Mylar bags are a game-changer for long-term food storage. They keep out air, moisture, light, and pests—giving your dry goods decades of shelf life. But here’s a crucial fact: not everything belongs inside them.

Even though 5 gallon mylar bags and heavy duty Mylar bags are designed for durability, some foods and materials can spoil, leak, or even damage the bag over time.

If you’re prepping or planning bulk storage, it’s just as important to know what not to store in Mylar bags as it is to know what works best. Let’s go through the main things to avoid and why.

1. Foods with High Moisture Content

Moisture is the enemy of long-term storage. When food has too much water, it can create an environment where bacteria and mold grow—even without oxygen.

Avoid storing these in Mylar bags:

• Fresh fruits and vegetables

• Cooked or wet foods

• Cheese, butter, or dairy products

• Fresh meat or fish

Even if you seal these in heavy duty Mylar bags, the moisture inside can spoil the contents in weeks. Mylar’s purpose is to preserve dry foods, not perishable or moist ones.

Instead, stick to freeze-dried or dehydrated foods for safe storage that can last decades.

2. Oily or Fatty Foods

High-fat foods might seem harmless, but they don’t age well inside Mylar bags. Oils can go rancid over time, even when oxygen is removed. This leads to bad smells, off-flavors, and food waste.

Foods to avoid include:

• Nuts and seeds

• Granola or energy bars

• Peanut butter

• Chips and snacks

• Whole wheat flour

If you do want to store nuts or seeds, use small portions and rotate them frequently—within 6 to 12 months. For long-term storage, prioritize low-oil, low-moisture foods.

3. Sugar and Salt (Without Caution)

Here’s an interesting one. You can store sugar and salt in Mylar bags, but not with oxygen absorbers.

When oxygen absorbers are used, they can cause clumping or hardening because of the chemical reaction with these ingredients. Your sugar might turn into a solid brick, and salt can become rock-hard.

To store sugar or salt safely:

• Use 5 gallon Mylar bags without oxygen absorbers.

• Keep them sealed and dry.

• Store in a cool, dark space.

That way, your pantry staples will stay fresh and easy to use.

4. Powdered Foods with High Fat Content

Some powdered foods, such as powdered milk or protein powder, may seem perfect for Mylar storage. However, if they contain fats or oils, they’ll eventually spoil or lose quality.

To store powdered items safely, check the fat content first. Low-fat milk powder, for example, can last much longer in heavy duty Mylar bags than full-fat versions.

5. Foods with Active Yeast or Moisture

Anything that can ferment or grow bacteria shouldn’t go in Mylar bags. Foods containing active yeast, baking soda, or baking powder can lose their effectiveness over time when sealed airtight.

Avoid storing:

• Bread dough mixes with yeast

• Pre-made baking mixes

• Items containing moisture or leavening agents

These are better stored in airtight containers for short-term use, not for multi-year preservation.

6. Canned or Bottled Foods

Canned foods already come in sealed, oxygen-free containers. Putting them in 5 gallon Mylar bags doesn’t offer extra benefits—it only adds unnecessary bulk.

Plus, if a can leaks or corrodes over time, it can damage the Mylar around it. The same goes for bottled items like sauces or syrups.

Mylar is best reserved for dry goods, not liquids or pre-packaged wet items.

7. Foods With Strong Odors

Even though heavy duty Mylar bags are designed to block odors, it’s better to avoid storing extremely strong-smelling items like:

• Spices (garlic powder, curry, chili)

• Onions or dried onions

• Certain herbs and flavoring agents

Over time, powerful scents can slightly permeate or affect nearby foods if not double-sealed. For these, use smaller Mylar bags and store separately in sealed containers.

8. Items with Sharp Edges

While heavy duty Mylar bags are tough, sharp or pointed objects can still puncture them. Avoid storing items like:

• Dry pasta with sharp edges (like spaghetti or lasagna)

• Metal utensils or tools

• Anything with sharp corners or packaging

If you do store pasta, cushion it with softer foods or wrap it in paper first to prevent damage.

What You Should Store in Mylar Bags

To get the best use out of your 5 gallon Mylar bags, focus on dry, low-moisture foods. These are proven to last decades:

• White rice

• Dried beans and lentils

• Rolled oats

• Pasta

• Powdered milk (low-fat)

• Flour (white, not whole wheat)

• Cornmeal

• Dehydrated fruits and vegetables

Pair them with oxygen absorbers, seal tightly, and keep in a cool, dark location.

Why 5 Gallon Mylar Bags Are Perfect for Long-Term Storage

When you store the right foods, 5 gallon Mylar bags offer unmatched convenience and protection. They’re ideal for bulk storage because they:

• Fit perfectly into food-grade buckets

• Offer strong protection from pests and moisture

• Can hold large quantities of dry goods

• Are easy to seal and label

For maximum longevity, place your 5 gallon Mylar bags inside buckets with tight-fitting lids. This adds another layer of security against light and rodents.

Heavy Duty Mylar Bags: Built for Safety and Strength

If you’re planning to store food for decades, heavy duty mylar bags are the way to go. Their thicker layers (5–7 mils) resist punctures, block UV light, and prevent odor leaks.

They’re especially useful for storage in garages, basements, or outdoor sheds where environmental conditions are unpredictable.

Even so, remember—Mylar bags are not magic. Their success depends on what you put inside them and how you handle them.

Common Mistakes to Avoid

Here are a few quick tips to prevent spoilage and waste:

• Don’t use damaged or thin Mylar bags.

• Don’t skip oxygen absorbers for long-term dry storage.

• Don’t reuse bags that once stored strong-smelling foods.

• Don’t store Mylar bags in sunlight or near heat.

• Don’t ignore labeling—always mark the date and contents.

Conclusion: Store Smart, Store Right

Mylar bags are incredible for food preservation—but they aren’t for everything. Avoid storing wet, oily, or high-fat foods, and skip using oxygen absorbers with sugar or salt.

When used properly, 5 gallon Mylar bags and heavy duty Mylar bags can protect your dry goods for decades. Focus on low-moisture, long-lasting foods like rice, beans, and oats, and you’ll get the full benefit of Mylar’s powerful barrier.