Dried sucrose-containing products from separate feeds

A process for producing solid sugars wherein separate feeds of sucrose solution and of fine sucrose particles are dispersed in a current of heated air, whereby the particles are coated with the solution which is evaporated leaving a solid product containing substantially all the sugar fed to the process.

This invention relates to processes for the production of cane sugar 
(sucrose) and to the products obtained. Such products may or may not 
contain notable proportions of invert sugar, depending on the starting 
material used. 
In the conventional methods of producing sucrose, the virgin syrup, as 
extracted from sugar cane or sugar beets, is first decolorised and 
deionised. The clarified syrup is then evaporated and fractionally 
crystallised in a series of precisely controlled steps, caramelisation 
being reduced as much as possible by the use of vacuum to reduce the 
evaporation temperature. Fractional crystallisation is essential since, 
during processing, inversion of the cane sugar takes place, usually to the 
extent of about 15% by weight of the original sucrose content by the time 
processing is completed. This invert sugar, which is substantially 
uncrystallisable, is discarded together with up to about 20% of 
non-recoverable sucrose and finds its way into commerce as animal feed or 
other low grade sugar products generally referred to as molasses. 
We have found that virgin syrups or syrups containing notable proportions 
of invert sugar may be evaporated to the solid state to give a 
substantially complete recovery of the sugar content in a form suitable 
for human consumption. Throughout the present description and claims such 
products will be referred to as edible sugars in contradistinction to low 
grade sugars fit only for animal feed. 
According to the present invention, separate feeds of sucrose solution and 
of fine sucrose particles are dispersed in a current of heated air so that 
the particles become coated with the solution and water in the latter is 
evaporated to yield a solid product. The recovery of the sucrose is 
substantially 100% and moreover the process brings about substantially no 
inversion of the sucrose. The process may be applied to virgin cane syrups 
or to syrups containing notable proportions of invert sugar, e.g. the 
mother liquors from one of the fractional crystallisation stages of the 
conventional sugar process referred to above. In the former case the 
product consists of microcrystalline sucrose, while in the latter case the 
product consists of microcrystalline sucrose embedded in an amorphous 
matrix formed of a mixture of sucrose and invert sugar. This matrix may 
well correspond with the uncrystallisable product obtained at the end of 
series of fractional crystallisations in the conventional sugar process. 
FIGS. 1, 2 and 3 of the accompanying drawings are photo-micrographs,

These products are agglomerates ranging in size from about 1,000 microns 
(roughly the size of the individual crystals of commercial cane sugar) 
down to about 50 microns. The agglomerates consist of clusters of 
microcrystals of sucrose held together by a matrix consisting of an 
amorphous matrix of invert sugar and sucrose. 
When clarified virgin syrup is used as starting material the product 
consists almost wholly of agglomerates of microcrystalline sucrose. 
The products of the invention are free flowing solids which may be stored 
and utilised in a manner similar to crystallised sucrose of commerce. 
Their free flowing and ready solution properties make them particularly 
useful in the manufacture of chocolate and other confectionery and in the 
production of soft drinks. The agglomerates are readily friable and break 
up quite quickly in any single mixing process. They may therefore be fed 
directly as agglomerates to operations requiring a feed of very finely 
divided sugar. Examination of the products using conventional X-ray 
diffraction techniques indicates that the products have a crystallinity 
ranging from about 45% to about 85%. Useful edible products may be 
obtained from starting materials containing as much as 20% of invert sugar 
based on the total sugar present. The bulk density of the present products 
is markedly different from that of commercial crystallised sucrose. Thus 
while the latter has a bulk density of about 50 to 55 pounds per cubic 
foot, the bulk densities of the present products range from about 30 to 
about 43 pounds per cubic foot. 
