U.S. patent number RE28,488 [Application Number 05/506,424] was granted by the patent office on 1975-07-22 for milk fermenting product.
This patent grant is currently assigned to Microlife Technics, Inc.. Invention is credited to Stewart M. Farr.
United States Patent |
RE28,488 |
Farr |
July 22, 1975 |
Milk fermenting product
Abstract
A method of producing a mixed bacterial concentrate which
comprises separately incubating in separate culture media two or
three types of bacteria, the first type being selected from the
group consisting of Streptococcus lactis, Streptococcus cremoris,
Lactobacillus bulgaricus and Streptococcus thermophilus, the second
type being selected from the group consisting of Streptococcus
citrovorus and Streptococcus paracitrovorus, and the third type
consisting of Streptococcus diacetylactis, concentrating the
respective media to obtain separate concentrates of the two or
three type of bacteria, mixing together the two or three types of
bacteria in the desired proportions to produce a mixed concentrate
without permitting further growth of the bacteria, and then
freezing the mixed concentrate so that it can be stored for a long
time without major loss in the viability of the bacteria. A
stabilized mixed bacteria concentrate consisting essentially of a
substantially neutralized mixture of two or three types of
bacteria, as aforesaid, the concentrate being stabilized by the
admixture of a stabilizing agent and a nutrient medium and the
concentrate being frozen so that it can be stored for a long period
of time without major loss in the viability of the bacteria.
.[..[.This application is a continuation-in-part of my co-pending
application Ser. No. 285,858, filed June 6, 1963, now
abandoned..]..]..Badd.
Inventors: |
Farr; Stewart M. (Sarasota,
FL) |
Assignee: |
Microlife Technics, Inc.
(Sarasota, FL)
|
Family
ID: |
27023606 |
Appl.
No.: |
05/506,424 |
Filed: |
September 16, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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285858 |
Jun 6, 1963 |
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Reissue of: |
417134 |
Nov 19, 1973 |
RE028276 |
Dec 17, 1974 |
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Reissue of: |
404526 |
Oct 16, 1964 |
03420742 |
Jan 7, 1969 |
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Current U.S.
Class: |
435/252.4;
426/43; 435/253.4; 435/260 |
Current CPC
Class: |
A23C
9/1236 (20130101); C12N 1/20 (20130101) |
Current International
Class: |
A23C
9/123 (20060101); A23C 9/12 (20060101); C12N
1/20 (20060101); C12K 003/00 () |
Field of
Search: |
;195/56,53,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Lamprech (thesis), 62-4703, Production and Storage of Dairy Starter
Organisms, Univ. of Wisconsin, May 1962. .
Longworth et al., Journal of Bacteriology, Vol. 29, No. 6, pp.
595-607 (1935). .
Hargrove, Journal of Dairy Science, 1961, Vol. 44, pp. 1799 to
1810. .
Lamprech et al., Journal of Applied Bacteriology, Vol. 26, No. 3,
December 1963, pp. 359-369. .
Journal of Dairy Science, Vol. 45, pp. 1263 to 1266 and 1290 to
1294, October 1962..
|
Primary Examiner: Shapiro; Lionel M.
Attorney, Agent or Firm: Miller, Morriss, Pappas &
McLeod
Parent Case Text
This is a divisional reissue application of reissue application
Ser. No. 417,134, filed Nov. 19, 1973, now Reissue Patent No. Re.
28,276, reissued Dec. 17, 1974 of Original No. 3,420,742 and is a
continuation-in-part of application Ser. No. 285,858, filed June 6,
1963, now abandoned..Baddend.
Claims
What is claimed is: .[..[.1. The method of producing a mixed
bacterial concentrate .Iadd.useful for culturing milk which
comprises: .Iaddend.
