JP2667984B2 - Raw milk processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for the production of milk, either whole milk or skim milk, with a reduced bacterial content, to the products of said process and to a process for distributing milk to consumers.

[0002]

2. Description of the Prior Art Known well-known methods for killing bacteria contained in milk.
Warm sterilization has been used for decades. Unfortunately,
The relatively high temperatures used in the pasteurization process
Has a negative effect on lavers. Moreover, such high
Even at high temperatures, the pasteurization process is
It doesn't remove all the fungus,
Storage stability will result.Bacillus cereus
(Bacillus cereus) Is pasteurized process
Can withstand milk, grows at low temperatures, promotes milk rot
Is often relatively old, usually
It is the main bacterium found in processed milk. Product storage
Increases milk stability by increasing stability and eliminating the pasteurization process
In order to improve the flavor, both whole and skim milk
There is a general need for a method of reducing bacterial content. Extinction
The very expense currently needed to deliver milk to the hands of the consumer
Need to eliminate costly and labor-intensive distribution methods,
It is very economically important. For every dairy factory
Process the raw milk through homogenization and other processes.
After that, fill the container with the milk for distribution to consumers.
It is now necessary to transport the milk under refrigerated conditions.
It is important. This means that every dairy factory consumes processed milk.
Significant numbers to transport to points for distribution to consumers
Need to buy and maintain refrigerated trucks
You. By providing sterile or almost sterile dairy products
Eliminates the need to transport milk under such refrigerated conditions
It becomes possible. Unfortunately, the pasteurization process is thin.
Producing aseptic products only by producing milk with reduced bacteria
It is not possible.

[0003] In addition, the ability to produce sterile dairy products can obviate the need to store milk under refrigerated conditions at distribution points. Eliminating the need for large refrigerated compartments, such as in a typical food store, is also a huge economic benefit.

[0004] Even with current pasteurization processes, in some cases it is particularly important to obtain milk with reduced bacterial content prior to pasteurization. For example, certain batches of raw milk may be very contaminated, and mere pasteurization may not even provide a sufficient shelf life according to current specifications.

[0005] Furthermore, in some applications, the bacterial content is greatly reduced, such as the initial value (original value).
It is important to be able to provide processed milk reduced to about one-hundredth of that of e). For cheese production, it is particularly important to provide milk with a relatively low bacterial content, as inappropriate bacterial cultures can destroy cheese. It is usually inappropriate to simply heat treat milk to a degree sufficient for use in cheese production, because such heat treatment results in low yields of cheese and adversely affects coagulation time. Because there is. To alleviate this problem, additives are usually used. However, it is often preferred to avoid the use of such additives.

[0006] Various methods are known in the art for producing milk with reduced bacterial content by use of filtration, but none of them has found widespread acceptability. Prior art processes generally produce poor flow rates, either making the process uneconomic on a large scale or adversely affecting the properties of the milk, making the product less acceptable to consumers. is there.

[0007] Conventional filtration means for producing milk with reduced bacterial content have been attempted. Swedish Patent Publication 380,422 discloses a method of splitting whole milk by microfiltration into a filtrate fraction and a concentrate fraction. The filtrate passing through the pores of the filter (porosity is generally in the range of 0.1 to 10μ) consists of milk with a substantially reduced fat content, the concentrate, the fraction retained by the filter surface, It consists of a cream because the filter substantially retains not only bacteria but also fat globules.

[0008] Swedish published patent application SEA671
No. 5081 discloses a method of sterilizing milk in which fat is first separated from skim milk. The fat fraction is then sterilized by heat and the skim milk fraction is sterilized by bacterial filtration (filter porosity is not described). Finally, the sterilized fat fraction and the skim milk fraction are remixed to obtain a sterile dairy product. In order for the skim milk fraction to be sterilized in this way by bacterial filtration, the porosity of the filter must be small enough to prevent the passage of bacteria, resulting in poor production rates and reduced fat globule and protein content from milk. Will be suspended.

US Pat. No. 5,064,674 is about 5k
The present invention relates to a method for producing low-allergenic milk by an ultrafiltration method using a membrane through which a molecule having a molecular weight of Da or less passes. Excluded components captured by the membrane include milk proteins, live or non-live bacteria, bacterial protein antigens, and milk fat. Thus, the filtrate recovered from the ultrafiltration process is not only free of bacteria and bacterial protein antigens, but also of fat and milk protein, producing a product unsuitable for use as milk itself.

It is clear that the pores of the bacterial filter used in the technology, which are effective for sterilizing milk, remove not only bacteria but also fat globules and at least part of proteins. Such filters are quickly clogged by the capture material; therefore, the flow rate through the filter drops rapidly, and the filter must often be cleaned or replaced. The high cost of such inadequate processes also generally hinders. In addition, the quality of milk is adversely affected since the filter retains fat globules and proteins.

From the above considerations, there remains a need for an improved milk filtration process that can produce aseptic or nearly aseptic products with improved shelf life and that does not adversely affect milk quality. Clearly there is.

[0012] The use of cross-flow or tangential-flow filtration devices in the processing of milk has hitherto been attempted, and such devices are known in the art.

Several types of filtration devices have been disclosed which enable such cross-flow or tangential flow filtration to be achieved. In 1961, Zhavenovatii, A. et al. I. Perhaps the oldest of such known devices, as described in Russian Patent No. 142,626 to U.S. Pat. The suspension to be passed passes at high speed under load through the annular space between the two tubes and the filtrate flows through the porous tube. An improvement of similar construction uses two concentric cylinders, the inner cylinder being formed by a microporous membrane, and the liquid being exposed to a forced helical flow around such an inner cylinder.

Another cross-flow device comprises a series of superimposed filtration elements in the form of a plate or disk, on both sides of which a microporous membrane is arranged, for example, around a filtrate collection tube,
The suspension to be filtered passes sequentially between the disks in a spiral path.

Many other variations on cross-flow filtration systems have been developed. For example, US Pat. No. 5,009,781
The invention relates to a cross-flow filtration device having a filtrate network, comprising several longitudinal filtrate chambers and one or more filtrate channels traversing these filtrate chambers. US Patent 5,
No. 035,799 relates to a cross-flow filter assembly having a filter leaf assembly disposed in parallel in a filter tank having a pressurized inlet for creating a turbulent cross-flow of fluid over the filtration material.

US Pat. No. 5,015,397 discloses a spiral wound wedge wire.
e) a cross-flow filtration device including the tube and a filtration method. The contaminated influent enters at one end, and as it flows through the tube, becomes increasingly concentrated by contaminants and the clarified liquid permeates through the tube wall. US Patent No. 5,04
No. 7,154 relates to a method and apparatus for enhancing the flow rate of a cross flow filtration system. U.S. Pat. No. 4,569,759 relates to a tangential filtration device and a plant containing such a device.

Cross-flow filtration differs from once-through filtration in that the liquid feed stream is introduced parallel to the filter face and filtration occurs in a direction perpendicular to the direction of the feed stream. In cross-flow filtration systems, the direction of the feed stream is generally tangential to the membrane surface and the accumulation of filtered solids on the filter media is reduced by the shearing action of the stream. Thus, cross-flow filtration offers the possibility of quasi-steady-state operation with an almost constant flow rate when keeping the driving pressure difference constant. Unfortunately, however, this theoretical possibility has not been achieved in practice. Therefore,
The problem of reduced filtration flow rates has plagued conventional cross-flow filtration systems. Most of the suspended solids are retained on the tube walls and quickly form a dynamic membrane (also called a "filter cake" or "sludge layer"). This dynamic membrane is largely responsible for the subsequent filtration.

Particles that initially enter the wall matrix are eventually trapped in the matrix due to the irregularities and tortuous nature of the pore structure. As microfiltration proceeds, the penetration of additional small particles into the wall matrix is suppressed due to the presence of the dynamic membrane. The formation of a dynamic membrane, together with a possible blockage of the tube pore structure by trapped particles, results in a reduced filtration flow rate. In a typical system, this decrease is approximately exponentially proportional to the filtration time.

