EP0153447B1 - Process and apparatus for preparing dry products from sugar syrups - Google Patents

Abstract

To convert syrups deriving from sugar production and other foodstuffs into a powder or granulated form subsequent to appropriate preliminary concentration and while preserving the product subject to the most extensive possible maintenance of the original composition, a sugar solution with at least 70% dry matter and up to 15% non-sucrose materials in the dry matter is brought by product-preserving rapid heating to a high temperature. Subsequently the vapors are allowed to escape to a dry-matter content of at least 90% and the thickened syrup is converted into a dry and pourable product just by cooling and sudden extraction of the residual water through crystallization. This preferably occurs in equipment comprising a steam-heated spiral-tube heat exchanger with a spiral tube that tapers out to 150 to 200% of its original free cross-section and has built-in twist generating baffles, a vapor precipitator to atmospheric pressure, and a crystallizer below the precipitator.

Description

The exploitation of the positive enthalpy of crystallization of sucrose is known. For example, large quantities of sugar are produced in Brazil and Portugal using the so-called amorphous or aerado process. In this case, the sugar solution is thickened in batches in one, but usually two, series-connected, heated containers equipped with powerful stirrers until crystallization occurs, indicated by seed crystals, whereby the remaining water evaporates and an amorphous-crystalline, free-flowing powder is formed (VE Baikow, Manufacture and refining of raw cane sugar, Sugar series volume 2, pages 445 to 447, Elsevier Science Publishing Company Inc., New York, 1982).

In order to use this "transformation" of the supersaturated sugar syrup in a continuous process, the supersaturated sugar syrup is subjected to continuous beating to cause nucleation and to break up the crystallizing sugar masses while at the same time blowing in air for heat dissipation. This process requires complicated equipment and high energy input (US Pat. No. 3,365,331).

In the other, continuous process, littered sugar syrup is subjected to a shear force with a velocity gradient of at least 5000 cm / sec / cm to cause the sudden, suddenly forced homogeneous crystal nucleation, and then the crystallization is allowed to proceed. The required high shear forces are caused by complicated equipment, e.g. High-speed colloid mills, caused (DE-PS 25 16 253).

Surprisingly, it has been shown that, with special process control, the expensive apparatuses which generate the mechanical shear forces can be dispensed with, as well as the complex cooking systems required for the Brazilian amorphous process, including de because of the very high power requirement, energy-intensive high-performance agitators.

If in the following we talk about sugar, whether in the form of solutions or as a syrup, then it means sucrose, which can contain up to 15% non-sucrose substances. This can be other types of sugar, e.g. Dextrose, fructose, malt sugar, glucose syrups, starch, dextrins, maltodextrin, cocoa, coffee, tea extracts, medicinal tea extracts and extracts of tea-like products, fats, milk powder, fruit powder, edible acids such as lactic acid, citric acid, tartaric acid, table salt, other mineral salts, spices , Colors, flavors or vitamins.

The invention is based on the task of converting syrups from sugar production and mixtures with other foodstuffs, after appropriate preconcentration, in a manner that is gentle on the product while largely maintaining the original composition, in particular the accompanying substances present in the sugar solutions or syrups, in a powder or granule form.

The invention relates to a method for producing sugar dry products by spontaneous crystallisation of supersaturated sugar solutions, in which a sugar solution having at least 70% dry substance and up to 15% non-sucrose substances in the dry substance by gentle product Kurzze ⁱ thocherhitzung and closing Entweichenlassen the vapors to a dry solids content of at least 90% and the thickened syrup is only converted into a dry, free-flowing product by cooling and sudden removal of the remaining water by crystallization.

The short-term high-temperature heating is preferably carried out in a steam-heated spiral tube with forced passage. Before the vapors escape, the sugar solution is brought to a temperature of 135 to 155 ° C, depending on the content of non-sucrose substances. This temperature of high heating and the resulting dry matter content after the vapors have escaped, at which spontaneous crystallization of the sucrose begins, depends on the type and content of non-sucrose substances. If the syrups contain more than 95% sucrose in the dry substance, a thickening of 90 to 94% is sufficient. With a sucrose content of 85 to 95% in the dry matter, the concentration should be at least 94%, preferably 96 to 97%, of dry matter.

