Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Low Calorie, Low Fat Fruit-Containing
Yogurt Product and Method for Making Same
TECIINICAL FIELD
-
The present invention relates generally to a method
for making a fruit-containing yogurt product having the
appearance, texture and taste of conventional custard-
type fruit-containing yogurt and the product thereof;
more specifically the invention relates to a method for
making a fruit-containing yogurt product having a fat
and calorie content significantly below that of conven-
tional fruit-containing yogurt.
BACKGROUND ART
In recent years cultured milk products, referred to
as yogurt, have enjoyed immense popularity. The bene-
ficial effects on health due to the therapeutic proper-
ties of the bacterial cultures contained in yogurt are
well known. In addition, yogurt has become a popular
food among dieters. To increase its appeal, the sharp,
tangy taste charac-teristic of plain, unflavored yogurt,
which heretofore made yogurt unacceptable to many
people, has been masked in many yogurt products with
fruit and sweeteners. This practice has resulted in a
flavored yogurt product that is more palatable to a
wider segment of the population. However, the use of
these additives has been accompanied by an increase in
product calorie content from about 90 calories per eight
ounce (224 grams) serving of plain, unflavored yogurt to
about 250 to 270 calories per eight ounce (224 grams~
serving of the sweetened, fruit-containing yogurt. Such
a high
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calorie content renders the fruited product generally
unsuitable for inclusion in reducing diets since the
fruit yogurt uses up the majority of the calories
usually alloted to a single meal. As a result the
5 dieter has~difficulty choosing a sufficient variety or
quantity of foods to form a balanced meal within the
remaining calories allowed. Accordingly, a need has
developed for a fruit-containing yogurt product which
is low in calories, fat and carbohydrate content.
1~ Prior methods for producing sweetened or flavored
yogurt have succeeded in obtaining a product with a
relatively low butterfat content, for example, as low
as the 0.5% butterfat content of ordinary skim milk,
but none seem to have been able to produce a really low
15 fat, less than about 0.5%, yogurt product having the
characteristic creamy custard-type yogurt consistency
while at the same time overcoming the high calorie and
high carbohydrate problems accompanying the use of
fruited or flavored yogurt. One reason for this is
20 that yogurt previously made from really low fat milk
products, less than about 0.5% butterfat, has been
loose and watery and lacking in flavor rather than
creamy and custard-like with consumer acceptable
flavor, appearance and mouth feel. Efforts to overcome
25 this problem to obtain a palatable product have either
required adding flavor influencing milk solids, which
increases the yogurt calorie content, or increasing the
milk fat content, which has a similar effect~
Exemplary of prior methods for producing flavored
30 yogurt is U.S. Patent No. 3,969,534 to Pavey et al
which teaches the production of a fruited, flavored
yogurt which has a relatively low, about 0.5%,
butterfat content. However, the product produced by
the Pavey method does not appear to be low in
_3_ ~ 2 5 B ~o ~
carbohydrates or significantly lower in calories than
conventional flavored yogurt. In U.S. Patent No.
3,025,165, Metzger discloses a process for producing
yogurt which uses relatively low butterfat starting
materials, such as skim milk, to which is added about
1.5% to 6.4~ of an unsaturated vegetable oil. As a
result, a higher than desirable fat content for a
reducing diet is obtained without significantly reducing
the number of calories. Likewise, the fruited yogurt
product produced by the process disclosed in U.S. Patent
No. 3,269,842 to Mayer et al has a fat content of about
4% and appears to be a high calorie, high carbohydrate
product. Donay et al in U.S. Patent No.3,128,190,
discloses the use of a skim milk starting material.
However, the process for making Donay's fruit-containing
yogurt requires fruit which is precooked with sucrose to
prevent fermentation thereof by the yogurt cultures with
resultant unpleasant flavors. As a result of this pro-
cedure the Donay et al method neither produces really
low fat yogurt nor reduces the high calorie and carbo-
hydrate content of fruit-containing yogurt. In U.S.
Patent No. 4,110,476, Rhodes discloses a process for
preparing liquid, rather than custard-type, yogurt
products which utilize whey protein concentrate together
with milk products as the starting material ingredients
and contain higher sugar contents than are desirable for
a fruit-containing yogurt product suitable for a reducing
diet.
As disclosed in the prior art e.g., U.S. Patents
3,969,534, 4,096,287 and 4,110,476 (supra) conventional
nonfat milk solids can be used in the manufacture of
yogurt products.