(a) separately incubating in separate culture media two types of
bacteria, the first type being selected from the group consisting
of Streptococcus lactis, Streptococcus cremoris, Lactobacillus
bulgaricus and Streptococcus thermophilus .Iadd.which produce
lactic acid wherein the incubation culture medium contains skim
milk and wherein during the incubation the lactic acid produced is
neutralized as the pH of the medium drops by adding a neutralizing
agent to maintain the growth of the bacteria, .Iaddend.and the
second type being selected from the group consisting of
streptococcus citrovorus and Streptococcus paracitrovorus,
.Iadd.wherein the culture medium contains skim milk or a digest
milk to produce bacteria which are centrifugable from the media to
form a concentrate; .Iaddend.
(b) concentrating the respective media to obtain separate
concentrates of the two bacteria.[.,.]. .Iadd.containing at least
about 10.times.10.sup.9 cells/ml. each; .Iaddend.
(c) mixing together the two types of bacteria in the desired
proportions to produce a mixed concentrate having closely
controlled amounts of the two types of bacteria therein without
permitting further growth of the bacteria; and
(d) then freezing the mixed concentrate so that it can be stored
for a long time without major loss in the viability of the
bacteria..]..]. .[..[.2. The method of claim 1, including the steps
of mixing glycerol and a nutrient medium in the concentrates in
precise relative proportions..]..].
.[..[.3. The method of claim 1, including the step of neutralizing
the culture medium for said first type of bacteria to maintain the
pH thereof
between about 5.2 and about 6.6..]..]. 4. A stabilized, mixed
bacteria concentrate .Badd.containing at least about 10 .times.
10.sup.9 cells/ml each .Baddend.consisting essentially of a
substantially neutralized mixture of two types of bacteria
.Badd.which have been separately incubated, concentrated and then
mixed.Baddend., the first type being selected from the group
consisting of Streptococcus lactis, Streptococcus cremoris,
Lactobacillus bulgaricus and Streptococcus thermophilus .Badd.which
has been incubated in a culture medium containing skim milk so as
to produce lactic acid and wherein during the incubation the lactic
acid produced has been neutralized with a nuetralizing agent to
maintain the growth of the bacteria, .Baddend.and the second type
being selected from the group consisting of Streptococcus
citrovorus and Streptococcus paracitrovorus .Badd.which has been
incubated in skim milk or a digest milk, said bacteria having been
separated from the media and concentrated in a centrifuge
.Baddend.said concentrate being stabilized by the admixture of a
stabilizing agent and a nutrient medium so that the concentrate is
stabilized against rapid loss of viability, said concentrate being
frozen so that it can be stored for a long period of time without
major loss in the viability of the bacteria.
--------------
10.times.10.sup.9 cell per ml..]. 6. A stabilized mixed bacteria
concentrate according to claim 4, in which the stabilizing agent is
glycerol.
--------------
reissue. 7. A stabilized mixed bacteria concentrate according to
claim 4, in which the bacteria of said first type comprise of at
least about 88% of the total count in the bacteria concentrate.
