People ask this constantly, and most of the answers online are half right. So—can you ferment in plastic? Yes, but only in the right kind.
You can ferment in plastic if it’s food-grade HDPE (marked #2) or polypropylene (marked #5). Everything else should stay far from your ferments.
Fermentation is acidic, and acid slowly breaks down weak plastics. Cheap plastic can leach chemicals and shed microplastics over time. That’s why container choice matters—it’s not about looks, it’s about safety and taste.
Safe plastics You Can Ferment In
HDPE (#2)
Slightly flexible with a dull or matte surface, usually opaque white or natural-colored. You’ll see a “2” inside the recycling triangle and the letters “HDPE.” Common examples: milk jugs, food-grade five-gallon buckets, brewing fermenters, vinegar or juice jugs, and heavy water containers. Avoid any bucket that once held paint or chemicals—they’re not food-safe.
PP (#5)
Smooth, sometimes shiny, and either translucent or solid white. Marked with a “5” and “PP.” It feels a bit harder and more rigid than HDPE. Common examples: thick yogurt tubs, sour cream containers, reusable deli or takeout containers, and many fermenter lids or spigots.
How to Identify Food-Grade Plastic
Turn the container over and look for the recycling triangle symbol. Inside that triangle will be a number—the resin code.
• A 2 means HDPE (High-Density Polyethylene).
• A 5 means PP (Polypropylene).
Food-grade plastics are often stamped with “HDPE” or “PP” next to the number and may say food safe, BPA-free, or NSF/FDA approved.
Look and feel:
• HDPE – Slightly flexible, dull or matte surface, usually opaque or milky white.
• PP – Smooth, firm, and sometimes translucent or shiny.
If it’s thin, brittle, or unlabeled, skip it. Real food-grade containers feel sturdy and have no chemical smell.
Microplastics and Fermentation
Every time plastic gets scratched or flexed, tiny particles can separate from the surface. In acidic environments like a ferment, that process speeds up. These microplastics don’t change the taste, but they can end up in your food. HDPE and PP hold up far better than other plastics, but replace them once they turn cloudy, scratched, or rough.
Government guidance
The National Center for Home Food Preservation, in partnership with the USDA, confirms that “Food-grade plastic and glass containers are excellent substitutes” Read their full recommendations here: Suitable Containers for Fermenting Food – NCHFP/USDA.
Glass vs. Plastic
Glass and ceramic crocks are completely inert and last for life, which is why most seasoned fermenters eventually switch. Plastic is fine for getting started, testing recipes, or doing small batches. When you’re ready to invest, upgrade to glass jars or ceramic crocks—they’re safer, easier to clean, and don’t scratch.
If you’re setting up your first batch, read Best Containers for Fermentation to see how each option compares.
A Note About Metal
Never ferment directly in metal containers. The acid in brine reacts with most metals, releasing metallic flavors and sometimes toxic compounds. Even stainless steel can pit or corrode over time. Metal lids or weights are fine only if they’re coated or lined with food-safe enamel, glass, or plastic so the brine never touches bare metal.
Bottom Line
So, can you ferment in plastic safely long-term? Only if it’s food-grade HDPE or PP and replaced when wornYou can ferment in plastic if it’s food-grade, undamaged, and replaced when worn out. For long-term use, glass or ceramic is the old-school standard—safe, neutral, and built to last.