In the manufacture of yogurt products, however, the
use of conventional nonfat milk solids has not resulted
in the preparation of satisfactory low calorie yogurt
products having acceptable texture and mouth feel. It
has been found that it is only when,conventional nonfat
milk solids are used in conjunction with the uniquely
proportioned blend of three lactic acid producing bac-
terial cultures of the present
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invention, as is more fulLy described hereinafter, that
they con-tribute to -the production of low fat and low
calorie yogur-t product having a consumer acceptable
consistency, texture and mouth feel with a calorie content
significantly below that of known custard-type
yogurt products.
Disclosure of the Invention
In one form of the present invention there is
provided a fruit-containing yogurt product which
resembles conventional yogurt in appearance, texture and
taste, but which has a fat and calorie content signifi-
cantly below that of known custard-type yogurt products.
In yet another form of the present inven-tion there
is provided a nutritious, palatable, fruit-containing
yogurt product which has the creamy mouth feel and the
sweetr fruity, slightly tangy taste of conven-tional
custard-type yogurt but which has a fat content below
about 0.2~ by weight of the final product.
Another form of the present inven-tion provides a
method for making a very low fat and low calorie fruit-
containing, custard-type yogurt product.
In accordance with one embodiment of -the present
invention there is provided a method for making a less
than about 0.2% by weight fat and low calorie yogurt
product containing fruit in an amount up to about 20% by
weight of the yogurt product and 17 to 20~ by weight
total solids, the method comprising -the steps of: (a)
admixing pasteurized skim milk having a fat content of
less than about 0.2% by weight, stabilizers and an amount
of non-heat modified nonfat dry milk solids effective to
improve te~ture and flavor, the nonfat dry milk solids
having been subjected to no heat treating other than
pasteurization heat treating prior to spray drying; ~b)
heating the mix-ture to a temperature in the range from
about 1900 to 1950F (87.7 to 90.60C) for a time
1~25~34~0
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sufficient to form a uniform, substantially homogeneous
mixture and to effect pasteurization; (c) homogenizing the
pas-teurized mixture at pressure in the range 500 to 5000
psig (35.15 to 351.5 kg/cm2); (d) cooling the homogenized
mixture to a temperature of about 90 to 1200F (32.2 to
48.90C); (e) inoculating the cooled homogenized mixture
! with a lactic acid producing bacterial yogurt culture
mixture consisting essentially of, by weight, 30-50%
Lactobacillus acidophilus, balance Lactobacillus
bulgaricu_ and Streptococcus thermophilus in approximately
equal proportions; (f) maintaining the inoculated mixture
at a -temperature oE about 90 to 1200F (32.3 to 48.90C) for
a time sufficient to produce a pH in the range of about
3.8 to 4.8 and to form an acceptable taste and texture in
the inoculated mixture; (g) cooling the inoculated
mixture; (h) forming the cooled inoculated mixture into a
smooth textured product, (i) blending the smooth textured
product with low calorie frui-t preserves; and (j) cooling
the blend of fruit preserves and smooth textured product
to a temperature sufficiently low to stop farmentation.
In accordance with another embodiment of the present
invention there is provided a method for making a less
than about 0.2% by weight fat and low calorie yogur-t
product containing fruit in an amount up to about 20% by
weigh-t of the yogurt product and 17 to 20% by weight total
solids, the method comprising the steps of: (a) admixing
pasteurized skim milk having a fat content of less than
about 0.2% by weight, stabilizers and an amount of non-
heat modified nonfat dry milk solids effective to improve
texture and flavor, the nonfat dry milk solids having been
subjected to no heat treating other than pasteurization
hea-t treating prior to spray drying; (b) heating the
mixture to a temperature in the range from about 190 to
1950F (87.7 to 90.60C) for a time sufficient to form a
uniform, substantially homogeneous mix-ture and to effect
pas-teurization; (c) homogenizing the pasteurized mixture
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- 4b -
at pressures in the range 500 to 5000 psig (35.15 to 351.5
kg/cm2); (d) cooling the homogenized mixture to a temper-
ature of about 90 to 1200F (32.2 to 48.90C): (e)
inoculating the cooled homogenized mixture with a laetie
acid producing bacterial yogurt culture mixture consisting
essentially of, by weight, 30-50% Laetobaeillus
aeidophilus, balanee Laetobaeillus bulgarieus and
Streptocoeeus thermophilus in approximately equal
proportions; (f) adding the inoeulated mixture into
individual yogurt eontainers eontaining low ealorie ruit
preserves; (g) maintaining the fruit preserves and inoe-
ulated mixture at a temperature of about 90 to 1200F (32.2
to ~8.90C) for a time suffieient to produee a pH in the
! range of about 3.8 to 4.8 to form an aceeptable taste and
texture in inoeulated mixture, and (h) eooling the fruit
preserves and inoculated mixture to a temperature
sufficiently low to stop fermentation.
