CRYSTALLISATION OF SUGARS

Abstract: A process for controlling the crystallisation of a sugar from a solution thereof, characterised in that the crystallisation is carried out under the influence of a magnetic field.

Description: CRYSTALLISATION OF SUGARS The present invention relates to the crystallisation of sugars, e.g. sucrose, and to sugar crystals obtained thereby. Sugars such as sucrose are very widely used, mainly in the food and confectionery industries, and the final stage in the manufacturing process of the sugar is often crystallisation from an aqueous solution with the sugar then being used in crystalline form. Crystallisation of sugars is a complex process which is difficult to control so that the size and shape of the resulting sugar crystals is often unpredictable. Where crystals of a particular size and shape are required, for example in certain applications in the confectionery industry, it is difficult to produce crystals in the required form conveniently and consistently. Sucrose generally crystallises in anhydrous form although the formation of the hemipentahydrate (C^H^O^ .2.5H 2 0) and the hemiheptahydrate (C 12 H 22 0 11 .3.5H 2 0) has been reported on crystallisation at low temperature (-34 °C) (Young & Jones, J. Phy ' s. Colloid Chem., 53 , 1334 - 1350 (1949)). The formation of the crystalline hydrates was regarded as a problem in the storage of frozen fruits and investigations were undertaken to try to find ways of preventing their formation (Young et al , Food Research, 16 , 20-29 (1951)). Engelsen and Perez (Carbohydrate Res. 292 , 21-38 (1996) ) suggested on the basis of molecular dynamics simulation (a computer modelling technique) and crystallographic investigation of a sucrose/protein complex that sucrose may exist in hydrated form in aqueous solution but these conclusions remain controversial. Research into the effects of magnetic fields on chemical processes has been sporadic. It was suggested in the 1930s that application of a magnetic field could remove scale from water pipes but in the absence of a convincing rationale for the effect the technique remained controversial for many years before being confirmed experimentally some 50 years later (Donaldson, Tube International, January 1988, 39 and Grimes, Tube International, March 1988, 111). The effect of magnetic fields on precipitation and crystallisation in inorganic systems such as calcium carbonate and zinc phosphate is assumed to be on nucleation and coagulation and the effect in reducing scale formation or even removing scale which has already formed appears to be a result of changes in solubility of the inorganic compound. In the case of organic molecules, it was found that when benzophenone was crystallised in a high magnetic field, the direction of the long axis of the needles formed tended to align perpendicular to the direction of the magnetic field (Katsuki et al , Chemistry Letters, 1996 607-608). With a more complex organic molecule, a considerable degree of alignment was found when fibrin was allowed to polymerise in a magnetic field and a possible effect on blood clotting in vivo was suggested (Yamagishi et al , J. Phys. Soc. Jpn., 58 ( 7) , 2280-2283 (1989)). A recent report has also suggested that application of a magnetic field can influence the selectivity ratios in the nickel catalysed hydrogenation of fats such as sesame oil and soybean oil (Jart, JAOCS, 75 (4) , 615-617 (1997)). Experiments have been reported in which passing sucrose solution through a magnetic field appeared to reduce the boiling point of the solution although a drop in boiling point was also noted for distilled water and tap water. The magnetic field also affected viscosity and surface tension of the sucrose solution but the various effects were not proportional to the intensity of the magnetic field (Bisheng et al , Int. Sugar Jnl., 98 , 73-75 (1996)). It has also been suggested that the application of a magnetic field can reduce and control evaporator scale in the production of cane sugar (Cole & Clarke, Int. Sugar Jnl., 98 , 71-72 (1996) ) . There is no suggestion in either of these papers of any effect on the sucrose crystals themselves. The present invention relates to a method by which the crystallisation of sugars can be influenced so that a particular desired crystalline product can be formed conveniently and consistently. According to one aspect, the present invention provides a process for controlling the crystallisation of a sugar from a solution thereof, characterised in that the crystallisation is carried out under the influence of a magnetic field. The solution is preferably an aqueous solution but the invention is also applicable to solutions of sugars in organic solvents such as alcohols. The present invention can be applied to solutions, preferably aqueous solutions, of any sugar and, as used herein, the term "sugar" is used generally to refer to any water soluble crystalline mono- or oligo-saccharide. Sugars to which the present invention can be applied include in particular mono- and disaccharides such as sucrose, glucose, fructose, lactose, and sugar alcohols such as sorbitol, mannitol and erythritol. The invention is particularly applicable to sucrose. It has been found according to the present invention that the application of a magnetic field to a sugar solution prior to crystallisation or preferably during crystallisation influences such factors as crystal growth rate, nucleation rate, morphology and crystallinity and, in particular, the size and/or shape of the crystals produced can be influenced as desired. Once the particular type and orientation of magnetic field and the manner of its application has been determined which leads to crystals with the desired properties (size, shape, etc.,) then application of that field enables the desired crystals to be produced subsequently with a high degree of consistency. In the case of the application of a magnetic field during crystallisation, an immediate effect is observed on the crystals produced. When the magnetic field is applied to a sugar solution before crystallisation, a downstream effect is still observed when crystallisation takes place on undersaturated to supersaturated solutions of differing flow rates. An effect of the magnetic field can still be observed even when the field has been applied to the solution several hours and possibly even days prior to crystallisation. Preferably the magnetic field is applied during crystallisation or to the solution within 1 hour prior to crystallisation. Crystallisation of sugars, particularly sucrose, is a process of considerable economic importance which has been carried out on a considerable scale for very many years. Accordingly, it is surprising that the process can be influenced in the manner described above, particularly since the work referred to above on the application of magnetic fields to sucrose solutions did not suggest any effect on crystallisation as such or the nature of the crystals produced. The magnetic field which is used according to the invention can be applied in any desired manner including permanent magnets, any type of electromagnet (such as pulsed