DK145582B - PROCEDURE FOR PREPARING HIGH Fructose Content Syrup - Google Patents

Description

145582

This invention relates to a process for preparing a high fructose syrup by isomerizing a high glucose glucose syrup.

It is known to produce fructose syrup from glucose syrup 5 with high glucose content, e.g. 95%, and with a dry matter content of approx.

40% by passing refined glucose syrup through a column containing immobilized isomerase enzymes.

During passage through the column, part of the glucose is converted to fructose, and a fructose-containing syrup can be prepared with e.g. the following dry matter composition: 42% fructose, 53% glucose and 5% higher saccharides, and with a dry matter content of approx. 40%.

This corresponds to an inversion rate of approx. 44%. By degree of inversion is meant the extent to which glucose is converted to fructose.

The fructose syrup thus formed is usually refined by ion exchange and / or charcoal treatment, and the refined syrup is evaporated to give a dry matter content of approx. 71%. The syrup thus produced appears commercially under the terms fructose syrup, iso-syrup or HFCS (High Fructose Corn Syrup).

Theoretically, from glucose syrup of the above-mentioned type it is possible to produce a syrup with a dry matter-based fructose content of up to 45%, but since the isomerization is a reversible process, so large amounts of isomerase enzyme will be required to produce such a syrup is of no commercial interest.

25 Fructose syrup is used in many areas in direct competition with sugar (sucrose) or invert syrup made from it. In-host syrup consists of 50% fructose and 50% glucose. Since the sweetness of fructose is higher than the sweetness of glucose, the above-mentioned fructose syrup with a content of 42% fructose has a sweetness slightly lower than the sweetness of sugar or of inverted syrup.

Therefore, known methods have been developed for using a fructose syrup with e.g. 42% dry fructose fructose to produce a fructose syrup with a fructose content greater than 50% so that the sweetness of this product is equal to or higher than the sweetness of 35 sugar or inverted syrup.

These processes have, in principle, been based on fractionation either by chromatography using cation exchangers or a special absorption material.

In both processes, essentially 3 fractions are obtained, a high fraction of higher saccharides, a high glucose fraction and a high fructose content fraction. Both processes result in the desired products, e.g. a fructose syrup containing 55% fructose or higher. However, the process for both processes implies that large dilutions of water occur, so that the energy demand for evaporation in connection with the preparation of the finished syrup increases extremely strongly.

For example, 75 kg of water 10 must be evaporated by producing 100 kg of fructose syrup with a fructose content of 42%. If a fructose syrup with a fructose content of 55% is to be prepared using the above processes, 240 kg of water must be removed instead to produce 100 kg of syrup.

The object of the invention is to provide an economically and energetically favorable process of the kind mentioned above, with which syrups with a fructose content on a dry matter basis of 45% or higher can be prepared.

This is achieved by the process according to the invention, which is characterized in that the glucose syrup is mixed with a crystallization product recycled from a later step and containing dissolved fructose and glucose and glucose crystals to form a homogeneous solution, that the solution is isomerized by isomerase enzymes evaporating the isomerized product to a dry solids content of up to 80% and grafting with a graft containing glucose crystals or germs, cooling the grafted mixture to crystallize glucose and separating the resulting product into a crystallization product, at least part of which is recycled and mixed with glucose syrup, and a high fructose syrup.

The invention is based on the recognition that fructose content can be substantially increased in isomerized glucose syrup by crystallization of the glucose and that by recirculating separated crystals and admixing these with the glucose syrup can easily achieve both an increased concentration and an increased content of glucose. in the syrup, 35 to be isomerized and consequently a satisfactory fructose yield.

By the method according to the invention, a syrup with a fructose content of up to 70% can be prepared.

By the term "high glucose glucose syrup" is understood herein to mean glucose syrups containing at least 93% and preferably between 95 and 98% glucose.

Preferably, a refined glucose syrup is used. The refining of the glucose syrup is conveniently carried out by filtration followed by an ion exchange and possibly coal treatment.

As mentioned, the glucose syrup is mixed with a crystallization product prepared in the following step, and the resulting mixture is subjected to isomerization by isomerase enzymes, preferably immobilized isomerase enzymes, e.g. enzymes of a kind which are commercially available under the names "SWEETZYME", 10 TAKA-SWEET "and" MAXAZYME Gl-lmmob ".