The quick and thus gentle thickening to the required high dry matter content without partial oversaturation or overheating in the heat exchanger is made possible by the good heat transfer of the evaporation device used. Concentration takes place under atmospheric pressure in a steam-heated spiral tube that expands in the course. The high flow rate and the vapor bubbles that form guarantee high heat transfer. Due to the pump-controlled forced run, low throughput times of at most 60 seconds are ensured, so that no caramelization products are created that would be recognizable by browning the sugar mass. The invert sugar formation that is otherwise feared when products containing sugar are heated with regard to their shelf life is also less than 1%.

Typical of the process is the comparatively higher thickening of the syrup in an easily controllable, force-fed single-tube spiral heat exchanger. The physical-thermal conditions are therefore comparatively easier to define.

Apart from the short lead time, the range of stays is very narrow, i.e. the residence time for each volume unit is almost the same. The channel formation feared with other types of heat exchangers, particularly at high viscosities, is also excluded.

The concentration of the thickened syrup can therefore be very high almost without risk. Process parameters that can be reproduced very well are also guaranteed in continuous operation.

When leaving the spiral tube evaporator, it is ensured that the vapors can escape. This is preferably done in a separation room at atmospheric pressure. The crystallization is then triggered by a specifically initiated cooling. In the temperature and concentration range in question, a cooling down of 10 to 15 ° C already ensures sufficient supersaturation of the sugar syrup. The crystallization that occurs spontaneously due to the cooling can be recognized by the foaming of the sugar-containing mass, caused by the evaporation of the residual water. Because of this crystallization reaction occurring within about 30 to 60 seconds, if the mass is still to be conveyed through pipelines, it is necessary to apply a high pre-pressure corresponding to the water vapor partial pressure in the pipelines in order to thereby cause the crystallization or the blockage by separation of Prevent water vapor and solids. With appropriate insulation or heating of such pipelines, it is thus ensured that crystallization only occurs after the pipelines have emerged. This procedure is particularly advantageous if either larger volumes from about 1500 l / h or particularly highly thickened syrups are to be applied uniformly on a belt conveyor in order to ensure uniformly rapid cooling.

In the method according to the invention, it is therefore possible to dispense with the addition of excitation crystals, as in the Aerado method, or the nucleation caused mechanically by high shear forces.

The supersaturated sugar syrup with a dry matter content of 90 to 97%, depending on the content and type of non-sucrose substances, can then be metered continuously into any suitable conveyor system, whereby it must be ensured that the water vapor which forms due to the exothermic reaction can escape. Both slow-running, open screw conveyors and belt conveyors are suitable for this, but also vacuum scraper coolers, which should be cooled after the end of the crystallization phase to protect the product. When using belt conveyors, it is also advisable to heat the feed point in order to prevent excessive heat losses which lead to the formation of a glass-like, non-crystallizing melt.

If a steel strip is used as the crystallizer for the thickened syrup, it is heated in the transfer area and then cooled. In the transfer area, the steel strip should be preheated to a temperature of about 60 to 40 ° C below the temperature of the thickened syrup. If the steel strip is too cool, there is a risk of glass formation especially in the bottom layer, i.e. it does not produce the desired microkirstallin-amorphous instant product. If the temperature is too high, the crystallization is delayed so that the product is still too warm after leaving the crystallizer. The same applies to other crystallizers, e.g. an open belt conveyor cooled in the second part.

The microcrystalline structure is characteristic of the products produced by the process according to the invention. They therefore have an instant-like solution behavior and, as far as mixtures of sugar with other foods are concerned, excellent homogeneity.

