[0001] The present invention relates to a process for the manufacture of a sweetener from
milk-sugar or lactose and a sweetener manufactured according to the process.
[0002] Lactose can be derived from any type of milk product like whole milk, skim milk,
butter milk, whey, cottage cheese whey etc. Of particular interest is to make use
of lactose from whey which is often considered a non-useful rye side product. Lactose
has little sweet taste and for making use of lactose as a sweetener the lactose has
to be transformed or split up into glucose and galactose which are sweeter types of
sugar. It is known that such transforming of lactose is made by hydrolysis with some
acid, some ion exchanger or some enzym. Such a method and other hydrolysing methods
are described for instance in Journal of Dairy Science, Vol. 64, pages 1759-1771,
"Beta-Galactosidase: Review of Recent Research", M. L. Richmond, J. I. Gray and C.
M. Stine.
[0003] The said previously known methods for transforming lactose to glucose and galactose,
however, have been achieved with a relatively low content of dry matter and/or a relatively
low degree of hydrolysis, and the transforming speed during the hydrolysis has been
low. It has not been considered possible to hydrolyse lactose having a dry matter
content of more than about 20-40%, and therefore the degree of hydrolysis or the transforming
speed during hydrolysis has been unprofitably low. Due to the low degree of hydrolysis
in some previously known processes the sugar solution, in addition to glucose and
galactose, also contains some amounts of remaining lactose, which especially during
long storage at low temperature tends to separate as crystals. The low dry matter
content or the low degree of hydrolysis leads to the effect that the methods are disadvantageous
from an economical viewpoint and that the final product may be so diluted or may have
such composition that it must be treated further in order to become practically useful
for different purposes.
[0004] A method for hydrolysing of lactose is also known from the US Patent 4,067,748. According
to this known method the lactose is hydrolysed by means of a strongly acidic cation
exchanger preferably a strongly acidic polystyrene ion exchanger resin. In the patented
method it is stated that the hydrolysing can be made for a dry matter content of 20-40%,
for instance 30%, and that the hydrolysing is made by means of an ion exchanger resin
having a very low cross linking number, preferably a cross linking number of between
0,5 and 5%.
[0005] Even in the said patented method the lactose to be treated has a dry matter content
which is of such low magnetude that the hydrolysed lactose for many purposes is not
directly useful but has to be subjected to further treatments like evaporazation etc.
Further an ion exchanger resin having a very low cross linking degree. Such low cross
linking degree can be used and can be advisable for the indicated low dry matter contents,
but on the contrary it is not practically possible to use such low cross linking degrees
for higher dry matter contents since the osmothic pressure at high dry matter contents
is so high that there is a risk that the ion exchanger resin balls crack and thereby
are destroyed.
[0006] According to the patent the lactose transforming into glucose and galactose also
is made by stirring the lactose solution together with the ion exchange resin what
causes cracking and wear of the ion exchange resin balls. Alternatively it is indicated
that the lactose transformation can be made in that the ion exchange resin is allowed
to successively fall to the bottom of a column in counter current towards a rising
lactose bearing liquid and while the ion exchange resin is recirculated to the top
of the column.
[0007] As mentioned the previously known methods are disadvantageous both in that it is
necessary to keep low dry matter contents of lactose solution and in that has been
considered necessary or advantageous to carry out the hydrolysing by means of an ion
exchange resing having a very low cross linking degree what causes a destroying of
the ion exchange resin in case of high dry matter conetnts, and in that the process
is run while stirring the lactose solution and the ion exchange resin. In total the
known steps lead to long periods for transforming lactose into glucose and galactose.
[0008] It might be expected that the use of an ion exchange resin having a higher cross
linking degree than that mentioned in the above cited publications, or that a lactose
transforming treatment of a lactose solution having rather high dry matter contents
or a treatment of the lactose solution by having same pass through a fixed bed of
an ion exchange mass, should lead to long periods for transforming lactose into glucose
and galactose, or alternatively to a lower degree of hydrolysis for a maintained transforming
period. It has, however, surprisingly proved that this is not the case. According
to the invention, it is on the contrary, possible to treat lactose solutions having
high dry substance contents by using ion exchange masses having a rather high crosslinking
degree, and by providing the lactose transforming in a fixed bed of ion exchange mass,
and in spite thereof the lactose transforming periods are surprisingly short and the
hydrolysing degree is extreemly high.
