The Essential Guide to Propylene Glycol in Food & Beverage Manufacturing
Table of Contents
What you will learn
📋 What You'll Learn
This guide walks you through the essential guide to propylene glycol in food & beverage manufacturing with detailed instructions.
The Essential Guide to Propylene Glycol in Food & Beverage Manufacturing
How this GRAS-listed humectant improves texture, extends shelf life, and distributes flavors across the food industry
What Is Propylene Glycol?
Propylene glycol (1,2-propanediol, C₃H₈O₂) is a clear, colorless, nearly odorless synthetic liquid with a faintly sweet taste. It's classified as a diol—a molecule with two hydroxyl (OH) groups—which makes it both water-soluble and an effective solvent for many organic compounds. This dual solubility is what makes PG so valuable in food manufacturing.
At room temperature, propylene glycol is slightly viscous with a density of 1.036 g/cm³. Its hygroscopic nature—the ability to attract and retain water molecules from the surrounding environment—is the foundation of its humectant functionality in baked goods, confections, and other food products.
Key Chemical & Physical Properties
| Property | Value | Significance in Food Use |
|---|---|---|
| Molecular Weight | 76.09 g/mol | Small molecule, rapid diffusion through food matrices |
| Boiling Point | 188°C (370°F) | Stable during baking and cooking processes |
| Freezing Point | -60°C (-76°F) neat | Prevents ice crystal growth in frozen desserts |
| Viscosity (25°C) | 48.6 mPa·s | Provides smooth mouthfeel in liquid products |
| Water Activity Reduction | Significant at >5% | Inhibits microbial growth, extends shelf life |
| Flash Point | 99°C (210°F) | Safe under all normal food processing conditions |
How Propylene Glycol Functions in Food Manufacturing
PG serves four primary functions in food formulation, often simultaneously—which is why formulators value it as a multi-functional ingredient that simplifies ingredient lists.
🌊 Humectant (Moisture Retention)
PG's hydroxyl groups form hydrogen bonds with water, retaining moisture in baked goods, soft candies, and energy bars. At 1-5% concentration, it keeps products soft and prevents staling by reducing water activity without making products wet.
🎨 Flavor & Color Carrier
As an excellent solvent for both water-soluble and oil-soluble compounds, PG dissolves and distributes flavoring agents, food dyes, and essential oils uniformly throughout liquid and semi-solid products—preventing hot spots or uneven color.
⚖️ Emulsifier & Stabilizer
In oil-water systems like salad dressings, cream liqueurs, and flavored syrups, PG acts as a co-solvent that helps keep otherwise immiscible ingredients blended. It reduces interfacial tension between oil and water phases.
🛡️ Preservative Aid
By lowering water activity (aw) below 0.85—the threshold for most bacterial growth—PG extends shelf life without requiring higher levels of traditional preservatives. This is especially valuable in soft-baked products and intermediate-moisture foods.
Usage Rates by Food Category
The FDA permits propylene glycol as a direct food additive at concentrations up to 5% of total formulation weight in most categories, though typical usage rates are lower. Here are industry-standard concentrations for common applications:
| Food Category | Typical Usage Rate | Primary Function |
|---|---|---|
| Baked goods (cakes, cookies) | 1–3% | Moisture retention, anti-staling |
| Soft candies & fudge | 2–5% | Texture control, moisture balance |
| Ice cream & frozen desserts | 1–2% | Ice crystal inhibition, smoother texture |
| Carbonated beverages | 0.1–0.5% | Flavor solubilization and distribution |
| Energy bars & snack bars | 2–4% | Binding, moisture retention |
| Salad dressings | 1–3% | Emulsion stability, flavor carrier |
| Flavoring extracts | Up to 97% | Solvent carrier for concentrated flavors |
| Food colorings | Up to 50% | Dye solubilization and dispersion |
PG vs. Glycerin vs. Ethylene Glycol: Know the Difference
Food formulators often evaluate propylene glycol against glycerin (glycerol) for humectant applications. Understanding the differences helps you select the right ingredient for each formulation.
| Property | Propylene Glycol | Glycerin | Ethylene Glycol |
|---|---|---|---|
| FDA Status | GRAS | GRAS | ⛔ NOT permitted in food |
| Taste | Faintly sweet, neutral | Sweet (0.6× sucrose) | Sweet (toxic—do not taste) |
| Viscosity | Lower (48.6 mPa·s) | Higher (1,412 mPa·s) | Low (16.1 mPa·s) |
| Flavor Solvency | Excellent (dissolves many flavors) | Moderate | N/A |
| Moisture Retention | Good | Excellent | N/A |
| Caloric Value | 4 kcal/g | 4.32 kcal/g | N/A |
| Best For | Flavor carriers, beverages, neutral taste | Sweetened products, thick textures | Industrial antifreeze only |
In practice, many formulations use both PG and glycerin—PG for flavor distribution and glycerin for moisture retention and sweetness contribution. The two are fully compatible and can be blended in any ratio.