In accordance with a further embodiment of the
present invention there is provided a low calorie, low fat
and fruit-containing yogurt product, characterized in that
the yogurt produet has fruit and yogurt to resemble
eonventional fruited yogurt in appearanee, texture and
taste, and by having a fat content less than about 0.2% by
weight of the produet; a fruit eontent of up to about 20%
by weight of the produet; and a calorie content of about
150 calories per eight ounce serving.
In accordanee with a further embodiment of the
present invention there is provided a method ~or making a
less than about 0.2% by weight fat and low calorie yogurt
produet, ineluding the steps of admixing low fa-t eontent
pasteurized milk, stabilizers and non-heat modified
nonfat dry milk solids, heating the mixture to a
temperature in the range from about 190 to 1950F (87.7 to
90.60C), homogenizing the mixture at pressures in the
range 500 to 5000 psig (35.15 to 351.5 kg/em2), cooling
the homogenized mixture to a temperature of about 90 to
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- 4c ~
120OF (32.2 to 48.9OC), inoculating the cooled homogenized
mixture with a lactic acid producing bacterial yogurt
culture mixture, maintaining the inoculated mixture at a
temperature of about 90 to 120OF (32.2 to 48.9OC) for a
time sufficient to produce a pH in the range of about 3.8
to 4.8 and to form an acceptable taste and texture in the
inoculated mixture, the improvement comprising the lactic
acid producing bacterial yogurt culture mixture consisting
essentially of, by weight, 30-50~ Lactobacillus
!10 acidophilus, balance Lactobacillus bulgaricus and
Streptococcus thermophilus in approximately equal
proportions.
In accordance with still a further embodiment of the
present invention there is provided a method for making a
less than about 0.2~ by weight fat and low calorie yogurt
product containing fruit in an amount up -to about 20~ by
weight of the yogurt product and 17 to 20% by weight
total solids, including the steps of admixing low fat
content pasteurized milk, stabilizers and non-heat
modified nonfat dry milk solids, heating the mixture to a
temperature in the range from about 190 to 195OF (87.7 to
90.6OC), homogenizing the mixture at pressures in the
range 500 to 5000 psig (35.15 to 351.5 kg/cm2) cooling
the homogenized mixture to a temperature of about 90 to
120OF (32.2 to 48.9OC), inoculating the cooled
homogenized mixture with a lactic acid producing
bacterial yogurt culture mixture, maintaining the inocu-
lated mixture at a temperature of about 90 to 120OF (32.2
to 48.9OC) for a time sufficient to produce a pH in the
range of about 3.8 to 4.8 and to form an acceptable taste
and texture in the inoculated mixture and combining the
inoculated mixture with low calorie fruit preserves
either before or after the maintaining step, the
improvement comprising the lactic acid producing
bacterial yogurt culture mixture consisting essentially
of, by weight, 30-50~ Lactobacillus acidophilus, balance
~s~o~
- 4d -
Lactobacillus bulgaricus and Streptococcus thermophilus in
approximately equal proportions.
In accordance with one embodiment of the method of
the presen-t invention a process for making a low fat, low
calorie, fruit-containing yogurt product resembling
conventional fruit-containing yogur-t in appearance,
texture and taste which includes the steps of admixing
pasteurized s~im milk having a fat content of less than
about 0.2%, preferably less than about 0.1%, with
suitable stabilizers and an amount of nonfat dry milk
solids effective to improve texture and flavour; adding
optional vitamin and mineral fortification, sweeteners,
flavorants and/or colorants; heating the resulting mixture
with constant agitation to about 190 to 195OF (87.7 to
90.6OC) for a time sufficient to form a
uniform, substan-tially homogeneous mixture and to effect
pasteuriza-tion, generally for about 20 to 60 minutes;
adding optional heat liable vitamins, such as Vitamin C;
and homogenizing the mixture under conventional elevated
pressure conditions at 500 to 5000 psig (35.15 to 351.5
kg/cm2), desirably 1000 to 2000 psig (70.30 to 140.06
40~
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kg/cm2) and preferably at 1200 to 1500 psig (84.36 to
105.45 kg/cm2). The homogenized mixture is cooled to
about 90 to 120F (32.2 to 48.9C), preferably 110F
(43.3C), and inoculated with a uniquely proportioned
blend of standard yogurt cultures.