It is an important feature of the present process that the solid sugar used 
in the drying operation is of sufficient quantity and in a sufficiently 
fine form to provide sufficient surface to take up all, or substantially 
all, of the droplets syrup as a thin layer on the surfaces of the solid 
component. In addition the solid sugar should be distributed as uniformly 
as possible within the spray drying apparatus. In this way evaporation of 
water from the syrup can be made to take place very rapidly. Sticking 
together by the syrup of a number of solid particles and consequent 
shielding of the syrup from the evaporative action of the heated air is 
reduced to a minimum. In practice it has been found that when using an 
aqueous mixture (syrup) containing 60-70% by weight of cane sugars the 
ratio of 1 to 4 preferably 2 to 3 parts by weight of finely divided solid 
sugar to one part by weight of solid content of syrup gives good results. 
Other concentrations of syrup may be used, for example, solutions which 
contain as much as 80 to 90% by weight sugar. Such solutions have to be 
used hot to prevent premature crystallisation. The preheating of the syrup 
is generally advisable in that it is more economical to preheat the syrup 
than to supply the same amount of heat by way of hot air. Preheating of 
the syrup reduces the viscosity so that finer drops may be formed. 
Once the process has been started the solid particles of sugar may be and 
preferably are provided by recycle of part of the product after a light 
grinding if necessary so as to break up any agglomerates having an 
undesirable size. In the initial starting of the process a commercial 
grade of sucrose may be utilized, or if desired a store of the present 
product obtained by way of a previous operation may be used. If commercial 
sugar is utilized as a starting material, the concentration of the 
commercial sugar is subsequently minimized by operating the unit on 
recycle material. 
The rate of flow and the temperature of the hot air are conditioned by the 
consideration of advancing the solidification (crystallisation) of the 
syrup as far as possible by the time the particles carrying the syrup 
reach the end of their travel in the spray drying chamber. In practice, 
temperatures of the order of 100 to 150.degree. C. for the inlet air have 
given satisfactory results. A better criterion for practical purposes is 
to arrange or adjust the inlet air temperature and its rate of flow 
through the chamber so that air at the outlet has a temperature of the 
order of 55 to 75.degree. C. Using this criterion, discoloration of the 
product is almost entirely absent. However, as seen in the following 
examples, outlet air temperatures ranging from as low as 45.degree. C. to 
as high as 105.degree. C. can be employed with satisfactory results. In 
the earlier stages overheating is prevented by cooling due to evaporation 
of water. 
We prefer to use for the process a centrifugal type spray drying apparatus 
such as shown in FIG. 4 of the accompanying drawings. Referring to FIG. 4, 
the spray dryer 1 is provided with a centrifugal spray disc 2 carried by 
spindle 3 to the cover plate 4 and driven by suitable means not shown 
through pulley 6. Line 7 carries air from a heater 8 into the tower either 
by suction from the delivery end of the tower or by a fan in the heater 
line. Syrup from a container 9 is fed at a measured rate by a metering 
pump 10 to a well formed in the upper surface of the disc 2. Leading 
radially from this well are two or more bore holes which lead to the outer 
edge of disc 2. The bore holes are terminated by fine metal tubes 11 
having an inside diameter of about 2 to 4 mm. A screw conveyor 12 delivers 
recycle sugar at a measured rate to a point just above the level of the 
rotating disc 2 and the air currents created by such rotation serve to 
scatter the powder more or less uniformly through the mist of syrup 
droplets thrown from the disc. A distributor or baffle plate may be fitted 
at the top of the device to cause the powder to fall in a circle and form 
a cylindrical curtain of particles outside the effective orbit of tubes 11 
on disc 2. 
The tower 1 tapers at its lower end and is connected to a trunk 13 leading 
to collecting vessel 14. A side trunk 15 leads to a cyclone separator 16 
which serves to retain the finest particles of product and which also 
serves to provide suction to draw air through the system. 
In operation, we find that the rotational speeds of the disc which give 
orbital speeds at the outer ends of tubes 11 of 8,000 to 11,000 meters per 
minute give very satisfactory results with syrups containing about 70% 
sugar. Slightly higher speeds may be advisable with more viscous syrups, 
for example solutions which contain 80 to 90% by weight sugar. 
