic tongue,the three-point test and microbial methods.The results indicated that fresh milk had the best sensory quality in 4.1 days under the normal storage condition,the microbiological indexes were safe in 4.1-7.4 days,and the food cannot be eaten after 7.4 days.The soy milk was consumed at 1.3 days ago which had best sensory quality,the microbial quality was safe between 1.3 days and 5.2 days,corruption may occur after 5.2 days.