For the production of more or less pure sugar, the process according to the invention is considerably less capital and energy intensive than the conventional evaporative crystallization with subsequent centrifugation and thus reduces the overall production costs. Because of the gentle procedure, it is also possible according to the invention to produce dry food mixtures with a high sucrose content but heat-sensitive accompanying substances without the latter being chemically changed.

A device as described below in connection with the drawing is preferably used to carry out the method according to the invention. It is characterized by a steam-heated spiral tube heat exchanger 1 with a spiral tube 2, which increases increasingly to 150 to 200% of its original clear width, with swirl internals 3, a steam separator 4 under atmospheric pressure and an open belt screw arranged underneath, the second part provided with a cooling jacket 6. Conveyor 5. Natural whole cane sugar and a process for its production are the subject of EP-B-0 153 448 of the same priority and registered on the same day.

example 1 Mother liquor from the candy factory

360 kg/h Mutterlauge aus der Kandisfabrikation wurden nach Vorerwärmung auf 65°C mit einer drehzahlgeregelten Verdrängerpumpe in einen mit 4,6 bar dampfbeheizten Einrohrspiralverdampfer gefördert und in 40 bis 45 sec auf 142°C erhitzt; die Brüden wurden über einen Brüdentrennraum abgeschieden und der eingedickte Sirup auf ein Stahlband geleitet, das im ersten Viertel auf 80 bis 85°C angewärmt und im letzten Drittel gekühlt war. Innerhalb von 1 min trat bei ca. 130°C starkes Aufschäumen der Masse ein und nach einer Verweilzeit auf dem Band von insgesamt 6 min wurde das auf 1,2% Restfeuchte abgetrocknete, schuppenförmige bereits rieselfähige Trockenprodukt bei einer Abladetemperatur von 30 bis 40°C abgetragen. Der braune schnellösliche Instantzucker kann ohne jede Nachbehandlung verarbeitet werden und ist geschmacklich dem nach herkömmlichen brasilianischen Amorpho-Verfahren hergestellten Produkt eit überlegen.

After preheating to 65 ° C., 360 kg / h mother liquor from the rock candy production were conveyed with a speed-controlled displacement pump into a single-tube spiral evaporator heated with 4.6 bar and heated to 142 ° C. in 40 to 45 seconds; the vapors were separated via a vapor separation chamber and the thickened syrup was passed onto a steel belt which was warmed to 80 to 85 ° C in the first quarter and cooled in the last third. Strong foaming of the mass occurred at about 130 ° C. in the course of 1 minute and after a dwell time on the belt of 6 minutes in total, the flaky, free-flowing dry product, dried to 1.2% residual moisture, became available at a discharge temperature of 30 to 40 ° C. worn away. The brown, quick-dissolving instant sugar can be processed without any after-treatment and its taste is superior to that of the product made according to conventional Brazilian amorphous processes.

Performance in the test 256 kg dry goods / h.

Example 2 Vollertzucker

• Erhitzung von 1.250 kg/h auf 71% TS eingedicktem Zuckerrohrsaft in ca. 40 sec auf 152°C bei einem Heizdampfdruck von 6,5 bar; Aufschäumen der Zuckermasse bei ca. 140°C, Restfeuchte am Bandende 1,6%, Abtragtemperatur 40°C. Das Trockengut wurde ohne Nachtrocknung zu einem freifließenden Pulver vermahlen mit einem Schüttgewicht von 530 g/I.

The preparation was carried out analogously to Example 1 under the following conditions:

• Heating from 1,250 kg / h to 71% TS thickened sugar cane juice in approx. 40 seconds to 152 ° C at a heating steam pressure of 6.5 bar; Foaming the sugar mass at approx. 140 ° C, residual moisture at the end of the belt 1.6%, removal temperature 40 ° C. The dry material was ground without drying to a free-flowing powder with a bulk density of 530 g / l.

Yield: 902 kg / h.