[0009] The object of the invention is therefore to solve the problem of providing a new
process for the manufacture of a sweetener from lactose, which process allows a practical
and economical manufacture of the intended sweetener.
[0010] The invention also relates to a sweetener manufactured according to the said process.
[0011] A further object of the invention is to provide such a process, in which the dry
matter content in the lactose solution can be kept substantially higher than has so
far been possible, and in which the dry matter content of the final product is correspondingly
higher than previously considered possible without evaporating or further treating
the hydrolysed product.
[0012] A further object of the invention is to provide a process for the manufacture of
sweeteners of lactose, according to which a substantially higher dry matter content
is obtained than has previously been usual, at which a higher degree of hydrolysis
is obtained than has previously been usual and which process can be proceeded so that
the cycle speed is substantially higher than has previously been possible.
[0013] The starting material in the process according to the invention is lactose in a water
solution or permeate having a dry matter content of between 40 and at least 80%. Preferably
lactose solution is given a dry matter content of between 50 and 60 %. If the lactose
is to be dissolved in water the temperature is raised to between 80 and 150°C or preferably
between 90 and 120°C. At high temperatures lactose is dissolved more completely and
as a consequence a higher dry matter content is obtained than at lower temperatures.
The high dry matter content of the lactose solution ts advantageous in that a concentrated
solution is obtained which need not be evaporated and which gives the process a high
capacity. Depending of what starting material is used from which the lactose is otained
the pH-value of the lactose solution may vary, but normally the pH-value is less than
7 and preferably . the pH-value is between 5 and 6.
[0014] If found advisable the lactose solution may be filtered for the purpose of polishing
the solution, but this is not quite necessary. On the contrary the lactose solution
may be further treated for splitting the lactose up to glucose and galactose immediately
after having been dissolved in water.
[0015] This further treatment of the lactose solution is made by an acid heterogeneous catalysis,
in this case a hydrolysis, whereby the lactose solution is treated with a strongly
acidic cation exchanger for instance polystyrene-sulfonic acid or any other ion exchanger
built on a polymere.
[0016] In order to make it possible to keep the dry matter contents of the high magnetude
as mentioned above and at the same time keep the transforming cycle period short in
hydrolysing of lactose into glucose and galactose a cation exchanger for this purpose
preferably should have a moderately low cross linking degree, or for instance a cross
linking degree of 5,5-10% or preferably 5,5-6%. In this connection the strongly acidic
cation exchanger acts as a heterogeneous catalysor in which the hydrogen ions split
the lactose to glucose and galactose. The acid heterogeneous catalysis is proceeding
at a temperature of 80-150°C or preferably 90-120°C. Depending on how long the lactose
solution is kept in contact with the strongly acidic cation exchanger the process
can be proceeded to a hydrolysis degree of between 40% and practically 100%. For commercial
use and for maximum obtainable sweetness and best taste, the hydrolysis is preferably
proceeded to a hydrolysation degree of about 70-90%. At a hydrolysation degree of
less than 70-80%, there is a risk that lactose and/or galactose will crystallize after
long storing time and at low temperatures. If it is required to further increase the
sweetness of the hydrolysed lactose solution, a slight amount of extra lactose may
be added which will strengthen the taste of sweetness of the glucose and the galactose.
When combining the lactose solution with the strongly acidic cation exchanger the
acidity of the lactose solution is successively increased, and the glucose-galactose
product leaving the process may have a pH-value of 1.5-2.5. It may be considered advantageous
that the glucose-galactose solution is kept at a relatively low pH-value since the
microbiological resistance is high at low pH-value.
[0017] By starting with a lactose solution having as high dry matter content as between
40 and at least 80% or preferably 50-60% the capacity of the process becomes high,
and a flow cycle speed of 0.2-2.0 bed volymes per hour is quite possible for a degree
of hydrolysis of more than 80%. Such flow speed is substantially higher than has previously
been possible.
[0018] In spite of the relatively high temperature during the entire process there is only
a little, if any, risk of caramellizing and in the hydrolysed final product there
are very small and neglectable amounts of caramellizing products.
