GB2058105A - Continuous cooking of mixtures containing suspension of starch or similar hydrocolloids - Google Patents

Abstract

A process Starch or like hydrocolloid suspensions e.g. of flexible confectionery licorice are continuously cooked and gelatinised in a controlled manner by feeding a slurry to a first of a series of vessels where it is warmed and allowed to swell, fed to a second vessel and subjected to partial gelatinisation, delivered to a third vessel in series where gelatinisation is brought to a predetermined degree and then arrested, and fed to a further vessel where the total solids content is adjusted to a predetermined level. An apparatus for carrying out the process consists of a series of cylindrical vessels or chambers arranged end-to-end, each of which has a rotary mixing and forwarding device which mixes the ingredients and conveys the mixture to the next vessel. Each vessel or chamber may be provided with means for admitting further ingredients and for the controlled addition of heat, for example by steam.

Description

SPECIFICATION Continuous cooking of mixtures containing suspension of starch or similar hydrocolloids This invention relates to the continuous cooking of mixtures containing suspension of starch or other hydrocolloids, for example in the production of pharmaceutical or industrial products, foods, confectionery and the like.

There are a number of continuous cookers in existence. Their purpose is, amongst others, to convert starches or other ingredients containing suspensions into colloidal solutions, gels, creams, pastes or solid articles, continuously, and within the shortest possible time, under the influence of high temperatures, super-atmospheric pressure and/or mechanical means.

These cookers meet their purpose in many cases, but usually they can be used for a particular application only, and obtain limited results, or fail, when used in other cases. They are often employed without meeting the natural physical pre-conditions.

The objective of this invention is, to use a method and plant constructed on technological principles, and universally applicable on modulated lines and optionably extendable for the maximum number of products of high quality, continuous operation, in which the moisture content of the material under treatment can be higher than that of the finished articles.

The present invention seeks to provide a process and an apparatus by which it is possible to meet a great variety of physical pre-conditions and thereby to process almost any composition and desired end-product.

According to the invention, there is provided a process for the continuous cooking of a mixture containing a suspension of a starch or like hydrocolloid in water in a series of substantially closed interconnected vessels or chambers, wherein the mixture is in the form of a fluid slurry and said process comprises the steps of feeding the slurry into a first one of said vessels or chamers in which the slurry is warmed and in which the slurry remains for a dwell period during which the starch or hydrocolloid achieves maximum swelling, feeding said mixture to a second vessel or chamber of said series in which the mixture is subjected to a process of partial gelatinisation, delivering the partially gelatinised mixture to a third vessel or chamber of the series in which the gelatinisation is brought to a predetermined degree and then arrested, feeding the gelatinised mixture to a further vessel or chamber in which the moisture content of the mixture in relation to the total solids content of the mixture is adjusted to a predetermined proportion and discharging the mixture continuously from said further vessel or chamber. The gelatinisation may be asserted for example by the controlled addition of at least one further ingredient and/or by a further reduction of temperature or by discharging the mixture.

The imvention also provides an apparatus for the continuous cooking of a mixture containing a suspension of a starch or a like hydrocolloid comprising a series of substantiall cylindrical closed vessels or chambers inter connected in end-to-end relationship, each vessel or chamber being provided with means for the introduction of ingredients of the mixture at predetermined rates and in predetermined proportions, each vessel or chamber having mixing and forwarding devices by which the mixture is subjected to a continuous mixing and conveying action, the vessels or chambers being provided with means by which the process time, dwell period and temperature in each said vessel or chamber are controlled.

The following points may clarify the physical pre-conditions: In a mixture of starch or other ingredients (to be referred hereinafter as "starch") and water (hereinafter termed "suspension "or "slurry"), the starch granules are not soluble and retrograde and maintain their original properties at ambient temperatures of some 1 0-20 C.

If, in a second phase, this suspension is warmed up to a temperature of some 55-65"C under agitation, the granules swell and expand to many times their original size, lose their original shape and increase considerably the viscosity of the suspension. This may be termed the "Swelling Period".

