Note: Descriptions are shown in the official language in which they were submitted.
20~7~
A PROCESS FOR PRO~UCING YOGURT
[FIELD OF THE INVENTION]
The presen~ invention relates to a process for producing
yogurt. More particularly, the present invention relates to an
improved process for producing yogurt which comprises adding
highly purified whey proteins to the raw material for production
of yogurt or fermented products of said material whereby whey
separation in the final product is effectively prevented and the
final product having good texture and taste is obtained.
[PRIOR ART]
In general, yogurt is paste-like or liquid, and made by
fermenting animal milk or raw material for production of yogurt
containing milk solids equal or more than those of anlmal milk
with lactic acid bacteria and/or yeast. Depending upon the
composition of the product, yogurt can be classified into, for
example:
(1) Natural yogurt consisting only of animal milk
components;
(2) Flavored yogurt with added chocolate, coffee extract,
sugar, flavoring materials, or stabilizers;
(3) Fruit yogurt with fruit.
Yogurt can also be categorized, according to its properties and
manufacturing processes, as, ~or example:
(1~ Solid type yogurt (set yogurt);
(2) Paste-like yogurt (stirred yogurt);
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7 ~
(3) Liquid type yo~urt (drinking yoyur-t).
Ac-tually, in the food industry, b~ cornbining these
compositions, properties, and manufacturing processes, many
kinds of yogurt suiting the preferences largely held almost
wholly in common by various age groups, from children -to adults
to the aged, have been manufactured. However, it is not so
simple or easy to produce delicious yogurt that has an
appropriate solidity and viscosity, a smooth feel to the tongue,
and that melts pleasantly in the mouth. What is more, for
instance, one often sees yogurt in which, prior to the product's
expiration date, the whey separation is observed, thereby its
quality is seriously impaired. Thus, in order to solve these
problems, it has been quite common practice (a) to add milk
components such as skim milk powder, casein, or whey proteins
with low purity; (b) to add thickeners such as sodium algina~e,
gelatin, agar, or gum; or (c) to add milk components and
thickeners. However, it is required in the above method (a)
taht the addition of great amounts of milk components in order
to obtain a sufficient effect, and the addition of such large
amounts of milk components causes -the deterioration of taste in
yogurt, and an increase in manufacturing costs. On the other
hand, although an amount of addition of milk components in the
above methods (b) and ~c) are lower than that of method (a), the
concept as healthy food of the yogurt prepared by the above
methods (b) and (c) is remarkabl~/ lost because of including
additives other than milk components.
In view of the above prior art, the inventors of the
- 2 -
.
present invention have made efforts to ~evelop a new process for
producing yogurt which does no-t cause whey separation and does
not contain in~redients other than milk components. As a
result, the inventors discovered that whey separation ln the
final product was effecti~ely prevented by addition of highly
purified whey protelns to raw material for production of yogurt
or fermented products of said raw material.
[SUMMARY OF THE INVENTION]
Accordingly, it is an aim of the present invention to
provide an improved process for producing yogurt without whey
separation which causes deterioration of quality in yogurt.
It is a further aim of the present invention to provide a
yogurt without injury to the concept of yogurt as a healthy
food.
The present invention relates to an improved process for
producing yogurt which comprises adding highly purified whey
proteins with a purity of at least 90 percent (by weight)
(hereinafter referred to as percent for abbreviation) to the raw
material for production of yogurt or fermented products of said
material in a ratio of at least 0.6% of their total protein
content, whereby whey separation in the final product is
effectively prevented.
[DETAILED DESCRIPTION OF TEIE INVENTION]
The aforementioned highl~l purified whey proteins used in
the present invention can be prepared, for example, by the
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2 ~ 7 ~
following procedure.
The sweet whey or acid whey produced when making cheese or
casein, the whey powder made by processiny them, whe~ protein
concentrates, or any desired mix-tures of these (hereina~ter
these shall all be referred to as "whey"), are contact with a
weakly acidic cation exchanger having a carboxymethyl group, for
example CM-Sephadex C-50 (trademark; sold by Pharmacia Co.~ or a
weakly basic ion exchanger having a diaminoamylethyl group, for
example D~AE-Sephadex A-50 (trademar~; sold by Pharmacia Co.),
and the proteins in the whey are adsorbed with the ion
exchanger. The ion exchanger is then separated and washed with
water to completely remove the unadsorbed whey components.