[0019] In order to further improve the taste and remove possible caramellizing substances
of the ready hydrolysed glucose-galactose product, the milk sugar product may be polished
for instance by being filtered through activated carbon. Such a polishing step, however,
is only necessary for certain products in which a clear non-coloured product is required.
[0020] Upon demand the final sugar product may be evaporized, but since the dry matter content
is as high as 45-80% or preferably 50-60% evaporizing is generally not necessary.
The final hydrolysed product normally has a pH-value of 1.5-2.5. For adapting the
sugar product to its intended field of use the pH-value may be raised upon demand.
[0021] The sugar product, manufactured accoding to the process, is well suited for many
different purposes, for instance for use in food stuffs like bakery products of different
kinds, beverages such as beer, lemonades etc., or different types of canned products
for which some sweetener is desired, for cheese products like cheese dip, spreadable
cheeses, cream cheese etc., for sweetening of sweet meats and confiture, for dairy
products like condensed milk, acidified culture type of milk, sour cream, yoghurt
etc., for dry mix powders such as baking mix powder, pancake mix powder, sallad dressings,
sausages, hamburgers, soups etc. or for sweetening of ice-cream. There are numerous
fields of use which further can be envisaged. As mentioned above the product, manufactured
according to the process, has a high content of dry matter, and a high lactose to
glucose-galactose transforming speed, and it is possible to proceed the process, according
to the invention, to a very high degree of hydrolysis for the product.
[0022] It should be noted that it is very well possible to control the degree of hydrolysis
as far as +1 or 2% by varying the bed volymes, i.e. by varying the periods of time
for transforming lactose into glucose and galactose.
[0023] In the following some examples of the process according to the invention will be
described. In all examples an equipment for the treatment of 100 kg lactose solution
has been used, and when only the weight of the final product is mentioned in the following
examples it is consequently pre-supposed that in all cases 100 kg of a lactose solution
was added to the processing equpiment for treatment.
EXAMPLE 1
[0024] 40 kg lactose powder obtained from whey was added to 60 1 water having a temperature
of 80pC. The said temperature was maintained until the greatest part of the lactose
powder was dissolved, whereupon the lactose solution was treated with a strongly acidic
cation exchanger consisting of polystyrene-sulfonic acid having a cross linking degree
of 8%. The hydrolysis was proceeded to a hydrolysing degree of 40%, whereupon the
ready hydrolysed product was withdrawn and analysed. The transforming cycle speed
corresponded to a bed volume of 0.50 per hour. The product had a brown-yellow colour
and a soft caramel taste. After the product had been filtered over activated carbon
the brown-yellow colour had disappeared and practically all caramel taste had disappeared
and the final product was considered to have a moderate sweetness. After storing in
cooled condition at a temperature of less than 10°C the product by time became turbid
in that non-transformed lactose was crystallized and by time dropped to the bottom.
EXAMPLE 2
[0025] 65 kg lactose obtained from whey was dissolved in 35 1 water having a temperature
of 97°C. When all lactose had been dissolved in the water the pH was found to be 5.51.
With kept temperature of 97°C the lactose solution was treated with an ion exchanger
mass, which ion exchanger is a strongly acidic cation exchanger having a cross linking
degree of 5,5%. The hydrolysis was proceeded as far as a hydrolysing degree of 96%.
Immediately after the hydrolysis was finished the pH-value was found to be 1.82. The
treated product had a pure sweet taste without any substantial extraneous flavour.
The colour was slightly yellow. After the product had been polished over activated
carbon the product was clear and completely without any flavour. The transforming
cycle speed according to this example corresponded to 1.0 bed volyme per hour. Depending
on the high degree of hydrolysing no crystallization was observed, not even after
long storing at low temperatures.
EXAMPLE 3
[0026] 80 kg lactose obtained from whey was dissolved in 20 1 water of 140°C temperature
under a pressure of 3.10 bar. The pH-value of the lactose solution was measured to
5.0. With a maintained temperature of 140°C the lactose solution was treated with
a strongly acidic ion exchanger, based on a polystyrene-sulfonic acid having a cross-linking
degree (DVB-degree) of 6%. The'hydrolysis was run to a hydrolysing degree of 92%.
The transforming cycle speed corresponded to a bed volume of 1.1 per hour. The ready
product was brownish and had a slight caramel taste. Without being polished the product
was considered well suited for bakery purposes. Some tendency of cracking of the polystyrene
sulfonic acid balls was observed, what is supposed to depend on the high osmotic pressure
obtained at the high dry matter content in this example.