If it is desired to produce a Swiss style yogurt
which has pieces of fruit homogeneously mixed throughout
and a predominantly fruity flavor, the inoculated
mixture is maintained at this temperature until the
desired taste and custard body are achieved, which is
usually at a pH of about 3.8 to 4.8, preferably 4.5 to
4.7. The yogurt is then cooled to about 50 to 75F (10
to 23.9C), preferably 65 to 70F (18.3 to 21.1C), and
pumped through a small orifice, such as a screw or
pressure valve, to break up small pieces of coagulant
which are present and to produce a smooth, continuous
mass, all as is well known in the art. Low calorie,
preferably low carbohydrate fruit preserves are
thoroughly blended into the custard, and the resulting
product is packaged in suitable individual containers
and refrigerated at temperatures sufficiently low to
stop fermentation, generally 35 to 50F (1.6 to 10C).
The resulting low calorie and low fat product, which
resembles conventional Swiss type yogurt with its
smooth, creamy texture and slightly tangy fruity flavor,
contains pieces of fruit suspended throughout.
If it is desired to produce Western style yogurt in
which a deep layer of plain or unflavored yogurt custard
covers a shallow layer of fruit preserves, the inoculated
3L~S~O~
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milk-stabilizer-milk solids-vitamin flavorant mixture is
pumped into individual containers, such as
conventional 8 ounce (224 gram) yogurt containers to
which has already been added low calorie fruit preserves,
preferably in an amount of about 1.0 ounce (28 grams).
The containers are then maintained at about 90 to 120F
(32.2 to 48.9C), preferably 110F (43.3C) until the
desired taste and custard body has been achieved, which is
usually when the pH of the yogurt is about 3.8 to 4.8,
preferably 4.5 to 4.7, and are then cooled to a temper-
ature sufficiently low to stop fermentation, generally 35
to 50 F (1.6 to lO C), Preferably to conventional refrig-
eration temperatures, until ready for sale. The resulting
low calorie, low fat product has a smooth, creamy custard
texture and, unless sweeteners have been added, a typical
tart yogurt taste which becomes sweet and predominantly
fruity only when the preserves at the bottom are stirred
into the yogurt custard. And a still further aspect of
-the present invention, there is provided, in a method for
making a less than about 0.2% by weight fat, low calorie
yogurt product, including the steps of admixing low fat
content pasteurized milk, stabilizers and nonfat dry milk
solids, heating said mixture to a temperature in the range
Erom about 190 to 195F (87.7 to 90.6C), homogenizing
said mixture at pressures in the range 500 to 5000 psig
(35.15 to 351.5 kg/cm2), cooling said homogenized mixture
to a temperature of about 90 to 120 F (32.2 to 48.9 C),
inoculating said cooled homogenized mixture with a lactic
acid producing bacterial yogurt culture mixture, maintain-
,ing said inoculated mixture at a temperature of about 90
to 120 F (32.2 to 48.9 C) for a time sufficient to produce
a pH in the range of about 3.8 to 4.8 and to form an
acceptable taste and texture in said inoculated mixture,
the improvement comprising:
125~40~)
- 6a -
said lactic acid producing bacterial yogurt culture
mixture consisting essentially of, by weight, 30-50%
Lactobacillus acidophilus, balance Lactobacillus
-
bulgaricus and Streptococcus thermophilus in
approximately equal proportions. In a preferred
embodiment in the above method, there may be provided
the step of combining the inoculated mixture with low
calorie fruit preserves either before or after the
maintaining step. Still further, in the above, culture
mixture, a particularly preferred form is where the
culture mixture consists essentially of 40%
Lactobacillus acidophilus, 30% Lactobacillus bulgaricus
and 30% Streptococcus thermophilus.
The low calorie, low fat custard-type fruit
containing yogurt product of -the presen-t inven-tion
comprises a major amount of pasteurized, homogenized
cultured skim milk and minor amounts of low calorie
fruit preserves, stabilizers, vitamins, minerals and
flavorants. Most importantly, the product of the
present invention has a total fat content by weight of
less than about 0.2%, preferably less than about 0.1%,
and contributes only about 150 calories per eight ounce
(224 gram) serving to the diet. Desirably, the produc-t
has a p~ in the range 4.3 to 4.6, a total solids content
of about 19%, and contains up to 20~ by weight fruit.
~s .~
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Best Mode For Carrying Out The Invention
The present invention relates broadly to a low fat -
fruit-containing yogurt product which resembles conventional
custard-type ~ruit-containing yogurt in appearance, texture
and taste, but which has fat and calorie contents
substantially reduced below those of conventional
yogurt. As a result, the yogurt made by the method of tne
present invention is suitable for inclusion in the diets of
persons for whom a reduced intake of fat or calories is
necessary or desirable.