[0019] Cross flow filtration of milk has been attempted but has not yet been generally accepted due to the above problems. U.S. Pat. No. 5,028,436 discloses milk, which uses a microporous membrane having a porosity in the range of 0.1 to 2 microns, pretreated with an aqueous solution, dispersion or emulsion of lipids or peptides. Of soluble components and insoluble components of and the milk separated by the pretreatment membrane. In the method of this patent,
A first filtration step using a microporous membrane in a tangential flow mode is used.
A clear filtrate and a thick flowing concentrate are obtained. The filtrate contains all the salts, lactose, amino acids, oligopeptides and low molecular weight polypeptides in pure, undenatured form, and the filtrate contains practically all the casein and fat components of the milk. Thus, the filtrate cannot be considered to be "milk" since all fatty substances have been removed therefrom.

US Pat. No. 4,876,100 relates to a cross-flow filtration method for producing milk with reduced bacterial content. The raw milk is divided by centrifugation into one fraction consisting of cream and another fraction consisting of skim milk. The skim milk fraction is directed to a microfilter where small fat particles, proteins and some of the bacteria are separated. From the microfilter, a filtrate consisting of skim milk with reduced fat, protein and bacterial content and a concentrate with increased fat, protein and bacterial content are obtained. The concentrate is then pasteurized. Thus, the filtration method of U.S. Pat. No. 4,876,100, in addition to reducing bacterial levels in the filtrate, also reduces the fat and protein content of the filtrate, changing its properties from those of the original skim milk. become.

It is clear that the use of cross-flow filtration has not, to date, provided an acceptable method for reducing bacterial contamination of milk.

One means has emerged to overcome some of the problems associated with typical cross-flow filtration technology, known as dynamic microfiltration. The dynamic filtration process is
It overcomes the drawbacks of typical cross-flow technology because the liquid to be filtered is not simply guided tangentially over the membrane surface. As the solid at or near the membrane surface moves, the fluid at the interface between the rotor and the stator will be sheared. This shearing action tends to "scrub" the membrane surface, keeping it relatively free of particulate matter and preventing the filter cake from forming on the membrane surface. Otherwise, the particulate matter that accumulates on the membrane surface will remain in suspension, eventually
It is removed in a second stream, commonly referred to as a concentrate stream.

The dynamic microfiltration system can take various forms. For example, US Pat. Nos. 5,037,562, 3,
997,447, and 4,956,102 relate to dynamic microfiltration disc systems.

A cylindrical dynamic microfilter device is disclosed in US Pat. Nos. 4,956,102 and 4,900,4.
40, No. 4,427 ,. No. 552, No. 4,093,5
No. 52, No. 4,066,554, and No. 3,797,
662 and many other patents.
All patents referenced in this application are hereby incorporated by reference.

Dynamic microfiltration has never been applied to the processing of milk, and the use of cross-flow filtration of milk has been limited, in principle it has been used to fractionate milk into components based on fat content. Has been.

[0026]

By the practice of the method of the present invention, dynamic filtration of milk is successfully achieved without prior art problems such as milk quality degradation, premature filter blockage, and insufficient bacterial removal. This was surprisingly found this time.

[0027]

According to the present invention, milk, either whole milk or skim milk, is first homogenized,
Filter. By performing the homogenization step first,
The particle size of the milk fat small particles and other large suspended components is significantly reduced, allowing microfiltration of the milk without significant removal and entrapment of fat and other components.

Milk is a suspension of fat particles and protein particles in water. Homogenization reduces the emulsion particle size by passing it through a suitably sized microporous membrane, retaining bacteria in the microporous membrane and eliminating unwanted removal of milk fat and protein content. .

The milk after homogenization is filtered by dynamic filtration. Accordingly, the present invention provides an improved method for producing milk with reduced bacterial content without the need for pasteurization. The portion retained by the microfilter (concentrate fraction) can be recycled as part of the feed or discarded or used in other processes.

Accordingly, the present invention provides, in one aspect, a raw milk processing method for producing processed milk having a lower bacterial content than raw milk. This method homogenizes the milk and, within about 5 minutes of this homogenization, passes the milk through a micro-filter by passing the milk through a microfilter having an average porosity sufficient to reduce the bacterial content of the milk flowing through it. Carry out filtration,
Producing a filtrate having a lower bacterial content than the initial raw milk and a concentrate having a higher bacterial content than the initial raw milk. The resulting milk has a very low bacterial content, for example, less than about 10 ³ bacteria / ml, and possesses more organoleptic components than found in pasteurized milk having the same bacterial count.

The milk obtained as a result of the process according to the invention is generally more storage-stable than the milk obtained as a result of conventional pasteurization. Milk naturally contains some bacteria, and these bacteria survive the pasteurization process, so that after pasteurization, significant residual bacteria remain in the milk. Therefore,
Pasteurized milk must still be refrigerated to reduce bacterial growth and spoilage.

Unfortunately, some of the bacteria present in the raw milk are resistant to heat (bacteria resistant to pasteurization) and psychrotrophs (psychrot), such as Bacillus cereus.
rophic) (bacteria growing at low temperatures below 15 ° C.). The presence of anti-thermophilic, psychrotrophic bacteria in packaged dairy products is very disadvantageous because these bacteria grow very quickly even under refrigerated conditions, causing milk spoilage.

The present invention can produce sterile milk which can be stored at room temperature for a long period of time, for example, for 30 days or more. The sterile milk of the present invention is generally characterized by the absence of bacteria, and in particular by the absence of bacteria and pathogens, such as: Antithermic bacteria Micrococcus luteus (Micrococus) micro Staphylococcus roseus (M.roseus) Streptococcus pneumoniae (S.pneumoniae) (Streptococus) milk Streptococcus (S.lactis) Enterococcus faecalis (S.faecalis) Lactobacillus Deruburyukku bacteria (L.delbruecki (Lactobacillus) i ), Lactobacillus (L. lactis), Hell Bechikasu bacteria (L.Helveticus), Lactobacillus casei (L. casei), hairy lactobacilli (L.Trichodes) Staphylococcus aureus (S aureus) (Staphylococus) Staphylococcus epidermidis (S.epidermidi s) belonging to the genus Bacillus Bacillus cereus (B.cereus) (Bacillus) Bacillus subtilis (B.subtilis), Bacillus macerans (B.macerans) Clostridium butyric acid bacteria (C.butyrium) , (Clostridium) Clostridium Pasutoirianumu (C.pa steurianum), botulinum (C.b otulinum), Welch bacteria (C.perf ringens), Clostridium tetani (C.tetani) cold vegetative bacteria Pseudomonas aeruginosa (P. aeruginosa), (Psuedmonas) Pseudomonas fluorescens (P.flu orescens), fake nose Bacteria (P.pseud omallei) alkyl Nomo genus (Archnomobacter) Alcaligenes (Alcaligenes) reeds entry genus reeds entry Enterobacter Rigunieresshi (A.li (Acientbacter) gnieressii), reed entry Enterobacter Ekuiruri (A.equirli) Flavobacterium Flavobacterium Akuachiru (F.a (Flavobacterium) quatile), Flavobacterium Menigosepuchikamu (F.menigose pticum), Bacillus Bacillus cereus (B.cereus) (Bacillus) Bacillus subtilis (B. subtilis), Bacillus macerans (B.macerans), Bacillus stearothermophilus (B.s tearothermophilus) coliform bacteria Enterobacter Escherichia coli (E.coli), Salmonella Chifu (Enterobacter) skins (Salmonella Typhi) S. dysenteriae ( Shigella Dysen teriae ), Klebsiella lae Pneumoniae, and other Listeria spp. ( L. monocytogene (Listeria) es ) Therefore, the milk of the present invention is 30,0 as measured by the standard method.
The requirements for Grade A pasteurized milk, which requires the milk not to exceed a 00 / ml bacterial plate count and an E. coli type count of 10 / ml or more, can and typically are exceeded.