In a third phase, during which the temperature is further elevated, the swollen particles burst gradually and ultimately form a colloidal solution or a gel. This we may term as "Gelatinisation period". The appropriate temperatures at which this change takes place may be termed the "Gelatinisation Temperature", which in practice is not a particular, fixed temperature, but more a range of temperatures. This range of temperatures is subject to such factors as the nature of the starch, size of granules, proportion of amylose and amylopectin in the starch, quantity of water, certain other additives to the mix and mechanical forces exerted on the mixture.

The gelatinisation progresses faster or slower and more or less completely. A "cooked" product which contains incompletely burst starch particles may be classed as "undergelatinised" or as "well gelatinised" if only a few particles remain unbroken. If no unbroken granules can be detected by microscopic examination, we may call the product "fully gelatinised" or even "overgelatinised".

If the suspension contains sugar (or possibly proteins or other solids, briefly referred to as "sugar solution"), gelatinisation and swelling are retarded as the concentration of sugar or these other ingredients increases and need highertemperatures. The proportion of sugars and water in the suspension may be referred to as a weaker or stronger "Percentage of Sugar Solution". In the accompanying graph the required increase in gelatinisation temperature is shown in relation to the increase in strength of sugar solution in the suspension or slurry. In addition, the "boiling temperatures" of a pure sugar solution, and a slurry for the making of "flexible Confectionery Licorice" are given, to which reference will be made later by way of example.

The explain the significance of the aforesaid, comparing the existing continuous cookers and the present invention, the making of "Flexible Confectionery Licorice" will be described as an example.

To produce such an article, a slurry according to the following recipe may be used: Ingredients: Total Solids Water: Sugars: Kg: % Kg: Kg: Kg: 330 Weat Flour 8% Gluten 72% Starch 14% Water 33.97 284 46 (26 Gluten) 80 Refined Sugar 9.57 80 - 80 500 Molasses or Syrup 35 Sucrose 17% Invert sugar 28% Foreign matter 20% Water 47.85 400 100 260 60 Corn Syrup 63 DE 20% Water 5.74 48 12 48 30 Licorice Extract 20% Water 2.87 24 6 12 1000 Total Ingredients 100 836 164(=16.4%) 400 sugars 230 Water added - - 230 (426) 1230 Total Mix as Slurry 836 394 (=32%) -210 Water Evaporation 210 during cooking or drying process 1020 Finished Paste 836 184 (=18%) This formulation results in the following relationships:284 Flour Solids = 41.5% :: 400 kg Sugar Solids = 58.5% are satisfactory and governs taste and texture; 284 Flour Solids = 41.89% : 394 Water = 58.11% or 1 part:1.39 parts result in a freeflowing slurry and ample water for absorption and swelling of the starch, i.e. good pre-condition for gelatinisation; 394 Water 48% 426 Sugars (and proteins) = 52% sugar solution As can be seen from the accompanying graph, the boiling temperature of the mix is in the region of 106"C, and the gelatinisation temperature in the region of 108 C.

1. Cooking Method By Conventional Open Batch Cooker: MethodA.

The boiling temperature is just on the border line of the gelatinisation temperature. This results sometimes in undergelatinisation. A stronger sugar solution would eliminate gelatinisation completely.

Method B To avoid the above disadvantage this method is applied, in which, say, half of the Molasses or Syrups is retained, and a weaker sugar concentration produced in the slurry. This part is added to the cooker when the desired degree of gelatinisation has been reached and further gelatinisation is thereby stopped. In both Methods 1A and 1 B the paste is cooked to 25-30% moisture and subsequently has to be dried to 15-18% water to give an acceptable product.

2. A "Final Moisture Batch Cooker' can be adopted because better heat transmission, evaporation and turbulence to the paste is obtained. The paste can be cooked as method 1A or 1B but to 12-19% final moisture and no subsequent drying is needed.

3. Continuous Nigh Pressure Cooking: Three methods can be employed: A. Live steam is blown into a dry mix of flour, sugar and other ingredients under vigorous agitation. This system conflicts basic physical laws with the result that no swelling of starch can take place and therefore no gelatinisation can occur.

B. Live steam is blown by a jet, under pressure into a forward moving stream of slurry. Control of swelling and gelatinisation is very difficult and inaccurate during this momentary heating process. It can be used only for a product containing much water and little starch and not for cooking to final moisture.

