| Fresh-cut broccoli is convenient to cook with rich nutrients, and it satisfies theincreasingly rapid life. But the shelf-life of fresh-cut broccoli is short with nutrientslosing and organization yellowing, because of the exuberant respiration and promptmetabolism.Hypobaric storage can restrain the respiration of fruits and vegetables, eliminateharmful gases timely. There will be certain advantages of application of hypobaricstorage on preservation of fresh-cut fruits and vegetables. The establishment ofshelf-life prediction model can be used to monitor and forecast the quality changesof agricultural products during the storage and transport.In this research, hypobaric storage was studied on the application ofpreservation of fresh-cut fruits and vegetables. Chemical reaction kinetics andmicrobial growth kinetics were researched to establish the shelf-life predictionmodel of fresh-cut broccoli with hypobaric treatment. Concrete research contentsand results are as follows:(1) Hypobaric storage and controlled atmosphere storage were conducted usingfresh-cut broccoli as material at (4±0.5)℃. Physicochemical indexes weredetermined regularly, and the preservation effect of the two techniques werecompared. The results indicate that, hypobaric storage works better than controlledatmosphere storage on restraining the accumulation of MDA, reducing the loss ofVC and maintaining the hardness, springiness and chewiness. Significant differencesof chlorophyll and membrane permeability were not found.(2) The VC content, chlorophyll content, weight loss and total numbers ofbacteria of fresh-cut broccoli were determined during storing period while thefresh-cut broccolis under hypobaric treatment for36h were placed at0℃,5℃,10℃,15℃and20℃respectively. The reaction order and change rate k of everycharacteristic index were calculated by using knowledge of chemical reactionkinetics. The results show that, the4change rate k increase with increasingtemperature. The reaction order of VC and chlorophyll is first order, and the change of weight loss conforms to zero order reaction.Three shelf-life prediction models of VC(SLVC), chlorophyll(SLChio) and weightloss(SLWL) were established combined with Arrhenius equation and the accuracy ofmodels was evaluated later. Accuracy evaluation between predicted and observedshelf-life shows that the predictive accuracy of shelf-life prediction model SLVC(preexponential factor: k0=-3.19×1020, activation energy: Ea=118762.49, R2=0.9986)is highest, and the shelf-life of fresh-cut broccoli with hypobaric treatment can bepredicted at the storage temperature from273K to293K.(3) In this research, the Pseudomonad spp. number was determined during thestoring period while the fresh-cut broccolis were stored at five different temperatures(0℃,5℃,10℃,15℃,20℃) respectively after hypobaric treatment for36h. Thekinetics model of Pseudomonas at different temperatures was researched. The resultsindicated that, the S-shaped cruves of Pseudomonad on fresh-cut broccoli could bewell described by the modified Compertz equation. The temperature had nosignificant effect on Nmax(maximum cell concentration), and the average value ofNmaxwas determined to be8.3122±0.0651lg(CFU/g). It was observed thatμmax(maximum specific growth rate) increased with increasing temperature whileλ(lag time) decreased with increasing temperature.The temperature dependence of μmaxand λ was discussed using Belehradekequation, and the shelf-life prediction model SL of fresh-cut broccoli was establishedwith parameters: Nmax=8.3122lg(CFU/g), Ns=7.6990lg(CFU/g), bμ=0.0263,Tminμ=-11.9810, bλ=0.0294, Tminλ=-24.4572.Validation of the prediction model was conducted by comparing the growthcurve of Pseudomonas on fresh-cut broccoli at8℃.It shows from bais factor,accuracy factor and relative error that the shelf-life of fresh-cut broccoli withhypobaric treatment from0to20℃can be predicted availably by the predictionmodel SL. |
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