In another embodiment, the present invention relates to a method of processing raw milk for producing processed milk having a lower bacterial content than raw milk, comprising the following steps: (1) reducing said milk to a minimum of about 10%; Separating into a fat fraction having a fat content and a skim milk fraction; (2) homogenizing the skim milk fraction and removing about 5
Within minutes, the initial skimming is performed by subjecting the skim milk fraction to dynamic microfiltration by passing the skim milk fraction through a microfilter having an average porosity sufficient to reduce the bacterial content of the milk flowing through it. (4) producing a filtrate having a lower bacterial content than the milk fraction and a concentrate having a higher bacterial content than the initial skim milk fraction; (3) separately reducing the bacterial content of the fat fraction; And b.) Subsequently combining the skim milk fraction after microfiltration with the fat fraction with reduced bacterial content.

In still another embodiment, the present invention relates to a method for preparing
A process for producing milk having a fat content of: (1) homogenizing the skim milk fraction; within about 5 minutes of this homogenization, (2) reducing the bacterial content of the milk flowing therethrough. Dynamic microfiltration is performed on the skim milk fraction by passing the skim milk fraction through a microfilter having a sufficient average porosity to obtain a filtrate and an initial skim milk fraction having a lower bacterial content than the initial skim milk fraction. Producing a concentrate having a bacterial content higher than about 10%; and (3) reducing the bacterial content of the cream fraction having a minimum fat content of about 10%;
(4) subsequently combining the skim milk fraction after microfiltration with the cream fraction with reduced bacterial content.

The present invention also provides a method of processing milk for consumption by a consumer, comprising obtaining raw milk, homogenizing the milk,
Within about 5 minutes of this homogenization, the milk was subjected to dynamic cross-flow microfiltration by passing the milk through a microfilter having an average pore size sufficient to reduce the bacterial content of the milk flowing through it, Providing a filtrate having a lower bacterial content than raw milk, packaging the milk in a container for use by a consumer, and transporting the milk to a point of distribution to a consumer without refrigeration. To do.

Most generally, the present invention is a method of distributing milk for consumption by a consumer, comprising obtaining raw milk and reducing the bacterial content of the milk to a level of less than 10 ³ bacteria / ml. Allowing the milk to be packaged in a container for use by the consumer,
A method is provided that includes transporting the milk to a point of distribution to a consumer without refrigeration. This eliminates the need for refrigerated transport and refrigerated distribution vehicles.

The starting material is, for example, fresh, raw raw milk from livestock such as cows. The method of the present invention can be applied to processed milk that has already been pasteurized, but can be used to produce milk with improved organoleptic receptivity when compared to non-pasteurized milk. You can't get the full benefit like that.

The raw milk to be processed is first passed through a heat exchanger to adjust it to the appropriate temperature, and then, if desired, through a centrifuge to remove all or part of the cream fraction. Can also be removed as usual.

In overview, the raw milk is homogenized and passed through a dynamic microfilter at a reasonable speed to obtain a filtrate fraction and a concentrate fraction. The pores of the microfilter are sized to retain at least some of the bacteria. Some of the milk fraction passing through the retaining surface of the microfilter has no or reduced bacterial content (compared to milk before microfiltration), and the fat and protein content are essentially Consists of milk that does not change. The filtrate fraction can then be used directly for the production of other products, for example milk powder, or can be packaged without any further processing.

The filtrate fraction is more desirable than milk obtained by conventional pasteurization for a number of reasons. This milk retains more organoleptic components than pasteurized milk,
This makes this milk more preferred and more desirable from a consumer point of view. Furthermore, bacteria such as, for example, psychrotrophic bacteria, in particular Bacillus cereus , can be completely removed by the present invention, but are not possible using conventional pasteurization, so that the milk obtained by the present invention is It has a very long shelf life.

The concentrate fraction, which is retained by and collected from the retaining membrane surface of the microfilter, has an increased bacterial content (compared to the milk feed before microfiltration), and has a small fat particle and protein content. Consists of essentially unchanged milk. After this, the concentrate fraction can be discarded or used in other processes.

The filtrate can contain some bacteria,
The lower the bacterial content, the greater the storage stability of the product. Although complete sterilization is desirable, the initial growth rate of low residual bacterial concentrations is usually sufficiently low that the resulting dairy product has a very long shelf life.

The shelf life of the milk obtained by the process of the invention is substantially greater than that of normal pasteurized milk, since the concentration of Bacillus cereus is particularly greatly reduced.

Although the milk of the present invention is sterilized, the milk of the present invention may be sterilized under refrigerated or room temperature conditions, especially as the milk obtained by the use of conventional pasteurization methods cannot be sterile in nature. Has a very long shelf life if placed in a container under aseptic conditions. One means for accomplishing this is the use of the form-fill-seal method currently known in the packaging industry. This method is often used for packaging sterile solutions and the like, such as for the pharmaceutical industry. Milk produced according to the present invention can be packaged using a foam-fill-seal method, and such milk can have a very long shelf life even at room temperature.

The exact method or apparatus used to perform the filling is not critical. The following description is provided by way of example only, and as an illustration of how such a foam-fill-seal method can be used.

Some vertical foam, filling and sealing devices are unwound from the roll and by sealing the longitudinal edges together in the tube forming section,
A flat web of synthetic thermoplastic film, formed into a continuous tube, is used. In other devices, the tube is extruded from the resin melt at the time of use. The tube thus formed is advanced to the filling table, where it collapses across the cross section at the position of the cross section in the sealing device below the filling table. A transverse heat seal is formed by the sealing device at the collapsed portion of the tube. After the formation of the transverse seal, the quantity of the substance to be packaged, for example the quantity of liquid, is placed in the tube at the filling stand and fills the tube upward from said transverse seal.
The tube is then moved down a predetermined distance, sealed, and cut transversely in the second cross section.

One such vertical foam, filling and sealing device of the above type is sold under the trademark PREPAC. Another device is disclosed in U.S. Pat. No. 5,038,550.

[0049] The homogenized milk fraction before (if used) later and homogenized centrifugation, preferably heated or cooled to a temperature suitable for the first homogenization. The milk is then passed through a homogenizer where the fat emulsion size is reduced to a size sufficient to allow it to pass through the membrane. Preferably, the size of all suspended particles is less than about 1 micron. It is important that the homogenized milk be filtered relatively quickly after homogenization. Filtration is preferably performed in less than about 5 minutes, more preferably in less than about 2 minutes, and most preferably in less than about 30 seconds.

Again, the key factor is not the retention time prior to filtration, but the fact that filtration occurs before substantial coagulation of small particles, forming a substantial number of particles greater than about 1 micron. Is.

In order to properly emulsify, suspend and reduce the size of the milk fat component and other components to achieve proper filtration, the filtration must be performed prior to filtration through a cylindrical dynamic microfiltration unit. It is absolutely necessary to homogenize skim milk or whole milk. However, the rotating disc filter has a significant shear rate (sh) near the surface of the rotating disc.
(ear rate). Thus, some degree of homogenization of the milk can occur essentially simultaneously with the filtration. Such "self" emulsification of milk by the action of a dynamic microfilter enables the processing of skim milk by a rotating disk filter without the need for a separate homogenizer.

In practice, the rotating disk environment serves to homogenize and simultaneously filter the milk, but this is not achieved with a rotating cylindrical filter unit. The rotating disk filter produces a shear rate of about 200,000 sec- ¹ while the rotating cylindrical unit only generates 10,000
A shear rate of 000 sec ^-1 can be generated. Although there is substantial shear in the rotating disc filter unit, it is not considered to be sufficient in most cases to properly homogenize the whole milk.

Dynamic Filtration In the present invention, the effective flow of milk across the filter media is very high because the filtration is performed as dynamic filtration, ie, the media itself is maintained in constant motion. The particular physical shape of the dynamic membrane is not critical. Thus, the membrane filter media can take the form of, for example, a disk or a cylinder. Such dynamic microfiltration devices have been previously discussed and are suitable for practicing the present invention. Generally, dynamic microfilters include a cylinder or disk membrane element that rotates inside an outer impermeable cylinder. In a cylinder dynamic microfilter, when the fluid to be filtered is introduced into the gap between the stator and the rotating membrane, momentum from the rotating membrane is imparted to the fluid. Fluid near the inner cylinder experiences more centrifugal force than fluid near the outer cylinder. Under certain conditions, this phenomenon produces a flow pattern known as Taylor vortices, which prevents the formation of substantial residues on the membrane surface.