Another type of atomizing disc which may be employed which is not shown in 
the drawing possesses an upstanding peripheral flange bored with a series 
of rectangular holes having dimensions of 6 .times. 12 mm. (disc diameter 
150 mm. and number of holes about 30). 
Powdered sugar being fed to the well within the flange is thrown out 
through the radical hole, thus giving a very uniform distribution of 
particles. Syrup is fed through a hollow driving spindle to a cavity 
within the main body of the disc and ejected by centrifugal force through 
bore holes from the periphery to the cavity. Peripheral speeds of the same 
order as those mentioned above are suitable for operation for this type of 
disc. 
Using the apparatus illustrated in the drawing we find that removal of 
water from syrup is substantially complete in a very short time. A few 
seconds residence time in the apparatus appears to be sufficient. 
Crystallisation, on the other hand, is somewhat delayed. Thus, some of the 
material thrown against the sides of the drawing tower adheres to it. 
However, as crystallisation proceeds the material adhering to the side of 
the tower tends to flake off and fall to the bottom of the tower. This 
material represents product in the form of relatively large agglomerates 
which when crystallisation is complete is readily broken up. The remaining 
material flows gently down the tower and when viewed through a sight 
glass, has the appearance of a miniature snow storm. The material settling 
at the bottom is readily removed therefrom in the form of very small 
agglomerates, generally less than one mm. in diameter and the remainder in 
the form of finely divided powder. If crystallisation is not complete when 
the material is withdrawn from the apparatus, crystallisation and 
solidification occurs quickly if the product is left in the open air or if 
subsequently swept by a current of cooling air while spread out in thin 
layers. 
Although the use of centrifugal type spray drying apparatus is preferred, 
nozzle spraying apparatus can also be used. 
As has been previously indicated, the present product is in the form of a 
finely divided powder or clumps of readily disintegrated product. The 
present material possesses considerable advantages when used in the 
manufacture of chocolate both with regard to the quality of the final 
product and as to the ease of processing particularly in the refining 
step. The relative ease with which the new products may be incorporated or 
assimilated with other materials, particularly cocoa or chocolate liquor 
is in no doubt attributable in part to the fine particle size as well as 
the free flowing properties, high rate of dispersion, the porosity, the 
low bulk density of the agglomerates and the fact that the new products 
exhibit little or no tendency to cake. 
The novel solubility characteristics of the present sugar products can be 
readily appreciated by placing a small amount of the powder on the tip of 
the tongue. Solution is so rapid as to give the impression of a slight 
sharpness whereas in fact the sweeting properties are substantially the 
same as conventional sucrose. These same properties also facilitate the 
incorporation of the sugar with food products other than chocolate. 
The present process may be applied to the production of particulate sugars 
from a wide variety of raw materials. For example, edible molasses, raw 
sugar syrups and total beet or can syrups. It is also contemplated that 
solutions of sugars obtained in conventional sugar refining operations 
after the second, third or final crystallisation, i.e. strike syrups, may 
be utilized in our process. In all cases where a pure white product is 
desired, raw materials should where necessary be given a decolorization 
treatment such as with activated carbon and deionization. Also, the 
initial materials may be subjected to an evaporation or dilution step to 
provide a concentration suitable for process in the equipment available. 
Generally, it is found that the initial starting syrups will contain from 
about 1 to 20 percent invert based on the total sugar content present in 
the syrup. 
Unlike conventional processes for sugar manufacture, the present process 
does not give rise to any substantial inversion of the sucrose initially 
present in the syrup. Thus, when starting with a raw material containing a 
given concentration of invert sugar no subsequent increase invert content 
is noted due to the presently intended processing methods. It is noted 
that the present novel process provides a method for recovering 
substantially all the sugars present in a given raw material. This is in 
contrast to conventional sucrose processing procedure which employs a 
series of concentration of crystallisation steps which recovers only about 
70 to 80 percent of the sucrose originally present as a particulate dry 
salable commodity. In typical prior art operations from 20 to 30 percent 
of the sugars present in the initial cane extract is disposed of as low 
grade priced products unsuitable for human consumption. 
