Monosodium Phosphate (MSP) Is Still Irreplaceable in Food Formulation

📘 Introduction

Monosodium Phosphate (MSP, chemical formula: NaH₂PO₄), CAS No. 7558-80-7 (anhydrous) and 13472-35-0 (dihydrate), is a functional phosphate compound widely used in the food, beverage, pharmaceutical, and agricultural sectors. It is highly water-soluble, has excellent buffering capacity, and is biocompatible. Recognized under the EU additive number E339(i), MSP is a globally accepted food additive. It not only adjusts pH and stabilizes emulsions and dispersions but also serves as a nutritional source of sodium and phosphorus.

Thanks to the dissociation equilibrium of the H₂PO₄⁻ ion, MSP forms a stable buffer in acidic to neutral systems, effectively resisting pH fluctuations, preventing protein denaturation, fat separation, and metal ion oxidation. Its stability under high-temperature processing (e.g., baking and sterilization) makes it a key auxiliary agent in products like meat, bakery items, and beverages.

This article systematically reviews the physical and chemical properties of MSP, its compliance with international regulations (FCC, EU 231/2012, FDA, JECFA, and China’s GB standards), and explains its food-industry functionalities (such as moisture retention, leavening, and pH control). It also compares the anhydrous and dihydrate forms of MSP and forecasts future development trends, providing technical references for R&D, quality control, and trade compliance.

1. Discovery and Industrial Synthesis of MSP

🔬 1.1 Chemical Foundation (Late 19th Century)

Phosphate salts are among the earliest studied salts in inorganic chemistry. Reactions between phosphoric acid (H₃PO₄) and sodium generate a range of sodium phosphates:

• Monosodium Phosphate (NaH₂PO₄, MSP)

• Disodium Phosphate (Na₂HPO₄)

• Trisodium Phosphate (Na₃PO₄)

MSP was first synthesized in the lab through a neutralization reaction between phosphoric acid and sodium hydroxide:

 H₃PO₄ + NaOH → NaH₂PO₄ + H₂O

The resulting product is an acidic salt that dissociates into H₂PO₄⁻ in water. With high solubility, no odor, and good chemical stability, it evolved from laboratory synthesis into large-scale industrial production.

2. Discovery and Development of MSP as a Food Additive

🧪 2.1 Early Uses: From Industry to Food (Early–Mid 20th Century)

Initially used in water treatment and electroplating due to its excellent pH control and metal chelation properties, MSP caught attention in the food industry mid-20th century for its functional benefits:

• pH regulation in meat products to prevent protein precipitation

• Leavening agent in combination with sodium bicarbonate to improve baked goods

• Stabilization of beverage systems to prevent color oxidation and separation

As a result, agencies like the U.S. FDA and JECFA began assessing its safety and progressively added it to the food additive lists.

📘 2.2 Regulatory Milestones: From Local Approval to Global Recognition

Year	Country / Organization	Regulatory Event
1960s	JECFA (FAO/WHO)	Toxicological assessment and inclusion as food additive
1973	U.S. FDA	Classified as GRAS (Generally Recognized As Safe), approved for food use
1995	European Union	Assigned E number E339(i), categorized as acidity regulator
2010	China	GB 25564-2010 established food-grade standards for MSP
Ongoing	Japan, Australia-NZ, ASEAN	Included in national positive lists for dairy, beverages, baked goods, etc.

🎯 Summary Statement

MSP has been widely adopted in the global food industry due to its high safety profile and multifunctional benefits (e.g., pH regulation, moisture retention, leavening). Its regulatory approval is grounded in robust toxicological data and extensive practical application.

3. Safety and Regulatory Basis of MSP

✅ 3.1 Verified Safety

Evaluations by the EU EFSA and U.S. FDA conclude:

• No carcinogenic, mutagenic, or teratogenic risks

• Low acute toxicity (LD₅₀ > 4000 mg/kg)

• Metabolized into phosphate and sodium ions, naturally excreted

• Acceptable daily intake (ADI): 0–70 mg/kg body weight (as phosphorus)

EFSA states: "At typical usage levels in the food industry, MSP poses no significant health risk."

✅ 3.2 Key Regulations and Evolution

Year	Regulation	Description
1995	EU E339(i)	Defines MSP as acidity regulator, leavening agent, stabilizer
2010	GB 25564-2010 (China)	Specifies ≥98.0% purity, Pb ≤ 1 ppm
2012	EU Regulation 231/2012	Harmonizes purity and impurity limits for EU market access

✅ 3.3 Legislative Background: Standardization and Risk Mitigation

• Global coordination via JECFA to reduce trade barriers

• Industrial scaling of food production requires standardized additives

• Limits on impurities (e.g., As ≤ 3 ppm, F ≤ 10 ppm) mitigate contamination risk

4. Core Functionalities and Mechanisms of MSP in Food

🧪 Function 1: pH Regulator — Stabilizes System pH

MSP regulates pH via its ionization equilibrium: NaH₂PO₄ → Na⁺ + H₂PO₄⁻ H₂PO₄⁻ ⇌ H⁺ + HPO₄²⁻