Then, the ion exchanger is treated with aqueous solution of salt
selected from a group consisting of sodium chloride, potassium
chloride, magnesium chloride, and any desired mixture thereof,
and the adsorbed protein is eluted from the ion exchanger.
The eluate is concentrated with an ultrafiltration device,
and adjusted the salt content to 2 percent or less, thus the
required highly purified whey proteins are obtained. The highly
purified whey proteins can be used in the process for the
present invention as the solution. The powdered form of highly
purified whey proteins prepared by spray drying or freeze drying
in order to prolong shelf life is also used in the present
invention. The highly purified whey proteins have acceptable
taste, and also have excellent gelling, whipping, and
emulsifying properties.
Additionally, in using these highly purified whey proteins
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2 ~ 7 ll
for the present invention, their purity must be at least ~0
percent. In case of their purity is less than 90 percent, the
sufficient effect in the final product cannot be obtained.
In producing yogurt with the process of the presen-t
invention, highly purified whey proteins prepared by according
to the aforementioned procedures are added either to the raw
material for production of yogurt, or to fermented products of
said raw material. When adding highly purified whey pro-teins to
said raw material, powdered form of highly purified whey
proteins are added and dissolved, while solution of highly
purified whey proteins are added and mixed. When adding highly
purified whey proteins to fermented products of said raw
material, powdered form of highly purified whey proteins are
added and mixed af~er dissolving them in water and solution of
highly purified whey proteins are added and mixed with fermented
products of said raw material. The amount of highly purified
whey proteins added must be at least 0.6 percent of the total
amount of proteins in the raw material for production of the
yogurt or fermented products of said raw material, and
preferably from 1.5 to 15.0 percent.
The form of the yogurt to which highly purified whey
proteins are added with the process of the present invention may
be solid, paste-like, or liquid, and the lactic acid bacteria
used for fermentation may be of any kind, as long as they are
used in the manufacture of fermented milk products. There is no
limitation in particular on the species.
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20~6
(Test 1)
First the effec-t of the pur:ity of the whey proteins used
with the present invention was tested.
1) Preparation of sample
The compositon of the whey proteins used is showrl in table
1. Highly purified whey proteins were prepared by the same
method as used in Example 1, while the MILACT~AL 75 (Trade name:
made by the Milei company of Germany), HIPROTAL (made by the
Domo Co. of Holland), and whey powder (made by Morinaga), are
all commercial products. MILACTEAL 75 and HIPROTAL are both
manufactured ~y ultrafiltrating cheese whey to concentrate its
whey proteins, and finally spray drying. The whey powder is
produced by spray drylng cheese whey as is.
The raw material for production of yogurt was prepared
adding powder form of highly purified whey proteins (0.3%),
MILACTEAL 75 (0.36%), HIPROTAL (0.6%), and whey powder (2.25%)
separately to each 1 kilogram of commercial milk (total protein
content: 3%. The ratio of whey protein to the total protein in
the raw material was in all cases, 9%). These mixtures were
pasteurized or 10 minutes at 90~, yogurt starter CH-l (made by
CHR.Hansen Laboratory) was added at rate of 0.01%, and mixed
uniformly. Each lOOml of the mixture was poured into beakers
with 120ml volume, and were covered with aluminum foil, then
fermented for 3 hours at 42~ in an incubator to prepare four
kinds of natural yogurt. To obtain a control sample, natural
yogurt was also prepared by the above same method using same raw
material without adding any additional ingredients.
-- 6 --
~0~ 7~
2) Experimental Method
~ ach yogurt sample was stored for 14 days at 5~ in a
cooling room. Immediately a~ter manufacturiny, on days 4, ~,
10, and 14, to examine the effect of the addition of the whey
proteins, each sample was subjected to organoleptic test on
taste and visual observation of whey separation by 10 panelists
(consisting of 5 men and 5 women).