--------------
reissue. .[.8. The method of producing a mixed bacterial
concentrate which comprises separately incubating in separate
culture media three types of bacteria, the first type being
selected from the group consisting of Streptococcus lactis,
Streptococcus cremoris, Lactobacillus bulgaricus and Streptococcus
thermophilus, the second type being selected from the group
consisting of Streptococcus citrovorus and Streptococcus
paracitrovorus, and the third type consisting of Streptococcus
diacetylactis, concentrating the respective media to obtain
separate concentrates of the three bacteria, mixing together the
three types of bacteria in the desired proportions to produce a
mixed concentrate having closely controlled amounts of the three
types of bacteria therein without permitting further growth of the
bacteria, and then freezing the mixed concentrate so it can be
stored for a long time without major loss in the viability of the
bacteria..]. .[.9. The method of claim 8, including the steps of
mixing glycerol and a nutrient medium in the concentrates in
precise relative proportions..]. 10. A stabilized, mixed bacteria
concentrate .Badd.containing at least about 10 .times. 10.sup.9
cells/ml each .Baddend.consisting essentially of a substantially
neutralized mixture of three types of bacteria .Badd.which have
been separately incubated, concentrated and then mixed.Baddend.,
the first type being selected from the group consisting of
Streptococcus lactis, Streptococcus cremoris, Lactobacillus
bulgaricus and Streptococcus thermophilus .Badd.which has been
incubated in a culture medium containing skim milk so as to produce
lactic acid and wherein during the incubation the lactic acid
produced has been neutralized with a neutralizing agent to maintain
the growth of the bacteria.Baddend., the second type being selected
from the group consisting of Streptococcus citrovorus and
Streptococcus paracitrovorus .Badd.which has been incubated in skim
milk or in a digest milk .Baddend.and the third type consisting of
Streptococcus diacetylactis, .Badd.said bacteria having been
separated from the media and concentrated in a centrifuge,
.Baddend.said concentrate being stabilized by the admixture of a
stabilizing agent and a nutrient medium so that the concentrate is
stabilized against rapid loss of viability, said concentrate being
frozen so that it can be stored for a long period of time without
major loss in the viability of the bacteria.
--------------
.times. 10.sup.9 cells per ml..]. 12. A stabilized mixed bacteria
concentrate according to claim 10, in which the stabilizing agent
is glycerol.
--------------
reissue. 13. A stabilized mixed bacteria concentrate according to
claim 10, in which the bacteria of the second type comprise about
8% of the total count of the bacteria concentrate, the bacteria of
the third type comprise between about 1% and 4% of the total count
of the bacteria concentrate, the balance being bacteria of the
first type.
--------------
reissue. 14. A stabilized bacteria concentrate consisting
essentially of a substantially neutralized concentrate of a
.[..[.bacteria.]..]. .Badd.bacterium which is separately incubated
and concentrated .Baddend.selected from the group consisting of
Streptococcus citrovorus and Streptococcus paracitrovorus
.Badd.which has been incubated in a culture medium containing skim
milk or a digest milk, said bacteria having been separated from the
media and concentrated in a centrifuge .Baddend.said concentrate
being stabilized by the admixture of a stabilizing agent and a
nutrient medium so that the concentrate is stabilized against rapid
loss of viability, the concentrate being frozen so it can be stored
for a long time without major loss in the viability of the
bacteria, the concentrate containing at least about 10 .times.
10.sup.9 cells per ml.
--------------
reissue with amendments. 15. A stabilized, mixed bacteria
concentrate .Badd.containing at least about 10 .times. 10.sup.9
cells/ml each .Baddend.consisting essentially of a substantially
neutralized mixture of .Iadd.three .Iaddend..[.two.]. types of
bacteria .Badd.which have been separately incubated, concentrated
and then mixed.Baddend., the first type consisting of Streptococcus
lactis .Badd.which has been incubated in a culture medium
containing skim milk and wherein during the incubation the lactic
acid produced has been neutralized with a neutralizing agent to
maintain the growth of the bacteria.Baddend., the second type being
selected from the group consisting of Streptococcus citrovorus and
Streptococcus paracitrovorus .Badd.which has been incubated in skim
milk or a digest milk, and the third type consisting of
Streptococcus diacetylactis which has been incubated and
neutralized in the manner of the first type of bacteria, said
bacteria having been separated from the media and concentrated in a
centrifuge .Baddend.said concentrate being stabilized by the
admixture of a stabilizing agent and a nutrient medium so that the
concentrate is stabilized against rapid loss of viability, said
concentrate being frozen so that it can be stored for a long period
of time without major loss in the viability of the bacteria.
