Study On Extraction Of Pectin From Pomelo Peel By Pulsed Electric Field With Cellulase

With the continuous growth of pectin consumption,traditional pectin extraction sources and processes have been unable to meet the demand.It is urgent to develop new pectin extraction source and technology.In this paper,the extraction of pectin from pomelo peel by PEF combined with cellulase was studied,which was compared with PEF extraction,cellulase extraction and traditional hot-acid extraction.The main results are shown as follows:Response surface analysis was used to obtain the optimal parameters of pectin extraction from pomelo peel by PEF,which were p H 2.9,solid-liquid ratio of 1:20 g/m L,electric field strength of 3.5 k V/cm and pulse number of 15.The highest yield was 4.77±0.09%.Response surface analysis was used to obtain the optimal parameters of pectin extraction from pomelo peel by cellulase,which were p H 5.3,cellulase dosage of 780 U/g,extraction temperature of 50°C and extraction time of 90 min.The highest yield was 10.51±0.44%.Comparing the properties and structure of pomelo peel pectin extracted by PEF pretreatment,PEF post-treatment and simultaneous treatment of cellulase and PEF.The results showed that the best synergistic method was PEF pretreatment,resulting in highest pectin yield（12.08%）,best gel properties and antioxidant activities.The FT-IR results of the three pectin were the same,while the SEM results showed that different ways of synergy had significant effect on the micromorphology of pectin.Comparing the properties and structure of pomelo peel pectin（PP,EP,PEP,AP）extracted by PEF,cellulase,synergistic extraction of cellulase and PEF,hot-acid,the results showed that PEP had highest yield（12.08%）,total sugar（80.17%）and total phenol content（38.20 mg/g）.AP had highest protein content（1.27%）.The four pectin were all acid and high-esterified pectin,and their monosaccharide composition was mainly consisted of galacturonic acid,arabinose and galactose.The results of comparison of four pomelo peel pectin showed that AP had largest molecular weight of 94804 Da,and PP was the smallest of 8771 Da.PP and AP had higher viscosity,while PP,AP and PEP showed better gel texture characteristics and emulsifying properties.Comparing of DPPH,OH and ABTS scavenging activity and reducing power of four pectin,the results showed that PEP had the highest antioxidant activity,followed by PP,while EP and AP had the lowest antioxidant activity.FT-IR results of four pectin showed the same.But PP had lower absorption peak intensity.SEM results showed that were some differences in the micromorphology of pectin.Edible film prepared by pectin-sodium alginate ratio of 50:50（w/w）and sorbitol content of 50%had the highest transmittance of 91.78%,low water vapor transmittance of 0.57g·（m·d·MPa）^-1 and good mechanical properties.It had good fresh-keeping effect on strawberries,which effectively reduced the decay rate of strawberries.