Preparation Of Critical Temperature Indicator Based On N-caprylic Acid Capsules

For temperature-sensitive products,temperature control in the process of storage and transportation is the basis for ensuring its quality and safety.These irreversible changes can be monitored,recorded and directly showed temperature changes of products in the supply chain by temperature indicator.The critical temperature indicator can rapidly change(color or phase)during a certain period of time when the food environment temperature exceeds the warning line,indicating that the food storage environment has experienced high temperature.As a result,with the continuous improvement of the quality and safety requirements of the temperature sensitive products,the research and development of the critical temperature indicator is of great engineering value.This project was to build color reaction system based on coloration of acid-base neutralization reaction with n-caprylic acid as the acidic material,sodium hydroxide solution as alkaline substance,and Bromothymol blue phenol red as pH indicator.And controlled-Release microcapsules were prepared with Poly(methyl methacrylate)(PMMA),urea formaldehyde resin(UF)and calcium alginate as shell material,n-caprylic acid as core material.Different kind of critical temperature indicator(CTI)according to properties of the color reaction system and microcapsules combining practice requirement.The main research contents and results are as follows.(1)Properties of the microcapsules were studied by FT-IR,SEM,TGA and DSC to explore the influence from factors like core/shell ratio and species and dosage of cross-linking agent.The results proved that all the characteristic absorption peak of core and shell material were showed up in FT-IR spectrogram of microcapsules,which proved that the preparation of n-caprylic acid microcapsule was successful.Sample 35 DVB has the best formability,and encapsulation property of DVB series were better than TMPTA.Discoloration of 35DVB-T was delayed for 40 min,which confirmed the sustained release function of microcapsule.(2)Double shell microcapsules of PMMA/UF and PMMA/calcium alginate were prepared based on previous single shell microcapsules,and properties were also characterized.The results proved that all the characteristic absorption peak of core and shell material were showed up in FT-IR spectrogram of double shell capsules,which proved that the preparation of double shell microcapsule was successful.Single shell microcapsules were covered by UF as bag structure.Core weight loss rate of double shell microcapsules was improved because of UF but became worse as the rise of PMMA/UF ratio.Color test proved that DS-4 was fit for preparing CTI.For macro capsules FT-IR curses proved that the preparation of double shell macro capsules was successful.Single shell microcapsules were covered by Calcium alginate as bag structure.Coating strength of calcium alginate gel was improved with the increase of calcium chloride concentration and microcapsule dosage.The content of core material of double shell macro capsules was periodically changed as concentration of calcium chloride and microcapsules,and heat stability of TMPTA series macro capsules were better than DVB.According to color test,DS-4 and TCA-7 can be used to CTI.(3)CTI of different response time and temperature were designed and built based on slow release performance of the n-caprylic acid capsules and requirement of practical application.The slow release performance of CTI were also evaluated.The results showed three kinds of CTI used DS-4 and TCA-7 was successfully built.The response temperature were 1?,1? and 4? respectively.The error value were plus or minus 10 min,acceptability were 70%,90% and 90% in error range.