--------------
reissue with amendments. 16. A stabilized, mixed bacteria
concentrate .Badd.containing at least about 10 .times. 10.sup.9
cells/ml each .Baddend.consisting essentially of a substantially
neutralized mixture of three types of bacteria .Badd.which have
been separately incubated, concentrated and then mixed.Baddend.,
the first type consisting of Streptococcus lactis, .Badd.which has
been incubated in a culture medium containing skim milk and which
has been neutralized with a neutralizing agent during incubation to
maintain the growth of the bacteria, .Baddend.the second type being
selected from the group consisting of Streptococcus citrovorus and
Streptococcus paracitrovorus .Badd.which has been incubated in a
culture medium containing skim milk or a digest milk, .Baddend.and
the third type consisting of Streptococcus diacetylactis
.Badd.which has been incubated and neutralized in the manner of the
first type of bacteria, said bacteria having been separated from
the media and concentrated in a centrifuge, .Baddend.said
concentrate being stabilized by the admixture of a stabilizing
agent and a nutrient medium so that the concentrate is stabilized
against rapid loss of viability, said concentrate being frozen so
that it can be stored for a long period of time without major loss
in the viability of the bacteria.
--------------
reissue with amendments. .[..[.17. The method of producing a mixed
bacterial concentrate which comprises:
(a) separately incubating in separate culture media three types of
bacteria, the first type being selected from the group consisting
of Streptococcus lactis, Streptococcus cremoris, Lactobacillus
bulgaricus and Streptococcus thermophilus, which produce lactic
acid wherein the incubation culture medium contains skim milk and
wherein during incubation the lactic acid produced is neutralized
as the pH of the medium drops by adding a neutralizing agent to
maintain the growth of the bacteria, the second type being selected
from the group consisting of Streptococcus citrovorus and
Streptococcus paracitrovorus wherein the culture media contains
skim milk or a digest milk, and the third type consisting of
Streptococcus diacetylactis which is incubated and neutralized in
the manner of the first type of bacteria to produce bacteria which
are centrifugable from the media to form a concentrate;
(b) concentrating the respective media to obtain separate
concentrates of the three bacteria containing at least about
10.times.10.sup.9 cells/ml. each;
(c) mixing together the three types of bacteria in the desired
proportions to produce a mixed concentrate having closely
controlled amounts of the three types of bacteria therein without
permitting further growth of the bacteria; and
(d) then freezing the mixed concentrate so it can be stored for a
long time without major loss in the viability of the
bacteria..]..]. .[..[.18. The method of claim 17, including the
steps of mixing glycerol and a nutrient medium in the concentrates
in precise relative proportions..]..].
Description
This invention relates to a concentrated bacterial product useful
for fermenting milk in order to make cottage cheese, cheese,
butter, cultured buttermilk and other cultured milk products, and
also relates to a process for producing said bacterial product.
In the following description and claims, the term "acid-producing
bacteria" shall refer to bacterial capable of fermenting lactose or
other, similar carbohydrates rapidly at temperatures of about 70
degrees Fahrenheit to 110 degrees Fahrenheit with the production of
principally lactic acid, namely, Streptococcus lactis,
Streptococcus cremoris, Lactobacillus bulgaricus and Streptococcus
thermophilus. The term "flavor-producing bacteria" shall refer to
bacteria capable of fermenting citric acid or citrates at a
favorable pH with the production of biacetyl, actylmethylcarbinol,
volatile acids and carbon dioxide, namely, Leuconostoc citrovorum
(Streptococcus citrovorus) and Leuconostoc dextranicum
(Streptococcus paracitrovorus) and subspecies thereof.
Streptococcus diacetylactis (a species not recognized in Bergey's
Manual. Breed, Murray and Hitchins, 1957) produces some lactic acid
and also produces substantial amounts of flavor constituents.
Cottage cheese, cheese, butter and cultured buttermilk are
manufactured by a fermenting procedure using a suitable bacteria.
Dairies usually purchase an initial culture of a mixture of
suitable bacteria from a commercial organization supplying same.
This culture is then propagated in the diary by placing the culture
in milk and incubating it at a suitable temperature, usually at
around 70 degrees Fahrenheit, for a suitable period of time,
usually from 14 to 18 hours, in order to form a mother culture. The
propagation step is repeated a number of times using the bacterial
product of the preceding step as the inoculum and finally the
propagation is carried out in a rather large quantity of milk in
order either to produce a bulk starter, which can then be used for
fermenting the final batch of milk to make the end product, or to
produce cultured buttermilk.
