Study On Purification Process And Functional Product Of Inulin

Inulin is a linear polymer of D-fructose joined by β(1→2) linkages and terminated with a D-glucose molecule linked to fructose by an a (1→2) bond, as in sucrose. Inulin, a non-digestible carbohydrate, can preferentially stimulate the growth and activity of one or a limited number of desired bacteria in the colon, and thus improves host health. And more, positive effects on blood glucose attenuation, lipid homeostasis, mineral bioavailability and immunomodulation effects, along with the ability to add texture and improve rheological characteristics and nutritional properties of food allows inulin to be termed a functional food. Inulin has been increasingly used in various foods due to its beneficial nutritional attributes. Jerusalem artichoke is cultivated widely in the northern part of China for environment protection. Jerusalem artichoke tubers with 14～19% inulin can be a valuable source of inulin.In this thesis, the chemical analysis and detection of inulin was first studied. The extraction conditions for Jerusalem artichoke powder were optimized. Comparison of ultrasound-assisted extraction and conventional extraction techniques for the extraction yield and molecule structure of inulin was preformed respectively. The clarification conditions of lime—phosphoric acid were obtained. In addition, the mathematical model to predict a breakthrough curve on the adsorbent bed was studied. ISEP C920 operated on decoloration according to the results of single column experiments. A new potential functional food was developed at last. The main results were as follows.The inulin content was measured with the difference between total carbohydrate and reducing sugars. Total carbohydrate was determined by the modified phenol-sulphuric acid method using inulin (Wedin-P90) as standard. Reducing sugar was determined by the dinitrosalicylic acid method using D(—)-Fructose as standard. The harvested artichoke tubers must be manufactured as soon as possible because the internal hydrolysis and inverting of inulin have a great loss in storage.To optimize conventional extraction of inulin, various combinations of pH, time, temperature and solvent:solid ratio were used. Experiment design employed fractional factorial design (FFD), path of steepest ascent, central composite design (CCD) and response surface methodology (RSM). The empirical model developed by RSM was adequate to describe the relationships between thestudied factors and the response of inulin extraction yield. Based on canonical analysis, the optimal conditions for maximizing inulin extraction yield (83.6%) were at natural pH for 20 min at 76.7 °C and solvent:solid ratios of 10.56:1 (v/w). Moreover, comparison of conventional extraction, direct sonication extraction, indirect sonication extraction showed the indirect sonication extraction was a suitable method for inulin extraction.Orthogonal experiment design was used to clarify the extractive juice. The results suggested that the extractive juice was precipitated at pHl 1 using lime. After centrifugation, the supernatant was acidified with phosphoric acid at pH6 and 80 °C. Then, the juice flowed through strong acid cation exchanger Amberlite FPC1 INa column and weak base anion exchanger Amberlite FPA54 column in sequence. The chromatography process could remove pigment, ash and protein effectively but had a little effect on inulin. The final product of inulin can exist as a white powder after evaporation and drying.Ultrafiltration could separate monosaccharides and disaccharides, short chain molecules, long chain molecules from inulin. In the conditions of pH2.5 and 80°C, inulin could be hydrolyzed to fructose syrup.A method for the determination of the characteristic features of breakthrough curves of melanoidin decoloration by describing them with a function was presented. The function was derived on the basis of the probability of mass transfer in an adsorption zone of Amberlite FPA54 column. Some mass transfer parameters were obtained. The mathematical model to predict a breakthrough curve on the adsorbent bed was expressed according to following equation: y=1.2598x-4.3401. R2 = 0.9935 indicated the model was appropriate.The results of single column experiments deduced ISEP C920 operation condition. The verification test indicated the decoloring effect was stable. The decoloring technique in ISEP system included six zones: adsorption zone, elution wash, backwash, regeneration, regeneration wash and forward flush.A new potential functional food — carboxymethylinulin calcium (CMIC) was developed. Inulin was chemically modified by etherification with monochloroacetic acid in an alkaline reaction medium, and then conjugated with calcium. The structure determination by IR spectrum, SEM photograph, X-RD spectrum and 13C NMR spectrum showed the derivative obtained was carboxymethylinulin calcium.