The overall process by which the fruit-containing
yogurt produc-t is made involves admixing pasteurized skim
milk, stabilizers and nonfat dry milk solids, e.g., namely
nonheat-modified nonfat dry milk solids; adding vitamins and
minerals, sweeteners, flavorants and/or
colorants to the admixture; heating the resulting mixture to
a temperature of about 1900F to 1950F (87.7 to 90.60C)
adding optional heat liable vitamins, such as Vitamin C; and
homogenization means. The homogenized mixture is then
cooled to a temperature of about 90 to 1200F (32.2 to
48.90C), preferably llOoF (43.30C) and inoculated with a
uniquely proportioned blend of standard lactic acid
producing yogurt cultures. Depending on whether a Swiss
type or a Western style yogurt is desired, the inoculated
mixture is maintained at this temperature in the bulk
mixing vat until the desired taste and texture are achieved,
then cooled to about 500 to 750F (10 to 23.90C), pumped
through a screw or pressure valve and admixing with fruit
preserves prior to packaging and re~rigeration (Swiss style)
or placed in conventional yogurt containers to which
fruit has already been added and maintained at about llOoF
(43.30C) while in the containers until the product has
achieved an acceptable taste and texture before being cooled
at conventional refrigeration temperatures (Western style).
0~
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In order to prepare a yogurt product having a fat
content not greater than about 0.2% by weight the use of
fat contributing ingredients must be carefully controlled.
Inasmuch as the primary fat contributing ingredient in
yogurt is generally milk, a low fat content may be achieved
by selecting a skim milk with a butterfat content of less
than about 0.2~ by weight, and preferably less than about
0.1~ by weight, for use in the process of the present
invention. The term "milk" as used herein means the
1~ conventional milk of commerce (butterfat content ranging
from about 0.1% to 7% by weight) as well as equivalent
compositions formed by suitable admixtures of milk solids
and water.
The primary carbohydrate contributing ingredients in
yogurt are sugars, which may be added to the yogurt custard
to flavor it or, more typically, are added in the prepar-
ation of the fruit component. Typically, the fruit added
to yogurt resembles fruit preserves having discrete pieces
of fruit or whole berries in a thickened sugar syrup.
Fruit in this form effectively masks the flavor of the
yogurt with a predominantly sweet, fruity taste and is less
likely to be fermented by the yogurt bacteria. To prepare
a fruit-containing yogurt having a reduced carbohydrate
content, the amount of sugar added to the yogurt custard or
used in the preparation of the fruit must be carefully
regulated. In the past, this has presented a problem since
use of less than about 1% by weight of the final product of
sucrose, the sugar form most commonly used to prepare
fruit for use in yogurt products, does not result in a
sufficiently sweet product.
The yogurt products of the present invention can
employ a low carbohydrate fruit prepared to resemble the
preserves heretofore used in conventional yogurt, but which
have been produced with monosaccharide sugars having high
sweetening effects, instead of sucrose. For example, the
, .
~Y,~
~s~
use of fructose, a monosaccharide with a sweetening effect
substantially greater than that of sucrose, to form the
syrup results in fruit preserves which are as sweet as
those prepared with sucrose but which have a substantially
lower carbohydrate level. A preferred fruit preserve
preparation which has been found to achieve the desired
results contains 40% to 50% by weight fruit pieces or whole
berries cooked in a syrup made from invert sugar containing
at least 36~ fructose thickened with pectin. The resulting
preserves contain about 41% to 47~ solids, are a-t th~
normal pH for the specific fruit used, and contain not more
than 825 calories per pound (about 1817 calories per kg) of
preserves. Any of the fruits and berries commonly used in
conventional fruit-containing yogurt products, such as
strawberries, blueberries, cherries and the like, may be
prepared for use in the product of the present invention.
The combinati~n of a low level of carbohydrates and a low
level of fat results in a yogurt product having signiEi-
cantly fewer calories than prior products.
To prepare -the low calorie fruit-containing yogurt of
the present invention, pasteurized skim milk having a fat
content of less than about 0.2% by weight, preferably less
than about 0.1% by weight, is placed in a stainless steel
mixing vat or the like container. The skim milk may have
been pasteurized by any conventional means, although it is
preferred to use skim milk which has been pasteurized by
the high temperature, short time (HTST) method. To the
skim milk are added stabilizers and nonfat dry milk solids.