The taste was rated on the following basis: good, fair, or
poor, and the whey separation was rated on the basis noted on
the margin of Table 2. The table shows evaluations by more than
80% of the panelists.
3) Results
The resul-ts of the test are shown in Table 2. The taste
of the control sample without adding whey proteins was evaluated
as good even after they were stored for 14 days, but immediately
after manufacturing, slight whey separation was observed. Whey
separation of control sample steadily proceeded after 4th day,
and on the 10th day yogurt had no merchandise value. The sample
containing highly purified whey proteins on the other hand,
still had good taste and no whey separation was observed after
being stored for 14 days.
The taste of the sample containing MILACTEAL ?5 slightly
deteriorated after 14 days of storage, whey separation was
markedly observed, and its value as merchandise was lost. The
evaluation of the samples with HIPROTAL and whey powder to
prevent whey separation was no better than that of the control
sample, and the taste of the sample prepared by adding whey
-- 7 --
- 2 ~
proteins with low purity quickly deteriorated.
These results indicate that diferences in both the purity
of the whey proteins al~d their manufacturing procedure result in
slight differences in the content of lactose, or the content and
the type of ash and whey proteins which coe~ist in the products
of these processes, and that i-t is not possible to prevent whey
separation and produce good tasting yogurt even if the ratio of
the whey protein to the total protein content of the raw
material for production of yogurt is coordinated. In the case
of adding 4 kinds of whey proteins to the fermented products the
similar results were obtained. Accordingly, it is essential
that the purity of highly purified whey proteins to be used in
the present invention are at least 90 percent.
Next, the results of a experiment carried out to determine
the optimum proportions of the highly purified whey proteins
added to the raw material for production of yogurt, or fermented
products of said raw material are described.
(Test 2)
The effect of adding highly purified whey proteins to raw
material for production of yogurt were tested.
(1) Preparation of samples
Raw material for production of yogurt was prepared by
adding powdered form of highly purified-whey proteins (purity of
90 percent), obtained by the same method as described below in
Example 1, to lKg each of ordinary marketed milk (total protein
amount of 3.0 percent) in the proportions of 0, 0.02, 0.05, 0.1,
0.2, 0.3, 0.4, and 0.5 percent (the proportions of highly
- a -
purified whey proteins to the total amount of proteins in the
raw material were 0, 0.6, 1.5, 3.0, 6.0, 9.0, 12.0, and 15.0
percent, respectively), the raw materials were pasteurized at
gO~ for 10 minutes, cooled to 42~, and O.O1 percent of the
~ogurt star~er CH-1 (sold b~ CHR.Hansen Laboratory) was added to
each raw material and mixed uniformly. Each 100ml of thus
obtained liquid mixture was poured into beakers with 120ml
volume, were covered with aluminum foil, and fermented for three
hours at 42~ in an incubator, thereby eight kinds of solid type
natural ~ogurt samples were prepared.
(2) Experimental Method
~ ach sample was examined by the same method as used in
Test 1 supra.
(3) Results
The results of this test are shown in Table 3. The taste
of all samples were acceptable after being preserved for 14
days, but the control sample to which highly purified whey
proteins had not been added was already observed slight whey
separation at immediately after manufacturing. Whey separation
of control sample proceeded after the fourth day, and on the
tenth day the yogurt no longer had value as merchandise.
On the other hand,in the case of samples to which the
highly purified whey proteins had been added, when the added
protein proportion was 0.6 percent of the total protein amount
in the raw material, slight whey separation was observed on the
first day, but even after preserving for 14 days, whey
separation was not observed to the extent that the yo~urt would
2 ~
no longer have value as merchandise. A~d if the proportion
added addition was at least 1.5 percent, no whey separation was
observed in all samples even after 14 days of preservation.
(Test 3)
Next, ano-ther experiment on the effect of adding highly
purified whey proteins to fermented products was also carried
out.
~ 1) Preparation of samples
Nine kg of ordinary marketed milk (total protein content
3.0 percent) were pasteurized at 90C for 10 minutes, and cooled
to 42~; 0.01 percent of the yogurt starter CH-1 (made by CHR.