The isomerization with immobilized enzymes is traditionally carried out by passing the mixture through a column containing the immobilized enzymes.

After passing through the column, the isomerized product will typically have the following dry matter composition: 42% fructose, 54% glucose and 4% higher saccharides, corresponding to an inversion degree of 43.8% compared to an inversion rate of 44.2 % needed to obtain the same fructose content from a starting material with a glucose content of 95%.

The isomerized product is then suitably subjected to refining by an ion exchange and optionally a coal treatment.

Subsequently, the refined syrup is evaporated to give a dry matter content of up to 80%.

The evaporated product is then seeded with a graft material containing glucose crystals or crystalline germs, and preferably a recycled crystallization product is used. Then, the inoculated product is cooled, e.g. to a temperature of 35 ° C and then a further cooling, e.g. to a temperature of 15 ° C.

During the crystallization, which usually takes 60-100 hours, the mixture of syrup and crystals is stirred. The crystallization can be monitored, e.g. by sampling, filtering out crystals and measuring the fructose content of the mother liquor.

When the fructose content has reached a desired value, e.g.

55% solids-based fructose separates the crystals, e.g. by filtration on a filter press or by centrifugation to obtain the desired fructose-containing syrup. This syrup will typically have a solids content of 70-75% and the following sugar solids composition: 55% fructose, 38% glucose and 7% higher saccharides. However, this only applies at the start of the process. When recirculating crystal- 145582 4 mass tf! In the mixing step before isomerization, a fructose-containing syrup will gradually be obtained with the following dry matter composition:

Fructose: 55%, glucose: 40% and higher saccharides: 5%.

Some of the separated crystals, e.g. ca. 10%, as mentioned, can be used as graft material in the grafting of the above-mentioned evaporated isomerized product.

The rate of crystallization of syrups with a fructose content of up to 50-55% in the liquid phase (on a dry basis) is a linear function of time. Due to the crystal content, the apparent viscosity of the crystal mass increases, resulting in decreased crystallization rate.

By separating part of the glucose crystals formed and returning the liquid, fructose-rich phase for crystallization, it is possible to continue crystallization without decreasing crystallization rate, thereby reducing the crystallization time and / or a product with increased fructose content, e.g. 70% on a dry matter basis.

The invention will now be described in more detail with reference to the following example which illustrates a preferred method of the invention.

EXAMPLE

1000 kg of a refined glucose syrup with a glucose content of 95% and of the following composition: Fructose: 0%, glucose: 95%, 25 raised saccharides: 5% mixed with 667 kg of crystal mass with the following composition on a dry matter basis: 21% fructose, 77% glucose , of which 14% were in solution and the rest as crystals (glucose monohydrate crystals) and 1.8% higher saccharides. By mixing, the glucose monohydrate crystals were dissolved and a mixture 30 having a solids content of 40% and the following dry solids composition was obtained: 8% fructose, 88% glucose and 4% higher saccharides.

The mixture was isomerized and evaporated to give a product with a solids content of 75% and of the following dry solids composition: 41.9% fructose, 54.3% glucose and 3.8% higher saccharides. To the evaporated mixture containing 1667.0 kg of dry matter was then added a crystal mass containing 83.4 kg of dry matter and having the following dry matter composition: 21.0% fructose, 77.1% glucose, of which 62% was in the form of crystals, and 1.9% higher saccharides to give a mixture containing 1750 kg of dry matter with the following composition: 41.0% fructose, 55.3% glucose, of which 3.0% was in the form of crystals , and 3.7% higher sac-charides.

The mixture was then cooled and, after the crystallization was completed, the amount of glucose in the form of crystals had reached 26.8%, while the remaining glucose was still in dissolved state.

A separation was then made to form a crystal mass in an amount of 750.4 kg on a dry solids basis and a mother liquor in an amount of 1000 kg on a solids basis. The IV solids had the following 10 solids-based composition: 56% fructose, 39% glucose and 5.0% higher saccharides.

The crystal mass was divided into two portions, one of which, 83.4 kg on a dry solids basis, as mentioned above was recycled as graft material, and the other, 667 kg on a dry solids basis, was recycled and mixed with syrup with a glucose content of 95%.