The following examples illustrate the invention: 
EXAMPLE I 
A series of runs were conducted wherein various sugar syrups were subjected 
to the process. The apparatus utilized comprised a spray drying device 
such as that set forth in FIG. 4 of the drawing. In all, 11 runs were 
conducted, the operating details of which are summarized in Table I below. 
In Run 1 the liquid component added comprised water with no added sucrose 
or invert. Run 2 utilized a syrup which contained only sucrose. Runs 3-7 
utilized a syrup which contained sucrose along with a varying amount of 
invert. In Runs 1-5 sucrose was utilized as the initial particulate solid 
introduced into the spray drying apparatus. 
In Runs 8, 9, 10 and 11 various natural sugar solutions such as raw sugar 
dissolved, refined cane syrup and virgin cane syrup were utilized. In Runs 
7, 8, 9, 10 and 11 the initial recycle material used to start the run was 
derived from previous runs. In all runs a recycle ratio of about three 
parts by weight of particulate solid per one part by weight solids present 
in the syrup solution was utilized. In order to check the progress of the 
spray drying operations throughout the runs a number of recycles were 
conducted as indicated in the last column of Table I. A recycle comprised 
operating the unit with 100 pounds of dry material at a recycle ratio of 2 
to 1. Subsequently, in the next recycle 100 pounds of dry material 
obtained from the previous cycle was passed through the apparatus. 
TABLE I 
__________________________________________________________________________ 
Feed Air Temperatures, .degree. C. 
Test 
Number 
Syrup 
Invert, volume, 
Inlet 
Outlet time, 
of re- 
Run No. 
.degree. Bx. 
percent 
Initial recycle 
m..sup.3 /hr. 
air air Feed 
Tower 
Product 
hrs. 
cycles 
__________________________________________________________________________ 
1 0 0 Sucrose 2,200 
135 60 20 130 72 0.6 1 
2 68 0 " 2,200 
110 70 55 112 80 5.3 5 
3 70 7.25 
" 2,200 
110 45 75 80 65 5 5 
4 69 14.6 
" 2,200 
110 45 70 80 65 5 5 
5 68 19.2 
" 2,200 
110 45 80 85 85 4.6 4 
6 67 5.6 " 1,500 
185 105 70 85 4.3 4 
7 69 15.1 
4 1,600 
150 90 70 95 70 19 &gt;15 
8 .sup.a 70 
4.0 4 2,100 
120 60 80 100 80 4.2 5 
9 .sup.b 68 
23.1 
4 2,100 
110 55 80 90 80 2 4 
10 .sup.c 68 
0.58 
4 and 6 2,100 
110 55 75 85 75 2 4 
11 .sup.d 70 
3.5 6, 9 and 10 
2,100 
115 60 80 90 75 2.5 5 
__________________________________________________________________________ 
.sup.a Raw sugar. 
.sup.b Refined cane. 
.sup.c High-grade syrup. 
.sup.d Virgin cane. 
EXAMPLE II 
In order to determine the characteristics of the present novel products 
samples of product obtained from Runs 1-11 were analyzed to determine 
moisture, i.e. percent dry material, invert concentration, and particle 
size distribution as evidenced by sieve analysis. 
Also the percent crystallinity of each product was determined using 
conventional X-ray diffraction techniques wherein a commercial sample of 
crystalline sucrose was utilized as a standard to represent 100% 
crystallinity. The results of these analyses are set forth in Table II. 