Hansen Laboratory) was added and uniformly mixed. After
fermenting this liquid mixture for 3 hours at 42~ in an
incubator, it was sufficiently stirred and produced a paste-like
natural yogurt. Each lkg of the yogurt was poured in~o beakers
of 1.2 liter capacity. Eighteen percent of aqueous solution
containing highly purified whey proteins (purity of 90~), which
were prepared by the same method as in Example 1, were added to
the yogurt in the ratios of 0, 0.1, 0.25, 0.50, 1.0, 1.5, 2.0,
and 2.5 percent and mixed uniformly (the proportions of highly
purified whey proteins to the total amount of proteins in the
yogurt were 0, 0.6, 1.5, 3.0, 6.0, 9.0, 12.0, and 15.0 percent,
respectively). Each lOOml of the mixture wa5 poured into
beakers with 120ml volume, were covered with alminum foil,
thereby eight kinds of yogurt samples were prepared.
(2) Experimental Method
Each sample was examined by the same method as used in
-- 10 --
2 ~ 7 l~
Test l supra.
(3) Results
The results of -this tes-t are shown in Table 4. The taste
of all samples were acceptable after being preserved for 14
days, but the control sample to which highly purifled whey
proteins had not been added was already observed sligh-t whey
separation at immediately af-ter manufacturing. Whey separation
of control sample proceeded after the fourth day, and on the
seventh day the yogurt no lon~er had value as merchandise. On
the other hand, in the case of samples to which the highly
purified whey proteins had been added, when the added protein
proportion was 0.6 percent of the total protein amount in the
yogurt, slight whey separation was observed on the fourth day,
but even after preserving for 14 days, no whey separation was
observed to the extent that the yogurt would no longer have
value as merchandise. And if the proportion added was at least
1.5 percent, no whey separation was observed even after 14 days
of preservation.
From the results of the foregoing two experiments tTest 2
and Test 3) it was comfirmed that the amount of highly purified
whey proteins added, whether the proteins are added to the raw
material for production of yogurt, or to fermented products of
the raw material, should be at least 0.6 percent of the total
protein content, and that 1.5 to 15.0 percent was preferable.
[EFFECTS OF THE INVENTION]
The effects of the present invention are as follows.
7 ~
(1) Whey sep.lration ln the fermented products can be
effectively preventecl by using highly purif-ied whey proteins.
(2) The ~ogurt having good -texture, acceptable taste, and
no whey separat.ion can be prepared without injury to the concept
of yogurt as a healthy food.
(3) The value of whey proteins which were by-products of
dairy plant in the past, can be remarkably enhanced.
The present invention will be illustrated b-y the following
examples, but it is to be understood that the present invention
not limi-ted to these examples.
EXAMPLE 1
Preparation of Highly Purified Whey Proteins Powder
The pH of 16kg of acid whey (pH 4.6) was adjusted to 4.0
with diluted hydrochloric acid. Separately, 30g of the weakly
acidic cation exchanger (CM-Sephadex C-50 (trade name; sold by
Pharmacia Co.)) was swollen in warm water. To adsorbe whey
protein with the ion exchanger, these were mixed and kept by
stirring for 2 hours. The ion exchanger was then separated by
using a container with a strainer of stainless steel. The ion
exchanger was washed with water to remove unadsorbed whey
components, and packed into a column. About 1500ml of a 5%
sodium chloride solution was passed through the column at a
velocity of 2L/hrs. to elute the components which had been
adsorbed with the ion exchanger. About 1500ml of eluate were
obtained. The eluate was then ultrafiltrated by a filtration
device (sold by Danish Sugar Corporation) equipped with an
ultrafiltration membrane having a molecular weight cut-off of
- 12 -
20,000 at a circula-ting flow rate of aL/min. and an average
pressure of 3k~/cm2. Water was then added to obtained permeate,
and the sodium chloride frac-tion was removed by diafiltration,
thereby approximately 2400ml of aqueous solution containing 18%
whey proteins were obtained. The a~ueous solution was freeze
dried, thus about 40g of powder containing 90% whey proteins was
obtained.
