IL29157A - Bacteriocidal polyphosphates - Google Patents

Description

rgniun IHHinD -ηιπΐ"Ί ·Π PAT E NT ATTO R N E YS □ ' D 1 Q D " D U D PATENTS AND DESIGNS ORDINANCE SPECIFICATION Bacteriocidal Polyphosphates I/We STAUFFER CHEMICAL COMPANY, a corporation organized under the laws of the State of Delaware, of 299 Park Avenue, New York, N.Y, 10017, U.S.A. do hereby declare the nature of this invention and in what manner the same is to he performed, to he particularly described and ascertained in and by the following statement :- 29157/2 - la The present invention relates to the use of certain polyphosphates as bacteriocidal agents, and, more particularly it relates to retarding and eliminating spoilage in a wide variety of organic materials which are susceptible :of spoilage due to the growth of bacteria. Still more particularly, it relates to the application of certain polyphosphates to perishable food materials in order to preserve such materials against deterioration duo to the growth of bacteria.

The application of polyphosphates including tetrasodiu pyrophosphate, sodium tripolyphosphate, and sodium hexameta-phosphate is known in the art of preserving certain meat and fish products. U. S. Patent 2,735,777 (Meyer) teaches the incorporation of a polymeric phosphate such as sodium tetra-phosphate (Na6P40i3) or pyrophosphate ( a4P2C>7) into fresh meat to improve the taste, stability as well as color of the product. U. S. Patent 2,852,392 discloses the combination of a polymeric phosphate having a molecular weight at least in excess of 1000 together with sodium pyrophosphate as a composition useful in improving the texture and homogenity of ground meats.

U. S. Patent 2,735,775 teaches improving the appearance of glutinous sausages, e.g., by employing sodium hexametaphosphate in combination with an edible acid as a wash solution.

U. S. Patent 3,10^,170 teaches the prevention of organoleptic depreciation of poultry meat by the use of any non-cyclic salt of polyphosphoric acid. While the application of such phosphate materials in meat and fish has provided a satisfactory solution to problems including color and fat retention, a serious problem of spoilage of these foods and other foods of vegetable as well as animal origin etili exists. Therefore, it is the principal object of the present invention to overcome and eliminate the shortcomings inherent in the prior art and to provide a method for preserving food materials against spoilage caused, in particular, by the growth of bacteria.

In accordance with the present invention, we have now discovered, that nutrient containing materials, e.g., food materials of vegetable as well as animal origin, can be preserve against the action of deleterious bacteria in an unexpectedly highly effective manner by the incorporation therein of a small but effective amount of a substance comprising a medium chain length polymeric phosphate of the type: 0 0 Y wherein X represents hydrogen or an alkali metal including ammonium which is preferably sodium or potassium; and Y represents an alkali metal, including ammonium, which is preferably sodium or potassium; Nave represents an average chain length between about lk and about 100, preferably an average chain length between about 16 and about 3^· The term "average chain length" as employed herein is intended to represent a statistical average chain length or indication of the number of recurring units linked together comprising the anionic species. Such an average is determined by titration as described in Van Wazer et al Anal. Chem. 26, 1755-9 (19 ^)· In the practice of the present invention it has been discovered that when polyphosphates of the type represented above having various chain lengths were incorporated into media containing a variety of bacteria, on a pH adjusted basis, the anionic species of polymeric phosphates having average chain lengths within the above stated ranges are most effective as will be more fully hereinafter illustrated. It is, thus, apparent that salts as well as acids of such anions are included within the scope of the present invention.

The term "bacteriocidal" as employed herein is intended to refer to compositions which effectively retard the propagation as well as kill bacteria.