A preferred combination of stabilizers which has been found
to be successful contains agar, pectin, guar gum and
gelatin. However, other commonly used commercially
available dairy stabilizers could also be utilized either
alone or in combination. The stabilizer or combination of
stabilizers comprise less than about 1.0%, preferably about
0.7%, by weight of the final product. The nonfat dry milk
. . I
~ ~ . `v'
~5~400
solids comprise up to about 2%, preferably about 1.2%,
by weight of the final product. One manner of achieving
the low fat, low carbohydrate and low calorie levels of
the yogurt of the present invention while obtaining a
custard-type produc-t having a creamy consumer acceptable
appearance and mouth feel rather than the loose and
watery consistency of previously attempted low fat
yogurt products, is to use dry milk solids which can be
of the heat-modified type or any conventional type, i.e.
non-heat modified - i.e. it has been subjected to no
heat treatment prior to spray drying other than
pasteurization. Such a modified milk solids product is
commercially available from a number of manufacturers.
Examplary of suitable products are "PMC" available from
Pro-Mark Co. of Tulsa, Oklahoma, "Hi-Sorb"* available
from MPI Division of S-tauffer Chemical Company, Inc. and
"Crest Lac"* available from Crest Foods Co., Inc. of
Ashton, Illinois. Each of these products is a grade-A
conventional nonfat dry milk product which has been
modified primarily by heat for the purpose of increasing
the hydration of the pro-tein and for making the product
more effective in transmitting texture and flavor. See,
for example, U.S.
* Trade Marks
- 1 1 125~3~00
Patent No. 4,096,287 for a discussion of acceptable
methods for preparing the heat modified non-fat dry milk
product by heat treating, other than pasteurization heat
treating, including the essential step of non-
coagulative direct steam heating of condensed skim milk
prior to spray drying for modifying the milk protein.
It has been ~ound convenient to premix the
stabili7ers and nonfat dry milk solids in the amounts
normally used for production so that the non fat dry
milk solids serve as a carrier for the stabilizers. In
this connection, as previously indicated, it is
acceptable to use admixtures of nonfat dry milk solids
and water in lieu of the skim milk in the process of the
present invention. If this is done, preparation of the
milk starting ingredient must be consistent with the
desired 17 to 20~ by weight, preferably about 19% by
weight, total solids in the final product.
It is desirable to fortify the fruit-containing
yogurt product of the present invention with vitamins
and minerals so that an eight ounce (224 gram) serving
is nutritionally equivalent to a single serving of milk,
which is usually eight ounces (224 gram), and a single
serving of fruit, which varie$ according to the kind of
fruit. Such fortification, while not essential to the
present invention, results in a product of greater
nutritional value than a nonfortified product and
facilitates the intake of the recommended daily
allowances of these vitamins and minerals. Heat labile
vitamins and minerals, such as Vitamin C which is
destroyed by prolonged high temperatures, should not be
added at this stage of the process, but are preferably
added at a later time after high temperature heating has
taken place.
At this stage in the process, particularly if the
end product is to be a Western style yogurt in which the
fruit is on the bottom it may be desirable to add
- 12 _ ~ 2 5 8 4 00
a sweetener, flavor enhancer or colorant. Addition of one
or any combination of these ingredient materials produces
a yogur-t custard that is sweet, flavored and/or colored
without the frui.t being stirred therethrough. Any sweet-
ener used must not, in combination with the sweetenedfruit, exceed the desired carbohydrate level in the final
product. It is preferred, therefore, to use as the added
sweetener fructose or a similar high sweetening monosac-
charide. Any one of a number of commercially available
and well known flavor enhancers and/or certified food
grade colorings may also be used.
The skim milk-stabilizer-nonfat dry milk solids
mixture, which may contain vitamins, minerals, sweeteners,
flavorants and/or colorants is heated to a temperature in
the range from about 190 to 195F (87.7 to 90.6C.) for a
time sufficient to Eorm a uniform, subs-tantially homogen-
eous mixture and to pasteurize the'mixture, usually about
20-60 minutes. Heat treating at this high temperature
denatures the milk protein, causing water in the mixture
to be absorbed and helps to create a thicker, richer
product having a custard-type body and texture. The heat
labile vitamins and minerals, such as Vitamin C, may be
added once the heat treatment at 190-195F (87.7 to
90.6C) is comple-te and the mixture has cooled below the
temperature at which the particular vitamin and/or
mineral might be adversely affected. The mixture is
then homogenized by conventional homogenization means at
about 500-5000 psig (35.15 to 351.5 kg/cm2), desirably
1000 to 2000 psig (84.36 to 105.45 kg/cm2), after which it
is cooled to an optimum culturing temperature, generally
in the range 90 to 120F (32.2 to 48.9C) and preferably
about 110F (43.3C) in
~3, 1'~,5~340~
prcparation for )~a(~tcrial i!l~",~ i(,n, -I~]Jvu(Jll t:he
temperatuLe may va~y slightly acco~ding to the
bacterial culture or cultures used.
