| Strawberry fruit is rich in inorganic nutrients,amino acids and other organic nutrients,as well as a variety of health factors,by consumers love.However,due to the poor storage performance of strawberry peel it is easy to corrupt,which affects the edible quality and commodity value of the fruitIn this paper,the effects of sodium alginate/nano CaCO3 composite film on the quality and flavor of strawberry after harvest were explored through experimental analysis.Response surface method was used to optimize the formula of sodium alginate/nano CaCO3 composite film,and the effects of the optimized film on the physiological quality of strawberry,such as respiration intensity,weight loss rate,color difference,hardness,titratable acid,Vc,reducing sugar and soluble solid content,were measured.Through spme-gc-ms and electronic tongue technology,the qualitative and quantitative analysis of flavor substances in fresh strawberry and strawberry fruits treated with or without coating for different storage time was conducted to study the changes of volatile flavor substances and physiological indexes.The changes of non-volatile flavor substances in strawberry treated with and without coating were detected by electronic tongue technique Specific research results are as followsThe research found that:(1)Through the response surface experiment,the addition amount of sodium alginate,carboxymethyl cellulose(CMC)and nano-CaCO3 in the sodium alginate composite coating solution was optimized,and the water vapor transmission coefficient of the composite membrane was obtained as the response value.The regression equation is:Y=3.2+0.11A+0.086B+0.047C+0.065AB+0.012AC-0.1BC+0.4A2+0.43B2+0.46C2.According to the mathematical model established by response surface analysis,the optimal process conditions were as follows:sodium alginate 1.6g,CMC 0.85g,Nano CaCO3 0.05g.The mechanical properties of the optimized membranes are improved significantly(2)We compare the effects of sodium alginate coating,optimized membrane and control group on physiological indexes of strawberry fresh-keeping.It was found that both CTS membrane and CTSS membrane fresh-keeping strawberry can effectively alleviate the decline of strawberry physiological quality.Optimized membrane treatment can effectively alleviate the decrease of strawberry color difference,hardness,titratable acid.Vc,reducing sugar and soluble solid content.and inhibit the increase in respiratory intensity and weight loss rate of strawberries so as to alleviate strawberry aging and prolong shelf life.(3)A total of 55 volatile compounds were identified and quantified by SPME-GC-MS in strawberry fruit,24 of which were esters,accounting for 44%of the total volatile flavor of strawberry fruit;followed by ketones and alcohols,about 20%of the total volatiles on their own;relatively few types of aldehydes and furanones were detected.The esters are mainly methyl acetate,methyl butyrate,ethyl butyrate,ethyl acetate,laurolactone.etc.,and the ketones are mainly acetone,2-hexanone,2-pentanone,2-heptanone,and methyl ketone.The bases and the like include alcohols,linalool,1-butanol,2-methylbutanol and the like.Changes in the volatile flavors of the coated and uncoated strawberries indicated that the concentrations of ethyl acetate,ethyl butyrate,methyl hexanoate and ethyl hexanoate increased,so the sodium alginate nano-calcium carbonate composite coating film has the effect of delaying the development of flavor and prolonging the shelf life of the strawberry.(4)The electronic tongue technique was used to detect the changes of non-volatile flavor substances of strawberry which is treated with uncoated and uncoated film at different storage times.Through the qualitative analysis of the strawberry in different storage time by the taste radar chart,it was found that the response value of the sour taste and salty taste of strawberry decreased,while the response value of bitterness and salty taste increased.Principal component analysis found that the sour taste and astringency of strawberry fruit were observed.The bitter aftertaste and the sally aftertaste are poorly correlated and the scores of the latter three indicators are higher,so these four components can be used as indicators to describe the changes in strawberry flavorThe results of this study indicate that the preservation of sodium alginate nano-calcium carbonate composite film keeps the best flavor of strawberry,prolongs the storage period and shelf life of strawberry fruit,and provides a new research idea for strawberry post-harvest preservation. |
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