If sufficient care is not taken both in the manufacture of the
mother culture and in the propagation thereof, bacteriophage may
become present in the bulk starter, or perhaps earlier in the
propagation process, and may proliferate so as to hinder the growth
of or completely destroy the bacteria. This may cause delayed
setting or no setting of the milk. If this contamination occurs,
large quantities of milk are often lost and all of the time and
labor spent in propagating the culture are wasted. Contamination of
the initial culture is not a serious problem because the initial
culture is produced under carefully controlled conditions with
special equipment and by skilled personnel. However, few dairies
and the like, where most of the propagating is presently performed,
are so equipped. Thus, the incidence of such contamination during
the propagation of the bacteria according to present practices in
dairies is believed to be higher than necessary.
The initial culture most usually acquired from a supplier consists
of a mixture of at least two of the three types of bacteria
referred to above, namely, acid-producing bacteria and
flavor-producing bacteria and Streptococcus diacetylactis. The
types of bacteria must be properly balanced in order to produce
acceptable products and the proper bacterial balance for producing
one product, such as cottage cheese, is different than the proper
balance required for another product, such as cultured buttermilk.
The types of bacteria do not grow equally well in a propagation
process of the type described above because plain milk favors the
growth of the acid-producing bacteria at the expense of the
flavor-producing bacteria. Thus, even though the mother culture may
have the proper balance of the types of bacteria, there may be a
serious unbalance by the time the bulk starter has been made.
Moreover, this unbalance may not be discovered until an
unacceptable end product has been produced, which also results in
major economic losses.
It is possible to overcome these problems by suitable care and
control over the propagating process, but to do so requires
constant supervision by a skilled person having a sound knowledge
of dairy bacteriology, and it also requires a considerable
investment in equipment.
Moreover, because of the time required to produce the bulk starter,
dairies must anticipate their need for a cultured milk product
several days in advance. Thus, they may be unable to supply an
unexpected demand for a particular product on short notice. Also
they may find that by the time the bulk starter is made the
anticipated demand for the cultured milk product may not have
materialized and the bulk starter may have to be thrown away, all
of which involves considerable loss.
In addition, even under optimum conditions the present starter
cultures are bulky and have a relatively short life. They must be
used soon after they are made and they are not easy to store. For
example, in making a slow set cottage cheese approximately eight
(8) quarts of starter are required to inoculate one hundred (100)
gallons of milk; while in a fast set process, which is the one
commonly used, approximately five times this amount or 40 quarts of
inoculum are required. When it is realized that it is customary to
inoculate at least 10 times this amount of milk or 1,000 gallons at
one time, it will be seen that the preparing, storage and handling
of the inoculum becomes costly and, because of the necessity of
maintaining bacteria viability, it is a difficult problem.
Accordingly, a need exists for a bacterial product for use by
dairies which is free of bacteriophage and which contains
acid-producing bacteria and flavor-producing bacteria or
acid-producing bacteria, flavor-producing bacteria and
Streptococcus diacetylactis in the proper balance, which is of such
high potency or concentration that ample supplies are easy to
store, and which is prepared in such a manner that it will remain
viable in a stored condition for an extended period of time. This
bacterial product can be placed directly into milk for forming the
end product, without further propagation in the dairy, so that the
cultured end product can be produced rapidly and inexpensively. The
present invention is intended to meet the need for such a
product.
Further, there are certain types of cultured diary products, of
which yoghart is an example, for which the demand is low so that
they either are not produced at all or they are produced in such
small quantities that the cost to the consumer is quite high. If
consumers could obtain a bacterial product which would permit them
to make such products easily, conveniently and rapidly in the home
from plain milk, the demand for this type of product would be more
easily supplied and at a lower cost to the consumer. The present
invention also is intended to meet this need.