EXAMPLE 4
[0027] 50 kg lactose obtained from whey of cottage cheese was mixed with 50 1 water of 100°C.
The pH-value of the lactose solution was measured to 4.5. With maintained temperature
the lactose solution was treated with a strongly acidic cation exchanger having a
cross linking degree of 10% and the hydrolysis was run to a hydrolysis degree to 95%.
The transforming speed corresponded to a flow cycle speed of 0,7 bed volumes per hour.
The ready product was slightly yellow and had a good sweetness without any flavour.
After the product had been polished over activated carbon a clear non-coloured product
without any noticable flavour had been obtained. The product was considered well suitable
as a sweetener for beverages, i.e. beverages of the brewery inndustry like beer and
lemonades etc. In spite of the relatively high cross linking degree of the cation
exchanger the hydrolysis could be carried out as far as to a hydrolysing degree of
95% with a flow cycle speed of 0.7 bed volymes corresponding to a period for transforming
lactose into glucose and galactose of less than 1.5 hours.
EXAMPLE 5
[0028] 71 kg lactose powder obtained from whey was dissolved in 29 1 water and was mixed
at a temperature of 119°C and at a pressure of 1.9 bar. The pH-value of the lactose
solution was measured to be 1.8. With a maintained temperature, the lactose solution
was treated with a strongly acidic cation exchanger having a cross- linking degree
of 5.5%. The hydrolysis was run to a hydrolysis degree of 93%. The transforming speed
corresponded to flow cycle speed of 1.9 bed volumes per hour. The ready product was
slightly yellowish and had a pure sweet taste without any noticable flavour.
[0029] In spite of the high dry matter content, the high hydrolysing degree and the relatively
low cross linking degree of the cation exchanger the hydrolysis could be carried out
with a flow cycle speed of 1.9 bed volyme per hour corresponding to a period for transforming
lactose into glucose and galactose of not more than about half an hour. No substantial
crack formation or any other damage of the ion exchange resin could be noticed.
EXAMPLE 6
[0030] 60 kg lactose powder from whey was dissolved in 40 1 water of 100°C temperature.
The lactose mixture was treated with a strongly acidic cation exchanger which was
a mixture of 50% of a strongly acidic cation exchanger having a cross linking degree
of 5.5% and the remaining a cation exchanger having a cross linking degree of 8%.
The hydrolysis was run to a hydrolysing degree of 98% at a transforming speed cycle
of 1.5 bed volumes per hour. The product thereby manufactured was practically completely
clear and non-coloured and had a strong sweet taste.
EXAMPLE 7
[0031] 50 kg lactose powder was solved in 50 1 water at a temperature of 97°C. The lactose
solution was hydrolysed as far as to 96% by means of a strong acidic cation exchanger
having a cross linking degree of 5.5%. The hydrolysed lactose had a relatively sweet
taste. To the hydrolysed lactose was thereafter added 15% of non-hydrolysed lactose,
and a taste panel considered the sweetness of the product substantially higher than
the sweetness of the hydrolysed lactose without the addition of non-hydrolysed lactose.
[0032] An additional large number of tests have been made for which are made account in
the following tables:

[0033] In the above examples was used a strongly acidic cation exchanger having a low cross-linking
degree. The content of Divinylbenzene in this strongly acidic cation exchanger is
about 5.5%.
[0035] In the above examples was used a strongly acidic cation exchanger in the form of
a mixture of 50% having a cross linking degree of 8% and 50% of another cation exchanger
having a cross linking degree of 5.5% the combined cross linking degree being (DVB
content) 6.75%.
[0036] It should be noted that a strongly acidic cation exchanger having a low cross linking
degree within the above mentioned interval makes the hydrolysis run more easily, so
that a higher flow speed can be maintained without the risk that the hydrolysis degree
decreases. At a hydroli.sing degree of more than 80% the product is so stable that
there is practically no crystallizing, not even at long time of storing.