Regulatory Framework & Compliance
Propylene glycol's regulatory status is well-established across all major markets:
- FDA (USA): GRAS (21 CFR 184.1666). Permitted as a direct food additive at up to 5% in most food categories, up to 2.5% in seasonings, and up to 97% as a solvent in flavoring extracts.
- EFSA (EU): Authorized food additive E1520. Acceptable daily intake (ADI) of 25 mg/kg body weight/day. Subject to specific use limits by food category in Annex II of Regulation 1333/2008.
- WHO/JECFA: ADI of 0-25 mg/kg body weight, confirming safety at permitted usage levels across member countries.
- Health Canada: Permitted food additive under Division 16 of the Food and Drug Regulations.
Quality Control & Best Practices
Incoming Material Verification
Every lot of propylene glycol entering your facility should be verified against the COA. Key tests include specific gravity (1.035-1.037 at 25°C), refractive index, pH of aqueous solution, heavy metals (<5 ppm), and residue on ignition. Our guide to reading a chemical COA walks through the verification process.
Storage & Handling
Store USP propylene glycol in sealed HDPE or stainless steel containers at 60-80°F (15-27°C). PG is hygroscopic and will absorb atmospheric moisture if containers are left open, diluting the concentration and potentially introducing microbial contamination. Use dedicated food-grade transfer equipment—never share hoses or pumps with non-food chemicals.
Shelf Life & Stability
Properly stored USP propylene glycol has a shelf life of 2 years from manufacture. It doesn't degrade significantly under normal storage conditions, but monitor for cloudiness (contamination), off-odors, or pH changes. Once opened, use within 6 months and keep containers tightly sealed between uses.
Common Formulation Challenges & Solutions
Problem: Product Drying Out Too Fast
Solution: Increase PG from 1% to 2-3%. Consider combining with glycerin for dual-mechanism moisture retention. Ensure packaging provides adequate moisture barrier.
Problem: Flavor Doesn't Distribute Evenly
Solution: Pre-dissolve flavor concentrates in PG before adding to the batch. PG's solvency creates a homogeneous flavor solution that incorporates uniformly during mixing.
Problem: Ice Cream Has Large Ice Crystals
Solution: Add 1-2% PG to the mix before freezing. PG depresses the freezing point, promoting smaller ice crystal formation during churning and reducing crystal growth during freeze-thaw cycling in distribution.
Problem: Detecting a Slight Off-Taste
Solution: Reduce PG concentration below 3% and verify you're using USP grade. Technical-grade PG or concentrations above 5% can introduce perceptible taste. Run triangle tests to find the sensory threshold for your specific product.
Environmental & Sustainability Considerations
Propylene glycol is readily biodegradable—aerobic bacteria break it down to CO₂ and water within 20-30 days in wastewater treatment systems. It has low aquatic toxicity (LC50 >10,000 mg/L for most fish species) and doesn't bioaccumulate. For facilities managing sustainability metrics, PG's biodegradability and GRAS status make it one of the more environmentally responsible processing aids available.
Waste streams containing dilute PG (<5%) can typically be discharged to municipal sewer systems with POTW approval. Concentrated PG waste should be recycled through a licensed waste handler or reclaimed through distillation.
Source USP-Grade Propylene Glycol from Alliance Chemical
Every lot ships with a Certificate of Analysis. Available in 1-gallon bottles to 55-gallon drums and 275-gallon totes for production-scale operations.
Shop Propylene Glycol USP →Related Reading
Frequently Asked Questions
Why is propylene glycol used in food and beverage manufacturing?
Propylene glycol (PG) is GRAS-listed by the FDA and serves as a humectant (retaining moisture in baked goods), flavor carrier, emulsifier, anti-caking agent, and freezing point depressant. In beverages, it helps distribute flavors evenly. USP-grade PG is required for all direct food contact applications.
Is propylene glycol safe to consume in food products?
Yes, propylene glycol is Generally Recognized As Safe (GRAS) by the FDA. It's metabolized to lactic acid and pyruvic acid—normal metabolic compounds. The WHO sets an acceptable daily intake of 25 mg/kg body weight. It's fundamentally different from toxic ethylene glycol (antifreeze) and should not be confused with it.
What grade of propylene glycol should be used in food manufacturing?
Only USP (United States Pharmacopeia) or food-grade propylene glycol should be used in food production. USP grade meets strict purity standards with limits on heavy metals, specific gravity, and residue on ignition. Technical-grade PG may contain impurities unsuitable for food contact and must never be used in food applications.
How does propylene glycol function as a humectant in baked goods?
Propylene glycol attracts and retains moisture through hydrogen bonding with water molecules, preventing baked goods from drying out and extending shelf life. It's typically used at 1-5% of total formulation weight. It also inhibits mold growth by reducing water activity (aw) below the threshold for microbial growth.