The objects of the invention are met by providing a bacteriophage
free, stabilized and concentrated bacterial product consisting of a
mixture of acid-producing bacteria and flavor-producing bacteria or
a mixture of acid-producing bacteria, flavor-producing bacteria and
Streptococcus diacetylactis having a high total bacterial
concentration, about 5 cubic centimeters of the concentrate
containing approximately the same number of bacteria as are present
in one quart of fully fermented milk or, in other words, a
concentrate whose bacteria count is approximately 189 times the
bacteria count in fully fermented milk. Otherwise stated, the
bacterial concentrate has 10-60.times.10.sup.9 cells per ml. The
bacterial product contains by admixture at least about 2 percent by
weight of glycerol plus a suitable nutrient medium and is quickly
frozen whereby the viability of the bacteria is maintained at a
high level for a long time period. The ratio of the acid-producing
bacteria to the flavor-producing bacteria or the ratio of the
acid-producing bacteria to the flavor-producing bacteria and the
Streptococcus diacetylactis is carefully controlled and is adjusted
as needed in order to adapt the bacterial product to the production
of a particular type of cultured milk product. In general, the
percentage of the flavor-producing bacteria concentrate plus the
percentage of the Streptococcus diacetylactis concentrate ranges
from about 2 to about 12 percent of the total count and the
acid-producing bacteria concentrate constitutes the balance of the
end product.
According to the method aspects of the invention, it is a critical
feature of the invention that the acid-producing bacteria, the
flavor-producing bacteria and the Streptococcus diacetylactis be
grown and concentrated separately from each other. The three types
of bacteria are separately grown or propagated in their respective
culture media and then they are concentrated by centrifuging to
produce separate concentrated bacterial products. About five cubic
centimeters of each concentrate contain approximately the same
number of bacteria as would be present in one quart of milk which
had been fully fermented by the same bacteria. Because of the
variability of bacteria strains, the particular conditions under
which they are fermented and other variables, it is impossible to
give precise bacteria counts but, in general, each ml, of the
concentrates will contain 10-60.times.10.sup.9 cells per ml. The
two or three types of concentrated bacteria are then mixed with
each other in the proper proportions depending on usage and with
glycerol and with a nutrient medium and then the mixture is frozen
to produce the stabilized, concentrated, bacterial product of the
invention.
The three types of bacteria are grown in culture media in
accordance with conventional practice. The particular procedures
used for growing the three types of bacteria can be widely varied
and form no part of the present invention. However, the bacteria
must be grown separately in separate culture media and care must be
taken to insure that the bacteria are phage-free. Suitable
procedures are known to the dairy industry for maintaining
phage-free conditions in bacterial cultures. In general, such
procedures involve careful selection of the initial culture, the
provision of a suitable culture rotation system and the maintenance
of proper standards of cleanliness and sterilization in the
equipment and in the area in which the culturing operation is
carried out.
A preferred procedure for cultering the acid-producing bacteria
and, also, Streptococcus diacetylactis, so as to prevent
bacteriophage development without hindering culture activity, is
described in the "Journal of Dairy Science." October 1961, volume
XLIV, No. 10, pages 1799-1810 and U.S. Pat. No. 3,041,248.
Specifically, a culture medium is made by dissolving 5 pounds of
powdered skim milk, 10 pounds of lactose and 21/2 pounds of Basamin
Busch yeast in 60 gallons of water which has been preheated to 130
degrees Fahrenheit. 3.4 pounds of Na.sub.2 HPO.sub.4, H.sub.2 O and
5.1 pounds of KH.sub.2 PO.sub.4 are dissolved in distilled water
and are added to and mixed in the culture medium. The medium is
heated to 200 degrees Fahrenheit and held at that temperature for
1/2 hour. 1.5 pounds of K.sub.4 P.sub.2 O.sub.7 are dissolved in
distilled water and this solution is added to the culture medium
held at 200 degrees Fahrenheit. The solution is cooled to 72
degrees Fahrenheit and then it is inoculated with a mother culture
of the acid-producing bacteria or Streptococcus diacetylactis after
which it is incubated for from 18 to 20 hours at from 72 degrees
Fahrenheit to 77 degrees Fahrenheit.
