A process for producing a higher-fructose syrup containing more than 50% fructose was developed that involves a new system combining selective adsorption of fructose and an immobilized glucose isomerase reaction. Continuous countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlet of liquid streams without actual movement of the solid adsorbent, while the immobilized enzyme reactors are stationary. Two mathematical models, an intermittent moving-bed and a continuous moving-bed model, are presented for calculation the concentration profiles of glucose and fructose in the system. The validity of the models is experimentally confirmed, and a criterion for good production in the system is presented. This system requires less desorbent than a process using a fixed-bed adsorber and a simulated moving-bed process to produce the syrup with 45-65% fructose content, the level desired in food manufacture.

The continuous separation of a glucose/fructose mixture wasexperimentally performedusing a simulated moving-bed adsorber packed with the Ca2 + ion form of Y zeolite. In the adsorber, the continuous and countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlets of liquid streams, without actual movementof the solid adsorbent. Two mathematical models, i.e., an intermittent moving-bed and a continuous moving-bed type, are presented for calculating the concentration profiles of glucose and fructose in the simulated moving-bed adsorber. The validity of the models is experimentally confirmed, and a criterion for good separation in the simulated moving-bed adsorber is presented. IntroductionThe most commontype of fructose syrup, usually called a high-fructose syrup, contains 42% fructose, 52% glucose, and 6% oligosaccharides on a dry basis,9) and is used in place of sucrose in some foods and beverages. For some purposes, since fructose is sweeter and moresoluble in water at low temperatures than glucose, a syrup with 55 to 90%fructose, called a higher-fructose syrup, is desirable. Isomerization of glucose to fructose, catalyzed by glucose isomerase, is a reversible reaction with an equilibrium constant of 1.0 at 323 K.15) Therefore, to produce a syrup containing more than 50%fructose, a process to separate fructose from the equilibrium mixture is indispensable. A selective adsorption method using ion-exchangers7) seems to be promising for the separation. These methods may be classified into chromatographic and moving-bed operations. The chromatographic separation process is simple, but has the following disadvantages:40 (i) the whole adsorbent bed is not effectively utilized, (ii) a large amount of desorbent is consumed, (iii) a large difference in the adsorption equilibria between adsorbates is required, and (iv) the operation is discontinuous.

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