electromagnets and DC electromagnets) and radio frequency generated magnetic fields. The optimum field strength for any particular effect and the manner in which the magnetic field should be applied can be determined in a given case by routine experimentation. Both homogeneous and inhomogeneous fields may be used for this purpose. The effect of different types of magnetic field is discussed in more detail in the experimental work described below. However, in general terms DC electromagnetic fields promote euhedral growth (more rectangular crystal form) and also slow the crystal growth whilst the number of centres of growth (nucleation) increases with increasing field strength. Permanent magnetic fields reduce the number of centres of growth with increasing field strength. In general the crystallisation process according to the present invention is carried out by dissolving the sugar, for example sucrose, in a solvent, preferably water, and then allowing the solution to evaporate thereby inducing the sugar to crystallise, the magnetic field being applied to the solution within a suitable period before crystallisation and/or during crystallisation itself. Crystallisation is generally induced by evaporation of the solvent and can be carried out at any temperature at which the solvent evaporates up to the boiling point of the solvent. With aqueous solutions a preferred temperature is about 50°C although lower temperatures can be used as can higher temperatures even up to the boiling point of the sugar solution. In the laboratory scale work described below, crystallisation is carried out in Petri dishes. On a commercial scale, the crystallisation can be carried out in crystallisation apparatus commonly employed in the sugar industry. The use of techniques such as differential scanning calori etry (DSC) , scanning electron microscopy (SEM) , polarising light microscopy (PLM) and powder X-ray diffraction (XRD) has shown that in the case of sucrose the properties of the crystals formed are consistent with a significant proportion being sucrose hydrates, probably mixtures of the hemi-pentahydrate and the hemi-heptahydrate, in admixture with some anhydrous sucrose. Given that the literature discloses these hydrates as being formed only at low temperatures, it is surprising that they can be formed according to the invention at ordinary or elevated temperatures . According to another aspect, the present invention provides a process for the production of a crystalline sucrose product containing sucrose hydrate which comprises crystallising an aqueous solution of sucrose under the influence of a magnetic field. The invention also relates to a crystalline sucrose product containing sucrose hydrate obtainable by the process according to the invention. As used herein the term hydrate means a crystal containing extra water which may be tightly bound but is detectable for example by Karl Fischer measurement and which may also modify the DSC curve. The fact that the present invention enables sugars to be produced in a desired crystal size and/or shape more conveniently and consistently will be of benefit in most applications of the sugar in question where the sugar is to be used in solid form rather than being redissolved. However, there are certain applications in the confectionery industry where the ability to produce sucrose with a consistent crystal size is of particular advantage including the following: • In the production of coatings for chocolate buttons (such as the product sold under the trade mark SMARTIES®) it is important that the coating should have an attractive bright and shiny appearance. This appearance, which depends at least in part on the particle size of the sugar, can be controlled by use of microcrystalline sugar which can be produced conveniently and consistently by the process according to the invention. • In other confectionery applications, such as the production of fruit pastilles, large crystals of sucrose (lOOμ up to 2 or 3 mm) are required for coating the pastilles because of their particular properties of texture and light reflectance and such crystals can again be produced conveniently and consistently by the process according to the invention. Sucrose crystals of particular shapes can be produced according to the invention to obtain specific desired effects. The fact that the sucrose can be produced in the form of a crystalline hydrate may be an advantage in other areas of the confectionery industry. Thus the manufacture of milk chocolate involves the formation of so-called crumb which is a mixture of dried milk, sucrose and cocoa butter. Amorphous sucrose is formed during some crumb making processes and traps fat leading to an increase in the amount of fat which is needed in the final chocolate recipe. Milk fat is one of the most expensive ingredient in milk chocolate and the use of crystalline sucrose which does not trap fat means that the amount of this expensive ingredient can be reduced. Reducing the amount of fat in the chocolate would also have the effect of reducing the calorific value. In addition, sucrose represents about half of the total weight of milk chocolate and use of sucrose in the form of a crystalline hydrate where the water makes up about 10% by weight of the sucrose added would also reduce the calorific value of the chocolate. Accordingly, use of crystalline sucrose produced according to the present invention allows a significant reduction to be made in the calorific value of the chocolate without any adverse effects on the taste and other properties thereof the chocolate. According to a further aspect the present invention provides the use of a crystalline sucrose hydrate product as defined above for the manufacture of a confectionery product, preferably chocolate. According to a still further aspect, the present invention provides a confectionery product, preferably chocolate, containing a crystalline sucrose product as defined above. Lactose crystallised according to the invention can be used, for example, in sucrose-free chocolate. Erythritol crystallised according to the invention can be used in low calorie chocolate. The invention is illustrated and supported further by the following experimental work in which reference is made to the accompanying drawings a brief description of which is as follows: Figure 1 shows the orientation of the magnetic field referred to under 1.1(c) below. Figure 2 shows (a) wedge growth and (b) dendritic growth of sucrose crystals. Figure 3 is a diagram from above representing sucrose crystal growth under the conditions of a permanent magnetic field placed above and below the sample. Figure 4 is a diagram of pulsed magnet and sucrose solution apparatus . Figure 5 shows general euhedral sucrose crystal shapes obtained from DC field case (iii) below. Figure 6 shows surface texture of crystallised sucrose with no magnetic field viewed using SEM at x540 magnification. Figure 7 shows microcrystalline material on the surface of a sucrose crystal, crystallised in a 700G permanent magnetic field viewed using SEM at x470 magnification. Figure 8 shows flat surfaces of a sucrose crystal grown in an 80G permanent