Preparation, Bididobacteria-proliferation And Application Of Burdock Inulin

Burdock(Arctium Lappa L.) is a kind of biyearly vegetable with food or medicine properties.At present,burdock's economic value depends on burdock root exported to Japan and other European countries as edible vegetable.While international markets rigidly control the quality of exported burdock root,so the substandard root would be discarded. Burdock root resource could not be made full use.The fresh root of burdock is rich in inulin. Inulin is formed with some fructose connected by the bondβ(2→1) which terminal is the unit of glucose.The degree of polymerization is from 2 to 70,generally,the average degree is 10.Inulin has many excellent functions and has been successfully applied in food industry as textural improver,stabilizer,antifreezer or anti-ageinger.This paper firstly studied the extraction technique and structure of burdock inulin,and then analyzed its effects on the growth of bifidobacteria in vitro and in vivo,finally discussed the potential of using burdock inulin into low-fat milk system.The main contents are as follows:The extraction and purification techniques of burdock inulin by means of substandard burdock roots were studied.To optimize inulin extraction,various combinations of time, temperature,and solvent:solid ratio were used.The Response Surface Methodology(RSM) was used to analyze the data set.The optimal conditions were as follows:temperature at 80℃,extracting time for 114 min,solid:solvent ratio 1:15 m/V,times of continual extraction 2,the extraction rate was 93.86%.Deproteinized and decolored by ion-exchange resin(Amberlyste IRA-94 resin),separated and purified by Sephadex G-50 column chromatography from burdock substandard roots,pure sample was obtained.The purity was 99.47%.The structures of the inulin had been characterized by several analytical methods:gas chromatography,FT-IR spectrum and ¹H NMR,respectively,as well as ¹³C NMR analysis. The results showed that the burdock inulin were composed of fructose and glucose,which were confirmed by the composition of twelve fructose residues linked byβ-(2→1) glucoside bond and one glucose residue linked byα-(1→2) glucoside bond at the end of linear straight sugar chain.The average molecular weight(Mw) of inulin was 2168 Da and its degree of polymerization(DP) value was 13.The growth-promoting action of burdock inulin(B-INU) on bifidobacteria was studied in vitro.The results showed that burdock inulin was an effective bifidobacteria growth-promoting factor,and the strain of tested bifidobacteria grew significantly better in burdock inulin-containing media with 1.0%B-INU as the carbohydrate resource than in sucrose-containing media with 1.0%sucrose as the carbohydrate resource(P＜0.05). Bifidobacteria is an obligate anaerobe.With this kind of germ,varieties of carbohydrate could be fermented to form acetic acid and lactic acid.As a result,the pH value of the media was decreased.Bifidobacteria strains studied utilized fructooligosaccharides(FOS) and B-INU,as well as chicory inulin(C-INU).Long chain inulin(L-INU) did not enhance the growth of bifidobacteria significantly. To investigate the prebiotic potential of burdock inulin,the in vivo effects of B-INU on bacterial growth were studied.In vivo,B-INU significantly increased the number of lactobacilli and bifidobacteria(P＜0.05) in cecal content.Mice fed with B-INU,C-INU and FOS for 14 days had greater number of cecal beneficial bacteria population than those fed with L-INU for 14 days.The results indicated that utilization of inulin by bifidobacteria depended on the degree of polymerization of fructo-oligomeric chains.Feeding of a diet containing a prebiotic resulted in the stimulation on the growth of various bacterial groups, in particular acidogenic bacteria such as bifidobacteria and lactobacilli.Enterobacteria and Enterococci counts were not significantly affected by the different diets.The effect of inulin on the flow behavior of low fat milk system was investigated.After cooling and storage in refrigeration during 24 h,no visual change in the samples was observed,except for the samples with 8%and 10%(w/w) L-INU.It was probable that the sedimentation observed in the above mentioned samples was due to a recrystallization of the inulin.Therefore,the inulin concentration of 6%was chosen.Flow behaviors of low fat milk-inulin system with or without K:-carrageenan consisted of different inulin type:FOS, B-INU and L-INU were studied.All of the samples withκ-carrageenan showed typical characteristics of a weak gel system:the storage modulus was higher than the loss modulus (G'＞G") throughout the whole range of frequency.Low fat milk-inulin-κ-carrageenan systems with different types of inulin also affected the flow behavior of the system.Flow behaviors of corn starch-milk-inulin(CMI) pastes consisted of different starch levels(3% and 4%) and inulin type:FOS,B-INU and L-INU during heating to 95℃were studied.The registered apparent viscosity values were higher with the high starch concentration(4%) than that with the low starch concentration(3%),due to the increase in the volumetric fraction of the starch granules in the dispersion.The CMI pastes showed shear-thinning flow behavior in both starch concentrations and various inulin types as well as throughout the shear rates studied,resulting from stress-induced breakdown of the network structure. When starch concentration was increased,B-INU containing CMI showed higher viscosity than L-INU containing CMI did.Therefore,increase in viscosity of CMI due to increase in starch concentration was also dependent on the different type of inulin.Higher starch concentration increased both storage modulus and complex viscosity values.