THE ROLE OF PHOSPHATE

1 Introduction

At present, there are 8 kinds of phosphates approved for use in my country, including sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium acid pyrophosphate, dihydrogen pyrophosphate Disodium hydrogen, etc. Adding these substances in food helps to diversify food varieties, improve its color, aroma, taste and shape, maintain the freshness and quality of food, and meet the needs of processing technology. They are very important quality improvers.

During the processing of meat products, adding phosphate has the following effects: increase the pH value of meat; chelate metal ions in meat; increase the ionic strength of meat; dissociate actomyosin. Therefore, after adding phosphate, the water retention and yield of the product can be improved. However, the ability of phosphate to improve the water retention of meat and improve the texture of meat depends on the type of phosphate used, the conditions of the applied phosphate system and the amount of phosphate added.

Phosphate has the functions of maintaining the water holding capacity of meat and improving the binding force in meat products. In the process of freezing, refrigerating, thawing and heating, meat will lose a certain amount of water, which will make the meat hard and lose some nutrients such as soluble protein due to water loss. When phosphate is added to the meat, it can improve the water holding capacity of the meat, so that the meat can still maintain its moisture during processing, so that the nutritional content of the meat is less lost, and the tenderness of the meat is also preserved.

2. Function and use

The role in meat products:

①Water holding effect: The phosphate ion of phosphate has a chelating effect, which can chelate metal ions such as calcium, magnesium, iron, and copper. After adding phosphate to meat, a large number of anionic groups can be released, and these groups quickly act on cations such as calcium and magnesium that affect the water retention of meat to form stable conjugates, so that the negatively charged carboxyl groups The release increases the mutual repulsion of negative charges, destroys the main peptide chain in the protein structure, makes the structure loose, and increases the water absorption. Polyacid salt is a highly hydrophilic moisture retention agent, which can well stabilize the moisture contained in food. The quality of its water holding capacity is related to factors such as the type of phosphate, the amount added, 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 weaken.

② Increase the ionic strength in meat: Myosin dissolves in water and easily forms a gel. It dissolves in a salt solution with an ionic strength above 0.2. Under normal circumstances, its water absorption is very low. However, after adding phosphate, it can provide 0.6 The above ionic strength promotes the dissolution of myosin from myofibrils, achieves high water absorption, and makes myosin have a strong dispersion, peptization and emulsification. Phosphate is a kind of polymer electrolyte and has the characteristics of inorganic surfactant, which can disperse insoluble substances in water or form a stable suspension to prevent the suspension from adhering and agglomerating.

③Emulsification and dispersion: Since phosphate can make the protein hydrosol form a film on the fat globule, so that the fat can be more effectively dispersed in water, it is widely used in the phosphorylation of starch and the dispersion of pigments. , emulsified food (dairy products, ice cream, salads, 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.

④Enhancing protein and actomyosin can improve the hydration and water holding capacity of meat products, improve the permeability of water, promote the softening of food, improve the quality of food, and maintain the flavor of food. After the slaughter of livestock and poultry, due to the decrease of ATP level, actomyosin cannot be dissociated into actin and myosin, which reduces the water holding capacity of meat. However, phosphate with a low degree of polymerization has a similar effect to adenosine triphosphate, which can dissociate actomyosin into actin and myosin, thereby increasing the water retention of meat and improving the tenderness of meat. At the same time, phosphate in dairy products can prevent the coagulation of milk when it is heated, and prevent the separation of casein and fat water.

⑤ Chelation: Phosphate is easy to form soluble complexes with metal cations in the solution, thereby reducing the hardness of water, inhibiting the oxidation, catalysis, discoloration, and decomposition of vitamin C caused by metal cations such as Cu2+ and Fe3+, to achieve Prevent and delay fat oxidation, prevent meat, poultry, fish, and maintain the purpose of luster. Phosphate chelation depends on chain length and pH. Generally speaking, long-chain phosphates have a strong chelating ability for light metal ions, which increases with the increase of pH value; short-chain phosphates have a strong chelating ability for heavy metal ions, but with the increase of pH value, Chelation is weakened.

⑹ Antibacterial effect, prolonging the shelf life of food: the growth of microbial cells must rely on divalent metal cations, especially Ca2+ and Mg2+, and phosphate can chelate these metal cations, and it can reduce the stability of the cell wall during cell division It can 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, nitrite content and other factors. In general, as the chain length increases, the antibacterial effect increases.

Application of Phosphate in Grain and Oil Products

① The improvement effect of phosphate on noodles is mainly manifested in: increasing gluten strength, reducing starch leached matter; enhancing noodle viscoelasticity; improving noodle surface smoothness.