It may be necessary to neutralize the culture medium for the
acid-producing bacteria during the culturing step by adding
suitable neutralizing agents at selected times. Ordinarily, the
neutralizing agent is added when the pH of the medium drops to 5.2
and sufficient neutralizing agent is added to raise the pH to about
6.6. NaOH, Na.sub.2 CO.sub.3 or other neutralizing agents can be
used for this purpose. The foregoing described procedure has been
found to be highly satisfactory for culturing the acid-producing
bacteria while avoiding the development of phage so that the
product of this culturing step is especially satisfactory for the
purposes of this invention.
The preferred procedure for culturing the flavor-producing bacteria
is the same as that used for the acid-producing bacteria except
that the culture medium may be different and, for example, may be
trypsin digest milk, cottage cheese whey or corn steep plus
dextrose (which is preferred) because these latter media favor the
growth of the flavor-producing bacteria more than does a medium
consisting essentially of plain milk. With the flavor-producing
bacteria, it usually is not necessary to neutralize the culture
medium except when corn steep is used as the culture medium. In all
other respects, the procedure for culturing the flavor-producing
bacteria can be the same as that previously described with respect
to the acid-producing bacteria and Streptococcus diacetylactis and,
hence, needs no further description.
After the three types of bacteria have been separately grown as
above described, each is separated from the medium in which it has
been grown and is concentrated by passing the medium containing the
bacteria through a suitable centrifugal apparatus so that the
liquid is discharged from the apparatus and the bacteria collect on
the bowl of the apparatus from whence they may be scraped out or
mechanically ejected during the operation of the centrifuge. The
three types of bacteria are separately centrifuged so that separate
concentrates of the three types of bacteria are obtained. Apparatus
capable of centrifuging culture mediums to separate and recover
bacteria from them is commercially available and hence does not
need detailed description.
The three types of bacteria are then mixed with other materials
which serve to maintain the viability of the bacteria. It is
particularly preferred to mix an effective amount of glycerol with
the concentrated bacteria as this has been found to markedly
improve their viability. For example, 100 ounces of concentrate
scraped from the centrifuge bowl were mixed with 140 ounces of
fresh culture medium and then 60 ounces of glycerol were added to
the mixture so that glycerol amounted to about 20 percent by weight
of the total concentrate. However, as little as about 2 percent by
weight of glycerol can be used as a minimum while 25 percent or
more by weight of glycerol can be used, if desired. The higher
percentages of glycerol are not needed to maintain the viability of
the bacteria, but they can effect other advantages which make the
use of such amounts desirable in some instances. For example, use
of about 20 percent or more by weight of glycerol provides a
concentrate which is especially well suited for making yoghurt.
Such a concentrate remains liquid below 32 degrees Fahrenheit and
may, therefore, be more convenient for home use.
After mixing the glycerol and nutrient medium, the two or three
individual bacteria concentrates are then mixed together in
suitable proportions to form a mixed bacterial product which is
concentrated and phage-free. The amounts of the two or three
individual bacteria concentrates which are mixed together will
depend upon the particular fermented product to be formed by the
mixed bacterial product. Where the mixed bacterial product is to be
used for making buttermilk, about 1-4 percent of the total bacteria
of the mixed concentrate should be Streptococcus diacetylactis,
about 8 percent should be flavor-producing bacteria and the balance
should be acid-producing bacteria. Where cottage cheese or hard
cheeses are to be made, about 98 percent of the total bacteria in
the mixed bacterial concentrate should be acid-producing bacteria
and about 2 percent should be flavor-producing bacteria. One or the
other of the flavor-producing bacteria and Streptococcus
diacetylactis can be eliminated from the bacterial concentrate for
producing cottage cheese, depending on taste requirements.