C. Contact Heater, consisting of an outer steam-jacketed tube, in the centre of which a drum is rotating. The slurry is continuously pumped under pressure through the narrow space between the inner drum and outer heated tube from one end to the other where the thick, cooked paste emerges. Due to the pressure, higher temperatures than in the open Batch Cooker can be obtained, and therefore less water and a higher sugar concentration can be used. The degree of gelatinisation can be regulated only by temperature and dwell-time. With e short dwell-time of only between 10 and 30 seconds, it is very difficult to obtain a mean between over- and under-gelatinisation. Swelling is restricted by the high pressure, and the resistance offered by the emerging viscous paste.Slurry, according to the above recipe, can be cooked, but it has subsequently to be dried as it contains 20-31% moisture.

Attempts have been made to reduce the additional water from 230 kg to 45 kg to get near the desired final moisture of 20% = 209 kg. This produces a rather heavy slurry with 1 part flour to 0.73 parts of water, and is difficult to pump. The sugar concentration, increased to 67.1%, needs a gelatinisation temperature of more than 1 22CC and even then produces poor gelatinisation, due to insufficient swelling. The microscopic hydrogen bonds are substantially destroyed and result in a sticky product. The movement of the very viscose paste is rendered more difficult and slow, and the quality of the finished article is made worse. No genuine gelatinisation occurs, but the starch particles are ruptured into many minute, but still intact, particles which do not produce a "chewy" gel-like consistency, but a more crumbly, more bread-like structure.

As a compromise, the quantity of flour (starch) in the slurry is reduced, which needs less water, and the proportion of sugars correspondingly increased. This solves some mechanical problems, but does not improve the quality, and increases cost. This plant can therefore not be regarded as a versatile and purpose-built plant, as formula and method must be adapted to suit the plant, and does not give satisfactory results.

An example of the process of the invention and one exemplary embodiment of an apparatus by which the process can be carried out will now be described with reference to the accompanying drawings which show, schematically, the arrangement of a series of vessels and related devices for the continuous production of the cooked product, in this instance a flexible confectionery licorice.

In this example of an apparatus performing the process of this invention, a series of four generally cylindrical vessels are shown, which may be constructed of or subdivided into separable individual modular sections. The number of vessels can be extended or reduced, or the subdivisions changed according to the purpose or requirement of the article to be treated.

The apparatus shown in the drawing is designed to correspond with the aforementioned recipe for the continuous production of 1000 kg Licorice Paste per hour.

There are six sections of the apparatus, each serving a different purpose: A) Blending of dry raw material and turning same into a dough; B) Adding liquid raw material and water to turn the mix into a slurry whilst warming the slurry. The sections may be omitted in accordance with particular requirements, a prepared slurry being supplied to the apparatus at an appropriate location; C) Swelling the starch by further heating and beginning to turn the slurry into a firm paste; D) Further swelling and beginning to gelatinise the starch; E) Completing gelatinisation to the desired degree and terminating gelatinisation for example by adding further liquid sugars and or by temperature reduction, or by discharging the mixture; F) Evaporation of surplus water, and discharging the cooked paste to an extruder or forming machine.

A water cooled condenser (G) and a vacuum pump and water meter or scales (H) are also provided, although these are not essential to the basic process.

Each of the cylindrical vessels, apart from the vessel Al are at least partly surrounded by a steam heating jacket (5), the steam jacket for the vessel F4 extending only around 2/3 of the cylinder. Steam is supplied to each vessel by the main steam line (27), regulated by steam valves (6) and controlled by pressure gauges (7).

Condensed water is discharged through steam traps (8). At various points, test valves (9) are provided, by which samples can be taken for checking. At suitable points, observation windows (11) and lights (12) are fitted, to observe the progress of the operation. Between the individual cylinders of the vessels and at the outlet of the last one (4F), there are connecting trunkings with shutters (13) to adjust the flow of material. In each cylinder, a shaft (14) rotates which is provided with members to provide a kneading, mixing and forwarding action, such as flexible scrapers and kneading blades (15a), scroll sections (1 Sb) or flights (1 5c).