magnetic field and viewed using SEM at x65 magnification. Figure 9 shows layered crystal growth viewed on a sucrose crystal surface grown in a 700G permanent magnetic field viewed using SEM at xl70 magnification. Figure 10 shows the surface of a sucrose crystal grown with no magnetic field viewed using PLM at lOx magnification. Figure 11 shows microcrystalline material present on the surface of sucrose crystals formed in a 300G DC electromagnetic field. Figure 12 shows microcrystalline material present on the surface of sucrose crystals formed in a 150G permanent magnetic field. Figure 13 shows flat surfaces and angled corners shown on sucrose crystals grown in a 400G DC electromagnetic field. Figure 14 shows flat surface and angled corners shown on sucrose crystals grown in a 400G DC electromagnetic field. Figure 15 shows layered growth of sucrose crystal surfaces grown in a 150G permanent magnetic field. Figure 16 shows layered growth of sucrose crystal surfaces grown in a 350G DC electromagnetic field. Figure 17 shows the DSC melting profile for sucrose control ("no-field") crystals. Figure 18 shows DSC melting profile for sucrose crystals grown in a 300G permanent magnetic field. Figure 19 shows DSC melting profile for sucrose crystals grown in a 600G permanent magnetic field. Figure 20 shows a diagrammatic illustration of an apparatus for crystallisation of lactose under a permanent magnetic field at sides in parallel. Figure 21 shows a diagrammatic illustration of an apparatus for crystallisation of lactose under a permanent magnetic field above and below. Figure 22 shows a diagrammatic illustration of an apparatus for crystallisation of lactose under a pulsed magnetic field. Figure 23 shows a diagrammatic illustration of an apparatus for crystallisation of lactose under a DC electromagnetic field. 1. Static Crystallisation of Sucrose 1.1.0 Experimental 1.1.1 Preliminary studies Saturated solutions of sucrose were prepared in 5cm Petri dishes on a hot plate at 50 °C by addition of sucrose to an unspecified amount of de-ionised water until no more sucrose could be dissolved. In the cases of over-addition of sucrose, more water was added to water down the solution. The sucrose solutions in the Petri-dishes, placed in incubators at 50 °C, were left to evaporate and crystallise under the different magnetic environments (a) - (f) listed below. (a) No magnetic field around the crystallising sucrose solution. (b) Permanent magnets placed either side of the Petri-dish with field strengths of (i) 300G at edges, 265G at centre of Petri-dish (ii) 400G at edges, 350G at centre of Petri-dish (iii) 640G at edges, 540G at centre of Petri-dish (iv) 760G at edges, 63OG at centre of Petri-dish. (c) Permanent magnets placed in a square around the Petri- dish with field strengths as shown in Figure 1. (d) Permanent magnets placed above and below Petri-dish with a field strength of 60G. (e) A pulsed magnetic field that passes in two directions alternately with the Petri-dish placed above the centre. (f) DC electromagnets with poles placed at either side of the Petri-dish with field strengths of (i) 100G at edges, 50G at centre of Petri-dish (ii) 320G at edges, 14OG at centre of Petri-dish (iϋ) 500G at edges, 195G at centre of Petri-dish (iv) 600G at edges, 220G at centre of Petri-dish. Visual observations were recorded following crystallisation of the sucrose solutions and the crystals collected and dried. 1.1.2 Controlled conditions investigation Experiments were performed under the same format as before but with alterations listed below included in the preparation of samples before placement in incubators. (a) 10 ml de-ionised water was placed in the Petri-dishes, (b) 4.66g sucrose was added to the water (around 80% saturated) and heated on a hot-plate at 50 °C for two hours until fully dissolved, (c) samples were prepared free of dust or foreign material by covering the Petri-dishes during the sucrose dissolving stage. Each experiment was repeated 3 times and visual observations were noted. 1.2.0 Results and Discussion 1.2.1 Results from preliminary studies on static sucrose crystal growth The main aim of the experiment was to create a controlled environment which would allow evaporation of water from aqueous sucrose solutions, i.e. slow crystallisation of sucrose, and to investigate the effect on the crystal growth process of various magnetic fields. 5cm diameter Petri-dishes were utilised as a crystal growth container as its size allowed evaporation and crystal growth over the course of 2 days. The solutions for the preliminary trials were prepared in the Petri-dishes in an unmeasured amount of de-ionised water. Incubators were used as a means of controlling the temperature and included a fan that circulated the air inside to aid evaporation. Evaporation studies showed that over-saturation resulted in catastrophic solidification in the form of small rectangular crystals that formed a film across the solution/air interface within 2 hours. In general, lower levels of saturation resulted in crystal growth in a characteristic circular fan pattern. Growth begins from a point of nucleation and continues circularly outwards forming single crystal wedges with larger crystal growth faces (see Figure 2(a)). In some cases finer, needle-like crystals can be formed which will be referred to as dendritic and where the needles do not originate from the point of nucleation but from a point of growth at some distance from the centre (see Figure 2 (b) ) Since different forms were obtained from different levels of saturation the investigation was continued under controlled conditions. 1.2.2 Visual observations from controlled studies 1.2.2(a) Control or "no field" sucrose crystals Sucrose crystals grown without a magnetic field in general formed over 24 hours. The earliest centres of nucleation resulted in the largest circular diameters of growth that predominated most of the surface of the sucrose solution. On average there were five centres of nucleation with 3 larger that predominated the sucrose solution surface. The smaller crystal growths which will be referred to as secondary nucleations, formed in the remaining solution around the larger areas of crystal growth until there was no sucrose solution/air interface left. The crystal surfaces were in general, uneven, disordered and chunky, especially where the crystallisation from different centres of nucleation met, and were in the form of wedge growth. 1.2.2(b) Permanent magnetic fields The general forms of the sucrose crystals obtained from the permanent magnetic field studies were similar to the "no- field" situation i.e. circular growth patterns, but there were subtle differences worth noting. 1.2.2(b) (i) 300G at edges, 265G at centre of Petri-dish The weakest permanent field had a similar number of centres of nucleation i.e. on average around 6 or 7. The largest circular growth patterns came from three nucleation centres and there were on average 3 to 4 smaller growth patterns from secondary nucleations. The most obvious visual difference was the fine structure that made up the circular growth patterns. The crystals were very clear in appearance made up of many fine wedges that have grown in very straight lines outwards from the point of nucleation. Boundaries of the circular growth patterns formed almost straight lines and there were no chunky or disorganised regions. In general, the crystal growths were more ordered and had a finer structure. 