Quality Detection Of Postharvest "Hongyan" Strawberry Based On Flavour

Strawberry is very popular among consumers due to its gorgeous color,good mouth feel and abundant nutrition.In recent years,the technology of strawberry preservation has developed rapidly,which lead to its storage and circulation time greatly improved.The quality change of strawberry has the following characteristics.The quality change is less obvious in the early stage.Once strawberry corruption happened,pathogenic bacteria cross infection seriously,the quality of strawberry fall rapidly.Therefore establishing strawberry quality real-time monitoring method,monitoring the quality of strawberry,transfering out the initial corruption strawberry at the right time can greatly improve the utilization rate of strawberry and avoid unnecessary loss.In this paper,"Hongyan"strawberry was selected as test materials,with the storage temperature of 20 ℃ and 4℃respectively,humidity was between 85～95%,to detect the strawberry quality based on flavor.Electronic nose(e-nose)and the single ethanol sensor were used to collect the odor of strawberry during storage period.Establish the model of discriminant strawberry quality grade based on flavor by partial further squares discriminant analysis(PLS-DA)and support vector machine-classification(SVM-C)method respectively.And gas chromatography-masss spectroscopy(GC-MS)was used to determine the gas composition changes during strawberry quality decreased.At the same time,the model of predicting the decay index of strawberry based on ethanol concentration were built,and the change of ethanol concentration during strawberry storage and circulation was simulated in order to build a method to monitor the quality of strawberry change.1.Determination the quality grade of" Hongyan " strawberryThe strawberry is divided into four grades based on the changes of sensory evaluation score,weight loss,hardness,soluble solids content,titratable acid,decay index and color during storage.Classification standard of quality for " Hongyan " was as follows:strawberries eat good and had gorgeous color,good fruit type were graded 1.strawberries which color turned dark and hardness dropped slightly,but fruit texture and taste were still good were graded 2.Strawberries with spots shape and significantly soften,but owned acceptable appearance and taste were graded 3.Strawberries with edible value lost and corruption,browning and shrivel appearanced were considered corruption level.2.E-nose technology distinguish the quality level of" Hongyan" strawberryThe flavor change of strawberry during storage period was extracted by e-nose.Through correlation analysis of strawberry quality grade and sensor response values and principal component analysis of strawberry quality grade,determined the feature variable of distinguishing strawberry quality level were S6,S7,S8 and S9.The overall accuracy of modeling group and validation group were 89.2%,96.7%at 20 ℃ storage condition,84.2%,90.0%at 4℃ storage condition based on PLS-DA method.The overall accuracy of modeling group and validation group were 99.2%,100.0%at 20℃ storage condition,100.0%,98.3%at 4℃ storage condition based on SVM-C method.At the same time,the flavor change of strawberry during quality deterioration was determined by GC-MS.The results showed that the content of methyl ester,ethyl ester and lauryl alcohol increased during strawberry quality deterioration.The emergence of plant alcohol,linalool,olefins,olefine aldehydes,enol and sulfur-containing compounds were the signs of strawberry quality deterioration.3.Ethanol sensor distinguish the quality of " Hongya" n strawberryThrough extracting the flavor change of strawberry storaged at 4℃ by ethanol sensor,we established the model of decay index prediction of strawberry based on ethanol concentration.The R2 and Sig.were 0.9111 and 0.000 respectively of model.And the R2,Sig.and RMSEP were 0.9395,0.000 and 0.214 respectively of verification model.The overall accuracy of modeling group and validation group were 83.3%,85.0%based on PLS-DA method,89.2%,88.3%based on PLS-DA method.At the same time the change of ethanol concentration during strawberry storage and circulation was a good response to quality change.