A professional flexible packaging manufacturer with more than 8 years experience - KMJbag
Language
A professional flexible packaging manufacturer with more than 8 years experience - KMJbag
Mylar bags offer long-term food storage, but not all foods belong in them. Learn which foods should be kept out to prevent spoilage and contamination.
Mylar bags are known for long-term food storage, but not everything belongs in them. Some foods spoil faster, lose nutrients, or even become unsafe. Storing the wrong items can ruin your supply before you even need it.
So, how do you use Mylar bags the right way?
This article breaks down:
● What are Mylar bags, and how do they work?
● Which foods should never go in them—and why?
● Better storage options for those problem foods.
Get this wrong, and you might be wasting time and money. Keep reading to protect your food supply.
Mylar bags have a strong reputation in long-term food storage, but what makes them different from regular plastic bags? The secret lies in their multi-layer design and barrier properties that keep food fresh for years.
Mylar is a brand name for a type of polyester film, known as boPET (biaxially-oriented polyethylene terephthalate). It’s made by stretching plastic into thin, flexible sheets that are coated with metallic layers. This gives Mylar bags their shiny, foil-like appearance and makes them far more effective than standard plastic for blocking oxygen, moisture, and light.
When paired with oxygen absorbers, Mylar bags create a low-oxygen environment that slows down spoilage. Here’s how they protect food:
● Blocks Oxygen – Prevents oxidation, mold, and bacteria growth.
● Repels Moisture – Keeps food from absorbing humidity, which can cause spoilage.
● Shields Against Light – Reduces nutrient loss and prevents fats from going rancid.
● Seals Tightly – Provides an airtight barrier that locks out pests and contaminants.
Many survivalists, preppers, and bulk food buyers rely on Mylar bags because they:
● Extend shelf life—Grains, beans, and dry foods can last decades when stored properly.
● Prevent waste—No need to worry about mold, pests, or stale food.
● Work with buckets or bins—Adds another layer of protection in case of punctures.
● Are lightweight and flexible—Easy to store and transport without taking up much space.
But not all foods belong in Mylar bags. Some spoil faster, change texture, or become unsafe when sealed inside.
Mylar bags do an excellent job of keeping grains, beans, and dry goods fresh for years. But some foods don’t belong inside—no matter how well you seal them. The wrong foods can spoil, turn toxic, or even cause botulism, a deadly form of food poisoning linked to low-oxygen storage.
Moisture is a major factor in food spoilage. Any food with a water content exceeding 10% should never be stored in Mylar bags with oxygen absorbers. Trapping moisture inside an airtight environment creates the perfect breeding ground for bacteria, mold, and yeast, leading to rapid decomposition and potential foodborne illnesses.
Moisture inside sealed Mylar bags does not evaporate due to the material’s impermeability. Without airflow or dehydration, the excess water remains trapped, encouraging microbial growth. Even with oxygen absorbers present, anaerobic bacteria (such as Clostridium botulinum) thrive in low-oxygen, high-moisture conditions. This is why improperly stored foods can pose a botulism risk.
● Fresh fruits and vegetables – These contain 70–95% water and will begin to rot inside a sealed Mylar bag. Even dried fruits that retain too much internal moisture can grow mold over time.
● Soft cheeses and dairy products – Cheese contains varying moisture levels, ranging from 30% (hard cheeses) to over 50% (soft cheeses like brie and feta). High-moisture dairy products like milk powder or butter-infused items will also degrade quickly in airtight conditions.
● Cooked pasta and rice – While dry pasta and rice are excellent for long-term storage, their cooked counterparts retain 60–70% moisture and spoil rapidly when oxygen is removed.
Professional Storage Solution:
● Dehydrate foods to below 10% moisture before storage.
● Use freeze-dried alternatives, as freeze-drying removes up to 98% of moisture, making foods shelf-stable.
● Store high-moisture foods in vacuum-sealed freezer bags instead of Mylar.
Oxygen removal does not prevent fats from breaking down inside Mylar bags. Unlike dry carbohydrates, fats undergo oxidative rancidification, where they degrade due to natural chemical reactions—even without exposure to oxygen. This makes Mylar bags an ineffective solution for foods high in oils and fats.