Example 3 Tools for sausage production

• 0,09% Invertzucker
• 92,7% Saccharose
• 7,2% Pökelsalzmischung

1,100 kg / h sugar solution with 72% dry matter with a content of 92.8% sucrose and 7.2% pickling salt mixture (in each case based on dry matter) were, according to Example 1, after preheating to 75 ° C. within 35 seconds to 148 ° C. a heating steam pressure of 5.9 bar. After the vapors had been separated off, the thickened syrup was discharged in an open belt conveyor with a screw diameter of 0.8 m and a length of 7 m. The remaining water was almost evaporated after about 40 seconds. After passing through the screw conveyor, which is provided with a cooling jacket from the middle, a homogeneous, free-flowing instant product with a water content of 0.12% and based on TS was obtained:

• 0.09% invert sugar
• 92.7% sucrose
• 7.2% pickling salt mixture

Yield: 793 kg / h.

Example 4 Herbal tea beverage powder

According to Examples 1 to 3, 1,050 kg of sugar solution with a total dry matter content of 70.5% with a dry matter content of 88.05% sucrose, 10% glucose, 1.0% honey and 0.95% herbal tea extract were consisting of 20 herbal extracts such as peppermint, eucalyptus, chamomile, anise, etc., after preheating to 68 ° C within 40 seconds to 152 ° C (heating steam pressure 6.5 bar) and then discharged according to Example 3 in a belt screw conveyor. After about 20 seconds, the remaining water had evaporated after a brief foaming.

At the outlet of the screw conveyor, a free-flowing instant product with a moisture content of 1.6% was obtained, which can be used after fine grinding.

Yield: 752 kg / h.

Claims (12)

1. Process for preparing dry sugar products by spontaneous crystallisation of super-saturated sugar solutions, characterised in that a sugar solution having at least 70% dry substance and up to 15% non-sucrose substances in the dry substance is heated to a temperature of 135 to 155°C in less than 60 seconds by product-protecting heating and brought to a dry substance content of at least 90% by subsequently allowing the vapours to escape, and the thickened syrup is converted into a dry, pourable product only by cooling and sudden removal of the remaining water by crystallisation.

2. Process according to Claim 1, characterised in that the product-protecting heating is carried out in a spiral tube with forced circulation.

3. Process according to one of Claims 1 or 2, characterised in that the vapours are allowed to escape in a separating chamber at atmospheric pressure.

4. Process according to one of Claims 1 or 3, characterised in that the sugar solution by the product-protecting before the escape of the vapours is brought to a temperature of 135 to 155°C according to the content and type of non-sucrose substances.

5. Process according to one of Claims 1 or 4, characterised in that the thickened syrup is cooled by at least 10°C for crystallisation.

6. Process according to one of Claims 1 to 5, characterised in that the thickened syrup is allowed to drain away freely from the vapour separation chamber for crystallisation.

7. Process according to one of Claims 1 to 5, characterised in that the thickened syrup is sprayed for crystallisation.

8. Process according to one of Claims 1 to 7, characterised in that the thickened syrup is brought onto a steel belt preheated to 40 to 60°C below the syrup temperature and is then cooled.

9. Process according to one of Claims 1 to 8, characterised in that discharges from sugar-making with 75 to 85% dry substance, up to 88% sucrose and at least 12% non-sucrose substances are brought to 140 to 148°C in 40 to 50 seconds by product-protecting heating and are brought to a dry substance content of at least 95% by subsequently allowing the vapours to escape, and the thickened syrup is converted into a brown instant sugar by cooling by 15°C and sudden removal of the residual water.

10. Device for the production of dry sugar products, characterised by a steam-heated spiral tube heat exchanger (1) with a spiral tube (2) increasingly enlarging to 150 to 200% of its original internal width and having swirl fittings (3), a steam separator (4) which is under atmospheric pressure and a crystalliser arranged thereunder.

11. Device according to Claim 10, characterised in that the crystalliser is designed as an open spiral ribbon conveyor (5) provided in the second section with a cooling jacket (6).

12. Device according to Claim 11, characterised in that the crystalliser is a steel belt which is heated in the region of transfer and then cooled.

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