1.2.2(b) (ii) 400G at edges, 350G at centre of Petri-dish On average, use of a slightly stronger permanent field resulted in fewer centres of nucleation i.e. on average 5. In most cases, the majority of sucrose crystal growth came from 4 centres of nucleation that dominated the surface of the sucrose solution. In addition to the finer structure of the sucrose crystal growth observed in the weaker permanent field case, some flat clear wedges were observed. Boundaries between circular growth patterns were again almost straight lines and in general the sucrose crystals grown under these magnetic conditions were more ordered than the "no-field" situation. 1.2.2 (b) (iii) 640G at edges, 540G at centre of Petri-dish Fewer centres of nucleation (on average 4) were observed from the sucrose crystal growth under stronger permanent magnetic field conditions. However, since there were no secondary nucleation centres, crystal growth came from around four centres of nucleation resulting in larger diameters of growth. The sucrose crystal growth was fine at the centres of nucleation, but became wider, flat, clear wedges as growth continued away from the centre. Incomplete layered crystal growth could be seen on the flat, wedge surfaces and caused them to look opaque. Boundaries were again very even and the growth patterns more ordered than the "no-field" conditions. 1.2.2(b) (iv) 760G at edges, 630G at centre of Petri-dish Again fewer centres of nucleation (on average 2) were observed from the stronger permanent field sucrose crystal growth conditions. Where crystal growth was close to the centre of nucleation, the sucrose crystals were fine but dendritic. Some had the appearance of overlapping wedges. Growth away from the centre of nucleation resulted in large well formed wedges with layered growth visible. Boundaries of circular growths were in the form of interlocking zigzags indicating crystal twinning and were even and flat. Secondary nucleation was limited to a very small area and on average consisted of growth from only 1 or 2 centres. The resulting secondary nucleation sucrose crystals were ordered and fine. In summary, the growth patterns resulted in very ordered, and excessively large wedges in most cases with some evidence of dendritic growth. 1.2.2(c) Permanent magnetic fields in a square around sample The square orientation of the permanent magnets resulted in crystals with more needle shape. Growth was dendritic therefore wedge shapes were not observed. On average there were two larger spherulitic growths and 3 or 4 smaller ones. As the diameter of the spherulitic growth became larger more needles began to grow, and most had the dimensions of 2-3mm width with variable length. Boundaries between spherulitic growths are like interlinking zigzags (twinning) and are well ordered and flat. The overall impression is that it is more ordered crystal growth than the "no-field" situation as crystals are clear and well formed. 1.2.2(d) Permanent magnetic field above and below sample Crystal growth was again fine and ordered in appearance consisting mainly of fine wedges or needles. In addition, there appeared to be a favoured direction of growth for larger wedges (see Figure 3) . In addition, the numbers of centres of nucleation was on average 3, a reduction from the "no-field" case. In some cases, secondary nucleation was observed but was limited to very small growth areas. The boundaries of the circular growths had the appearance of interconnecting zigzags (twinning) and was ordered in appearance. The fine, almost needle-like wedges were very clear, however the larger wedges were opaque from the incomplete layers of crystal growth. In summary, the sucrose crystals grown under these conditions appeared to result in a more ordered crystal but demonstrated a favoured direction of growth. Figure 3 is a diagram from above representing sucrose crystal growth under the conditions of a permanent magnetic field placed above and below the sample. 1.2.2(e) Pulsed magnetic field The pulsed magnet is incorporated into a rectangular plastic device shown in Figure 4. The 5cm Petri-dish was placed on top of the magnetic unit as it was too large to fit in the square hole as normally used. Primary nucleation on several occasions occurred predominantly on the right hands side of the Petri-dish but growth on this side was slow. Secondary nucleation on the left hand side and was followed with increased growth rate. Most of the resulting sucrose crystallisation came from the left hand side from on average 3 or 4 centres of nucleation in large circular wedge fans. These were more ordered in appearance than the "no-field" situation and showed sharper edges. The right hand side had on average 4 or 5 very small, fine circular wedge growths. This result was not always reproducible and so the experiment was repeated several times more. On one occasion there was no nucleation on the right hand side, only large wedged growth from centres of nucleation on the left hand side. Two other experiments showed a selection of smaller circular growth patterns, on average 10, occurring with fine dendritic growth. 1.2.2(f) DC electromagnetic fields The general forms of the sucrose crystals obtained from the DC electromagnetic field studies were altered in the stronger field cases from the "no-field" situation with in general euhydral growth predominating. 1.2.2(f) (i) 100G at edges, 50G at centre of Petri-dish The sucrose crystals under DC electromagnetic field conditions had on average 3 large circular growths that predominated most of the surface of the sucrose solution. These fine wedge growths showed a small amount of dendricity and were very ordered in appearance. There were in addition around 3 or 4 smaller circular growths that were finer but less well ordered with some disorganised areas. Boundaries of the circular growths were interlocking zigzags and were ordered. In summary, the sucrose crystals were fine and more ordered than the "no-field" situation. 1.2.2(f) (ii) 320G at edges, 140G at centre of Petri-dish More large centres of nucleation (on average 5) were observed under these conditions of sucrose crystal growth, with around 3 or 4 smaller circular growths. In general, there is more dendricity, and more irregular patterns within the expected circular growth patterns. Layered growth can be seen very clearly from most of the wedges and crystals are predominantly more needle shaped from the increased dendricity. In summary, nucleation has increased but growth is more irregular than in the weaker field case, although crystals are more ordered than the "no-field" case. 1.2.2 (f) (iii) 500G at edges, 195G at centre of Petri-dish The stronger DC electromagnetic field resulted in more centres of nucleation (on average 6) with 3 or 4 smaller growths, but the main point of note was the shape of the crystals that were obtained. The centres of nucleation were not points as in all previous cases but were rectangular crystals. Growth from these rectangles was rectangular with definite flat edges as shown in Figure 5 and is normally termed euhydral. Crystals were more chunky in appearance and crystallinity appeared improved. The ends of the growth rectangles were square in shape and borders between circular growths were straight indicating no crystal twinning has occurred. In addition, the crystal growth time was slower taking around twice as long to crystallise over the sucrose solution surface/air interface. In summary, the DC magnetic field appears to have altered the sucrose morphology, growth rate and crystallinity. 