In this case, the dynamic filtration process is based on Tayl
Utilizing the generation of or vortices keeps the membrane surface free of possible residues, where the components of the residues remain suspended in the fluid to be filtered. This process divides the feed into a filtrate (the fluid portion that permeates the membrane) and a concentrate (a fraction containing suspended particles that usually adhere to the membrane surface and block the membrane). In such a method, the high flux through the membrane (flux)
rate can be maintained for a long time. Feed and concentrate amounts must be controlled to produce a stable fluid flow. Even with a low flow rate of the concentrate, it is possible to maintain a stable fluid flow on the surface of the membrane.

Dynamic microfiltration allows for a wide range of effective surface speeds on the filter media depending on the milk feed. For example, about 3 m / sec to about 50 m / sec, especially about 5 m / sec to about 3
An effective surface speed of 0 m / sec, most preferably from about 8 m / sec to about 20 m / sec is useful.

To obtain the desired surface velocity, about 2.5
A typical filter media as a cylinder having an inch diameter must be rotated at a speed of about 1,000 to about 6,000 revolutions per minute (rpm), typically at a speed of about 5,000 rpm.

When using a dynamic disk filtration device,
Typical disk media has a size of about 2 to about 48 inches in diameter. Such discs, depending on the particular dynamic microfilter design used, can have, for example, 1,000 discs.
rpm to about 8,000 rpm, typically about 1,000 rpm
It can be rotated at a speed from about rpm to about 6,000 rpm. Preferably, the shear rate of such a disc filter is from about 1,000 sec- ¹ to about 400,000 sec- ¹ . The preferred disc filter is 1991 1
Concurrent US Patent Application Serial No. 07/81, filed February 24,
There is a filter of the type disclosed in US Pat. No. 2,123, the specification of which is hereby incorporated by reference.

The pores of the microfilter are sized to retain bacteria present in the milk but still maintain an acceptable flow rate through the microfilter. Useful membranes include hydrophilic microporous membranes having good flow properties, narrow porosity distribution, and consistent bacterial removal performance for the bacteria in question. Porosity rating of the microporous membrane is art known methods, by measurement with a known test as "bubble point" (ASTM F-316-86) and K _L method (U.S. Pat. No. 4,340,479) , About 0.01 to about 5.0 microns. Preferably, the porosity grade is from about 0.1 to
About 1 micron. Most preferably, a filter having a porosity rating of about 0.2 to about 0.5 micron is used. Such microporous filters are well-known and readily available.

Preferred microporous membranes that can be used according to the invention include the trade names Ultipor N ₆₆ , Flu
Pall Co at Orodyne and Posidyne
What is marketed by Rporation, trademark Ze
sold by Cuno Corporation under tapor and Mil under the trademark Durapore
There are some that are being shipped from lipore.

Some of the cylinder membrane elements used in the present invention can be leak proof mounted on the support by methods known in the art.

Finally, the bacteria should be concentrated in a stream that is less than about 5% of the feed, and more than about 95% of the solids and proteins normally found in milk will cause the membrane to prolong. You should pass.

Dynamic microfilters can be operated in a single pass without having to recycle the concentrate. If desired, the concentrate can be recycled to the feed. If a cylinder dynamic microfilter is used, it can be operated at different ratios of filtrate stream / total feed stream (concentration). However, cylinder dynamic microfilters require about 90% in order to preferentially produce a filtrate with very low bacterial content as the desired product.
%, Especially with a filtrate / feed ratio of more than about 95%, especially more than 98%.

Similarly, if a rotating disk dynamic microfilter is used, it can also be operated with various ratios of filtrate stream / total feed stream. However, rotating disk dynamic microfilters require a wide range of filtrate flow /
It can be operated at a feed flow ratio. Choosing a higher ratio simply reduces the throughput, while operating at a lower ratio increases the throughput. To maintain a stable flow through the filter, operation at a ratio of about 40% is considered advantageous, but other ratios can be used.

The filtration of the freshly homogenized milk is carried out hot at 40 ° C. to 60 ° C., which is a crystallization temperature of the high melting point component of the milk fat of about 40 ° C. or somewhat higher. This is lower than the temperature used in normal heat pasteurization. Alternatively, the flow rate may be reduced slightly so that the milk is at a very low temperature, eg about 15 to about 35 ° C., especially about 20 to about 2.
It can also be filtered at 5 ° C.

After general microfiltration, the concentrate can be discarded in an acceptable manner, further processed, or used directly.

The process of the present invention is advantageously used when the desired end product is either whole milk, standardized milk or skim milk.

The flow rate of milk with reduced fat through the bacterial retention membrane is usually higher than that of milk with higher fat content.
In some circumstances, by combining filtered skim milk with filtered fat content, such as 2% fat milk,
It is economically advantageous to produce milk with a high fat content. This fat fraction may be a cream fraction having a minimum fat content of about 10%.

The filtration of the cream fraction is carried out, for example, in application No. 07 /
952,337 or using a bacteria retention filtration cartridge closed at one end.
This filtration can be performed in an industry accepted manner by heating the fat composition to a temperature at which it is in a liquid state and is easily filtered through a microporous membrane. The preheated fat can be homogenized before filtration. Alternatively, the fat composition can be pasteurized to reduce its bacterial content, or a combination of pasteurization and microfiltration can be used.

Further, if the purpose of the method is to obtain a protein concentrate from the milk of a transgenic animal, such as a transgenic cow, then a microparticle having a porosity rating of about 0.2 microns or less. Microfiltration is performed with a porous membrane to obtain a high concentration of concentrate.

Suitable devices for carrying out the method of the invention include centrifuges, microfilters, sterilization units,
It can be constructed by interconnecting conventional equipment, including heat exchangers and pumps. Persons skilled in the art will be able to operate such devices and provide flow and pressure control valves and other necessary support equipment to make further customary improvements to such devices as required in specific cases. Could be easily done.

All of the above references are hereby incorporated by reference.

The following examples further illustrate specific embodiments, but are in no way intended to limit the scope of the invention, which is defined by the claims.

General Methods The general methods used in the examples were as follows.

Method A: Control of Milk Temperature Unless otherwise indicated, the milk used in the following examples was commercial milk obtained from retail stores. Prior to filtration, the milk temperature was adjusted to the appropriate process temperature. Preferred operating temperature (4
0-6O <0> C) because most of the fat in milk is not in a crystalline form at such temperatures. Fermenter with 35 liter jacket (Chemap
A. G. FIG. Mold 3000 from a processer (proces)
s vessel). The processor was filled with milk and the contents were heated to about 50 ° C. by a hot water jacket unless otherwise indicated. The milk was agitated during this heating process to enhance heat transfer.

Once the milk has reached the desired process temperature,
The milk was fed to the homogenizer at a rate of about 1 liter / minute.

Method B: Upon entering the homogenizer of milk (Model 15MR from APV Gaulin, Inc.), the milk underwent a two-stage homogenization process, the first of which was at about 2500 psi and the second was at The stage was at about 500 psi.
The normal starting and operating procedures described in the APV Gaulin operating manual for this unit were followed. After homogenization, the milk was typically transferred to an intermediate surge tank, which was jacketed and maintained at the desired process temperature. This tank served as a fluid buffer between the homogenizer outlet and the feed to the filter. If desired, recycle the homogenized milk through a homogenizer,
A certain amount in the surge tank can be maintained.

Method C: Introducing Bacteria into the Milk Feed Stream In some experiments, the artificial titration of milk with bacteria and using the very high titers (ti) possible with the present invention.
ter) A decrease was demonstrated. The bacterial inoculum was added to the feed stream by a metering pump between the processor and the homogenizer. The inoculum flow rate was maintained to reach the desired bacterial concentration level of about 10 ⁶ bacteria per ml of milk. As the bacteria were introduced before the homogenizer, the bacteria were well mixed in the process fluid before entering the filtration device. In most examples, E. coli strain ATCC152
24 was used.

