What is Potassium Dihydrogen Phosphate (E340i) in Food and Uses as a Fertilizer?

Production | Property | Uses | Safety

Potassium dihydrogen phosphate (abbreviation MKP or KDP), the soluble phosphoric acid salt of potassium with the chemical formula KH2PO4, also known as monopotassium phosphate or potassium phosphate monobasic. It is more acidic than dipotassium phosphate.

This ingredient can be used as a buffer, sequestrant and nutrient supplement in food with the European food additive number E340(i). However, its more common uses is as a high efficient water-soluble fertilizer of phosphate-potassium for plants.

How is Monopotassium Phosphate Made? 

There are several manufacturing processes that can be employed to synthesize this ingredient, including neutralization, extraction, ion exchange, crystallization, and direct method. 

Among them, the neutralization method (neutralization phosphoric acid with potassium carbonate or potassium hydroxide) is mostly adopted in commercial production. 

The following are the chemical equation:

  • H3PO4+KOH=KH2PO4+H2O
  • 2H3PO4+K2CO3=2KH2PO4+H2O+CO2


Other names Monopotassium monophosphate, Monopotassium orthophosphate, Potassium acid phosphate, Potassium biphosphate
Chemical formula KH2PO4
Molecular weight 136.09
CAS number 7778-77-0
Appearance White crystalline granular or powder
Solubility Freely soluble in water, insoluble in ethanol
PH 4.2 to 4.8 (1% solution)

It dissociates HPO42- and H+ after dissolved in water. Meanwhile, it reacts with water to form phosphoric acid and potassium hydroxide as the following chemical equation indicates:

  • H2PO4- = HPO42- + H+
  • H2PO4- + H2O → H3PO4 + OH-

What are the Uses of Monopotassium Phosphate?

MKP can be used in food, agriculture, pharmaceuticals and chemical industry. 


You may have noticed MKP in energy beverages, coffee creamers, processed cheese, and low-sodium products.

It functions as a nutritional source of potassium and phosphorus, flavoring agent, chelating agent, buffering agent, and a leavening acid (in baking powder) in food. 

MKP may be found in the following food (1):

  • Infant formulae
  • Cereals
  • Dietary foods for infants for special medical purposes and special formulae for infants


In Coca Cola’s beverages, the purpose of monopotassium phosphate is a source of potassium (an electrolyte), an essential nutrient for the body, also used to keep a healthy blood pressure. (2). We can find this ingredient in the label of Coca-Cola Vitamin Water. (3)

It also can be found in sports drink (e.g. Gatorade) as a nutritive source of phosphorus and potassium. (4)


As a water-soluble agricultural fertilizer, monopotassium phosphate is widely used in seed soaking, root soaking, and foliar spraying of plants.

It can be used together with urea and ammonium phosphates, and commonly used in wheat, corn, sugarcane, soybeans, cotton, fruits, vegetables and other crops, especially suitable for citrus.


  • A high-concentration phosphate-potassium compound fertilizer, provides both phosphorus and potassium supplement for plants.
  • High nutrient content: it can be totally absorbed by crops in the form of H2PO4- and K+. P2O5 is 52%, K2O is 34%
  • Chlorine-free potassium fertilizer.
  • A suitable low pH and low salt index.
  • With the properties of stability, odorless, tasteless, easily soluble in water, low hygroscopicity, non-caking, so suitable for various soils and crops.


  • Promote photosynthesis. Potassium enhances crop photosynthesis during growth and accelerates the production and transformation of nutrients.
  • Improve crop resistance. Monopotassium phosphate can resist dry & hot wind, and prevent lodging of crops.
  • Improve fruit quality. Spraying during the fruit swelling period can protect the fruit and promote the fruit swelling, improve the quality of the fruit, increase the coloring, and improve the taste.
  • Enhance crop growth. Monopotassium phosphate has the effect of a regulator, which can increase the number of flowering, strengthen flower buds, blooms and roots, increase fruit setting rate, and can effectively promote the growth and development of roots.


As a nutrient, urine acidifier

Other potassium phosphates

MKP can be used to manufacture dipotassium hydrogen phosphate, tripotassium phosphate and potassium pyrophosphate.

Is Monopotassium Phosphate Safe to Eat?

Its safety as a food additive has been approved by the U.S. Food and Drug Administration (FDA) and European Food Safety Authority (EFSA), as well as the Joint FAO/WHO Expert Committee on Food Additives (JECFA).


Food grade Monopotassium phosphate is generally considered as safe (GRAS) when used in food. (5)


Its safety when used as a food additive has been re-evaluated by EFSA in 2019 and established an ADI expressed as phosphorus of 40 mg/kg body weight (bw) per day. (6)


Function Class: food additives, buffer, neutralizing agent, sequestrant, yeast food. (7)

Tolerable Intake: MTDI 70 mg/kg bw (as P) set in 1982. (8)


Now you may have a good knowledge of the food additive and fertilizer – Potassium dihydrogen phosphate E340(i), from its production, property, uses, and approved safety.

What kinds of food or fertilizer packagings have you found this ingredient in? Let me know in the comments.

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