1.2.2(f) (iv) 600G at edges, 220G at centre of Petri-dish The effects from the last DC electromagnetic field were emphasised under these stronger conditions. Around 10 or 11 centres of nucleation were observed in most cases, with euhydral growth predominant. In addition, the growth rate appeared to be even slower than case (f) (iii) , taking around 3 days to crystallise over the sucrose solution surface. In summary, an increased DC electromagnetic field has reduced, the growth rate, increased the nucleation rate, changed the morphology and increased the crystallinity. Results are summarised in the following Table: TABLE 1.2 1.3.0 Conclusion These preliminary results suggest that static sucrose crystal growth can be affected by external magnetic fields. Magnetic fields appear to have altered crystal characteristics such as growth rate, nucleation rate, morphology and crystallinity. 1.4.0 Further investigations of static crystallisation of sucrose in magnetic fields Differential Scanning Calorimetry (DSC) was carried out using a Perkin Elmer DCS7. Powder X-Ray Diffraction (XRD) was carried out using a Philips PW 1710 diffractometer with Cu K a radiation. Scanning Electron Microscopy (SEM) was carried out using a Cambridge 5250 stereoscan. Karl Fischer titrations (KF) were carried out using an Orion Research Inc. Turbo 2 Titrator. Scanning Electron Microscopy (SEM) was used to look at the smaller structure of sucrose crystals produced as described above at around x50 to x500 magnification. Here also, some very large differences in surface texture could be seen. The control samples ("no-field") showed a very irregular surface texture made up of blobs of sucrose on the surface. These were poorly crystallised lumps and the surface was almost amorphous in texture (see Figure 6) . By comparison, all samples of sucrose that were crystallised in a magnetic field showed a large amount of microcrystalline material (see Figure 7) . These crystals are well formed and angular with very flat surfaces. In addition, the larger crystals had very flat, smooth surfaces with definite angled faces of growth as demonstrated in Figure 8. These surfaces also showed very definite layered crystal growth which appear to the naked eye as opaque (or cloudy) surfaces (see Figure 9) . Polarising Light Microscopy (PLM) at xlO magnification showed similar features on the sucrose crystals. The control ("no-field") samples had lumpy, irregular surfaces shown in Figure 10, while the samples crystallised in magnetic fields showed a large amount of micro-crystalline material present shown in Figures 11 and 12. Flat regular surfaces are shown in Figures 13 and 14 and again layered growth in Figures 15 and 16. Differential Scanning Calorimetry (DSC) gives the melting profile of the sucrose crystals. Normally sucrose crystals are anhydrous (i.e. devoid of water) and melt around 180- 192 °C. A DSC trace for anhydrous sucrose is shown in Figure 17. There are literature reports (referred to above) of the formation of hydrated sucrose but the product has been formed exclusively at -30° to 0°C. In every case of sucrose crystallisation within a magnetic field reported herein, two or three other features appear on DSC with a second melting point around 150°C and in some cases a third melting phase around 170°C in addition to the normal sucrose melting peak at 180-192 °C. These are shown in Figures 18 and 19. Two possible explanations for the presence of additional peaks on DSC could be (1) formation of sucrose hydrates, or (2) a new crystalline sucrose phase. The % moisture content (by weight ratio) of the sucrose crystals was measured using Carl Fischer titrations. Bottled crystalline sucrose had a moisture content of around 0.02%, while the control (i.e. no magnetic field) samples had a moisture content of around 0.06%. The most significant change in moisture content was for a sucrose crystal grown in a permanent magnetic field (field strength of around 380 Gauss) that was a 15 fold increase in water inclusion within the sucrose crystal to give a moisture content of around 1%. There are three possible explanations for the additional water inclusion (1) surface water that is weakly bound to the sucrose crystal surface, (2) "packets" of trapped water (water inclusions) within the uneven packing of the crystal that would again be weakly bound to the sucrose crystal, or (3) water molecules have been incorporated into the sucrose crystal lattice and are very tightly held within the sucrose molecular structure. To eliminate the possibilities of both (1) and (2) , ground sucrose crystals produced according to the invention were dried over phosphorus pentoxide for 40 hours to allow for removal of any weakly bound water. The resulting DSC trace of the dried sucrose crystal showed melting peaks at 150 °C and 180 °C suggesting that removal of the weakly bound water did not alter the melting profile of the sucrose crystal. In order to identify the nature of this water, solid state proton NMR was carried out on the sample. Immediate data collection following crushing of the sample revealed a broad peak indicative of weakly bound water from inclusion water, i.e. sucrose syrup at around 5.5 ppm. A sample ground several days before would be expected to be devoid of water inclusions but showed a sharper peak at around 5.5 ppm. This is indicative of bound water within the sucrose crystal. Therefore, the results of the moisture content investigations provide support for a novel sucrose hydrate production at 50°C. Powder X-ray diffraction (XRD) of sucrose crystals produced according to the invention, revealed a complex diffraction pattern when compared to literature powder XRD data recorded for sucrose hemi-pentahydrate and sucrose hemi-heptahydrate. The diffraction patterns when compared to that of standard sucrose showed many broader peaks that were off-centre, with d-spacings both greater and smaller than the standard sucrose values, and were of greater intensity. The diffraction patterns of the samples were consistent with the presence of a mixture of the two hydrates and anhydrous sucrose. In conclusion therefore, it is most likely that sucrose hydrates have been prepared by the application of magnetic fields around the crystallising samples. 