An alternative method for inoculating the milk with bacteria is to add the bacteria at the desired concentration directly to the processor. Such a method is undesirable because it exposes the bacteria to temperatures above ambient temperature for extended periods of time. This will result in undesirable growth or excessive killing of the bacteria before entering the filtration device, depending on the strain used.

Method D: Bacterial Analysis Test Mesophilic Bacteria: Serially dilute samples, pass appropriate dilutions through sterile 0.2 micron membrane, Mueller-Hinto
Bacterial concentrations were measured by culturing on n agar at 32 ° C. for 24 hours. These methods are described in the Manual of Clinical Microbiology (Manual of Clinical).
Microbiology), 2nd edition, 1974, A
It is described in detail in a publication entitled "SM, Washington".

Listeria monocytogenes ( Listeria mon)
octogenes ) ATCC 43256 was the test pathogen. The population level in the sample was measured by the method used by Agello et al. (Agello, G., et al.
Hayes, P .; Seeley, J .; Abstrac
ts of the Annual Meeting ,
1986, ASM, Washington, p. 5).

Method E: Cleaning Method Disinfection and disinfection were performed using 0.1N sodium hydroxide before all experiments. In the sterilization process, all of the membrane and associated equipment was first flushed with water and then treated with 0.1 N sodium hydroxide at 50 ° C. for about 時間 hour. Next, the caustic solution was neutralized with phosphoric acid. The system was then flushed with the neutralized solution until all parts were neutral. A filtration test was performed immediately after this treatment. At the end of each test, the entire device and the membrane elements were disinfected using a sterilization method.

Method F: Integrity Check
Each membrane element before 査 bacteria tested were examined for completeness. Publication NM900a, "The Pall Ultipo
r member filter guide ",
The forward flow test described in copyright 1980, available from Pall Corporation, was used for integrity checking.

Description of Filtration Device 1. Cylinder dynamic microfilter The cylinder dynamic microfilter (cylinder DMF) used in these experiments was Sulzer Brothe
rs Limited, BDF-01 manufactured by Winterthur, Switzerland. This device is R
ebsamen et al. (Dynam
ic Microfiltration and Ult
raftration in Biotechno
(Journal of the IVth World Filtration Congress, 1986, (Ostend, Belgium)). U.S. Pat. No. 4,066,
See also 554 and 4,093,552, which are incorporated herein by reference.

2. Description of the Membrane Filter Element The membrane filter elements used in these experiments are typically various grades of nylon membranes and are available from Pall Corporation.
Ultipor N ₆₆ and Posidyne, commercially available from Tion (Glencove, NY)
Met. The porosity used was 0.2, 0.30, 0.45,
0.65 microns. This membrane element has a surface area of 0.0
4 m ⁴ .

3. Dynamic microfilter in disk form The disk form consists of a 6 inch diameter membrane support disk mounted on a hollow shaft and contained in a leakproof housing with the required inlet and outlet connections. The support disk has a device for sealing the membrane sheet on its surface in a leak-proof manner, allowing the filtrate to flow through the membrane and the disk,
It contained a drainage space for removal through the shaft. The effective membrane area is 0.014 m ² and 4500 r
Rotation speeds up to pm were available.

Any of the previously described dynamic disk microfiltration units can be used in the practice of the present invention. See also US patent application Ser. No. 07 / 812,123, filed Dec. 24, 1991, for a description of another disc-shaped dynamic microfiltration device that can be used in the practice of the present invention.

4. Description of the membrane filter element This membrane filter element was of the same grade as the membrane described in the section on cylinder DMF. Typically, the membrane is a disc DM
An annular flat sheet "donut" cut to fit F. When incorporated into a dynamic microfilter, the use of an O-ring sealed the filtrate chamber from the feed. This membrane filter element is 0.014
It has a surface area of m ² .

Method G1: Cylinder dynamic microfill
Prior to the operational filtration of the filter, the filter elements were incorporated into a cylinder dynamic microfilter (DMF) as described in the filter assembly section. Disinfection and sterilization were performed using the method described in Method E. After observing the starting method described in Method G2, the milk to be filtered was supplied by a positive displacement pump from a surge tank into a cylinder DMF.
The amount of concentrate was controlled by a second pump or a pressure relief valve attached to the concentrate port. Feed, filtrate and concentrate temperatures and flow rates, and feed pressure were measured at various points in the course of the experiment, typically at 10 minute intervals. Standard operating conditions for cylinder DMF are 5000 rpm rotation speed, filtrate / feed ratio greater than 95%, about 1.3-.
The feed pressure was 2.0 bar. All experiments with this device were performed at constant feed rates.

Method G2: Dynamic Filter Start Before milk was introduced into the dynamic filter, the associated equipment was started by passing 0.2 micron filtered deionized hot water through the system. The rotation speed of the dynamic filter was adjusted to the operating speed by the water flowing through the system. When the system reaches equilibrium,
The milk flow was started. The milk eliminated the water in the system and filtration began.

Method H: Operation of the Disk Dynamic Filter The disk DMF filter element described in the filter assembly section was incorporated into the disk DMF. Disinfection and sterilization were performed using the method described in Method E. Method G
After observing the starting method described in paragraph 2, the milk to be filtered was supplied from a surge tank into a disc DMF. Concentrate volume and feed pressure were controlled by valves located at the concentrate port. At various points in the course of the experiment, the feed, filtrate and concentrate temperatures and flow rates, and feed pressures are typically
Measurements were taken at minute intervals. About 960ml for all experiments
/ Min feed rate was maintained. The reported filtrate flow rates were obtained when the flow was stabilized in the filtration unit.

[0091]

【Example】

The cylinder DMF with Example 1 0.45 micron Ultipor N ₆₆ membranes were fed skim milk at room temperature for about 600 ml / min. Operating conditions in DMF were specified in Method G1 and were maintained as summarized in Table 1. The feed pressure began to rise rapidly within a few minutes after the start of the test, indicating a blockage of the microporous membrane.

Example 2 Skim milk was heated to 50 ° C. according to method A and homogenized according to method B. The homogenized milk was stored in a surge tank for about 4 hours, during which time the temperature of the milk was maintained at about 50 ° C.
After this 4 hour delay period, the milk was
Approximately 6 in a cylinder DMF with tipor N ₆₆ membrane
It was fed at a feed rate of 00 ml / min. The preferred conditions for DMF operation, as specified in Method G1, were maintained. The feed pressure began to rise rapidly within just a few minutes after the start of the test, suggesting occlusion of the microporous membrane.

Example 3 Skim milk heated to 50 ° C. according to Method A and homogenized according to Method B was fed to a cylinder DMF equipped with a 0.45 micron Ultipor N ₆₆ membrane, homogenization was within 5 minutes . The preferred conditions for DMF operation as described in Method G1 were maintained. 10 until milk supply stops
A stable filtrate flow of 80 l / h / m ² was obtained.
No increase in feed pressure was observed during the course of this experiment.

When all milk was processed, the feed was switched to 50 ° C. non-homogenized milk without interrupting the operation of the system. Within a few minutes, the milk filtrate flow decreased rapidly and the system pressure increased, suggesting that membrane occlusion had occurred. This example provides for significant flow through the microfiltration membrane,
It clearly indicates that homogenization of the milk is necessary.

Examples 1 to 3 show that, prior to filtration, the milk is given sufficient shear (in this case by homogenization) to sufficiently reduce the emulsion particle size of the milk and to allow passage through the microporous membrane. Enable and demonstrate that it is necessary to perform proper filtration. In particular, Example 2 demonstrates that the particle size distribution returns to a large particle size within a short time after homogenization. For this reason,
For a suitable filtration, within a short time before filtration, for example within less than 5 minutes before filtration or preferably even within a shorter time,
Homogenization must be carried out.