The bacteria against which the various polyphosphates were tested differ appreciably in their sensitivity toward the polyphosphates. The polyphosphates having an average chain lengt ih to 100 are extremely effective, especially against gram positive bacteria, e.g., Staphylococcus aureus, even when applied at a level as low as 0.2|$ by weight of polyphosphate. Gram negative bacteria are more resistant to the polyphosphates although each strain which was investigated was at least retarded in its growth by the action of the polyphosphates ° In general, it was found that sodium polyphosphates (Nave between ±6 and >h) when applied at concentration levels between about 1<$> and about 2$ controlled the growth and propagation of gram positive and gram negative bacteria in liquid media. The inhibiting effect of these polyphosphates of medium chain lengths against specific strains of bacteria was found to vary, however, with the concentration of polyphosphate employed which may vary from as low as 0.1 against certain bacteria no as high as 5$· Other factors which influence the bacteriological effect include the bacteriological population at the start of the experiment, incubatior time,; temperature and pressure, as well as pH. In the practice of the present invention it has been determined, however that sodium polyphosphates having an average chain length from l6-3k are significantly more effective in controlling the growth and propagation of bacteria than sodium hexametaphosphate or lower polyphosphates when compared on an equal pH basis. The polyphosphates having chain length higher than k exhibit a decline in bacteriocidal activity but are still useful and within the scope of the present invention. Salts of medium chain length polyphosphates (ik-ioo) exert a pH of about 6-7 whereas sodium tripolyphosphate (STPP) and tetrasodium pyrophosphate (TSPP) exhibit considerably greater alkalinity (pH 8-10). hen STPP and TSPP are employed without pH adjustmen they are effective especially against gram negative bacteria. Thus, although it has been found that the bacteriocidal activity of the lower phosphate anion is significantly weaker than that o the medium chain length polyphosphates, the combination of a low phosphate, in particular, sodium tripolyphosphate or tetrasodium pyrophosphate employed as an alkaline buffer and a medium chain length polyphosphate is extremely effective against both gram positive as well as gram negative bacteriological populations.

The medium chain length polyphosphates of the present invention have been found to exhibit synergistic action in combination with other food preservative agents including benzoates, sorbates, propionates, etc. The effect of destroying microorganisms by the use of elevated temperatures, e.g., by the process of pasteurization, has been found to be enhanced by the application of the medium chain length polyphosphates to the material susceptible of attack by the microorganism. It is contemplated that in the process of pasteurizing eggs more effective destruction of bacteria, in particular Salmonella, can be achieved by treating the eggs with medium chain length polyphosphate prior to the heat treatment. It is theorized that these polyphosphates sensitize the microorgahsim and thereby enhance their destruction upon heating. Thus, the use of the polyphosphates of the present invention in combination with other chemical agents as well as in physical process such as pasteurizationj is within the scope of the present invention.

Polyphosphates can be incorporated into the food material susceptible of bacteriological attack and spoilage by any suitable method or means known in the art including but not limited to incorporation by surfa e treatment operations such as dipping, flooding, spraying^as well as incorporation by direct admixture either to form a solution or blend with the food to be consumed. When the polyphosphates are incorporated by direct admixture, the preferable range of concentration of the polyphosphate in the food, on a weight basis, is between about 0.5» and about 2,0^. In situations where a surface treatment of foods is employed, the preferable concentration of the polyphosphate in the liquid dip, flood, or spray solution is preferably within the range between about 5 and about 20> on a weight basis.

The method of the present invention finds specific application in food areas including the following which are considered representative only; potatoes (including Irish as well as sweet potatoes), vegetables, e.g., onions, tomatoes, fish and poultry meats (including, incorporation of phosphates in the ice used to preserve these materials), malt, grain (prior to milling) , natural cheese. The method of application of phosphate preferred for the above listed food products comprises surface treatment, e.g., flooding or dipping. Other representative specific applications include eggs (control of Salmonella), process cheese (control of thermophilic bacteria), animal feeds, pet foods, juices, beers, wines, and refrigerated doughs. The preferred method of incorporation of phosphates into the latter group of food materials is by way of admixing the polyphosphate in the product to be consumed.

While the list enumerated above relates specifically to edible food materials, it is apparent that the medium chain length polyphosphates of the present invention, likewise, can be incorporated into a wide variety of organic materials which provide nutrients for bacteriological organisms and which are therefore susceptible of bacteriological spoilage.