2. Dynamic investigations into sucrose crystallisations using magnetic fields The investigation was set-up to allow the flow of a sucrose solution to pass through a magnetic field up to 8 times. An aliquot of solution was removed after each pass and allowed to crystallise normally under controlled temperature conditions at 50 °C. The general visual differences in the sucrose crystals formed were similar to those observed under static conditions. In summary, DC electromagnetic fields promote euhydral growth (i.e. more rectangular form) and appear to slow crystal growth while increasing the number of centres of growth (i.e. nucleation) with increasing field strength. Permanent magnetic fields appear to reduce the number of centres of growth with increasing field strength and the resulting crystals are more crystalline compared to the control "no-field" situation. Differential Scanning Calorimetry (DSC) measurements show the same melting profile as the static sucrose samples confirming the formation of sucrose hydrates. 3. Preliminary Studies on the Static crystallisation of Lactose Crystallisation of lactose was investigated under static conditions in the presence and absence of magnetic fields. Early observations suggest that the crystal forms are altered by the magnetic fields. The crystals formed under the influence of a magnetic field are white in appearance and have surface texture as compared to the clear, glassy white surface observed in the control ("no-field") crystals. 4. Further Studies on the Crystallisation of Lactose 4.0 Experimental A 20% undersaturated solution of -lactose monohydrate (340. OOg, 0.944 moles) was prepared and stored in an incubator at 50°C. Deionised water was used for preparation of the solution and the solvent bottle was covered to prevent contamination from foreign materials. Care was taken to keep this stock solution away from any magnetic fields. In general, 10 ml of the undersaturated lactose solution was evaporated in Petri dishes without lids at 50 °C in an incubator. At the bottom of the incubator, a tray of silica gel was used to absorb any excess moisture ensuring that crystallisation was not affected by the humidity of the atmosphere in the incubator. The Petri dishes containing lactose solution were subjected to various magnetic fields with differing strengths are described in more detail hereinafter. 4.1 Controlled Environment Studies A stock solution of α-lactose monohydrate was accurately prepared and stored in an incubator at 50 °C. A series of nine experiments were carried out on the solution, each repeated three times. 4.1.1 Control A pipette was used to place lactose solution (10ml) into a Petri dish (5cm diameter) with the lid in place until placed in the incubator. The solution was kept at 50 °C in the incubator until the following day when crystallisation was complete. 4.1.2 Weakest Permanent Field at Sides in Parallel Permanent magnetic fields were placed in a wooden base in parallel. The 5 cm diameter Petri dish containing the lactose solution (10ml) was placed in the centre between the magnets on another empty Petri dish (as a raised platform) . The field strengths were measured being -3OOG at the edges and -265G at the centre. The solution was kept overnight to crystallise. 4.1.3 Medium Permanent Field at Sides in Parallel Permanent magnetic fields were placed in a wooden base in parallel with two more placed on either side on the outside. The 5 cm diameter Petri dish containing the lactose solution (10ml) was placed in the centre between the magnets on another empty Petri dish (as a raised platform) . The field strengths were measured being -64OG at the edges and -54OG at the centre. The solution was kept overnight to crystallise. 4.1.4 Strongest Permanent Field at Sides in Parallel An additional two magnets were placed around those in Experiment 3, making the field strengths -760G at the edge and -63 OG at the centre. The 5 cm diameter Petri dish containing the lactose solution (10ml) was placed in the centre between the magnets on another empty Petri dish (as a raised platform) . The solution was kept overnight to crystallise. The arrangement used in Experiments 2 to 4 is shown diagrammatically in Figure 20. 4.1.5 Permanent Field in Parallel Above and Below The wooden block containing the strongest permanent field set-up was turned on its side and the Petri dish with the lactose solution (10ml) was placed centrally between the parallel magnets on a raised platform. The field strengths were measured at -630G throughout the sample. The solution was then left overnight to crystallise. The arrangement used is shown diagrammatically in Figure 21. 4.1.6 Pulsed Field A hydroflow pulsed magnet was placed on its side with a Petri dish containing lactose solution (10ml) balanced on top. The solution was then left overnight to crystallise. The arrangement used is shown diagrammatically in Figure 22. 4.1.7 strongest DC Electromagnetic Field A DC electromagnet was placed inside the incubator with the connectors and tubing pulled out through the side hole of the incubator. A water flow system was set up to ensure that the DC magnet did not overheat. The field strength of the electromagnet was measured to be 600 to 220 Gauss and the Petri dish containing the lactose solution (10ml) was placed on a raised platform between the two poles of the magnet. The solution was left overnight to crystallise. 4.1.8 Weakest DC Electromagnetic Field The field strength of the electromagnet was measured to be 50 to 100 Gauss and the Petri dish containing the lactose solution (10ml) was placed on a raised platform between the two poles of the magnet. The solution was left overnight to crystallise. 4.1.9 Medium DC Electromagnetic Field The field strength of the electromagnet was measured to be 160 to 420 Gauss and the Petri dish containing the lactose solution (10ml) was placed on a raised platform between the two poles of the magnet. The solution was left overnight to crystallise. The arrangement used in Experiments 7 to 9 is shown diagrammatically in Figure 23. 4.2 Results and Discussion 4.2.0 introduction The purpose of the studies was to investigate the effects of applied fields on the crystallisation of lactose under static conditions with a regulated temperature and humidity environment. A 20% undersaturated solution was used to ensure that crystallisation did not occur too quickly allowing the effect of the applied fields on the lactose solution to be at an optimum level. Five methods were used to investigate the morphology, size and properties of the lactose solutions crystallised under the influence of the applied field these being as follows: 1. Visual observation 2. Differential scanning calorimetry 3. Powder X-ray diffraction 4. Scanning electron microscopy 5. Karl Fischer titrations. The lactose crystals were removed from the Petri dishes and visual observations were made noting any changes in brittleness or firmness and placed in a sintered glass Buchner funnel to dry. The crystals were then stored in sample tubes at room temperature before being subjected to the other four investigations. 