[0096] after preheating by the Example 4 skimmed milk method A, was fed to the disc DMF equipped with a 0.45 micron Ultipor N ₆₆ membranes. The method described in Method H was used. A steady flow of filtrate was established and maintained for about 100 minutes until milk supply was stopped. Disc DMF operating conditions result in a calculated shear rate of about 200,000 sec ^-1 at the interfacial gap between the rotating disc and the membrane. This shear is within the range of shear generated by the homogenizer with the conditions of Method B.

This example demonstrates that the required shear before filtration is obtained in one step, ie without the need for a separate homogenizer. This example demonstrates that the membrane is not occluded by solids in the milk, and that the shear of about 200,000 sec- ¹ caused by the rotation of the disc reduces the particle size of the skim milk and allows it to pass through the microfilter membrane, thereby reducing It clearly demonstrated that it was sufficient to achieve a good filtration.

Table 1 summarizes the results of Examples 1-4; this data shows that a steady state filtrate flow through the membrane is obtained when the milk is sufficiently sheared within a short time before filtration. Show.

[0099]

[Table 1] Example 5 Skim milk was heated according to Method A and homogenized using the method described in Method B to investigate the relationship between particle size and time after homogenization. The particle size distribution over time after homogenization was measured. Particle Measurement Sy
Integra available from STEM, Colorado
ted Micro-OpticalLiquid V
olumetric Sensor (IMOLV-.
The particle size distribution was measured using 2). The laser particle counter is designed to measure a particle size distribution in the range of about 0.1-5.0 microns.

The milk samples were diluted 1: 300,000 and the analysis was performed as specified by the operation manual of the IMOLV device. For dilution of milk samples 0.04 micron filter with less than 50 particles / ml 18
Meggerohm DI water was used.

FIG. 2 shows the results of the particle analysis. The figure shows a plot of the number of particles compared to the number of particles at 5 seconds versus particle size. Clearly, this figure demonstrates that as the time after homogenization increases, the number of large particles increases.
As the number of small particles correspondingly decreases during this period, it is clear that the small particles aggregate over time to form large particles.

Examples 6-9 Cylinder DMF was tested for various porosity membranes and bacterial retention to determine the amount of steady filtrate flow of milk that could be achieved. The general methods used in Examples 6 to 9 are shown below.

1. The preferred membrane filter element was incorporated into a cylinder DMF.

2. An integrity check as described in Method F was performed. Membrane filter elements that do not pass this test were discarded.

3. The device was disinfected according to Method E.

4. The milk to be filtered was preheated by the method described in Method A.

5. The milk was homogenized according to Method B.

6. The starting method described in Method G2 was performed.

7. Breast milk from surge tank cylinder DM
Transfer to F at any flow rate.

8. Operating parameters were set using the guidelines of Method G1.

9. Appropriate measurements were made.

Typically, the cylinder DMF was operated at 5000 rpm in the filter, corresponding to about 10,000 sec- ¹ . The supply temperature is 50 ° C. and the supply pressure is 1.
The range was from 3 to 2.0 bar. In each of these examples, the filtrate / feed ratio was maintained above 95%. The flow rates reported in Table 2 are typically 15
The steady state filtrate flow rate obtained after minutes. Since the milk filtration was always 30 liters, the total experiment time varied in each case.

[0113] The Example 6 This example uses a 0.2 micron Ultipor N ₆₆ membranes. 330 using a feed rate of 250 ml / min
A steady state filtrate flow rate of 1 liter / hour / m ² was obtained. Filtration lasted about 130 minutes until no more milk was present in the processor and there was no apparent drop in filtrate flow rate.

Example 7 This example includes 0.30 micron Ultipor N ₆₆
A membrane was used. Using a feed rate of about 550 ml / min,
The experiment was terminated after about 60 minutes, with a steady state filtrate flow rate of 75 liters / hour / m ² .

Example 8 This example includes 0.45 micron Ultipor N ₆₆
A membrane was used. Using a feed rate of 740 ml / min, 10
A steady state flow rate of 80 liters / hour / m ² was obtained. Filtration lasted about 40 minutes without any noticeable decrease in flow rate, at which point the milk supply was stopped and the experiment was terminated.

Example 9 This example includes a 0.65 micron Ultipor N ₆₆
A membrane was used. 1 using a feed rate of 1100 ml / min
A steady state flow rate of 680 liters / hour / m ² was obtained. The filtration lasted about 30 minutes, at which point the milk supply was stopped and the experiment was terminated.

Examples 6 to 9 are summarized in Table 2. This data shows that by using the filtration process of the invention, stable filtrate flow rates are obtained with various grades of bacterial retention membranes. This table shows that in the process of the present invention, membranes with small pores and thus increased bacterial retention can be used at the expense of filtrate flow.

[0118]

[Table 2] Example 10 In this example, using a 0.2 micron Ultipor N ₆₆ membranes having a positive surface charge. The membrane used has its pore surface in which quaternary ammonium groups are present and has a high absorption capacity for biological substances.

Using a feed rate of 260 ml / min, 36
A steady state flow of 0 liter / hour / m ² was obtained. The filtrate flow rate was the same as that obtained with the uncharged membrane described in Example 6. Filtration continued for about 120 minutes until there was no more milk in the processor and there was no apparent decrease in flow. A filtrate / feed ratio of greater than about 97% was maintained throughout the experiment. Other experimental conditions are described in Table 3.

A large amount of protein from milk binds to the membrane surface,
Eventually, it is possible to block the membrane. This example showed that membranes that normally show protein affinity work well in a dynamic format.

Example 11 Using a feed rate of 740 ml / min of whole milk, a stable filtrate flow rate of 1130 l / h / m ² was obtained. Other experimental conditions are described in Table 3. The filtration lasted about 40 minutes, at which point the milk supply was stopped and the experiment was terminated.

This example shows that whole milk can be filtered using the method of the present invention. The observed differences in filtrate flow rates between whole milk and skim milk (as in Example 9) appear to be primarily due to differences in their viscosities. The filtrate flow ratio of whole milk / skim milk is approximately equal to the viscosity ratio of whole milk / skim milk.

[0123]

[Table 3] Examples 12-16 The examples for measuring filtrate flow through various bacterial retention membranes were repeated using a disk dynamic microfilter. The general methods of Examples 12 to 16 are shown below. The stated conditions apply generally to each example, unless stated otherwise.

[0124] 1. The preferred membrane filter element was incorporated into a disc DMF.

[0125] 2. An integrity check as described in Method F was performed. Membrane filter elements that do not pass this test were discarded.

3. The device was disinfected according to Method E.

[0127] 4. The milk to be filtered was preheated by the method described in Method A.

5. The milk was homogenized according to Method B.

6. The general starting method described in Method G2 was performed.

7. Milk from surge tank disc DMF
At an arbitrary flow rate.

8. Appropriate measurements were made.

Typically, a disc DMF has a 35 corresponding to a calculated shear rate of about 200,000 sec- ¹ in the filter.
Operated at 00 rpm. The feed temperature was 50 ° C. and the feed pressure was maintained at about 0.2 bar. Milk was fed to the filter at a rate of 960 ml / min to maintain a high cross-flow velocity across the membrane. The filtrate / feed ratio was adjusted in particular for the membrane porosity, the feed temperature and the rotor rpm. The unfiltered portion of the feed was recycled into the processor.
The flow rates reported in the table below are typically 1
The steady state flow rate obtained through the membrane as a filtrate after / 2 hours.

Example 12 In this example, 0.2 micron Ultipor N _{66 is used.}
A membrane was used. A steady state filtrate flow rate of 850 liters / hour / m ² was obtained.

Example 13 In this example, 0.45 micron Ultipor N
₆₆ membranes were used. A steady state filtrate flow rate of 1600 liters / hour / m ² was obtained.

Example 14 In this example, 0.45 micron Multipor N
₆₆ membranes were used. A steady state filtrate flow rate of 1600 liters / hour / m ² was obtained.

The data shown in Table 4 summarize Examples 11-13. This data shows that using the filtration process of the present invention, a stable filtrate flow rate is obtained with disk DMF using various grades of bacterial retention membranes. This table shows that in the present invention membranes with small pores and thus increased bacterial retention (decreased titer) can be used at the expense of filtrate flow rate.