[0037] Cation exchangers having a low cross linking degree, however, are rather sensitive
to pressure or are brittle, and as mentioned above the osmotic pressure at high dry
matter contents becomes so high that there is a risk that the cation exchanger is
damaged. When using high dry matter contents it is therefore often considered necessary
to use cation exchangers having a higher cross linking degree than the above indicated
cross linking degree interval of 5.5-10% than should have been desired, depending
on operating technical viewpoints.
[0038] In all of the above mentioned examples an apparatus has been used, which is illustrated
in the accompanying figure 1, and the lactose or the permeate respectively have been
treated mainly at the temperatures in relation to the dry matter substance as illustrated
in the accompanying curve, figure 2, in which the dry matter content is plotted along
the vertical axis and the temperature in centigrades have been plotted along the horizontal
axis.
[0039] The apparatus illustrated in figure 1, comprises a closed container 1 having a top
dome 2 and a bottom dome 3 and an intermediate bottom 4 adjacent the bottom dome 3.
On the intermediate bottom 4 and up to about half the height of the container has
been applied a bed 5 of a cation exchanger, and on a level slightly above the upper
surface 6 of the cation exchanger bed there is an inlet 7 for lactose. The inlet 7
is connected to a spreading device having several nozzles (not illustrated) which
spread the lactose evenly over the surface of the ion exchanger bed. At the intermediate
bottom 4 there are several screen type nozzles 9 for letting the hydrolysed lactose
out to a volyme 10 between the intermediate bottom 4 and the bottom dome 3, and the
hydrolysed lactose is withdrawn through an outlet conduit 11. On a level slightly
above the inlet 7 for lactose there is another inlet 12 for introducing regenerating
acid which inlet 12 likewise is formed with a spreading device 13 for evenly distributing
the regenerating acid over the surface of the ion exchanger bed. On a level above
the upper surface 6 of the ion exchanger bed there is a further inlet 14 for pessurized
air or any other gas.
[0040] When hydrolysing the lactose the acid inlet 12 and the air inlet 14 are closed and
the lactose solution is pumped into the container in a predetermined amount per unit
of time, preferably by means of a positive pump. The lactose is spread over the surface
6 of the ion exchanger bed 5 by means of the spreading device 8. The lactose successively
passes through the ion exchanger bed at a certain speed, but if the lactose is pumped
into the container with a higher speed than can pass through the ion exchanger bed
5 a layer 15 of lactose solution appears on top of the surface 6 of the ion exchanger
bed. It is considered advisable to maintain a layer of about 5 centimeters of lactose
solution 15 on top of the surface 6 of the ion exchanger bed, but if the level 16
of the lactose solution tends to rise pressurized air is blown dose by dose into the
pressure chamber 17 above the ion exchanger bed, whereby the lactose solution under
pessure is brought to pass through the ion exchanger bed. The level 16 of the lactose
layer may in automatical way be maintained rather constant dose by dose letting pressurized
air into the pressure chamber 17. The hydrolysed lactose may batchwise or continuously
be withdrawn through the outlet conduit 11 at the bottom of the container. Since the
ion exchanger bed is fixed there is no wear of the ion exchanger balls. The lactose
solution which is pumped into the container through the inlet 7 always meets the strongest
part of the acid at or adjacent the outlet, even if the acid of the ionexchanger resin
is partly consumed, what is advantageous in order to maintain the highest possibly
degree of hydrolysis.
[0041] The acid content of the ion exchanger resin successively is reduced during the hydrolysing
process, and at a certain stage it is necessary to regenerate the ion exchanger resin.
This is made in that the inlet tube 7 for the lactose, the spreading device 8 and
the ion exchanger bed 5 are flushed clean by means of water, whereafter water is pumped
into the ion exchanger bed from underneath through the outlet conduit 11, whereby
the ionexchanger bed is lifted and is loosened. By means of air from the pressurized
air 14 the ion exchanger bed 5 is thereafter forced down to its original level, acid,
for instance hydrochloric acid, of about 5% concentration is pumped into the container
through the acid inlet 12 and the spreading device 13 and is allowed to pass through
the ion exchanger bed 5 from above until the ion exchanger mass is saturated. Excess
of acid is removed by flushing water through the bed, and thereafter the equipment
is ready for once again being taken into use for hydrolysing lactose into glucose
and galactose.