There is no pressure pump in the system, and empty spaces can be provided if and where needed (for example for unrestricted expansion).

At one end of each cylinder, detachable covers with bearings (16) are provided, so that the shafts can be extracted for cleaning. On the other end of the cylinders, bearing housings (17) are fitted with couplings for the extractable shafts. A common motor (18) is provided to drive shafts (14). Where preferred, separate driving motors can be provided.

Cylinder 1A is fitted with a hopper (20). At one end of it, vibrators or metering devices are provided which fill continuously 330 kg wheat flour (or starch) (22) and 80 kg dry sugar (23) per hour into the hopper (20).

Whilst these materials drop into the hopper, 75 kg water are atomised by a nozzle (21) and mixed with the dry materials to form a fairly stiff dough by means of the rotating shaft and blades (1spa). The scroll section (15b) forces the dough through a perforated plate (19) and forms a seal against the slurry between section 1A and 1 B. As soon as the dough emerges from this plate in section B, it is met by the remaining water fed at 230 kg per hour, metered by a metering device and valve (24), and a little later, half of the 500 = 250 kg molasses or syrup per hour, regulated by a metering device and valve (25). This operation in section B will produce a fairly fluid slurry, smooth and free from lumps.The sugar concentration is reduced from 52% to 42% and thereby the gelatinisation temperature reduced from about 1 08"C to 100"C. No pressure is needed to raise the temperature. The fluid and pre-warmed slurry enters section C in which the temperature of the slurry is further increased, so that the starch can swell to its maximum, and convert the slurry into a solid paste by the time it reaches section D. Here the gradual gelatinisation commences, and continues in the first part of section E. Contrary to the known continuous cookers, the dwell-time is prolonged at a lower temperature, so that large and small starch granules are equally treated and undergo genuine gelatinisation without being split into minute, still intact particles (wrongly termed as gelatinised particles).During the extended dwell-time it is also possible to regulate the desired degree of gelatinisation with some accuracy. As soon as this degree has been reached (checked by sample, taken from valve 9 in section D), further gelatinisation will be arrested in section E by the incorporation ofthe remaining 250 kg syrup per hourthrough the metering device and valve (25), and 60 kg corn syrup or glucose per hour through metering device and valve (26). By the increase of sugar concentration and slight temporary reduction in temperature, no further gelatinisation will take place and during the further travel of the paste in section E, the added sugars will be thouroughly blended. The incorporation point may be changed as required for a particular product.At the end of section E, the paste passes through trunkings (13) to section F, in which, possibly under vacuum, 210 kg surplus water per hour will be extracted as vapour. The vacuum in section F will be maintained by a seal of paste, regulated by the shutters in trunkings (13). The vacuum will be adjusted by valve (31) to such as degree that the emerging 1020 kg of finished paste enters the extruder (37) forming the section J at a temperature in the region of 85 C, and maintains a regular viscosity. Cylinder F is provided with a vapour hood or dome (28) which is connected by a pipe (30) with a condenser (29) in section G provided with a vacuum gauge (32) and a cooling water inlet and outlet (33).The condensed water from the paste is led through pipe (35) into the suction pump (34) at section H, and discharged through flowmeter (36) to registerthe 210 kg per hour or evaporated and condensed water.

Depending on the consistency of the finished product, it may be poured into moulds from the outlet of the vessel or chamber F or it may be pressed between rollers into flat sheets or shapes. The extruder (37) as illustrated may form the product into sheets, ribbons, rods or tubes.

By using the process and the apparatus of this invention it is possible to - continuously cook products of almost any formulation without having to adapt the recipe to suit the plant; - continuously cook products to their final moisture content even if the moisture content of the recipe is higher than that in the finished article; - adjust and control during the process the degree of gelatinisation, moisture content, and viscosity of the product; - add ingredients during processing: : - swell and gelatinise starches or the like genuinely by the provision of an adequate quantity of water, dwell time and space during processing; - prepare continuously a smooth slurry or mix; - carry out each essential function simultaneously, or successively in separate sections; - add or take away certain sections in the process as required for the particular product, obtainable by the modulated construction of the apparatus; - accurate control of the temperature of the finished article and its moisture content.

