The characteristics of phosphate and its role in food processing

The characteristics of phosphate and its role in food processing

Phosphate has two main functions in food processing: one is a quality improver to improve the structure and taste of food; the other is a mineral nutrient fortifier.

The role of phosphate in food processing is mainly based on the following characteristics of phosphate:

1. Buffering effect: The pH value of phosphate ranges from moderately acidic (PH~4) to strong alkaline (PH~12). When different phosphates are combined in different proportions, the pH value can be stabilized at pH 4.5 -Different levels of buffer between 11.7. In the PH value range of most foods (PH3.5-7.5), phosphate can be used as an efficient pH regulator and pH stabilizer to make food taste more delicious. The most substantial buffering effect is orthophosphate. For polyphosphates, as the chain length increases, the buffering capacity will decrease.

2. Water holding effect: Polyphosphate is a water retention agent with solid hydrophilicity, which can stabilize the water contained in food well. The quality of its water holding capacity is related to the type of polyphosphate, the amount of addition, the pH value of the food, and the ionic strength. For meat products and seafood, pyrophosphate has the best water holding capacity, followed by tripolyphosphate. As the chain length increases, the water holding capacity of polyphosphate will decrease.

3. Polyanion effect: Polyphosphate is a polymerized dielectric and has the characteristics of an inorganic surfactant. It can disperse insoluble substances in water or form a stable suspension to prevent adhesion and aggregation. Because polyphosphate can make the hydrosol of protein include a gel film on the fat globules so that the fat is more effectively dispersed in the water, it is widely used in the phosphorylation of starch, the dispersion of pigments, and emulsified food (milk). Products, ice cream, salad, sauces, etc.) and used as a dispersion stabilizer for sausages, minced meat products, and surimi products. For linear polyphosphate, its emulsifying and dispersing ability increases with the increase of chain length.

4. Chelation: Polyphosphate easily forms soluble complexes with metal cations in the solution, thereby reducing the hardness of water and inhibiting the effects of oxidation, catalysis, discoloration, and decomposition of vitamin C caused by metal cations such as Cu2+ and Fe3+, To achieve the purpose of preventing and delaying fat oxidation, preventing meat, poultry, fish from spoiling, and maintaining the color, to extend the shelf life of food.

The chelating ability of polyphosphate to metal ions (g/100g polyphosphate)

Polyphosphate	Ca2+	Mg2+	Fe3+
Sodium Pyrophosphate	4.7	8.3	0.273
Sodium tripolyphosphate	13.4	6.4	0.184
Sodium tetrapolyphosphate	18.5	3.8	0.092
Hexametaphosphate	19.5	2.9	0.031

The chelating effect of polyphosphate depends on the length of the chain and the pH value. Generally speaking, long-chain polyphosphate has a robust chelating ability to light metal ions. It increases with the increase of PH value; short-chain polyphosphate has a solid chelating ability to heavy metal ions, but it varies with the pH value. It was increased weakened chelation.

5. Protein function: Phosphate has a strengthening effect on protein and globulin, so it can improve the hydration and water holding capacity of meat products, improve the water permeability, promote the softening of food, improve the quality of food, and maintain the flavor of food. Simultaneously, phosphate in dairy products can prevent milk condensation during heating and prevent the separation of casein and fat.

6. Leavening effect: Acidic phosphates (such as sodium acid pyrophosphate, calcium hydrogen phosphate) are usually used as leavening acid for bakery products and react with bicarbonate carbon dioxide gas for the baking process.

7. Anti-caking effect: Tricalcium phosphate is usually used as an anti-caking agent to improve the free-flowing properties of powdered or hygroscopic foods. Tricalcium phosphate has a large specific surface area. It can bind more water, and its particular spherical crystal structure can produce a "ball effect" so that the powder has good free flow properties.

8. Extend the shelf life of food: Polyphosphate can enhance the storage stability of food and extend the product's shelf life. This effect is mainly based on: (1) PH regulation; (2) Bacteriostatic effect: the growth of microbial cells must rely on divalent metal cations, especially Ca2+ and Mg2+, and phosphate can chelate with these metal cations, and it can reduce the stability of the cell wall during cell division, and also reduce the thermal stability of many cells, thereby effectively inhibiting the growth of bacteria. The antibacterial effect of polyphosphate is related to its type (chain length), content, PH value, salt content, nitrate content, and other factors. Generally speaking, as the chain length increases, the antibacterial effect increases.

