Use of Phosphates in Sausage

Use of Phosphates in Sausage

Lynn Knipe. 1983.  Use of Phosphates in Sausage.  Proceedings of the Third Annual Sausage and Processed Meats Short Course.  pp. 105-108.

            A 1982 ruling of the Food Safety and Inspection Service of the United States Department of Agriculture (USDA) allows the use of selected potassium phosphates and expanded use of all approved phosphates and sodium hydroxide in a wider range of poultry and red meat products.  This ruling includes, for the first time, the direct addition of phosphates during the process of cooked sausages.

            Phosphates are quite different from other ingredients conventionally added to emulsion meat products.  There are eleven different phosphates which have been approved for use in meat products and each one is somewhat different from the rest in its functional properties in meat.  Unlike ingredients such as salt (sodium chloride), phosphate is not phosphate.  The following discussion focuses on some of the properties of phosphates.

            First of all, the nomenclature applied to phosphates can be quite confusing.  A particular phosphate may be described by several different names.  The approved phosphates wit their chemical formulas and synonyms appear in Table 1. 

            Secondly, phosphates vary in cost.  A comparison of the current phosphate price is shown in table 2.  These prices may vary from supplier to supplier and can be expected to increase as the cost of the energy used in manufacturing increases.  Furthermore, blending of phosphates by suppliers will further increase the price.  Processors need to compare the cost versus benefits of all phosphates (particularly in blends) used to determine whether they are cost effective.

            Furthermore, phosphates are hygroscopic, which means they attract moisture from the air.  Comparatively speaking, potassium tripolyphosphate, tetrapotassium pyrophosphate, and sodium hexameta-phosphate are more hygroscopic than salt.  Extra precaution should be taken in storage to prevent their contact with moist air.  In contrast, sodium tripolyphosphate and tetrasodium pyrophosphate are less hygroscopic than salt. 

            Similarly, phosphates vary in their solubility in water.  Low solubility has always been a problem when using sodium phosphates in curing pickles.  This is the reason tetrasodium pyrophosphate has not been used much in the past in cured ham and bacon.  Low solubility will probably not be such a problem with emulsion products, particularly if a bowl chopper is used.  Still, we have observed some undissolved tetrasodium pyrophosphate in emulsions prior to cooking.  No undissolved phosphate had been found however, in any cooked products.

            More specifically, sodium hexameta-, potassium tripoly- and tetra potassium pyrophosphates are more soluble in water than sodium tripolyphosphate which, likewise, is more soluble than tetrasodium pyrophosphate.

            In terms of phosphates’ effects on flavor, some researchers have indicated that phosphates, particularly at high levels, result in “soapy” or bitter tastes.  At phosphate levels belowthe approved limits (e.g. 0.3 percent) we have only found tetrapotassium pyrophosphate to give an undesirable after taste in emulsion products.  At the maximum level of addition, tetrasodium pyrophosphate – treated franks were found to result in a “metallic” taste when the product was first removed from the smokehouse; however, when vacuum packaged and stored for 60 days, the phosphate-treated product was determined to be slightly preferred by a consumer-type panel over conventional product without added phosphate. 

            Furthermore, polyphosphates are hydrolyzed and/or converted to other forms in meat systems.  This hydrolysisis enhanced by the phosphatase action of meat proteins and micro-organisms.  What this means to processors is that given sufficient time, polyphosphates will be hydrolyzed to the orthophosphate form which has been shown to result in a surface “snow” and efflorescence on phosphate treated meat products.  With the exception of preblended meats, the hydrolysis of polyphosphates would not be a problem in emulsion products cooked immediately after comminution.

            Polyphosphates also chelate or “tie up” divalent cations (calcium, magnesium or iron) form hard water supplies.  While this allows phosphates to serve as water conditioners, once phosphates have “tied up” cations, their capacity to increase water-holding capacity tin meat is reduced.  This suggests that deionized or softened water should be used with phosphates.  Magnesium (Mg++) is chelated to a much greater extent than calcium (Ca++) by phosphates and is best chelated by tetrasodium pyrophosphate.  In addition, the chelation of Ca++ is much greater than that of iron (Fe++), and is accomplished best by hexametaphosphate.  If distilled or deionized water is not available, the type of water available may dictate the type of phosphate added to the meat. 

            The alkaline phosphates will enhance the stability of emulsion products and improve the binding of meat chunks in sectioned and formed meat products.  Phosphates also protect emulsion products from variations in emulsifying and cooking temperatures, and would be extremely valuable in the production of low-sodium meat products.

             The emulsion stabilizing action of alkaline phosphates is due to a number of functional properties of phosphates.  First, as expected, alkaline phosphates raise the pH of meat products.  These phosphates exhibit a high pH in water (the pH value listed in phosphate specifications), but since meat is a buffer itself, phosphates’ effect on meat pH is considerably less.  Even the limited increase in pH (approximately 0.6 unit maximum) appears to increase water-holding capacity and protein solubility.  On the negative side, this increase on pH will reduce cured color development.

            Secondly, phosphate anions act as poly-electrolytes and increase ionic strength.  This addition of electrolytes will cause an increase in water-holding capacity by direct binding of water to the phosphate anions and by the repulsion of protein groups due to the increase in and predominance of negative charges on the protein groups.  This repulsing effect opens up protein structures to allow for more water to be contained in the meat system. 