4.2.1 Visual Observations Visual observations made with the naked eye are summarised in the following Table Table 4.2.1 2(1) 2(2) 2(3) Quite similar results to those seen in experiment 1, but crystals were slightly more brittle, again white-grey coloured 3(1) 3(2) 3(3) White-yellow coloured, two different layers seen. The bottom layer was crystalline and glassy with tiny "gaps" in the macroscopic structure. The top layer had a rough texture. The phase in between the layers was very crystalline. 4(1) 4(2) 4(3) Observations similar to those seen in experiment 3. 5(1) 5(2) 5(3) Similar to experiments 3 and 4, the crystals were thin and crusty at the edges with an uneven upper surface. Again tiny spaces/gaps were observed, especially on the bottom layer. Crystals were more brittle than those seen in experiment 4 6(1) 6(2) 6(3) Observations were similar to those seen in experiment 5. 7(1) 7(2) 7(3) Similar observations to those seen in experiment 5, however the crystals were more brittle, fine and powdery and very difficult to remove from the Petri dish. 8(1) 8(2) 8(3) Observations were similar to those seen in experiment 7. 9(1) 9(2) 9(3) Observations were similar to those seen in experiment 8. The first notable observation was the colour change. The controls appeared to be glassy-grey whilst the samples crystallised under the influence of an applied field had a more "whiter" appearance. The samples subject to a permanent field, parallel at sides (experiments 2(1) to 4(3)) were visually quite similar to the controls except for the slight colour change and the increase in brittleness. Experiments conducted using a permanent magnet above and below (experiments 5(1) to 5(3)) and a hydroflow pulsed magnet (experiments 6(1) to 6(3)) produced yet more brittle crystals with a rougher texture. The DC electromagnetic field (experiments 7(1) to 9(3)) resulted in a very brittle and powdery crystal. The results suggest that crystallinity of α-lactose monohydrate is improved and that there are more well formed discrete crystals and less amorphous glassy lactose. The improved level of brittleness could possibly be attributed to a more ordered structure which consequently leads to a better cleavage of the crystal in addition to less amorphous glassy lumps within the crystal. 4.2.2 Differential Scanning Calorimetry (DSC) DSC gives a thermal analysis of the lactose crystals by controlled heating resulting in a melting profile. The results are shown in the following Table where melting temperature in °C is stated for each of the three samples for each experiment. Table 4.2.2 5 148.2. 151.8 145.0, 150.6 141.2, 150.4 6 144.9, 218.2 143.0, 150.0 143.4, 219.2 7 143.0, 149.9 142.9, 216.5 143.4, 219.2 8 148.5, 221.2 143.8, 150.8, 198.0 142.2, 149.7 9 143.2, 148.6 141.2, 149.1 142.1, 217.7 Results from the literature show that α-lactose monohydrate has a melting temperature at -143 °C and -147 °C and -209 °C where decomposition occurs simultaneously with melting and 3-lactose has a melting temperature at. ~236°C. Most of the experimental results obtained correspond to the melting temperature of α-lactose whilst a few samples produced a higher melting peak at -219 °C which is indicative of β- lactose. More particularly, most of the experiments showed two melting peaks, one at -142 °C and the other at -152 °C, indicative of α-lactose. Some of the samples subject to medium permanent field (experiment 3(3)), pulsed field (experiments 6(1) and 6(3)) and DC field (experiments 7(2), 7(3), 8(1), 8(2) and 9(3)) showed a higher melting point at ~219°C in addition to a melting point at ~140°C which indicates the presence of β-lactose within the crystal. These observations can be explained by the mutarotation properties of lactose and more particularly the fact that α- lactose monohydrate mutarotates to form β-lactose until an equilibrium is set up where there is a higher concentration of jS-lactose. The sample shows that in some cases -lactose is crystallised with the α-lactose, since the higher melting points of -219 °C are measured. 4.2.3 X-Ray Diffraction (XRD) The characteristic d-spacings of different lactose crystal forms are shown in the following table: Table 4.2.3 Detailed XRD data are not shown but the patterns produced were most likely to be α-lactose monohydrate where the characteristic peaks matched those observed. Characteristic peaks from other lactose structures did not correlate well with observed patterns and this eliminates possibilities that the structure of the crystals found could be of the β- form, α-anhydride or a mixture of both isomers. Accordingly, with reference to standard crystal forms it could be concluded that all samples appeared to be α-lactose monohydrate. However, the results did not correlate exactly with literature values where d-spacing values seemed to be either slightly larger or smaller than expected. For example, for experiment 1(1) a d-spacing of 6.91A rather than 7.08A was obtained and for experiment 1(2) a value of 7.23A (again rather than 7.08A) was seen. Other examples were experiment 3(1) where a value of 5.37A was obtained rather than 5.4lA and experiment 4(2) where 5.5lA was seen rather than the literature value of 5.4lA. It should be noted that these variations were seen only for values around the region of 7.08A and 5.4lA whereas other results seem to correlate well with the literature values. The variation in d-spacing could indicate a change in interplanar spacing due to water incorporation into the lactose crystal although in this case the d-spacing would be expected to be consistently larger in all cases rather than fluctuating around the actual value. The possibility of inaccuracy in the powder XRD equipment cannot be ruled out. 4.2.4 Scanning Electron Microscopy (SEM) The lactose solution crystallised at two different interfaces, these being: • solution/glass where the lactose solution was in contact with the Petri dish • solution/air where the lactose solution was in contact with the air and is generally amorphous. These regions were examined as was a third region: • crystals of solution where the lactose solution crystallised in between the two interfaces. Individual SEMs are not shown. 4.2.4.1 Solution/Glass Interface In all cases where crystallisation had occurred in a magnetic field the solution/glass interface had less amorphous material and was more defined and angular compared to the controls. Experiment 1 consisted of flaky layers of chunky crystals where the surface appeared to be quite textured. Experiment 2 showed crystals to be longer, flatter and more crystalline than those seen in experiment 1, growing in the direction of the field lines. The crystals seen in experiment 4 were well defined with angular shapes and had a reduction in the amorphous material surrounding them compared to the controls. Experiment 5 produced "chunky" crystals with large flat surfaces and the growth appeared to be almost layered. More defined, discrete, flat, angular shaped crystals were seen in experiment 7 and in addition more flaky layers and less amorphous material was seen when compared to the controls. Experiments 8 and 9 showed similar results to those seen in experiment 7. 