The pasteurized, homogenized mixture is
- innoculated with a uniquely proportioned blend of
lactic acid producing bacterial cultures commonly used
in yogurt production in order to confer upon the final
yogurt product the proper combination of acidity,
tartness and body appropriate for a custard-type yogurt
product. Preferred as constituents of the customized
10 yogurt culture for use in the process of the present
invention are h~ct__acillu~ bulgaricus, ~eptococcus
t_ermo~hil~ and hacto_aCillus acido~hilus. It has
been found that when all three of these bacterial
cultures are simultaneously employed in predetermined
15 proportions, even very low fat milk-containing mixtures
can be cultured to achieve the important custard-type
creamy body and mouth feel of conventional yogurt
while, at the same time, achieving the desired tartness
and acidity. This uniquely proportioned blend of the
20 three aforementioned bacterial cultures is one of the
main features of the present invention and the desired
yogurt product of the present invention cannot be
successfully achieved with other than all three
bacterial cultures employed in the following proportions
25 by weight:
Lactobacillus acidophilus 30-50%
~actobacillus k_lgaricus 25-35%
Streptococcus thermophilus 25-35%
The proper combination of cultures is generally
30 determined by the amount of Lactobacillus acidophilus
required to culture the low fat milk mixture to a
string.y, rubbery body texture which will yield an
acceptable custard-type creamy mouth eel. The
~ac~a~illus bulgaricus and ~tre tococcus thermophilus
35 comprise the balance of the culture in about equal
proportions.
To this point in the process there is no
84~)0
- 14 -
significant difference in processing between the
preparation of Swiss style yogurt, which has a
predominantly fruity flavor and contains pieces of
fruit uniformly dispersed throughout the yogurt
5 custard, and the preparation of Western style yogurt,
which has a shallow layer of fruit preserves on the
bottom of the yogurt container covered by a deep layer
of yogurt custard. The primary difference in
processing the two types is that the Swiss style is
10 cultured in the bulk mixing vat before packaging while
the Western style is cultured in the individual
containers in which it is packaged.
If a Swiss style yogurt is desired, the cultured
mixture is maintained at about 110F. (43.3C.) until a
15 yogurt custard with an acceptable body and taste is
produced. Although taste and texture are highly
subjective and will vary from producer to producer,
experience has shown that when the product reaches a pH
in the range of about 3.8 to 4.8t preferably about 4.5
2Q to 4.7, which typically takes about two to four hours,
an acceptably firm yogurt custard with a pleasantly
sharp, tangy taste has been produced. When an
acceptable product from the standpoint of taste and
texture has been produced, the yogurt is cooled to
25 about 50 to 75F. (10 to 23.9C.), preferably about
65 to 70F. (18.3 to 21.1C.), to slow the
fermentation while maintaining a sufficiently fluid
mixture so that it can be readily pumped through a
screw or pressure valve. The cooled mixture is then
30 pumped thro~h a screw or pressure valve to achieve a
- smooth texture. Fruit preserves prepared with high
sweetening monosaccharides, preferably fructose, are
thoroughly blended into the yogurt custard, preferably
at a level of about 15% to 20~ by weight fruit in the
- 15 _ l~S~0~3
final product. The resulting product is packaged in
coventional yogurt containers and held at conventional
refrigeration temperatures, preferably about 35 to
~0~. (1.6 to 404C.), to fully terminate fermentation.
- ~- When maintained under conventional refrigeration
temperatures, the product has a shelf life of about 30
days.
If a Western style yogurt is desired, about one
ounce (28 grams) of fruit preserves prepared with high
sweetening monosaccharides, preferably fructose, is
10 placed in the bottom of conventional eight ounce (224
gram) yogurt containers. On top of this is added about
seven ounces (196 grams) of the culture-containing,
pasteurized, homogenized mixture. The fruit comprises
preferably about 15% to 20% by weight of the final
15 product. The filled containers are maintained at about
110F. (43.3C.) until an acceptable taste and texture
are produced in the yogurt custard. If a sweetener has
been added to the yogurt mixture this may affect
somewhat the perception of when an acceptable yogurt
20 taste has been achieved. However, as with the Swiss
style yogurt, the notion of what constitutes a suitable
product is likely to vary, with acceptable results
generally reached when the pH of the product is about
3.8 to 4.8, preferably 4.5 to 4.7. This pH level is
25 generally reached in about two to four hours. The
containers are thereafter cooled to and maintained at
conventional refrigeration temperatures to stop the
fermentation, preferably 35 to 40F. (1.6 to 4.4C.).
Under these conditionsl the product has a shelf life of
30 about 30 days.
The following examples illustrate the practice of
the present invention and are intended to exemplify and
to limit in any respect the content and scope thereof.