• In acidic systems, H₂PO₄⁻ absorbs H⁺ to form H₃PO₄, preventing excessive acidity

• In alkaline systems, H₂PO₄⁻ releases H⁺ to buffer excess alkalinity

• A 1% solution has a pH of 4.1–4.7, suitable for acidic to neutral foods

Applications:

• Juice: Stabilizes pH at 4.0–5.0, prevents Vitamin C oxidation and pulp settling

• Pickled products: Adjusts acidity to 5.0–6.0, suppresses microbial growth

🧪 Function 2: Moisture Retention & Texture Enhancement

MSP binds with proteins (e.g., actin, casein), disrupting hydrogen bonds and promoting water retention during processing.

Food Category	Role	Effects
Meats (ham, sausages)	Binds actin	Reduces cooking loss by 10–15%, improves juiciness
Baked goods (bread, cakes)	Enhances gluten hydration	Increases moisture content by 5–8%, improves softness
Dairy (cheese, yogurt)	Stabilizes casein	Prevents dehydration, ensures uniform texture

🧪 Function 3: Leavening Agent Component

In combination with sodium bicarbonate: NaH₂PO₄ + NaHCO₃ → Na₂HPO₄ + CO₂↑ + H₂O

The CO₂ released creates a porous structure and enhances product texture.

Applications:

• Biscuits, cakes: 20–30% increase in volume, crisp texture

• Fried dough products: Reduced oil absorption, fluffier texture

🧪 Function 4: Emulsifier & Stabilizer

MSP helps stabilize emulsions through:

1. Adjusting interfacial charge — fat particles repel each other

2. Enhancing protein-based emulsifying films — improves oil-water interface stability

Applications:

• Plant-based milks (e.g., oat, soy): Prevents precipitation in coffee

• Ice cream: Stabilizes fat dispersion, prevents ice crystals, smooth texture

🧪 Function 5: Chelating Agent — Extends Shelf Life

H₂PO₄⁻ binds Fe³⁺ and Cu²⁺ ions to block oxidation reactions: H₂PO₄⁻ + Fe³⁺ → [Fe(H₂PO₄)]²⁺ (stable complex)

Effects:

• Fried foods, nuts: Reduces rancidity, extends shelf life by 30%

• Fruit & vegetable juices: Prevents browning from metal ions, preserves color

5. Comparison Between Anhydrous and Dihydrate MSP

A. Key Property Comparison

Property	Anhydrous (NaH₂PO₄)	Dihydrate (NaH₂PO₄·2H₂O)
Molecular Formula	NaH₂PO₄	NaH₂PO₄·2H₂O
Molecular Weight	120 g/mol	156 g/mol
Appearance	White powder	White crystalline granules
Purity	≥98.0%	≥98.0%
Solubility (25°C)	85 g/100 mL water	67 g/100 mL water
Hygroscopicity	High, prone to caking	Low, more stable
Loss on Drying	≤2.0%	20–25% (crystal water)
Main Application	Pharma, premium blends	Baking, food-grade additive
Price	Higher	Lower

B. Selection Guide

Consideration	Recommended Form
High-purity requirement	✅ Anhydrous
Cost-sensitive production	✅ Dihydrate
Humid storage environments	✅ Dihydrate (low moisture uptake)
Rapid dissolution (e.g., beverages)	✅ Anhydrous
Large-scale production	✅ Dihydrate (easier handling)

6. Global Market Overview and Future Outlook

6.1 Market Size and Regional Trends

Metric	2024 Estimate	2030 Forecast
Global Market Size	USD 520 million	USD 720 million
CAGR	—	5.5%
China's Market Share	>40%	Expected to maintain lead
Key Growth Regions	Asia-Pacific (China, India), Southeast Asia	—

6.2 Growth Drivers

• Expansion of the food sector: Rise in ready-to-eat and plant-based foods

• Technological advancement: Low-sodium MSP blends with KCl meet salt-reduction trends

• Emerging markets: Southeast Asia growing at 6%+ annually

6.3 Challenges and Responses

• Environmental pressure: Control phosphorus discharge, develop green technologies (e.g., water recycling)

• Regulatory tightening: EU REACH and FDA increasingly strict on impurities — purity standards must rise

• Competition from alternatives: Natural leavening agents gaining attention, but MSP remains indispensable due to multifunctionality

📗 Conclusion

Monosodium Phosphate (MSP) is a multifunctional phosphate that plays a critical role in food processing through pH regulation, moisture retention, leavening, and emulsification. The anhydrous and dihydrate forms cater to different needs — from premium formulations to conventional applications.

Global regulatory standards (e.g., E339(i), GB 25564-2010) ensure MSP’s safe and compliant use. Its balance of functionality and safety continues to support its application in reduced-sodium and plant-based food trends.

Attention: The above information is for commercial reference only due to the diversity of information collected, and Kelewell is not responsible for the authenticity of the data.