The following examples are presented in order to illustrate the discovery upon which the present invention is predicated as well as specifi application thereof.

EXAMPLE 1 The following data presented in Table I illustrates the unexpected, enhanced bacteriocidal effect of polyphosphates (l6-5¾) as compared with lower polyphosphates (up to 12) and higher polyphosphates against the gram positive, Staphylococcus aureus when applied at the 1¾ level. The initial bacteriological population in the nutrient broth was 6 x 1Q6 per ml. and the temperature was maintained at 37 C under atmospheric pressure. The pH of each solution was maintained the same at about 6-7 except for the sodium tripolyphosphate solution which had a pH TABLE I Phosphate Turbidity Bacterial Count Additive (measure of Growth) per ml. (By plating) Chain AFTER Length 2k hrs. 5 days 10 days 8+ Na2HPO.¾ + KH2PO4 Heavy Turbid Est. 10" 10 10 Sodium Acid PyrophosTurbid 2 x 106 108+ 108+ phate + Tetra Sodium Pyrophosphate Sodium Clear 2 x 10s 2 x 103 50 Tripolyphosphate Sodium Polyphosphate 12 Clear 10s 20 20 16* Clear k x 103 0 0 18 Clear k x 103 0 0 3 Clear 2 x 103 0 0 Clear 2 x 103 00 1+0 8 8 NaCl (Cont Heavy turbid 108 10 10 When sodium tripolyphosphate is compared at a pH 6-7 in a nutrient broth under the conditions of Example 1, the approximat percent bacteria which survive after 2k hours is about 2o# as compared with 3$ at a pH of 8-9. Thus,, the lower polyphosphate anions^ e.g. , the tripolyphosphate anion, is significantly less effective against bacteriological organisms than the phosphates having a chain length between Ik and 37- EXAMPLE 2 The following data presented in Table II, below, illustrates the unexpected effectiveness of the polyphosphate anion (chain length 16-3 ) against: gram negative bacteria, viz., Escherichia col . The percentage growth is shown for various initial populations after an incubation period of 76 hours from treatment. The temperature was maintained at 37° C. under atmospheric, pressure; and the initial bacteriological population is as shown in the. table. The pH of each solution was maintaine the same at about 6-7 except in the tripolyphosphate solution which had a pH about 8-9.

TABLE II Phosphate Amount # Growth Vitrafos 0. 5$, 29 36 k 6 Potassium polyphosphate (1000+) in 0„5# Vitrafos 70 70 73 NaCl (Control) 8? 85 85 No additive IGQ'i 100$ 100 Alkali metal polyphosphates of medium chain length (chain lengths i6- 3k ) were also tested and found highly effective against S reptococcus faecalis. Pseudomonas fluorescens, Salmonella typhimurium., Salmonella senftenberg, Achromobacter, and Clostridium sporogenes. In the practice of the present inventio it has been found that the sodium polyphosphates are more effective as antibacteriological agents than potassium polyphos-phates and that the medium chain length polyphosphates are most effective against gram positive bacteria.

EXAMPLE 3 Test media containing egg whites were innoculated with Staphylococcus aureus in initial microbial populations of 103 per ml. and then treated by incorporation of 1$ polyphosphates of various chain lengths between 3 and 1000+.. An incubation period of three days at 3T°C. was permitted. The most effective polyphosphate was found to be sodium polyphosphate having an average chain length of about 18. It was noted that the bacteria population was decreased employing sodium polyphosphate (18) during the incubation period.

EXAMPLE k Test media containing ground fish fillet were innoculated wi h Staphylococcus aureus and tested in the same manner as in Example 3. Sodium polyphosphate (average chain length about 18) was found to be the most effective on this case. It was n t fed that no bacteriological propagation occurred in the sample containing sodium polyphosphate (l8) during the incubation period.

EXAMPLE 5 Test media containing beef broth were innoculated with Staphylococcus aureus under the conditions and with the results shown in Table III, following.