Even in an oxygen-free environment, fatty acids degrade over time due to lipid hydrolysis and autoxidation. This is caused by residual moisture, temperature fluctuations, and exposure to trace oxygen levels that remain inside improperly sealed bags. Once a food turns rancid, it develops an unpleasant odor, bitter taste, and loss of nutritional value.
● Nuts and seeds – Contain 30–80% oil content, making them prone to rancidity. Whole nuts last longer in the shell but still degrade within 6–12 months in Mylar storage.
● Whole wheat flour – Unlike white flour, whole wheat flour includes the bran and germ, which contain natural oils that spoil quickly. Even in sealed storage, it can develop rancid flavors in as little as six months.
● Granola and trail mix – Often contain a mix of nuts, seeds, and dried fruit, all of which have a high-fat content. The presence of sugars and fats accelerates oxidation, causing the mix to degrade within a short period.
Professional Storage Solution:
● Store oily foods in vacuum-sealed bags inside a freezer to slow oxidation.
● Use CO₂ or nitrogen flushing (common in commercial food packaging) to delay rancidity.
● Purchase freeze-dried versions of high-fat foods, which have an extended shelf life.
Certain foods rely on air circulation to maintain texture, prevent spoilage, and preserve chemical stability. Storing them in an airtight Mylar bag disrupts their natural composition, leading to spoilage or loss of function.
Some food items, particularly leavening agents and hygroscopic substances require controlled air exposure to maintain their integrity. Without airflow, they either lose their effectiveness (in the case of yeast and baking powder) or harden into unusable bricks (such as brown sugar and salt).
● Yeast and baking powder – These contain living or reactive chemical agents that require oxygen and humidity control to remain effective. Storing them in Mylar bags destroys their ability to leaven dough, rendering them useless.
● Brown sugar – This is a hygroscopic substance, meaning it naturally absorbs moisture from the air. When sealed in Mylar, it loses its moisture equilibrium, hardening into a solid block that becomes difficult to use.
● Salt and sugar – While these do not spoil, they are prone to clumping if stored in a humid environment. While Mylar bags protect against moisture ingress, any trapped humidity can cause crystallization, making them harder to use.
Professional Storage Solution:
● Store leavening agents in airtight, resealable containers away from excessive humidity.
● Keep brown sugar in a moisture-balanced container to prevent clumping.
● For long-term sugar and salt storage, use food-grade buckets with moisture absorbers instead of Mylar.
Mylar bags combined with oxygen absorbers create a low-oxygen environment that preserves many foods. But some bacteria thrive in these conditions—including Clostridium botulinum, which causes botulism. The CDC warns that botulism can grow in improperly stored food, leading to paralysis or even death (CDC).
High-risk foods for botulism:
● Raw potatoes and garlic – Can develop botulinum spores without oxygen.
● Homemade jerky – If not dried properly, bacteria can grow.
● Wet beans and legumes – A breeding ground for botulism if sealed with moisture.
Mylar bags work best for dry, low-moisture foods like rice, oats, and beans. But high-moisture, oily, and air-dependent foods need a different approach. Using the wrong storage method isn’t just a waste of food—it could be a serious health risk.
Storing food long-term isn’t as simple as sealing everything inside Mylar bags and hoping for the best. Some foods thrive in low-oxygen environments, while others spoil faster, lose their quality, or even become hazardous. Understanding what works—and what doesn’t—helps you make better storage decisions and protect your investment.
Here’s a quick recap of what we covered:
● Mylar bags create a powerful barrier against oxygen, moisture, and light, making them ideal for storing dry, low-fat foods.
● High-moisture foods (above 10%) will develop mold or bacteria, even in airtight storage.
● Oily and fatty foods turn rancid due to natural chemical breakdown, even without oxygen exposure.
● Leavening agents, salt, and sugar need airflow to retain their function and texture.
● Custom Mylar bags can be designed with specific thickness, size, and sealing options to improve food storage efficiency.
Using Mylar correctly means knowing when to use it—and when to skip it. If you need custom Mylar bags for food preservation, bulk storage, or specialized applications, choosing the right specifications will help you store food more effectively.
By applying these best practices, you can extend shelf life, reduce waste, and keep your stored food safe for years to come.
Shenzhen Mega Packaging Co.,LTD
The luckiest thing for us is to meet you,We are looking forward to do business with you!
Copyright © 2025 Shenzhen Mega Packaging Co.,LTD - www.kmjbag.com All Rights Reserved.
