Figuring Out Phosphates

Figuring Out Phosphates

By Lynn A. Kuntz 
Editor

Phosphate not only plays a major role in human metabolic systemsespecially in energy-transfer systems, and bone growth and healthits also the key element in phosphate compounds that provide innumerable functions in the food industry. Phosphates can aid processing or improve eating quality of many foods, including meat, poultry and fish products; process cheeses; and tortillas. The baking industry uses them in leavening systems, and soft-drink manufacturers add phosphate to cola drinks to enhance flavor. They work as emulsifiers in dairy products and as buffering agents in many different applications.

The term phosphate refers to a salt of phosphoric acid. When many phosphate units are linked together into a more-complex structure, they go by the name of polyphosphates. The food and beverage industry uses simple phosphates, pyrophosphates with two phosphate units, tripolyphosphates with three units, or polyphosphates that contain more than three phosphate units.

Cheesy functions 

Phosphates help cheese keep its shape and modify its melting properties. Sodium phosphate provides emulsification to cheese; the method isnt fully understood, but is probably due to its interaction with dairy proteins, such as casein, preventing the separation of fat and water.

According to Gene Brotsky, meat and dairy specialist, Innophos, Cranbury, NJ, orthophosphates, such as disodium and trisodium phosphate, and polyphosphates, such as tetrasodium pyro and sodium hexametaphosphate, are approved for cheese use. For standardized cheese products, 3.0% phosphate is allowed, though usually 1.8% to 2.5% phosphate is used, he says. Beyond this level, phosphate can cause crystals to appear in the cheese. If crystals are a problem, sodium aluminum phosphate can be used to avoid them.

Meating industry needs 

Processors add phosphates to meat, poultry and fish for many reasons, but especially to achieve moisture retention along with a higher yieldand flavor protection in processed meats. Phosphates can reduce oxidation, help retain marinade and cook juices, chelate metals, preserve color, and lend freeze/thaw stability.

Grinding or chopping meat can form a meat emulsion that needs to hold up during cooking and processing, such as smoking. Adding phosphates enhances stability in finely chopped meat systems, such as bologna or hot dogs, by influencing the pH, ionic strength, protein extraction, divalentcation binding and viscosity.

Meat emulsions extract and solubilize the proteins into a solution; this is enhanced by high ionic strength and pH. Additional chopping or mixing disperses the proteins around muscle cells and fat particles so that, when cooked, the protein coagulates to form a gel that stabilizes the matrix. Phosphates help extract proteins from meat, whether chopped or whole muscle. Phosphate type and pH are critical for optimal performance in meats, says Brotsky: Pyro is the most effective phosphate for meats; pH choice varies by application. Tetrasodium pyrophosphate extracts muscle proteins to a greater degree than just accounted for by its effects on ionic strength, pH, etc.

Alkaline phosphates increase meat pH approximately 0.1 to 0.6 units, depending upon the particular phosphate: Pyrophosphates have the greatest effect, while hexametaphosphates may have little effect. Acid pyrophosphates can decrease meat pH. Increasing or decreasing the pH away from the meat proteins isoelectric point increases its water-holding capacity.

In addition, Brotsky notes that: Phosphate solubility is critical where phosphate powder is added directly to the meat. If not completely dissolved, white phosphate particles will be noticed in the meat. Tetrasodium pyrophosphate is the most-difficult phosphate to dissolve. Properly processed tripolyphosphate and a new pyro molecule introduced to the United States by Innophos, trisodium pyro, have good solubility (when) added dry to meats.

Rise and shine 

Phosphates shine in chemical leavening systems where acids react with an alkali, typically sodium bicarbonate, to produce carbon dioxide gas in batters and doughs of baked products. The resulting gas causes the matrix to form an open, honeycomblike structure that greatly influences texture.

Bakery leavening systems commonly use anhydrous monocalcium phosphate (MCP), dicalcium phosphate dihydrate, sodium aluminium phosphate and sodium acid pyrophosphates. MCP also can act as a dough conditioner.

Ideally, the combination of the acids and soda should react completely, without leaving any acid or alkali. To achieve this, formulators need to look at the neutralization value (NV), a measure of how much baking soda is required to completely neutralize a given amount of that acid. For example, an MCP with an NV of 80 needs 80 grams of sodium bicarbonate to neutralize 100 grams of the acid. Higher neutralization values require less acid for a given amount of soda; lower ones require more acid.

In addition to NV, speed of reaction is an important characteristic. For example, different grades of sodium acid pyrophosphate (SAPP) are usually designated by a number that indicates the percent of carbon dioxide gas released after eight minutes, or dough rate of reaction. Those with higher numbers will release more carbon dioxide more quickly. The specific application, other ingredients and the products processing influences the required rate of reaction.

A dash of nutrition 

In addition to these food functions, calcium phosphates, usually in the form of di- or tricalcium phosphate, are widely used for food fortification, providing two essential human nutrients. The Recommended Dietary Allowance for phosphorus for adults is 700 mg per day.

Being inert, phosphate salts do not affect a foods flavor profile. However, depending on the application, solubility can be an issue, especially in the neutral range. Product designers can select grades with smaller particle sizes for beverages to ensure the particles remain suspended in solution and provide a smooth mouthfeel.

While each application has to be examined to determine which phosphate best meets its needs, its a task that reaps valuable results.