TABLE III Test Medium Beef Broth Beef Broth Initial Microbial 6 x 105/ml 6 x loVml Concentration Incubation 3T°C. 37°C Conditions 7 days 10 days Level of 0. $ Polyphosphate Most effective Sodium polyphosphate Sodium polyphosphate Polyphosphate Ave. chain length Ave. chain length to control growth 16 or 18 30 Remarks All bacteria killed 0.0001$ good growth with recovered potassium polyphosphate (1000+) EXAMPLE 6 Test media were innoculated with Pseudomonas fluorescens under the conditions and with the results shown in TABLE IV, below.

TABLE IV Test medium Beef Broth Beef Broth Initial microbial k x loVml. h x 102/ml. population Incubation conditions 37°C 37°C days 10 days Level of polyphosphate 1$ 1$ Most effective polySodium polyphos. Sodium polyphosphate phosphate to control Ave. chain length Ave. chain length growth 16 or 1.8 18 Remarks No turbidity All bacteria in broth killed Additional experiments carried out with polyphosphates having average chain lengths up to 78 show that the polyphosphate of higher average chain lengths exhibit a decline in bacteriocida activity.

Having thus described the invention, many modifications alterations, and specific applications thereof will become apparent to those skilled in the art without departing from the spirit and scope thereof.

Claims (4)

1. CLAIMS 1. The bacteriocidal method which comprises applying to the habitat of the bacteria an effective amount of a substance comprising a medium chain length polyphosphate of the type: wherein X is selected from the group consisting of hydrogen and alkali metal; and Y is alkali metal; and Nave represents an average chain- length between about Ik and about 100.

2. The method of Claim 1 in which Nave represents an average chain length between about 16 and -about j . 3· The method of Claim 1 in which X represents hydrogen. k . The method of Claim 1 in which X represents an alkali metal. , 5. The method of Claim k in which said alkali metal is sodium. ' ^ 6. The method of Claim k in which said alkali metal is potassium. 7· The method of Claim 1 in which Y represents sodium. 8. The method of Claim 1 in which Y represents potassium. ÷ 15 - 9· The method of preserving food materials from spoilage caused by the growth of bacteria which comprises incorporating in such food material a small but effective amount of a substance comprising a medium chain length polyphosphate of the type: wherein X is selected from the group consisting of hydrogen and' alkali metal; and Y is alkali metal; and N ^ represents ave an- average chain length between about 14 and about 100. 10. The method of Claim 9 in which N Q represents a average chain length between about 16 and about 34··■ 11. The method of Claim 9 wherein said food material is fruit juice. 12. The method o Claim 9 wherein saB food material is beer, 1

3. The method of Claim 9, wherein said food material is refrigerated dough. 1

4. The method of Claim 9# wherein said food material is wine. 15· The method of Claim 9, wherein said food material is potatoes. 16· The method of Claim 9, wherein said food material is animal feed. 29157/5 p - 16 - 17i The method of Claim 9» wherein said food material is eggs.. 18. The method of Claim 17 which includes thefUrther steps of treating said eggs with said polyphosphates a d then subjecting said so treated eggs "to the heat treatment of pasteurization. 19. The method of Claim 9, wherein said food material is fish. 20. The method of Claim 19, wherein .aid fish is packed in ice and said polyphosphates are incorporated in siid ice, 21., The method of Claim 9, wherein said food material is poultry. 22. The metDd of Claim 21, wherein s id poultr is packed in ice and said polyphosphates are incorporated in said ice* 23· A composition of matter inhibited against spoilage caused by the growth of bacteria and having improved taste appeal, which comprises a food material having incorporated therein between about 0,1 and about 5 b weight of a polyphosphate of the type: wherein X is selected from the group consisting of hydrogen and alkali metal} Y represents alkali metal; and ^a e represents an average chain length of between about 14 and about 100* 24. The composition of Claim 23 uherein said food ma erial comprises an edible liquid. 25· The composition of Claim 24» wherein said food material comprises a fruit or vegetable juice. ND:EH.