[0042] In figure 2 there is shown a diagram of suitable handling temperatures. Along the
vertical shaft is plotted the dry matter content in percent and along the horizontal
shaft is plotted the solution temperature for lactose or permeate respectively in
water. It is evident that the temperature for completely solving lactose of for instance
40% dry matter content in water is about 92°C and that the temperature becomes higher
corresponding to a higher dry matter content to about 140°C for a dry matter content
of 80%. The above temperatures relate to the lactose curve L. Corresponding temperatures
for permeate P are about 55°C for a permeate having a dry matter content of about
40% and about 100°C for a permeate of 80% dry matter content.
[0043] Arla, ekonomisk förening "Process for the manufacture of a sweetener based on milk
and a sweetener manufactured according to the process"
[0044]
1 container
2 top dome
3 bottom dome
4 intermediate bottom
5 bed of cation exchanger
6 upper surface (of 5)
7 inlet (for lactose)
8 spreading device
9 screen type nozzle
10 volume
11 outlet conduit
12 inlet (for regenerating acid)
13 spreading device
14 inlet (for air or gas)
15 layer (of lactose solution)
16 level (of lactose solution)
1. Process for the manufacture of a sweetener, characterized in that lactose is dissolved
in water having a temperature of 80-150°C or preferably 90-120°C, to a dry matter
content of 40 to at least 80% or preferably 50-60%, or a lactose permeate having the
same dry matter content is heated to the same temperature, whereupon the lactose solution
thereby obtained is hydrolysed by being treated with a strongly acidic cation exchanger
having a cross linking degree of 5.5-10%, whereby the lactose is transformed to glucose
and galactose, and the hydrolysis is run to a hydrolysing degree of 40-100 % or preferably
70-90% for a flow cycle speed of 2.0-0.5 bed volymes per hour corresponding to a period
of time for transforming lactose to glucose and galactose of 0.5-2.0 hours, whereupon
the glucose-galactose product thereby obtained is cooled to a temperature of 10-200°C
and is withdrawn for direct use, for intermediate storing or for further treatment.
2. Process according to claim 1, characterized in that the hydrolysis is proceeded
without change of the temperature at which the lactose is dissolved in water or to
which the lactose permeate is heated.
3. Process according to claim 1 or 2, characterized in that the lactose solution is
polished before the hydrolysis treatment.
4. Process according to any of the preceding claims, characterized in that the lactose
solution in a parallel flow is pressed through a fixed bed of the strongly acidic
cation exchanger.
5. Process according to claim 4, in which the strongly acidic cation exchanger is
polystyrene-sulfonic acid or any other polymere based acid ion exchanger having a
cross linking degree of preferably between 5.5 and 6%.
6. Process according to claim 1, in which the glucose-galactose product obtained by
the hydrolysis is filtered through activated carbon for polishing of the product and
for removing possible caramel taste.
7. Process according to any of the preceding claims, characterized in that the ready
hydrolysed product is subjected to one or more of the following treatments: filtering
through activated carbon, evaporation to any required dry matter content, control
of pH-value according to the product for which the sweetener is intended.
8. Process according to any of the preceding claims, characterized in that the lactose
solution is given a pH-value of 1-7 or peferably 5-6 before the catalysing treatment,
and in that the ready hydrolysed product is kept at a pH-value of 1.5-2.5.
9. Sweetener manufactured following the process according to any of the preceding
claims by hydrolysis of lactose obtained from whey, characterized in that the sweetener
without having been evaporated has a dry matter content of 40 to at least 80% or preferably
50-60%.
10. Sweetener according to claim 9, characterized in that the lactose by hydrolysis
is transformed to glucose and galactose with a hydrolysing degree of 40-100% or preferably
70-90%.
11. Sweetener according to claim 9 or 10, characterized in that it contains an addition
of 1-20% of lactose added after the lactose solution has been hydrolysed.
12. Sweetener according to any of claims 9-11, characterized in that it has a hydrolysing
degree of less than 60% and in that it contains an addition of more than 20% lactose
added after the lactose solution has been hydrolysed.
13. Sweetener according to any of claims 9-10, characterized in that it has a hydrolysing
degree of more than 80%, and in that it has an addition of not more than 20% lactose
added after the lactose solution has been hydrolysed.
14. Sweetener according to claim 9 or 10, characterized in that the sweetener after
the hydrolysing step has a pH-value of 1.5-2.5 or after adjustment a pH-value of 4-7.