TABLE II 
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Percent Sleve analysis, microns, 
Percent 
Product of 
Dry crystal- 
Run No. 
substance 
Invert 
&gt;1,000 
&gt;500 
&gt;250 
&gt;150 
&gt;75 &gt;75 linity 
__________________________________________________________________________ 
1 99.95 &lt;1 85 
2 99.5 &lt;1 85 
3 99.3 6.5 60 
4 99.1 10.6 55 
5 99.1 14.3 70 
6 99.2 3.3 2.6 1.6 6.2 
42.2 
40.0 
7.8 60 
7 99.1 11.5 
2.8 13.4 
56.8 
24.0 
2.8 
0 60 
8 99.2 7.1 0.2 2.0 11.6 
34.6 
44.0 
8.4 85 
9 99.3 16.2 
5.9 11.8 
36.8 
35.2 
11.0 
0.2 70 
10 99.1 5.2 1.8 3.6 15.8 
37.4 
40.0 
1.8 60 
11 98.9 5.7 4.2 2.2 5.8 
24.8 
62.2 
1.6 55 
__________________________________________________________________________ 
EXAMPLE III 
To illustrate the utility of the present invert-sucrose sugar product in 
the manufacture of sweetened chocolate, the sugar products obtained by way 
of Runs 9 and 10 were compared with conventional crystalline sucrose in 
the preparation of conventional coating-chocolate compositions. 
A series of three compositions were prepared each of which contained the 
following ingredients: 
______________________________________ 
Component: Percent by weight 
______________________________________ 
Chocolate liquor 39.120 
Sugar 48.840 
Lecithin 0.350 
Ethyl vanillin 0.208 
Salt 0.625 
Van bean base 0.938 
Cocoa butter 11.513 
______________________________________ 
The sugar component in the three samples constituted (A) cane sugar (FIG. 
1), (B) sugar of Run 9 (FIG. 2), and (C) sugar of Run 10 (FIG. 3). To 
prepare the compositions the following procedure was used. 
Sample A--A conventional sucrose was subjected to dry milling to obtain a 
powdered sugar. The sugar was then combined in a conventional mixing 
apparatus with the remaining ingredients. 
Sample B--The sugar of Run 9 was combined without intermediate milling with 
the remaining ingredients. 
Sample C--The sugar of Run 10 was combined with the remaining ingredients 
and mixed. 
To determine the characteristics of the products identified as Samples A, 
B, and C, the finest of the particle sizes in the mixture, viscosity and 
fat content were determined, and are set forth in Table III below. 
TABLE III 
______________________________________ 
Fine Viscosity Fat 
Sample (microns) (cps.) (percent) 
______________________________________ 
A 10 123 34.1 
B 10 124 34.1 
C 10 136 35.8 
______________________________________ 
To determine the suitability of the above compositions as coating for 
candy, caramel centers were coated with the composition using a standard 
technique and the quality thereof judged using conventional standards. The 
procedure involved in coating the centers comprised first melting three 
pounds of the coating composition in a saucepan, and subsequently cooling 
the coating to 80.degree. F. while maintaining agitation. Subsequently, 
the coating composition was heated to a temperature of 89.degree. F. and 
agitated for 30 seconds. The caramel centers were dipped in the coating 
and subsequently placed in a cooling tunnel which was maintained at a 
temperature of 54.degree. F. The initial coatings produced by all three 
samples were found to possess uniform and acceptable characteristics. To 
test the ageing characteristics of the coatings, the coated candy was 
subjected to a cycling test and a controlled temperature chamber. The 
temperature within the chamber was cycled three times for a period of 16 
hours at 67.degree. F., 50% relative humidity, followed by 8 hours at 
85.degree. F. at 50% relative humidity. 
Subsequent to cycling under these conditions, it was found that the 
coatings B and C which contained nonmilled sugar of the present invention, 
possessed quality and appearance similar to that set forth in the control 
sample A. 
The invention, in addition to producing products having new and 
advantageous properties, has substantial economic advantages in that 
substantially the whole of the sugar content of the starting materials is 
recovered in an edible solid form, the processing time is reduced to 
seconds rather than hours with substantial avoidance of caramelisation, 
and the necessity for heavy evaporating and crystallising pans coupled 
with means for applying vacuum conditions is eliminated.