The features of this invention can not be obtained by any of the known continuous cookers.

Claims (14)

1. A process for the continuous cooking of a mixture containing a suspension of a starch of like hydrocolloid in water in a series of substantially closed interconnected vessels or chambers, wherein the mixture is in the form of a fluid slurry and said process comprises the steps of feeding the slurry into a first one of said vessels or chambers in which the slurry is warmed and in which the slurry remains for a dwell period during which the starch or hydrocolloid achieves maximum swelling, feeding said mixture to a second vessel or chamber of said series in which the mixture is subjected to a process of partial gelatinisation, delivering the partially gelatinised mixture to a third vessel or chamber of the series in which the gelatinisation is brought to a predetermined degree and then arrested, feeding the gelatinised mixture to a further vessel or chamber in which the moisture content of the mixture in relation to the total solids content of the mixture is adjusted to a predetermined proportion and discharging the mixture continuously from said further vessel or chamber.

2. A process according to claim 1 wherein the fluid slurry is prepared by feeding the starch or hydrocolloid and at least one other ingredient of the mixture in predetermined ratios and at predetermined rates into a first mixing vessel or chamber with the addition of water supplied at a predetermined proportion and rate and forwarding the mixture to a second mixing vessel or chamber in which the mixture receives further ingredients and additional water at predetermined rate and proportions, and in which the mixture is further mixed until it forms said fluid slurry.

3. A process according to claim 1 or claim 2 wherein the mixture in each vessel or chamber is continuously subjected to a mixing and forwarding action throughout its passage through each vessel or chamber.

4. A process according to any one of claims 1 to 3 wherein during the swelling stage of the process, the proportion of water is adjusted to ensure maximum swelling of the starch or hydrocolloid without fracturing of partially or insufficiently swollen particles.

5. A process according to any one of claims 1 to 4 wherein the process time and temperature in each vessel or chamber are controlled to predetermined values and each vessel or chamber can be supplied with additional ingredients of the mixture and/or heat controlled rates and proportions at selected locations throughout the process.

6. A process according to any one of the preceding claims wherein the final moisture content is adjusted by the extraction of water under reduced atmospheric pressure.

7. An apparatus for the continuous cooking of a mixture containing a suspension of a starch or a like hydrocolloid in accordance with any one of claims 1 to 7, comprising a series of substantially cylindrical closed vessels or chambers interconnected in end-to-end relationship, each vessel or chamber being provided with means for the introduction of ingredients of the mixture at predetermined rates and in predetermined proportions, each vessel or chamber having mixing and forwarding devices by which the mixture is subjected to a continuous mixing and conveying action, the vessels or chambers being provided with means by which the process time, dwell period and temperature in each said vessel or chamber are controlled.

8. An apparatus according to claim 7 wherein the last vessel of the series is provided with means for extracting moisture from the mixture associated with the region of said vessel where the final mixture is continuously discharged from the apparatus.

9. An apparatus according to claim 8 wherein the means for extracting moisture from the mixture includes means for reducing the atmospheric pressure in said last vessel of the series.

10. An apparatus according to any one of claims 7 to 9 wherein each vessel or chamber is constructed from a plurality of modules which are interchangeable with one another, the number of vessels or chambers being determined in accordance with the requirements of a selected process and the length of each vessel or chamber being determined by the number of modules of which it is formed in accordance with the requirements of the selected process.

11. An apparatus according to any one of claims 7 to 10 wherein each vessel or chamber is provided with means for the introduction of ingredients of the mixture and/or heat in metered volumes and at controlled rates, said introduction being effected at selected locations along said series of vessels or chambers, each vessel or chamber being provided with means for inspecting and testing the mixture during its passage through the apparatus.

12. A process for the continuous cooking of a mixture containing a suspension of a starch or like hydrocolloid substantially as hereinbefore described and with reference to the accompanying drawings.

13. An apparatus for the continuous cooking of a mixture containing a suspension of a starch or like hydrocolloid substantially as herein before described and with reference to the accompanying drawings.

14. The product produced by the process as hereinbefore described and according to any one of claims to to 6 and claim 12.