Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Bacteria or actinomycetales; media therefor
Reexamination Certificate
1995-05-15
2001-10-02
Lankford, Jr., Leon B. (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Bacteria or actinomycetales; media therefor
C426S034000, C426S036000, C426S041000, C426S042000, C426S043000, C435S236000, C435S235100, C435S252900, C435S253400
Reexamination Certificate
active
06297042
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the art of cheese making and, more particularly, to a method of improving the productivity of the cheese making process and the quality of a cheese product by preventing bacteriophage attack on bacteria used in the cheese making process.
BACKGROUND OF THE INVENTION
Cheese is a milk product that is generally rich in flavor and contains many high-quality nutrients. There are a great many varieties of cheese but all are produced in a similar manner. First, raw or pasteurized milk is cultured, clotted by acid, rennet or both. The resulting curd is then cut and shaped into the desired form with or without pressing. Fresh cheeses such as cottage cheese or cream cheese do not require any further processing. Other varieties of cheese are, however, subsequently cured or ripened to obtain a desired consistency, flavor and aroma. These characteristics are produced by a partial breakdown of milk proteins and fat by the action of microbial, milk and rennet enzymes.
The acid produced during the manufacture of cheese results from the fermentation of the milk sugar, lactose. Generally, this fermentation is initiated by the addition to the milk of a culture of specially selected acid bacteria. Known as a starter culture, many different types of lactic acid bacteria may be utilized for this purpose. The acid production in the cheese curd resulting from the activity of the starter culture advantageously functions to retard the growth of other bacteria that would otherwise cause undesirable fermentations in the cheese. Further, the acid production also favors the expulsion of the whey and the fusion of the curd particles.
The lactic acid starter cultures utilized in cheese making may comprise single or mixed strains of bacteria. All, however, must convert milk sugar in the curd into lactic acid within a reasonable time if a high quality cheese is to result. Several factors may, however, prevent this conversion. Of these factors, the most important is bacteriophage attack. Specifically, cheese production loss due to phage attacks on lactic culture is the number one problem faced by the dairy products industry today.
Bacteriophages or phages, are viruses that attack a lactic acid bacteria cell, commandeer the biosynthetic or reproductive machinery of the cell, produce new phages and in the process lyse the bacteria cell. Phages are prevalent in cheese making facilities. They may contaminate the milk in a number of ways including through use of infected starter cultures or through contact with phage-carrying dust particles.
Phages effectively slow down or totally inhibit the activity of the starter culture. As a result, the milk fermentation medium is often insufficiently soured and insufficient acid is produced to retard the growth of undesirable bacteria that cause undesired fermentation products. Hence, the cheese spoils resulting in an undesired consistency, flavor, and/or aroma.
It is known that phage multiplication is influenced by temperature, pH and calcium content of the medium among other factors. While phage outbreaks can be at least partially controlled by rigorous hygienic handling of starters, by culture rotation and/or by culturing starters in calcium-reduced media, further improvements in controlling phage proliferation and attacks on starter cultures are desired. Toward this end, however, it should be appreciated that attempts to isolate phage-resistant strains have generally not met with success. A need is therefore identified for an improved method of controlling bacteriophage attacks on lactic acid bacteria utilized in the cheese making process.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide an improved method of reducing or preventing bacteriophage attack on bacteria used in the cheese making process, overcoming the above-described limitations and disadvantages of the prior art.
An additional object of the present invention is to provide a simple and effective method of controlling bacteriophage attacks on lactic acid bacteria used in the cheese making process wherein the bacteria are protected against attack. Specifically, blocker peptides are produced and collected. These blocker peptides attach to sites on the cheese making bacteria and subsequently prevent attachment of bacteriophages so that the bacteria may continue to function normally, fermenting milk sugar and producing the desired curd more effectively and efficiently. As a direct consequence of the resulting faster processing time, if any bacteriophage infection does take place it is limited and localized and, therefore, does not have a substantial adverse effect on the resulting cheese product. Superior quality and greater productivity is therefore insured.
Still another object of the present invention is to provide a related method of making cheese with bacteriophage resistant cheese making bacteria as well as a relatively high quality cheese with more uniform consistency, flavor and aroma.
Additional objects, advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, a method is provided for controlling (e.g. reducing or preventing) bacteriophage attack on bacteria such as lactic acid bacteria starter culture used in a cheese making process. The method includes the steps of treating a blocker peptide precursor selected from a group consisting of a source of immunoglobulins, bacteriophages, bacteriophage parts or mixtures thereof with a protease enzyme that hydrolyzes the blocker peptide precursor. The method also includes the collecting of the blocker peptides produced by the hydrolysis of the blocker peptide precursor and the formulating and heat treating of a starter media with the blocker peptides. Finally, the method includes the additional steps of growing bulk cultures of bacteria used in the cheese making process in a peptide containing starter media and adding the bacteria grown in the peptide containing starter media to a fermentation medium for producing cheese.
More specifically describing the invention, the source for immunoglobulins may include raw whey, dried whey, whey protein isolates, non-fat dried milk, blood serum protein isolates, purified immune protein preparations and mixtures thereof. Preferably, the bacteriophage parts includes spikes, tail fibers, filaments and mixtures thereof. Also, the enzyme used in the present method is preferably selected from a group consisting of papain, bromelain, ficin and mixtures thereof. Of these, papain appears to be the most preferred enzyme.
In accordance with a further aspect of the present invention, a method of making cheese with bacteriophage resistant cheese making bacteria is provided. In addition to the above steps, this method includes the cutting of the curd. Specifically, the curd is cut at a selected time in an effort to increase cheese yield and maximize the result and quality of the cheese. For example, the curd may be cut in accordance with the method set forth in my co-pending U.S. Pat. No. 5,172,193 entitled “Method of Predicting Cut-Time of Milk Coagulum in Cheese-Making Process”. Further, the method may include the additional step of curing the curd to provide a cheese of desired consistency, flavor and aroma. Any known method of curing may be utilized to produce a cheese of desired qualities. Cheeses produced in accordance with the present method are also the subject of the present invention.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown a
King and Schickli PLLC
Lankford , Jr. Leon B.
University of Kentucky Research Foundation
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