Preparation Of Pectins And Pectin-Oligosaccharudes And Its Effect On Bifidobcterium In Vitro

The citrus production of China is leading in the world, while a lot of citrus peel citrus was wasted after being processed. It has been reported citrus peel contains a lot of functional compounds such as pigment, flavonoid, essential oil, pectin and so on. It had been reported citrus peel contains rich of pectin, which helps lower cholesterol and blood sugar, anti-tumor, anti-diarrhea, treat cardiovascular disease, maintain intestinal health and so on. In this study, high and low ester pectin were extracted from citrus peel, and different pectin fraction were obtained by the ultrafiltration method. In order to assess the prebiotic function of pectin, bifidogenic properties of pectin fraction were evaluated, and the short-chain fatty acids (SCFA) content were determined. The main findings of this paper were:1. Extraction and optimization of pectin from citrus peelThe crude pectin were extracted from the citrus peel with hydrochloric acid extraction and alcohol precipitation method. To get the best extraction process of pectin, the Box-Benhnken of response surface method were used to optimize the pH, extraction time, temperature, and solid-liquid ratio. The experimental data was analysis by multiple regression and ANOVA. The best condition of extraction was determined to be:extraction pH of 1.75, extraction time of 88min, extraction temperature of 83℃ and solid-liquid ratio of 1:40. Under the condition, the yield of the pectin was 22.01%, which was highly close to the predictive value of 22.15%. Pectin were purified by TCA method and actived carbon. The proportion of decolorization, deproteination and pectin retention was 63.7%, 81.4% and 74.2% respectively, the esterification degree was 75.6%, which was belong to high ester citrus pectin.2. Preparation and optimization of low ester citrus pectin(LM) with alkali methodThe HMP pectin was deesterified with alkali method to get LM. To get the best conditions, the reaction time, pH and reaction temperature were examined by the orthogonal experiment method. The result showed the best conditions of alkali method were as follow: reaction time of 110min, reaction temperature of 40℃ and pH of 9.5. The variance analysis showed that pH had a significant effect on the yield of LMP. Under the conditions, the yield of LMP was 81.33%, and the esterification degree was 30.15%. The characterization of pectin by FT-IR analysis showed the typical absorption of pectin. The peak of LMP in 1630cm-1 is stronger than the HMP, while the peak of low ester pectin in 1741cm’1 is weaker than the HMP, which showed that the degree of esterification was decreased significantly.3. Preparation of the pectin-oligosaccharides fraction by ultrafiltrationThe pectin-oligosaccharides of HM and LM was prepared with physical method under 121℃ for 30min. The best ultrafiltration conditions was got: the pectin concentration of 1g/L, operating pressure of 0.020MPa and liquid temperature of 35℃. The LM and HM pectin-oligosaccharides were passed through the 10kDa,5kDa and 3kDa ultrafiltration membrane to get different pectin fraction: HMPOS1, HMPOS2, HMPOS3, LMPOS1, LMPOS2, LMPOS3. The basic physical and chemical properties of pectin fraction were determined. The result showed that the degree of esterification was lower after degradation. The viscosity molecular weight of pectin fractions was similar to the ultrafiltration molecular weight. The light transmittance and ash content of pectin was decreased with the molecular weight decreased, which showed that the ultrafiltration played a certain role in the purification of pectin. Analysis by the FT-IR showed that the six pectin fractions have the typical absorption of pectin.4. The bifidogenic properties of pectin and pectin-oligosaccharide fractions in vitroThe growth characteristics of three Bifidobacterium were investigated. And HM, LM and six pectin-oligosaccharide fractions(HMPOS1, HMPOS2, HMPOS3, LMPOS1, LMPOS2, LMPOS3) were fermented by three strains of Bifidobacterium in vitro as the sole carbon. The results show that: the prebiotic effect of LM and its pectin-oligosaccharide fractions were better than HM. The prebiotic effect of pectin was get better after degradation, and the probiotic effect increase with the molecular weight decreased. The pH of the fermentation broth medium of each samples were significantly lower after 48h, which indicate that Bifidobacterium produced acidic metabolites during fermentation.5. Effect of pectin on short-chain fatty acids (SCFA) fermented by BifidobacteriumThe SCFA production of three Bifidobacterium cultures with HM, LM and six pectin-oligosaccharides as sole carbon source were studied by high performance liquid chromatography. The results showed that: pectin and pectin-oligosaccharides fraction fermented by Bifidobacterium can produce high amount of SCFA. The molecular weight and esterification degree influented significantly. The LM and low ester pectin fractions produced more SCFA than HM and high ester pectin fractions. The pectin-oligosaccharides fractions produce more SCFA than pectin. Bifidobacterium adolescentis produce higher amount of SCFA (mainly the acetic acid) than the other Bifidobacterium.