~ ~5840(~
- 16 -
E~ample_l
A low calorie, low fat Swiss style yogurt was
prepared in the following manner:
2125 pounds (964.75 kg) of MTST
- ~- pasteurized skim milk (less than 0.2% by
weight butterfat) was placed in a
stainless steel culturing vat equipped
with an agitator. To this milk was added
40 pounds (18.16 kg) of a premixed
stabilizer-nonfat dry milk mixture which
contained about 8 pounds t3.63 kg) of a
mixture of agar, pectin, guar gum and
gelatin and about 32 pounds (14.53 kg) oF
"PMC" brand heat modified nonfat dry milk
solids, and a mixture of vitamins (except
Vitamin C) and minerals in quantities
which, in the final product, would be the
nutritional equivalent to those contained
in an 8 ounce (224 gram) serving of milk
and an average serving of fruit. The
resulting mixture was thoroughly blended
and vat pasteurized at 190 to 195F.
(87.7 to 90.6C.) for 30 minutes.
Vitamin C was added and the mixture was
homogenized at 1500 psig (105.45 kg/cm2).
The homogenized mixture was then cooled
to about 110F. (43.3C.), innoculated
with a mixture, by weight, of 40%
hactobacillus ac`dophilius 30%
hactobacillu~ b~l~aricus and 30%
Streptococcus ther_oph lu cultures and
maintained in the vat at this temperature
until the mixture reached a pH of about
3.8 to 4.8 and had an acceptable custard
~s~o~
- 17 -
consistency. The yogurt was cooled to
about 65 to 70F (18.3 to 21.1C) and
then pumped through a pressure valve to
give it a smoother texture. Five hundred
pounds (227 kg) of blueberry preserves
having less than 825 calories per pound
(1817 calories per kg) were mixed into
the yogurt custard. The blueberry pre-
serves contained 40% to 50% by weight-
whole blueberries in a syrup made from
invert sugar con-taining at least 36% to
38% fructose to which pectin had been
added to thicken it. The resulting low
calorie low fat yogurt had a smooth,
creamy texture, contained blueberries
uniformly mixed throughout, was the color
of blueberries mixed with cream and had
a predominantly sweet blueberry taste in
combination with a slightly sharp and
tangy yogurt taste. The product was
packaged in conventional eight ounce
yogurt cups, contained 150 calories,
0.2% by weight fat, 12-13% by weight
carbohydrate, 4% by weight protein and
19% by weight solids per eight ounce
(224 gram) serving, and remained stable
for about 30 days at 35 to 40F (1.6 to
4.4C).
Example II
A low calorie, low fat Western style yogurt was
prepared in the following manner:
2202 pounds (999.7 kg) of HTST pasteur-
ized skim milk (less than 0.2% by
weight butterfat) was placed in a
, i
!
. .
1~5~340(~
- 18 -
stainless steel vat equipped with an
agitator. To this milk was added 93
pounds (42.22 kg) of invert sugar which
contained 36% to 38% fructose, minor
- !~ 5 amounts of flavor enhancers and certified
color, 40 pounds (18.16 kg) of the same
premixed stabilizer-nonfat dry milk
additive used in Example I and a
substantially identical mixture of
vitamins and minerals as in Example I.
The resulting mixture was thoroughly
blended and vat pasteurized to 190 to
195QF. (87.7 to 90.6C.) for 30 minutes~
~itamin C was then added and the mixture
was homogenized at 1500 psig (105~45
kg/cm2). The homogenized mixture was
cooled to about 110F. (43~3Co) and
innoculated with a mixture, by weight of
40% LactQkacillus ncidQ~h lus 30~
2Q hacto~acillus bul~aricus and 30%
~_ eptococcus thermophilus cultures. 335
pounds (152.09 kg) of blueberry preserves
in an invert sugar syrup was prepared as
described in Example I and one ounce (7-8
grams) of these preserves was pumped into
each of a number of conventional eight
ounce (224 gram) yogurt cups. The cups
were then filled with the innoculated
~ 110F. (43~3C~) homogenized mixture and
maintained at 110F. ~43~3C~) until the
yogurt reached a pH of about 3.8 to 4.8
and had an acceptable custard
consistency. The cups were cooled to 35
to 40F. (1.~ to 4.4C~), at which
~s~o~
- 19 -
temperature the product remained stable
for about 30 days. The resulting low
calorie and low fat yogurt had a smooth,
creamy texture which had a slightly
sweet, predominantly sharp yogurt taste
before the preserves were stirred u~ from
the bottom. This yogurt looked and
tasted like the Swiss style and had the
same calorie, fat, carbohydrate, protein
and solids content.
~;t
