GB2087400A

GB2087400A - Process for the Production of a Syrup Having a High Fructose Concentration

Info

Publication number: GB2087400A
Application number: GB8134020A
Authority: GB
Original assignee: DDS Kroyer AS
Current assignee: DDS Kroyer AS
Priority date: 1980-11-14
Filing date: 1981-11-11
Publication date: 1982-05-26
Also published as: YU43049B; HU182414B; BE891093A; FR2494088B1; DK145582B; YU268281A; FR2494088A1; AR224976A1; AU544659B2; CA1169289A; FI813576L; GB2087400B; AU7743881A; FI72742B; DE3145185A1; JPS57118796A; DK488880A

Abstract

Syrup having a high fructose concentration is prepared by admixing glucose syrup having a high glucose concentration with a crystallisation product containing dissolved fructose and glucose as well as glucose crystals to form a homogeneous solution, isomerising said solution with isomerase enzymes, evaporating the isomerised product and seeding said product with a seeding material containing glucose crystals or germs, cooling the seeded product to crystallize glucose, separating the product thus formed into a crystallisation product, of which part is recycled to the mixing step, and a syrup having a higher fructose concentration than syrups prepared by prior art processes.

Description

SPECIFICATION Process for the Production of a Syrup having a High Fructose Concentration This invention relates to a process for the production of a syrup having a high fructose concentration by isomerising a glucose syrup having a high glucose concentration.

It is well known that fructose syrup can be obtained from glucose syrup having a high glucose concentration, e.g. 95%, and a solids content of about 45% by passing refined glucose syrup through a column containing immobilized isomerase enzymes.

During the passage through such a column part of the glucose is converted into fructose and a fructose-containing syrup is obtained. Such a syrup may have the following composition based on dry matter: Fructose: 42% by weight, glucose: 53% by weight, higher saccharides: 5% by weight, at a dry matter content of about 40%.

This corresponds to a degree of inversion of about 44%. The degree of inversion defines the extend to which glucose has been converted into fructose.

The fructose syrup thus formed is normally refined by ion exchange and/or treatment with active carbon and the refined syrup is evaporate to obtain a dry matter content of about 71%. The syrup thus obtained is commercially available under the names fructose syrup, isosyrup or HFCS (High Fructose Corn Syrup).

In theory it is possible to prepare a syrup having a fructose concentration based on dry matter of up to 45% from a glucose syrup of the above mentioned type but since the isomerisation is a reversible process, so large amounts of isomerase enzyme are required to prepare such a fructose syrup that the production of such a syrup is without commercial interest.

Fructose syrup finds many applications which are in direct competition with sugar (saccharose) or invert syrup prepared from saccharose. Invert syrup consists of 50% fructose and 50% glucose.

Since the sweetening effect of fructose is higher than that of glucose, the above mentioned fructose syrup containing 42% fructose has a sweetening effect which is slightly lower than that of sugar or invert syrup prepared from sugar.

Therefore, processes have been developed to prepare from fructose syrup containing for example 42% fructose based on dry matter a fructose syrup containing above 50 fructose. The sweetening effect of the latter product is equal to or higher than that of sugar or invert syrup prepared from sugar.

In principle these prior art processes are based on the fractionation of a fructose syrup either by chromatography of by means of cation exchangers or a special absorption material.

Both types of processes produce in principle three fractions, viz. a fraction having a high concentration of higher saccarides, a fraction having a high concentration of glucose and a fraction having a high concentration of fructose.

In both types of processes the desired product, e.g. a fructose syrup having a concentration of fructose of about 55% or higher, is obtained.

However, both types of processes require that large amounts of water are added and concequently the energy consumption for the evaporation of the water in connection with the production of the final syrup is excessive.

Thus, 75kg of water have to be evaporated in the production of 1 OOkg of fructose syrup having a fructose concentration of 42%. If a fructose syrup having a fructose concentration of 55% is to be prepared by the above mentioned processes, 240kg of water have to be removed to prepared 1 OOkg of syrup.

The object of the invention is to provide a more economical and less energy consuming process of the above mentioned type to prepare syrup having a fructose concentration based on dry matter of 45% or higher.

This object is achieved by the process according to the invention, said process being characterized in admixing the glucose syrup with a crystallisation product containing dissolved fructose and glucose as well as glucose crystals to form a homogeneous solution, isomerising said solution by means of isomerase enzymes, evaporating the isomerised product and seeding said product with a seeding material containing glucose crystals or germs, cooling the seeded mixture to crystallize glucose, separating the product thus formed into a crystallisation product, of which at least part is recycled and admixed with the glucose syrup, and a syrup having a high fructose concentration.

The invention is based on the discovery that the fructose concentration of isomerised glucose syrup can be significantly increased by crystallising the glucose and that by recycling the separated crystals and admixing these crystals with the glucose syrup it is possible to increase the dry matter content as well as the glucose concentration of the syrup to be isomerised.

Consequently, a satisfactory yield of fructose can be obtained without increasing the consumption of isomerase enzymes.

In fact, a syrup having a fructose concentration of up to 70% can be prepared by the process according to the invention.

The term "glucose syrup having a high glucose concentration" is to be understood as glucose syrups containing at least 93% and preferably between 95 and 98% of glucose and fructose.

The glucose syrup used in preferably refined glucose syrup. The refining of glucose syrup is preferably effected by a filtration followed by an ion exchange treatment and optionally a treatment with active carbon.

As mentioned above the glucose syrup is mixed with a crystallisation product formed during a subsequent step and the mixture thus obtained is subjected to isomerisation by means of isomerase enzymes, preferably immobilized isomerase enzymes, e.g. enzymes of the type which are commercially available under the trade names "SWEETZYME", "TAKA-SWEET" and "MAXAZYME Gl-lmmob".