4.2.4.2 Solution/Air Interface The solution/air interface shows more crystalline, fibrous material in all magnetic fields compared to the control which is almost amorphous with crystalline regions. Experiment 1 showed the amorphous material to have some form in the shape of fans. Less amorphous material was seen in experiment 2, indicated by more crystalline regions on the surface. Experiment 6 produced long, fibre-like formation on the surface and compared to the control the samples had definite texture and well formed fibrous crystals. Ordered chunks on the surface pointing in a similar direction on an elongated axis were observed in experiment 7 and the surface was not amorphous like the controls. Experiment 8 showed crystals having long fan like projections and appearing to be fibrous. Non-amorphous but needle-like or fibrous crystals were seen in experiment 9. 4.2.4.3 Crystals of Solution Elongated, plate-like crystals were observed in the solution crystals in all magnetic field samples, particularly with DC fields. Experiment 1 showed crystals having a regular, cuboid shape with flat surfaces and angled corners, coated with r amorphous material. Experiment 2 produced crystals less defined than the controls having rounded corners covered with amorphous material. Well defined and angular shapes with predominating layers were seen in experiment 4 and there also appeared to be less amorphous material than seen in the controls. Experiment 6 showed crystals to be better formed with flatter and more angled surfaces than those seen in the controls. Experiment 7 produced crystals that were longer and more layered with less amorphous material then the controls. Experiments 8 and 9 showed layer formation again with elongated and well formed crystals. Generally a more defined crystal with less amorphous coating was produced when solutions were crystallised under the influence of a magnetic field. In addition very prominent layer formation of elongated crystals was observed in the samples crystallised under applied fields compared to the more random formation of crystals seen in the control experiments. 4.2.5 Karl Fischer Titrations (KF) The expected moisture content of α-lactose monohydrate is 4.9997%. Each sample was titrated three times and the mean wt/wt and standard deviations recorded. Data for individual samples are not shown Experiment 1 (control) showed mean values from 5.34% to 5.42% with a standard deviation of ±0.10%. If the mean wt/wt percentages (considering standard deviation) were within this range then the results for moisture content would not be regarded as significantly different. A general rule of thumb is to extend the limits to two standard deviations. Results from the titrations show that samples crystallised in DC fields have an increase in moisture content of around 7.5 to 11% wt/wt compared to the controls and permanent fields (above and below) show an increase in moisture content of -7% wt/wt. Other samples did not have a significantly higher moisture content. In addition to the measurement of additional water within the lactose molecule, these results confirm the powder XRD results that the α-monohydrate crystal form is obtained in all cases. 4.2.6 Conclusions It is clear that magnetic fields affect the crystallisation of lactose and a summary of all the results is shown in the following Table 4.2.6. Powder XRD and KF titrations show that the crystal form is not altered by applied fields and remains the α-lactose monohydrate. Crystallinity of the lactose crystal increased, i.e. a well formed, more brittle and powdery crystal was produced when the lactose solution was subject to magnetic fields during crystallisation. SEM results showed the formation of layers and different morphology where crystals were seen to be more elongated and regular rather than being uneven blocks as seen in controls. The amorphous content of the crystals was seen to decrease when a magnetic field was applied. Karl Fischer titrations indicate additional water in the lactose crystal when subject to magnetic fields. The water may be strongly bound in the crystal lattice or weakly bound as water inclusions. Powder XRD did not rule out any of these possibilities. Table 4.2.6 KF = Karl Fischer titration (% wt/wt) α-l'ose m'hyd = α-lactose monohydrate 5. Production of Milk Chocolate The following (headed "Old Recipe") is a recipe for milk chocolate based on Jackson in "Industrial Chocolate Manufacture and Use", Blackies, 1988, page 254, Table 13.5 together with a modified recipe (headed "With Sucrose Hydrate") to take account of the use of sucrose hydrate containing 10% water: Percentage Composition Old Recipe With Sucrose Hydrate Cocoa Mass 12 11.4 Milk Powder 14 13.3 Sugar 52.25 49.8 Added Cocoa Butter 21.35 20.3 Lecithin 0.3 0.3 Water in Hydrate 5.0 Calories/g (calculated) 5.5 5.2 The chocolate can be manufactured using conventional methods, for example as set out in the reference mentioned above. The figures for calories/gram are calculated on the basis of fat = 9 cal/g, carbohydrate and protein = 4 cal/g and assuming about 2.5% fibre,

Claims: CLAIMS 1. A process for controlling the crystallisation of a sugar from a solution thereof, characterised in that the crystallisation is carried out under the influence of a magnetic field. 2. A process according to claim 1 wherein the solution is an aqueous solution. 3. A process according to claim 1 or 2 wherein the sugar is sucrose, glucose, fructose, lactose, sorbitol, mannitol or erythritol and mixtures thereof. 4. A process according to claim 1 or 2 wherein the sugar is sucrose. 5. A process for the production of a crystalline sucrose product containing sucrose hydrate which comprises crystallising an aqueous solution of sucrose under the influence of a magnetic field. 6. A process according to any of claims 1 to 5 wherein the magnetic field is applied to the sugar solution prior to crystallisation and/or during crystallisation to influence crystal growth rate, nucleation rate, morphology or crystallinity 7. A process according to any of claims 1 to 5 wherein the magnetic field is applied to the sugar solution prior to crystallisation and/or during crystallisation to influence size and/or shape of the crystals produced. 8. A process according to any of claims 1 to 7 wherein the magnetic field is applied by means of a permanent magnet, an electromagnet or by a radio frequency generated magnetic field. 9. A crystalline sucrose product containing sucrose hydrate obtainable by a process as claimed in any of claims 1 to 8. 10. Use of a crystalline sucrose hydrate product as claimed in claim 9 for the manufacture of a confectionery product. 11. A confectionery product containing a crystalline sucrose product as claimed in claim 9. 12. A confectionery product as claimed in claim 11 which is chocolate. 13. A food product containing generic sugar ingredients obtainable by a process as claimed in any of claims 1 to 8.

Inventors: BECKETT STEPHEN THOMAS, DONALDSON JOHN, GRIMES SUSAN, MILLER MARINA, BECKETT, STEPHEN, THOMAS, DONALDSON, JOHN, GRIMES, SUSAN, MILLER, MARINA
Applicants: BECKETT STEPHEN THOMAS, DONALDSON JOHN, GRIMES SUSAN, MILLER MARINA, NESTLE SA, BECKETT, STEPHEN, THOMAS, DONALDSON, JOHN, GRIMES, SUSAN, MILLER, MARINA, SOCIETE DES PRODUITS NESTLE S.A.
Application year: 1998
Main classification: C13F1
IPC codes: A23G1, A23G3, C13F1