②The application of phosphate in the production of quick-frozen steamed buns is mainly characterized by improving the texture and taste of steamed buns; increasing the water retention capacity of steamed buns, reducing the water loss of steamed buns during the cooling process after forming, proofing and steaming; increasing the bulkiness of steamed buns; Reduce the cracking of steamed buns after thawing; make the air pockets of steamed buns more uniform, delicate in texture and good in taste.

③ Compound phosphate also has certain influence on quick-frozen dumplings. Adding phosphate can inhibit the color of dumpling skin from deepening after thawing. The application of compound phosphate in seafood processing can effectively solve the problem of the loss of seafood flavor and nutrients, prevent and reduce oxidation; reduce the discoloration and taste of the flesh, so that the muscle tissue has better water retention and flavor better and improves its water holding capacity when thawed.

3. Use (meat products)

Phosphates allowed to be used in meat products include sodium pyrophosphate, sodium tripolyphosphate and sodium hexametaphosphate.

①Sodium pyrophosphate: white powder or crystal. Relative density 2.534, melting point 880°C, boiling point 93.8°C, specific gravity 2.534, colorless transparent crystal or white crystalline powder, easily soluble in water, solubility in 100g water at 20°C is 6.23, its aqueous solution is alkaline; insoluble in alcohol. The aqueous solution is stable below 70°C. When boiled, it will be hydrolyzed into disodium hydrogen phosphate. It will be weathered in dry air and lose crystal water at 100°C. It will easily absorb water and deliquesce in the air.

This product plays a great role in the stability of the product, and has the functions of increasing elasticity, improving flavor and anti-oxidation. It is often used in meat products such as sausage and Western-style ham, and the amount used alone should not exceed 0.5g/kg. It is often used in combination with sodium tripolyphosphate. Generally 0.3-0.5%, 0.9% in cheese; 0.3% in meat; 0.5% in milk powder, cream powder, quick-frozen fish, shrimp; 0.2% in condensed milk and beverages.

②Sodium tripolyphosphate: white powder, melting point 622 ℃, easily soluble in water, has remarkable chelating ability to metal ions such as calcium and magnesium, can soften hard water, make suspension into solution, has weak alkalinity, and is non-corrosive , is an inorganic surfactant that has a strong emulsifying effect on lubricating oil and fat. The bulk density is usually divided into low density 0.35-0.5g/cm 3 , medium density 0.51-0.65g/cm 3 , and high density 0.66- 0.9g/cm 3 ; According to the structure and shape, it can be divided into white powder anhydrous (Na5P3O10) and rectangular parallelepiped crystal hexahydrate. Anhydrous can be divided into type I and type II.

In the food industry, it is mainly used as a quality improver and moisture retention agent for meat food, canned meat, fruit juice drinks, dairy products, soybean milk, etc. It is mainly used for tenderizing canned ham and softening bean skin in canned broad beans. It can also be used as a softener and thickener .

③Sodium hexametaphosphate (alias: sodium phosphate vitreous body, Graham's salt): it is colorless powder or white fibrous crystal or glass block, melting point 616°C (decomposition), relative density 2.484g/cm3 (20°C) , Soluble in water, insoluble in organic solvents. Colorless transparent glass flake or white granular crystal. Hygroscopicity is very strong, exposed to the air can gradually absorb water and become viscous. It is mainly used as quality improver, chelating agent, fermentation leavening agent, pH regulator, etc. It has strong chelating, buffering and dispersing effects on metal ions. This product can promote protein coagulation. It is often used as a compound phosphate by mixing with other phosphates, or it can be used alone. The maximum dosage is 1g/kg.

Sodium hexametaphosphate is used in meat products, fish sausage, ham, etc., which can improve water holding capacity, increase adhesion, and prevent fat oxidation:

·Used in bean paste and soy sauce to prevent discoloration, increase viscosity, shorten fermentation period, and adjust taste;

·Used in fruit drinks and cool drinks, it can increase the juice yield, increase the viscosity, and inhibit the decomposition of vitamin C;

When used in ice cream, it can improve the expansion ability, increase the volume, enhance the emulsification, prevent the paste from being damaged, and improve the taste and color;

·Used in dairy products and beverages to prevent gel precipitation;

Adding it to beer can clarify the liquor and prevent turbidity;

·Used in beans, canned fruits and vegetables, it can stabilize natural pigments and protect food color.

·In addition, the aqueous solution of sodium hexametaphosphate is sprayed on the cured meat, which can improve the antiseptic performance.

Sodium hexametaphosphate can also be used as a water softener in industrial production, such as in dyeing and finishing, to play a role in softening water.