The isomerisation with the immobilized enzymes is effected in ordinary way by passing the mixture through a column containing the immobilized enzymes.

After the passage through the column, the isomerised product typically has the following composition based on dry matter: Fructose: 42%, glucose: 54% and higher saccarides: 4%, which corresponds to a degree of inversion of 43.8% compared to a degree of inversion of 44.2% which has to be obtained in order to produce a syrup having the same fructose concentration from a starting material containing 95% glucose.

Preferably, the isomerised product is then refined by ion exchange treatment and optionally by a treatment with active carbon. The refined syrup is subsequently evaporated to obtain a dry matter content of 7580%.

The evaporated product is then seeded with a seeding material containing glucose crystals or germs and preferably with a recycled crystallisation product The seeded product is then cooled, e.g. to a temperature of 35 or, and then further cooled, e.g. to a temperature of 150C.

During the crystallisation which normally takes 60-100 hours, the mixture of syrup and crystals is stirred. The crystallisation should be controlled, e.g. by taking samples, separating the crystals by filtration and determining the fructose concentration of the mother liquid.

When the fructose concentration has reached a desired value, e;g. 55% glucose based on dry matter, the crystals are separated, e.g. by filtration on a filter press or by centrifugation so as to form the desired fructose-containing syrup. The syrup thus obtained typically has a dry matter content of 7075% and the following composition based on dry matter: Fructose: 55%, glucose: 38% and higher saccharides: 7%. However, this applies only to cases in which there is no recycling of the separated crystal mass. By recycling the crystal mass to the mixing step prior to the isomerisation, a fructose-containing syrup having the following composition based on dry matter is eventually obtained: Fructose: 55%, glucose: 40% and higher saccharides: 5%.

As mentioned above part of the separated crystals, e.g. about 10%, may be used as seeding material for the seeding of the above mentioned evaporated isomerised product.

The rate of crystallisation of syrups having a fructose concentration of up to 5055% (based on dry matter) in the liquid phase is a lineary function of time. However, due to the presence of the crystals, the apparent viscosity of the crystal mass is increased and this results in a reduced rate of crystallisation.

By separating part of the glucose crystals formed and recycling the liquid fructose-rich phase to the crystallisation, it is possible to continue the crystallisation at the same rate of crystaliisation and consequently to reduce the crystallisation time and/or to obtain a product having an increased concentration of fructose, e.g. 70%, based on dry matter.

The invention will now be further described with reference to the following example which illustrates a preferred embodiment of the process according to the invention.

Example 1000kg of a refined glucose syrup having a glucose concentration of 95% and the following composition: Fructose: 0%, glucose: 95%, higher saccharides: 5%, were mixed with 667kg of crystal mass having the following composition based on dry matter: Fructose: 21%, glucose: 77%, of which 14% were dissolved and the remainder was crystals (glucose monohydrate crystals), and higher saccharides: 1.8%.

During the mixing operation the glucose monohydrate crystals were dissolved so as to form a mixture having a dry matter content of 40% and the following composition based on dry matter: Fructose: 8%, glucose: 88% and higher saccharides: 4%.

The mixture was isomerised and evaporated so as to produce a product having a dry matter content of 75% and the following composition based on dry matter: Fructose: 41.9%, glucose: 54.3% and higher saccharides: 3.8%. A crystal mass containing 83.4kg of dry matter and having the following composition based on dry matter: Fructose: 21%, glucose: 77.1%, of which 62% were crystals, and higher saccharides: 1.9% were added to the evaporated mixture containing 1 667.0kg of dry matter so as to form a mixture containing 1 750kg of dry matter and having the following composition: Fructose: 41.0%, glucose: 55.3%, of which 3% were in the form of crystals, and higher saccharides: 3.7% The mixture was then cooled and when the crystallisation was completed, the amount of glucose in the form of crystals had been increased to 26.8%. The remaining amount of glucose was still present in dissolved state.

The crystals were then separated so as to form a crystal mass in an amount of 750kg based on dry matter and a mother liquid in an amount of 1000kg based on dry matter. The mother liquid had the following composition based on dry matter: Fructose: 56%, glucose 39% and higher saccharides: 5.0%.

The crystal mass was divided into two portions of which one portion, 83.4kg based on dry matter, was recycled as seeding material as described above, and the second, 667kg based on dry matter, was recycled and mixed with syrup having a glucose concentration of 95%.

Claims

1. A process for the production of a syrup having a high fructose concentration by isomerising glucose syrup having a high glucose concentration, characterized in admixing the glucose syrup with a crystallisation product containing dissolved fructose and glucose as well as glucose crystals to form a homogeneous solution, isomerising said solution by means of isomerase enzymer, evaporating the isomerised product and seeding said product with a seeding material containing glucose crystals or germs, cooling the seeded mixture to crystallize glucose, separating the product thus formed into a crystallisation product, of which at least part is recycled and admixed with the glucose syrup, and a syrup having a high fructose concentration.

2. A process according to claim 1, characterized in that part of the crystallisation product is recycled and used as seeding material.

3. A process according to claim 1, characterized in using glucose syrup having a glucose concentration of between 95 and 98%.

4. A process according to claim 1, characterized in that the isomerised product is refined prior to the evaporation and seeding steps.

5. A process according to claim 1, characterized in that the isomerised product is evaporated to a dry matter content of 7580%.

6. A process according to claim 1, characterized in that the seeded mixture is cooled to a temperature of between 1 5 and 300C.

7. A process according to claim 1 or 2, characterized in using about 10% of the crystallisation product as seeding material.

8. A process according to claim 1 or 2, characterized in continuously or discontinuously effecting a separation of crystals by filtration during the crystallisation and recycling the filtrate for further crystallisation.