[0137]

[Table 4] Example 15 0.45% skim milk at 18 ° C homogenized by Method B
Disc DM with micron Ultipor N ₆₆ membrane
Feed into F. Filtration was performed at a feed rate of 860 ml / min, at which feed rate a steady state filtrate flow rate of about 860 liters / hour / m ² through the membrane was obtained. The filtered milk was measured at 25 ° C. Other conditions for this example are listed in Table 5.

In this example, refrigerated skim milk contained about 18 parts.
Demonstrates that it can be processed through bacterial retention membranes by the method of the invention at 0 ° C. It is believed that the lower filtrate flow rate at this lower temperature reflects the higher viscosity of the milk at this temperature as compared to the higher temperature.

EXAMPLE 16 0.45 micron Ultipor N on disk DMF
Equipped with ₆₆ membranes. Whole milk is supplied to the disc DMF at a rate of 900 ml / min and passed through the membrane at about 850 liters / hour / m
A steady state filtrate flow rate of ² was obtained. The experiment was conducted without recirculation of the unfiltered portion of the feed.

[0140] This example demonstrates that whole milk can be filtered using disc DMF by the method of the present invention. Under essentially the same conditions, skim milk produced a near steady state filtrate flow of about 1600 liters / hour / m ² . The observed difference in filtrate flow between skim milk and whole milk approximately corresponds to the ratio of fluid viscosity, the difference.

Example 17 Filtration experiments were performed on disk DMF using the method described previously, while maintaining a high filtrate / feed ratio. The supply of skim milk was maintained at 115 ml / min. A filtrate flow rate of 460 l / h / m ² was obtained.

[0142]

[Table 5] Example 18 To demonstrate long-term operation, use large volumes (500 liters)
The experiments were performed using unpasteurized raw skim milk. The milk was preheated to 50 ° C. by passing it through a plate heat exchanger. This is then homogenized by method B and
It was fed into a cylinder DMF equipped with a micron membrane. In this example, a dynamic microfilter is typically 50
It was kept at 00 rpm. At a feed rate of about 1300 ml / min, the feed pressure varied in the range from 1.3 to 1.5 bar. The filtrate / feed ratio was maintained above 95%. A steady state filtrate flow rate of about 1680 liters / hour / m ² was obtained. No decrease in filtered milk flow, 5
There was also no increase in feed pressure during the 6 hours of continuous operation required to process 00 liters.

This example demonstrates that the filtration method of the present invention can be used for a long period of time.

Example 19 This example demonstrates that the method of the present invention can be used to filter milk using disc DMF to recover proteins from milk. Protein in milk is generally about 0.02
~ 0.30 micron size range (DGS
chmit, P .; Walstra, W.M. Buchhei
m, Neth. Milk DairyJ. 27 (197
3): 128), which makes them easier to recover by the method of the present invention. This can be achieved by transgenic animals, such as transgenic cows, sheep, etc., which have been genetically altered by methods known in the art to stimulate the production of biologically important proteins. It is of particular importance for recovering such proteins.

A disk DMF equipped with a 0.2 micron nylon filter was used. Milk filtration is 840ml /
At a feed rate of 35 minutes at this feed rate.
At a rotor speed of 00 rpm, a steady state permeate (permea) of about 850 l / h / m ² through the membrane
te) In the process of the present invention where a flow rate was obtained, the retentate was recycled and the permeate was discarded. The feed, permeate and retentate were periodically sampled and analyzed for total protein by the Kjeldhal method. It was found that the protein content in the retentate was initially the same as the protein content of the feed, but increased as retentate recirculation continued (4.9% retentate, 3.1% feed).

If a less porous membrane is used, better concentration of the protein into the concentrate stream should occur.

Examples 20 and 21 These examples were performed to confirm that no fractionation of the milk component occurred during the filtration process of the present invention. In these examples, the filtrate and concentrate were analyzed at various times during filtration to confirm protein concentration by the Kjedahl method and total solids by evaporation.

Example 20 Feeds, filtrates, concentrates were taken at various times during the trials described in Example 18 and analyzed for total solids in each stream. The data in Table 6 shows that there is no significant consumption of total solids from the filtrate when using a 0.65 micron membrane.

Example 21 As Example 13 was run, samples of feed, filtrate and concentrate were taken at various time points and analyzed for total solids and proteins in each stream. The data is shown in Table 6. Again, there was no significant depletion of solids or protein from the filtrate milk when using the 0.45 micron membrane.

[0150]

[Table 6] Examples 22-28 Examples 22-28 were performed to demonstrate that the present invention can remove bacteria from milk. The general procedure was maintained as in the experiments of Examples 6-18;
In this case, bacteria were added to the process stream by Method C.
Escherichia coli (E. coli) that is normally detected in milk, unless otherwise indicated, were used to inoculate these experiments. Samples of feed, filtrate and bacterial concentrate were taken at various times during filtration using aseptic techniques. These samples were analyzed for bacteria using the method described in Method D,
The results are reported in Table 7. As shown in this table, the present invention can significantly reduce the bacterial content of milk. From the high removal rate of E. coli, the high removal rate of Bacillus cereus can be known directly, and the Bacillus cereus cannot be completely removed by the usual pasteurization method. It is known that Escherichia coli has a rod-like structure having a size of about 1.1 to 1.5 μm × 2 to 6 μm, and Bacillus bacteria such as Bacillus cereus also have a similar size, about 1.0 to
It has a rod-like structure with a size of 1.2 μm × 3-5 μm. Thus, the ability to remove E. coli as shown in Table 7 means that this method also removes the highly objectionable Bacillus cereus, producing milk with a very long shelf life even at room temperature.

Examples 22, 23 and 24 Except that E. coli was introduced into the processing stream by Method C,
Examples 6, 8, and 9 were repeated. Samples of feed, filtrate and concentrate were taken for bacterial analysis. Table 7 shows the titer reduction data.

Example 25 Example 13 was repeated except that bacteria were introduced into the feed stream by Method C and the bacterial concentrate was not recycled to the processor. A steady state milk flow of about 1600 liters / hour / m ² was obtained. Table 7 shows the microbiological data.

The filtered milk contains only very low levels of 7-10 bacteria / ml of milk, which is clearly lower than the feed level of 10 ⁶ / ml. The titer reduction in this case was greater than 10 ⁵ . As a comparison, only a normal only about 10 ² to 10 ³ titer decreased during pasteurization of the milk is obtained.

Example 26 The experimental conditions and method of Example 12 were repeated except that E. coli was introduced into the feed stream by Method C and the concentrate was not recycled to the processor. About 850 liters / hour / m
A steady state milk flow of ² was obtained. Samples of feed, filtrate and concentrate were taken for bacterial analysis. The data shown in Table 7 demonstrate a titer reduction of greater than 10 ⁶ .
Since no bacteria were detected in the filtered milk, sterile milk was obtained. This embodiment shows that the method of the present invention
It demonstrates that bacteria can be completely removed from milk using MF and appropriately selected membranes. Therefore, sterile milk can be obtained.

Example 27 Raw milk that has not been pasteurized is produced by Escherichia coli-type bacteria such as Escherichia coli, Listeria monocytogenes and campylobacter (campyl).
and a wide range of microorganisms, including pathogenic bacteria such as B. bacterium) and B. cereus. In this example, milk was tested for native or "native" bacteria without external bacterial inoculation of the raw milk.

During the performance of Example 18, samples of the feed, filtrate and concentrate were taken for bacterial analysis.
Was analyzed for native bacteria.

Only 14 bacteria / ml were detected in the filtrate. The feed has 2500 bacteria / ml and the concentrate is 2
x10 ⁴ had a bacteria / ml. Furthermore, no psychrophilic bacteria were detected in the filtrate. Psychrophilic bacteria are bacteria that grow at low temperatures and cause spoilage of refrigerated milk.

Table 7 summarizes experiments 22-27. The data show that large titer reductions are obtained at the expense of filtrate flow rates for both cylinder and disk formats. This table also shows that sterile milk filtrate can be obtained by selecting the appropriate membrane.