EXAMPLE 2
Producing Flavored Yogurt
One hundred kg of skim milk (3.3% total protein), 8kg of
sugar, 20g of vanilla flavoring, and 0.1kg of the highly
purified whey proteins powder (purity of 90 percent) obtained by
the same method as in Example 1 were put into a 150 liter
fermenter and dissolved uniformly (the proportion of highly
purified whey proteins to the total protein in the mixture was
2.7 percent). After pasteurizing for 10 minutes at 80~, the
mixture was cooled to 42~, and then 0.01 percent yogurt starter
CH-1 (sold by CHR.Hansen Laboratory) was added, and sufficiently
mixed. The mixture was poured into 100ml yogurt cups in 90ml
amounts, and fermented for three hours at 42~ in a incubation
chamber to prepare solid type flavored yogurt. After
fermentation was complete, the yogurt was stored at 5~ in a
cooling room. Even after 14 days, the taste and texture of the
yogurt were acceptable, and no whey separation was observed.
EXAMPLE 3
Producing Natural Yogurt
One hundred kg of skim milk (3.3% total protein) and 0.3kg
~ 13 -
2 ~ 7 ~
of the highly purified whey proteins powder ~purity of 90
percent) obtained by the same method as in ~xample 1 were put
into a 150 liter fermerlter and dissolved uniformly (the
propor-tion of highly purified whey proteins to the total protein
in the mixture was 8.2 percent). After pasteurizing for 10
minu-tes at 80C, the mixture was cooled to 42~, and then o.O1
percent yogurt starter CH-1 (sold by CHR. Hansen Laboratory) was
added, and the mixture was fermented for three hours. After
fermentation was complete, the fermented product was
sufficiently stirred while being cooled to 20C, and poured into
lOOml yogurt cups in 90ml amounts. In this way, paste like
natural yogurt was prepared and stored at 5~C in cooling room.
Even after 14 days, the taste and texture of the yogurt were
acceptable, and no whey separation was observed.
EXAMPLE 4
Producing Fruit Yogurt
One hundred kg of skim milk (3.3% total protein) and 3kg
of sugar were put into a 150 liter fermenter and dissolved
uniformly. After pasteurizing at 80C for 10 minutes, the
mixture was cooled to 42~C, 0.01% yogurt starter CH-1 (sold by
CHR. Hansen Laboratory~ was added, and the mixture was fermented
for three hours. After fermentation was complete,
2kg of an aqueous solution containing 18 percent highly purified
whey proteins obtained by the same method as in Example 1, and 5
kg of strawberry conserves were added, and cooled to 20C while
mixing these in uniformly. The mixture was then poured into
lOOml yogurt cups in 90ml amounts. In this way, paste-like
- 14
1 7 l~
fruit yogurt (the proportion of highly purified whey proteins to
the total protein in the yoyurt was 10.9 percent) was prepared
and stored at 5~ in a cooling roorn. Even after 14 days, the
taste and texture of ~he yogur-t were acceptable, and no whey
separation was observed.
EXAMPL~ 5
Preparation of Highly Pu_ified Whey Proteins
The procedure of Example 1 was repeated except tha-t weakly
basic ion exchanger (DEAE-Sephadex A-50 (trade mark; sold by
Pharmacia Co.)) was used, and 40g of highly purified whey
proteins obtained in powdered form were dissolved in 3000ml of
water. Then the procedure of Example 1 was repeated in twice.
Thus about 30g of powder containing 92 percent of whey proteins
was obtained.
EXAMPLE 6
Preparation of Natural Yogurt
The procedure of Example 3 was repeated except that highly
purified whey proteins prepared by the same procedure as used in
Example 5 were used. Even after 14 days, the taste and texture
of the obtained yogurt were acceptable, and no whey separation
was observed.
Having now described the invention, it will be apparent to
one of ordinary skill in the art that may changes had
modifications can be made thereto without departing from -the
spirit or scope of the invention as set forth herein.
- 15 -
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-- 19 --
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