Extraction Of Decolorized Okra Pectin And Its Application In Yogurt By Ultrasonic Technology

Pectin,as a food additive,is widely used and in great demand.At present,pectin mainly extracted from orange peel and apple residue,Due to source constraints,it cannot meet the diversity and multifunctional application of pectin products.Therefore,okra pectin,with wide source and low price,has great potential to be a new resource of pectin.However,the large amount of pigment in okra has a negative impact on pectin application,so decolorization is a necessary pretreatment step before okra pectin(OP)extraction.Reuse of the removed pigment can not only reduce the pressure on the environment,but also prevent the waste in the actual production process and realize the graded utilization of resources.At present,it is known that ultrasound and drying methods have a great impact on the extraction and quality of pectin.On this basis,the effect of powder mesh size after drying on the quality of pectin was studied in detail.At the same time,ultrasonic-assisted pectin extraction and its mechanism in yogurt fermentation were studied.In this paper,two typical drying methods,namely hot air drying and freeze-drying(HD and FD)were used to dry okra,then okra was ground into three kinds of powders with different mesh numbers,namely 60,80 and 120 mesh(M60,M80 and M120),the pigment(OPI)was removed and then applied to noodles.Controlled temperature coupled with ultrasound assisted extraction(CTUAE)was used to extracted OP in powder,the effect of pretreatment and ultrasound on OP was studied,and the optimized pectin and controlled temperature coupled ultrasound assisted fermentation(CTUAF)technology was applied to yoghurt.The main contents and results of the research are as follows:The main contents and results of the research are as follows:(1)Based on different drying methods and,sieves,the effects of different pretreatment methods on the extraction rate,stability and antioxidant activity of OPI were studied..The extracted OPI was finally applied to noodles to reveal the color change of OPI during the drying and cooking process of noodles,and to study its influence on the texture of noodles,it provides the possibility for the application of OPI in noodles.The results showed that the yield of FD-OPI was higher than HD-OPI and the color was greener.The extraction yield was M60-OPI > M80-OPI >M120-OPI,and the antioxidant activity was M120-OPI > M80-OPI > M60-OPI.In addition,M80-OPI had the darkest color at the same concentration,and the stability was better.So it is more suitable for application as a dyeing agent to noodles.The hardness and viscosity of noodles are increased by 7.12% and 43.25%,respectively.(2)On the basis of pretreatment,in conjunction with CTUAE technology,its effects on the extraction yield,physicochemical and functional characteristics and molecular structure of OP were studied.Furthermore,effects of two representative drying methods on apparent morphologies of OP molecular chains were explored.The relationship between physicochemical characteristics,such as GalA,DE,Mw,particle size,chain conformation and functional characteristics,such as gel,rheological,emulsifying,WHC,OHC and thermal properties was revealed.The time-frequency domains of acoustic fields during extraction process of OP were monitored to explore the effects of ultrasonic technology.The results showed that,Compared with HD,FD prevents the cracking of the pectin backbone(HG),thereby increasing the extraction yield of OP,Gal A,DE and Mw,and maintains a smaller particle size with increment of viscosity,but HD OP is more prominent in WHC and OHC than HD OP.In addition,HD OP are dendritic rigid chains,while FD OP are flexible chains with multiple branches.Lastly,CTUAE technology increased the extraction yield and Gal A,and decreased DE,Mw and particle size of OP.CTUAE technology also improved gel hardness and resilience,enhanced ES,WHC and thermal stability,reduced viscosity of OP.(3)Pectin can replace fat as a stabilizer for yogurt,providing a favorable means for making green low-fat yogurt.In this paper,the addition amount of OP in stirred yoghurt was optimized,and CTUAF technology was used.the time-frequency domain of the ultrasonic field during the fermentation process was monitored,and the influence of the solution properties on the ultrasonic field due to the addition of OP was discussed.The effects of ultrasound and OP on the physicochemical and structural properties of yoghurt were studied,to reveal the effects on the transportation and storage properties of yoghurt.Results showed that the optimal amount of OP in yogurt was 0.1%(ω).Adding OP increased the intensity of the ultrasonic field,and also promoted ultrasonication to improve the efficiency of yogurt fermentation.It was observed that ultrasound and OP can reduce the loss of whey and improve the hardness,rheological property,quality and odor of yogurt,based on the changes in these apparent physiochemical properties,the microstructure and interaction of OP and casein binding were further studied.It was observed that its cross-linking with casein increased and filled with casein cavity.OP also improved the survival of probiotics in yogurt storage,and prevented post-acidification of yogurt and stabilized yogurt texture.In summary,the necessary decolorization steps of pectin extraction were transformed into pigment extraction,and the pigment and pectin were successively extracted from okra powder with different drying methods and powdere size,and the pigment and pectin were applied to noodles and yogurt respectively.Ultrasound was used to improve the extraction rate of pectin,pectin was modified,and yogurt fermentation was promoted..