Where the mixed bacterial concentrate is to be stored for any
appreciable period of time, i.e., more than a week or so, it should
be frozen after it is formed and, preferably be held at about -4
degrees Fahrenheit because in such condition the viability of the
bacteria will be maintained for a long time.
A suitable amount of the concentrated and mixed bacterial product
can be mixed with milk, either fresh, whole milk, skim milk or
reconstituted dry milk, so that the milk can be fermented thereby
in order to form a fermented milk product. The concentrated, mixed
bacterial product can be placed directly into the milk to be
processed without any intermediate propagations. In other words,
the concentrated, mixed bacterial product of the invention serves
in place of the bulk starter conventionally used for this purpose.
In all other respects, the method of fermenting the milk to form
the end product can be in accordance with conventional procedures.
The high bacteria concentration in the mixed bacterial concentrate
of the invention make it possible, however, to prepare fermented
milk products in a much shorter period of time than is required
according to conventional procedures, simply by using larger
amounts of the concentrate. Specifically, by adding relatively
large amounts of the concentrate to milk, it is possible to reduce
the time of setting the milk to an hour or so. In this fashion, it
is possible for a consumer to make certain types of cultured milk
products, such as yoghurt, in the home. Also, a dairy can use this
technique to produce small quantities of cultured milk products
rapidly.
Furthermore, this invention eliminates the troublesome problem,
especially for small operators, of anticipating the demand for
certain cultured milk products, which is presently necessary,
several days in advance when he must start the propagating
sequence. That is, he can keep a supply of phage-free, concentrated
mixed bacterial product on hand for use on relatively short notice
in precise quantities, so that the desired end product can be
produced rapidly, usually on the same day that the need for same
becomes apparent.
Example I. -- Preparation of Cottage Cheese
100 gallons of milk were pasteurized by heating to 200 degrees
Fahrenheit for about a half-hour or longer. The milk was cooled to
70 degrees Fahrenheit and then 60 ccs. of the mixed bacterial
concentrate containing about 98 percent by weight of acid-producing
bacteria and about 2 percent by weight of flavor-producing
bacteria, was added to it and thoroughly mixed. The mixture was
incubated at 78 degrees Fahrenheit for about 14 hours and there was
obtained a cottage cheese product of pleasing flavor and proper
consistency.
Example II. -- Preparation of Cultured Buttermilk
100 gallons of milk were pasteurized by heating to 200 degrees
Fahrenheit and holding for about a half hour. The milk was cooled
to 74 degrees Fahrenheit and was inoculated with one ounce of the
bacterial concentrate containing about 90 percent by weight of
acid-producing bacteria and about 8 percent by weight of
flavor-producing bacteria and 2 percent of Streptococcus
diacetylactis. The mixture was incubated for approximately 14 hours
at 74 degrees Fahrenheit until its titratable acidity expressed as
lactic acid reached about 0.85 to 1.0 percent. The mixture was then
cooled and agitated to a smooth consistency to produce a cultured
buttermilk product.
Example III. -- Home Preparation of Yoghurt
14 ounces of evaporated milk, 1 pint of water, 2 ounces of instant
powdered milk and one cubic centimeter of the mixed bacterial
concentrate containing 20 percent by weight of glycerol were mixed
together and then allowed to stand at 74 degrees Fahrenheit for 24
hours until thickened. The yoghurt product has a pleasing flavor
and the typical consistency of yoghurt preparations. By using
larger amounts of the concentrate or faster growing bacteria, such
as L. bulgaricus or by incubating at a higher temperature the time
for incubation can be reduced to as little as one hour or so.
Although particular, preferred embodiments of the invention have
been disclosed herein for illustrative purposes, it will be
understood that variations or modifications of such disclosure,
which lie within the scope of the appended claims are fully
contemplated.
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