9. Mineral nutrient fortification: Calcium phosphate, magnesium phosphate, iron phosphate, and zinc phosphate are often used as mineral enhancers in food processing. The addition of iron phosphate and zinc phosphate to the gastric juice can enhance the biological effect of the gastric juice due to its better solubility. It will not promote the occurrence of natural oxidation.

Application of phosphate in food

1. Application in the processing of meat products and poultry products:

1.1  To improve the quality of meat products, phosphate is usually added in the processing of meat products, and its functions are:

a. Improve the cohesiveness of meat products and improve the slicing performance of meat products;

b. Improve the water holding capacity of meat so that meat products can still maintain their natural moisture during processing and cooking, reduce the loss of meat nutrients, preserve the tenderness of meat products, and increase the rate of finished products;

c. Control the PH value of meat products in the most suitable range for protein swelling and make the meat products produce the best color;

d. Improve emulsification performance and emulsification stability, and effectively prevent the separation of fat and water;

e. Block metal cations, delay the oxidation reaction in the processing of meat products, effectively reduce the rancidity rate of the products, inhibit the decolorization and rancidity of meat products, and extend the shelf life of meat products;

f. Improve the processing performance of meat products and increase production efficiency.


1.2  The water holding capacity of meat generally refers to the water retention capacity of the meat and the water added to the meat during processing. The water holding capacity is directly related to the texture and yield of meat products. The addition of phosphate can effectively improve the meat products’ water holding capacity.

How to reasonably use phosphate and other additives without affecting the flavor of meat products, maximize the water holding capacity and cohesiveness of meat products, and reduce the cooking loss of meat products has always been an essential topic in meat product research and development.

1.3  Reasonable use of phosphate in meat processing:

In practical applications, the appropriate phosphate type and addition amount should be selected according to the type of meat product, texture requirements, production process, raw materials, etc., combined with the characteristics of various phosphates. Meat products added with pyrophosphate can restore and enhance the natural water retention capacity of muscle protein. Polyphosphate can quickly be converted into pyrophosphate under the action of muscle enzymes so that the same effect can be achieved. Although pyrophosphate has the best water retention effect, its solubility is too poor, so it cannot be used alone in most cases. It is often used in combination with long-chain polyphosphate or potassium phosphate with better solubility. Besides, to play a synergistic effect between phosphates and phosphates and other additives, different compound meat product modifiers are often used.

a. For sausages and minced meat products, pyrophosphate and medium-chain polyphosphate are usually used, added in the form of dry powder when chopping. The pH value of the composite phosphate used is generally around 7, and sometimes a blended phosphate with a pH value higher than nine is also used.

b. The composite phosphate used for saline injection must meet the following requirements: 1) Good solubility in ice salt water; 2) High dissolution rate; 3) Good stability in ice saltwater.

The pH value of the composite phosphate used is generally 8.5-9.5. To achieve the best muscle protein activation effect when preparing ice saltwater for injection, it is best to dissolve phosphate in ice water first and then add salt. Generally, this order cannot be reversed.

c. The added amount of mixed phosphate is generally 0.1-0.4%, but the amount should be strictly controlled when using it. If the addition amount is too high, the original flavor of the meat will be damaged, and the color development will be affected due to the increase in the pH value.

2. Application in seafood processing:

2.1  Phosphate, as an excellent water retention agent, pH regulator, and antifreeze agent, is widely used in the processing of seafood, especially frozen seafood, and its functions are:

a. Effectively improve the water holding capacity of seafood, make the meat juice richer, and effectively maintain nutrients and moisture;

b. Inhibit the oxidation of fat and effectively extend the shelf life of seafood;

c. Reduce dripping loss after thawing and reduce cooking weight loss;

d. Maintain the natural color and flavor of seafood;

e. Synergize with carbohydrates to effectively prevent frozen denaturation of surimi protein.

2.2  When processing frozen shrimp, fish, and shellfish seafood, the product is usually soaked in a 3~10% compound phosphate solution (temperature less than 10℃). The concentration of the saturated solution and the soaking time is based on shrimp, fish, and shellfish. The type, size, and fishing time of seafood are determined.

The following factors should be considered when choosing the compound phosphate for soaking reasonably:

a) Can effectively improve the water holding capacity of seafood;

b) Good solubility in ice water;

c) Dissolve quickly in ice water;

d) Good stability in ice water.