            With an increase in the water-holding capacity, one would expect purge in vacuum packaged products to decrease.  However, we have observed sodium tripoly- and pyrophosphates to only slightly decrease purge of franks held 2 months under vacuum compared to products without added phosphates.  On the other hand, sodium hexameta- and acid pyrophosphates were observed to increase purge considerably compared to products without added phosphates.  In addition, sodium acid pyro-, hexameta-, tripoly- and pyrophosphates prevented the “milky” purge found in the vacuum packages of franks made without added phosphate.  This would suggest that at conventional cured meat salt levels, phosphates are improving the microbial quality of meat products.  However, this was not further investigated. 

            The increased negative protein charge may also cause better distribution of fat particles in emulsion product, owing to the increased dispersion of protein throughout the mixture.  The better fat particle distribution may prevent the clumping of fat particles that occurs during over-chopping, and subsequent “fatting out” of the finished product.

            Pyrophosphates also serve to dissociate, or separate, actomyosin into its component parts: actin and myosin.  This is very advantageous, as myosin by itself is more beneficial than actomyosin for emulsification and bind in sausage products.  Tripolyphosphates, as stated previously, are hydrolyzed by phosphates into the pyrophosphate form.  This,then, gives tripolyphosphates an actomyosin-dissociating potential.

            Similar to the chelation in water, phosphates may also chelate divalent cations in meat.  A classical theory claims that phosphates bind divalent cations away from the protein crossbridges, allowing the protein structure to open up and hold more water.  However, some research suggests that phosphates may only affect free cations (having no effect on cations already bound to muscle proteins).  The cation chelation by alkaline phosphates protects cooked meats from “warmed-over” flavors, and also stabilizes cured color.

            One other phosphate effect allows increased chopping time with less temperature rise.  We have demonstrated that emulsions made with the addition of tetrasodium pyrophosphate require more chopping time to reach a specified temperature than emulsions made without; this extra chopping time could further increase emulsion stability by increasing protein extraction.  This is probably due to decreased emulsion viscosity, which would decrease the rate of emulsion temperature rise.  Decreased emulsion viscosity would be advantageous when pumping emulsions over long distances.  However, a decrease in temperature rise, per pass trough emulsifiers may result in less stable emulsions, if the final emulsion temperature is not carefully monitored.

            Salt (both sodium chloride and potassium chloride) is very important to the action of phosphates.  At the levels of addition that phosphates are limited to, the addition of salt has a major effect on ionic strength and more specifically, the chloride ionserves a valuable role in causing electrostatic repulsion of muscle proteins.  Emulsion stability of phosphate-treated emulsions is dramatically reduced in the absence of salt.  At lower salt levels (0.75 percent and lower), the maximum allowable level of 0.5 percent would further enhance emulsion stability, if they could be used legally.  At conventional salt levels (2 – 2 ½ percent), we see no additional value in adding phosphates at more than about 0.3 percent of the finished product weight.  In addition, the effect of phosphates on increasing yields of emulsified product is less than with whole muscle products. 

            The order in which salt and phosphates are added to the chopper has been studied, and there seems to be no difference in protein solubility or emulsion stability, regardless of whether salt is added before, after or simultaneously with phosphate.

            The use of phosphates in comminuted meat products is not without some problems.  First of all, as mentioned previously, the addition of phosphates such as tripoly- and pyrophosphates reduce the cured color development.  The cured color of phosphate-treated meat can be improved by adding the phosphate later in the chopping process or by holding the product 30-60 minutes prior to cooking. 

            Another potential problem may be the combination of phosphates with high collagen meat.  It appears as though the addition of salt and phosphates to high collagen meat reduces the emulsion stability to a level below that of high collagen meat treated with salt alone.  This is currently being studied here at Iowa State University.


Table 1.  Approved Phosphates


Monosodium phosphate



Monosodium dihydrogen crthophosphate

Sodium phosphate monobasic

Sodium biphosphate


Tetrasodium pyrophosphate



Sodium pyrophosphate

Tetrasodium diphosphate

Sodium diphosphate


Sodium hexametaphosphate



Sodium polyphosphate

Graham’s salt


Monopotassium phosphate



Potassium dihydrogen orthophosphate

Potassium phosphate monobasic


Tetrapotassium pyrophosphate



Potassium pyrophosphate

Tetropotassium diphosphate


Disodium phosphate



Disodium monohydrogen orthophosphate

Sodium phosphate dibasic


Sodium Tripolyphosphate



Pentasodium tripolyphosphate

Sodium triphosphate


Sodium acid pyrophosphate



Disodium dihydrogen pyrophosphate

Acid sodium pyrophosphate


Dipotassium phosphate



Dipotassium monohydrogen orthophosphate

Potassium phosphate dibasic


Potassium tripolyphosphate



Pentapotassium triphosphate


Table 2.  Comparison of 1982 Prices




Sodium Tripolyphosphate (STP)


Tetrasodium Pyrophosphate (TSPP)


Sodium Acid Pyrophosphate (SAPP)


Sodium Hexametaphosphate (SHMP)


Potassium Tripolyphosphate (KTP)


Tetrapotassium Pyrophosphate (TKPP)


90/10 STP/SHMP Blend


Tripotassium Phosphate (TKP)


Monopotassium Phosphate (MKP)


                        *FOB Production Point Truckload Quantities