Mixed use

Mixing various phosphates is better than using them alone, and the mixing ratio is different, and the effect is also different. In the processing of meat products, the amount used is generally 0.1% to 0.4% of the meat weight.

The primary and secondary order of factors affecting the water retention of breast muscle protein gel in improving muscle protein water retention and gel strength is: sodium pyrophosphate > sodium tripolyphosphate > sodium hexametaphosphate, affecting the water retention of leg meat protein gel The order of factors is: sodium hexametaphosphate > sodium pyrophosphate > sodium tripolyphosphate. The difference in the effect of the two muscle types is mainly due to the difference in the muscle type and the mechanism of action of phosphate. Tests have shown that pyrophosphate has a significant effect on the water retention of breast meat. The reason is that pyrophosphate increases the PH value, improves the water retention of the gel through hydration, and simultaneously dissociates actomyosin into myosin and Actin, a protein molecule that binds water to increase water retention. Tripolyphosphate has no obvious effect on the water retention of leg meat protein gel. At this time, it is the structure of the gel that affects the water retention of the gel. The good water retention of the gel indicates that the network of the gel is relatively fine, and a large number of tiny pores are uniform. Distributed in the gel network, with the help of capillary force, some water is kept.

In terms of heat-induced gel strength of muscle protein, phosphate has a decreasing effect on its gel strength.

The principle that phosphate improves the water retention of meat products is that tripolyphosphate and pyrophosphate can increase the ionic strength of the meat system by changing the potential of the protein charge, and make it deviate from the isoelectric point, so that the charges repel each other, and in the protein There is a larger space between them, that is, the "swelling" of protein, so that the meat tissue can accommodate more water and thus improve water retention; hexametaphosphate can chelate metal ions, reduce the combination of metal ions and water, and make protein combine More moisture for increased water retention. The ratio of compound phosphate is: tripolyphosphate: pyrophosphate: hexametaphosphate: 2:2:1, and when its addition amount is 0.5%, it has the best tenderizing effect on beef and rabbit meat, and it is suitable to use Method of injection marinating for 16 hours. For ham, the optimal dosage is 0.4%, but for fish, the optimal dosage is 0.5%; the water retention effect of compound phosphate on surimi products is better than that of single phosphate, and the color, taste and texture of the products are uniform Better; but in chicken products, the optimal ratio of phosphate to obtain the maximum yield is 32.6% sodium hexametaphosphate, 45.6% sodium tripolyphosphate, and 21.8% sodium pyrophosphate. The greater the amount of compound phosphate added , the higher the yield, that is, the greater the positive effect on the water retention of the product, but when the dosage is greater than 0.4% for chicken and greater than 0.5% for fish, the rising trend of the yield of the product will slow down.

In practical application, the appropriate type and amount of phosphate should be selected according to the type of meat product, texture requirements, production process, raw materials and other conditions combined with the characteristics of various phosphates:

① For sausage and minced meat products, pyrophosphate and polyphosphate with medium chain length are usually used, and they are added in the form of dry powder when chopping. The pH value of the compound phosphate used is generally around 7, and sometimes a compound phosphate with a pH value higher than 9 is used.

② The compound phosphate used for saline injection must meet the following requirements: 1) good solubility in ice brine; 2) high dissolution rate; 3) good stability in ice brine. The pH value of the compound phosphate used is generally 8.5~9.5. In order to achieve the best muscle protein activation effect when preparing ice saline for injection, it is best to dissolve phosphate in ice water first, and then add salt. Generally, this order cannot be reversed.

③ When using mixed phosphate, the dosage should be strictly controlled. If the added amount is too high, the original flavor of the meat will be damaged, and the color will be affected due to the increase of pH value.

safe use

Phosphate is an active ingredient of human tissues, such as teeth, bones and enzymes, and plays an important and indispensable role in the metabolism of carbohydrates, fats, proteins and other important nutrients. Therefore, phosphate is often used as a food nutrition fortifier. But when there is too much phosphate in the diet, it will reduce the absorption of calcium, resulting in the loss of calcium in human bone tissue. If it lasts for a long time, it will also cause growth retardation and bone deformities. Therefore, phosphate must be added and used strictly within the scope of use stipulated by the state.

A phosphate-decomposing enzyme found in meat products breaks down phosphate and renders it useless. Therefore, in the production process of meat products, special attention should be paid to selecting the appropriate process to add to avoid destroying the effect of phosphate. Generally, in the production and processing of meat products, it is usually best to use it in the rolling and mixing after pickling; there is also a method of using solution pickling. At the same time, it is considered that excessive phosphate addition will also deteriorate the flavor and color of the product, and is not conducive to human health.

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