The pH value of the composite phosphate used is generally higher than 9. 2.3 Generally, the compound phosphates added to frozen surimi are mainly sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate, and the addition amount is 0.1-0.3% of surimi.

3. Application of phosphate in flour products

3.1  Application in bakery products: Acidic phosphates (such as acid sodium pyrophosphate, calcium hydrogen phosphate) are usually used as leavening acid for leavening agents in bakery products and react with bicarbonate to provide the required carbon dioxide for the baking process gas. Different phosphates have different dough reaction rates (ROR), and phosphates can be reasonably selected according to the expected baking effect (bulk volume, pore structure, taste). Besides, phosphate can also be used as a flour conditioner, dough improver, buffer, and yeast nutrient.

3.2  Phosphate as a noodle quality improver is widely used in the processing of instant noodles and ordinary noodles, and its primary functions are:

a. Increase the degree of starch gelatinization, increase the water absorption capacity of starch, increase the water holding capacity of the dough, and make the instant noodles rehydrate fast and easy to brew;

b. Enhance the water absorption and swelling properties of the gluten protein, improve its elasticity, and make the noodles taste smooth and chewy, resistant to boiling and foaming;

c. The excellent buffering effect of phosphate can stabilize the PH value of the dough, prevent discoloration and deterioration, and improve the flavor and mouthfeel;

d. Phosphate can complex with metal cations in the dough, "bridging" the glucose group, forming the cross-linking of starch molecules, making it resistant to high-temperature cooking, and high-temperature fried noodles can remain after rehydration. The viscoelastic characteristics of starch colloids;

e. Improve the smoothness of noodles;

4. Application in dairy products:

Phosphate is used as a stabilizer and emulsifier in UHT-sterilized milk, cream products, condensed milk, milk powder, coffee mate, milk beverages, and cheese products. Its functions are:

a. Buffer and pH stabilization;

b. Interaction with protein: Disperse food ingredients, stabilize the emulsification system, enhance the water-binding capacity of casein, and effectively prevent the separation of protein, fat, and water;

c. Chelate polyvalent metal ions, which significantly reduce protein aggregation and precipitation during heating and storage, thereby improving milk's thermal stability and storage stability. And can effectively delay the occurrence of lactose coagulation.

5. Phosphate is also widely used in the following food processing fields:

◎ Beverage: used as an acidity regulator, stabilizer, and mineral nutrient fortifier;

◎ Potato products: used as stabilizer and color retention agent;

◎ Rice products: improve product elasticity and improve product taste;

◎ Seasoning and instant soup: stabilizer, acidity regulator;

◎ Hygroscopic powdered food: prevent caking and improve its free-flowing performance;

◎ Starch products and modified starch;

◎ Baby food, functional food: mineral nutrient fortifier.

Type of food	Phosphate species	Main effect	Referral rate（‰）
Instant noodles	Sodium acid pyrophosphate, Three sodium phosphate, Sodium tripolyphosphate, Sodium metaphosphate	Reduce the rehydration time of the finished product, not sticky or rotten	≤2.0
Biscuits and pastries	Sodium acid pyrophosphate, Three sodium phosphates, Sodium tripolyphosphate, Sodium metaphosphate, Calcium hydrogen phosphate, Dicalcium phosphate	Shorten the fermentation time, reduce the product damage rate, adjust the loose gaps, and extend the storage period	≤2.0
Drink	Phosphoric acid, disodium hydrogen phosphate, Sodium pyrophosphate, Sodium tripolyphosphate, Potassium polyphosphate, Calcium phosphate	Control acidity, chelation, emulsification, stabilizer	≤2.0
Ice cream	Disodium hydrogen phosphate, Sodium pyrophosphate	Dispersion, shorten freezing time	0.2~0.5
Cooked meat and red sausage,etc.	Disodium hydrogen phosphate, Sodium pyrophosphate, Sodium tripolyphosphate	Ruddy color, good taste, good elasticity, high yield	0.2~0.4
Sausages	Sodium acid phosphate, Disodium hydrogen phosphate, Sodium tripolyphosphate, Sodium pyrophosphate	Speed up processing, improve taste, good color	0.5

Article source: Sharing by Xu Sheng, a netizen of the Food Forum, Guangzhou Julan Chemical