[0159]

[Table 7] Example 28 Pathogens such as Listeria monocytogenes, which are of practical relevance to the dairy industry, are also present in milk, apart from the bacteria tested for titer reduction (E. coli). These pathogens pose more serious problems than E. coli bacteria tested on dynamic filters.
Tests were performed by the method described in Method D to determine whether the membrane filter element used effectively removed these pathogens. This test was performed on an off-line test apparatus and not on a dynamic filter.

The data shown in Table 8 are specific bubble points (A
0.45 μm Ult with STM F316-86)
IPOR N ₆₆ film indicates that absolutely eliminate listeria.

[0161]

[Table 8] Example 29 Filtered skim milk obtained by the method of Example 16 is collected by an aseptic method.

A commercially available cream was heated to 65 ° C. and 10% for E. coli obtained from Pall Corporation (East Hill, NY).
0.2 micron Ulti, showing a minimum titer drop of ⁶
Filter through por N ₆₆ membrane. The filtered cream shows a substantial bacterial reduction, which is harvested in an aseptic manner.

[0163] The filtered skim milk and the filtered cream are mixed and homogenized to give 2% fatty milk with reduced bacterial content. Embodiments of the present invention are as follows. 1. In the method for processing raw milk for producing processed milk having a lower bacterial content than raw milk, the following steps are provided: (1) The milk is treated with a fat fraction and a skim milk fraction having a minimum fat content of about 10%. (2) homogenizing the skim milk fraction and, within about 5 minutes of this homogenization, defatting a microfilter having an average porosity sufficient to reduce the bacterial content of the milk flowing through it; Performing dynamic microfiltration on the skim milk fraction by passing the milk fraction, a filtrate having a lower bacterial content than the initial skim milk fraction and a concentrate having a higher bacterial content than the initial skim milk fraction (3) separately reducing the bacterial content of the fat fraction; and (4) subsequently combining the skim milk fraction after microfiltration with the fat fraction having reduced bacterial content. And a method comprising: 2. A method according to claim 1 wherein the bacterial content of the fat fraction is reduced by dynamic microfiltration. 3. 2. The method according to claim 1, wherein the bacterial content of the fat fraction is reduced by pasteurization. 4. In a method for producing milk having a fat content of about 2%,
Next step: (1) a step of separating raw milk into a fat fraction and a skim milk fraction, and homogenizing the obtained skim milk fraction;
Within minutes, (2) performing a dynamic microfiltration on the skim milk fraction by passing the skim milk fraction through a microfilter having an average porosity sufficient to reduce the bacterial content of milk flowing through it. Producing a filtrate having a lower bacterial content than the initial skim milk fraction and a concentrate having a higher bacterial content than the initial skim milk fraction; and (3) a cream fraction having a minimum fat content of about 10%. And (4) subsequently combining the skim milk fraction after microfiltration with the cream fraction with reduced bacterial content. 5. Filtrate and raw milk having a lower bacterial content than raw milk by passing the raw milk through a microfilter having an average pore size of about 0.2 to about 0.65 μm sufficient to reduce the bacterial content of the milk flow therethrough. A method of treating raw milk to produce a processed milk having a lower bacterial content by obtaining a concentrate having a higher bacterial content, wherein the raw milk is homogenized within about 5 minutes before filtering the raw milk. A method characterized in that: 6. The average pore size of the microfilter is from about 0.2 to about 0.1.
Item 6. The method according to Item 5, wherein the thickness is 5 μm. 7. A method of treating raw milk to produce processed milk having a lower bacterial content than raw milk, homogenizing the milk and reducing the bacterial content of the milk flow therethrough within about 5 minutes of homogenization The milk is subjected to dynamic microfiltration by passing the raw milk through a microfilter having an average pore size of about 0.2 to about 0.65 μm, which is higher than the filtrate and the raw milk having a lower bacterial content than the raw milk. A method comprising obtaining a concentrate having a bacterial content. 8. The average pore size of the microfilter is from about 0.2 to about 0.1.
The method according to claim 7, wherein the thickness is 5 μm. 9. A method of processing milk consumed by a consumer comprising preparing raw milk, homogenizing the milk, and within about 5 minutes of homogenizing,
The milk is subjected to dynamic microfiltration by passing the raw milk through a microfilter having a mean pore size of about 0.1 to about 0.5 μm sufficient to reduce the bacterial content of the milk flow therethrough, A method characterized in that a filtrate having a low bacterial content is obtained, the milk is placed in a container used by the consumer and the milk is transported to the point of distribution to the consumer without being frozen.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used by the method of the present invention.

FIG. 2 is a plot of particle size in milk after homogenization.

Front Page Continuation (72) Inventor Joseph W. Dean, Juneer United States New York 11023, Great Neck, Berkshire Road 52

Claims (9)

(57) [Claims] 1. A method of processing raw milk for producing a processed milk having a lower bacterial content than that of raw milk, comprising the steps of: (1) adding the fat fraction having a minimum fat content of about 10%. (2) homogenizing the skim milk fraction and within about 5 minutes from this homogenization an average porosity sufficient to reduce the bacterial content of the milk flowing through it; Performing dynamic microfiltration on the skim milk fraction by passing the skim milk fraction through a microfilter having a filtrate with a lower bacterial content than the initial skim milk fraction and a higher bacterial content than the initial skim milk fraction (3) separately reducing the bacterial content of the fat fraction; and (4) subsequently, skimming the milk fraction after microfiltration and the fat fraction having a reduced bacterial content. Combining the two. 2. The method of claim 1, wherein the bacterial content of the fat fraction is reduced by dynamic microfiltration. 3. The method according to claim 1, wherein the bacterial content of the fat fraction is reduced by pasteurization. 4. A method for producing milk having a fat content of about 2%, comprising the steps of: (1) separating raw milk into a fat fraction and a skim milk fraction, and obtaining the skim milk fraction obtained. Homogenizing; from this homogenization about 5
Within two minutes, (2) performing dynamic microfiltration on the skim milk fraction by passing the skim milk fraction through a microfilter having an average porosity sufficient to reduce the bacterial content of the milk flowing therethrough Producing a filtrate having a lower bacterial content than the initial skim milk fraction and a concentrate having a higher bacterial content than the initial skim milk fraction; and (3) a cream fraction having a minimum fat content of about 10%. And (4) subsequently combining the skim milk fraction after microfiltration with the cream fraction having a reduced bacterial content. 5. A dynamic microscopic method for raw milk by passing the raw milk through a microfilter having an average pore size of about 0.2 to about 0.65 μm sufficient to reduce the bacterial content of the milk flow therethrough. Processing the raw milk to produce a processed milk having a lower bacterial content by performing filtration to obtain a filtrate having a lower bacterial content than the raw milk and a concentrate having a higher bacterial content than the raw milk A method wherein the raw milk is homogenized within about 5 minutes prior to filtering the raw milk. 6. The microfilter has an average pore size of about 0.5.
6. The method of claim 5, wherein the thickness is between 2 and about 0.5 [mu] m. 7. A method of processing raw milk to produce a processed milk having a lower bacterial content than raw milk, wherein the milk is homogenized and within about 5 minutes of homogenization, the flow of the milk flow therethrough. About 0.2 to about 0.65μ sufficient to reduce bacterial content
characterized in that the milk is subjected to dynamic microfiltration by passing the raw milk through a microfilter having an average pore size of m to obtain a filtrate having a lower bacterial content than the raw milk and a concentrate having a higher bacterial content than the raw milk And how. 8. The microfilter has an average pore size of about 0.5.
The method of claim 7, wherein the method is from 2 to about 0.5 μm. 9. A method of processing milk for consumption by a consumer, comprising preparing raw milk, homogenizing the milk, and reducing the milk to about 5%.
Within minutes, the milk is subjected to dynamic microfiltration by passing the raw milk through a microfilter having an average pore size of about 0.1 to about 0.5 μm sufficient to reduce the bacterial content of the milk stream therethrough. Obtaining a filtrate having a lower bacterial content than raw milk, placing the milk in a container used by the consumer, and transporting the milk to a point of distribution to the consumer without freezing.