Dry goods and oily food packaging materials both appear as plastic films, but their material selection logic is entirely different. Using a bag designed for cookies to package edible oil, or using ordinary plastic bags for nuts and dry goods, can result in either compromised taste or oil oxidation. Many food companies have suffered losses due to improper packaging choices: either insufficient moisture resistance leading to cookie softening, or poor oil barrier properties causing oil leakage and significantly shortened shelf life. This article systematically compares the differences between packaging materials for dry goods and oily foods from four dimensions: barrier properties, printability, cost, and shelf life, helping you choose the right packaging solution all at once.
Core Differences Between Packaging Materials for Dry Foods and Oily Foods
The fundamental difference between packaging materials for dry goods and oily foods lies in the different objects they need to block. Dry goods (such as cookies, potato chips, nuts, tea, and powdered milk) are most afraid of moisture and oxygen—moisture can degrade the texture, and oxygen can cause rancidity in the oils. In contrast, oily foods (such as cooking oil, chili sauce, preserved meats, and fried foods) are concerned not only with oxygen but also with oil permeation and migration. Therefore, the key barrier for dry goods packaging is moisture resistance, while the key barrier for oily food packaging is oil resistance, oxygen resistance, and puncture resistance.
From a material structure perspective, dry goods packaging commonly uses 0 aluminum-coated film + PE 1 or 2 pure aluminum foil + PE 3 composite structures, utilizing the high barrier properties of the aluminum layer to retain moisture. For oily packaging, the focus is on the oil resistance of the inner layer, typically selecting CPP or modified PE as the heat-sealing layer, while pairing with PET or PA to enhance strength and puncture resistance. For reference on the selection logic of basic materials, you may consult our previously compiled information.Food Packaging Material Safety GuideFirst understand the basic properties of each layer of material, then discuss specific selection.
Dry Food Packaging: Moisture-proof and moisture barrier is the top priority
The main factor affecting the shelf life of dry goods is water activity. For example, once the water activity increases, the crisp texture of biscuits immediately deteriorates; tea loses its aroma when it gets damp and may even develop mold. Therefore, the water vapor transmission rate (WVTR) of packaging materials for dry goods is a critical parameter: ordinary PE bags have a high WVTR and are only suitable for short-term storage; for dry goods requiring a long shelf life, it is essential to use metallized or pure aluminum composite structures to reduce WVTR to single-digit levels.
In addition, dry goods packaging should also consider auxiliary methods such as nitrogen flushing or adding oxygen absorbers. For oily dry goods like nuts and potato chips, residual oxygen in the package can accelerate oil oxidation. Combining high barrier materials with oxygen absorbers can significantly extend shelf life. The combination of desiccants and high barrier bags is described in our previously published content.Introduction to Composite Packaging MaterialsThere is a more detailed introduction in the following.
Oil-based food packaging: emphasizing oil and oxygen barrier properties along with puncture resistance
The biggest challenge for oily food packaging materials is oil permeation. Oil molecules slowly pass through the film layers, causing oil stains on the bag, peeling of the printed layer, and in severe cases, oil leakage that contaminates the outer carton. Therefore, the inner layer of oily packaging must be selected as CPP or metallocene-modified PE with good oil resistance, while the outer layer should use PET or PA for strength. An aluminum foil may be added in the middle for oxygen barrier if needed.
Another often-overlooked issue is puncture resistance. Fried foods, bone-in processed meats, and frozen meat products are prone to puncturing packaging. Once the bag is broken, oxygen enters, leading to rapid oxidation and rancidity of the oils. The PA (nylon) layer, due to its excellent puncture resistance, is widely used in packaging for oily foods. At the same time, the sealing strength requirements for oily foods are higher, so the material selection and heat-sealing parameters of the heat-sealing layer need to be specially adjusted to prevent leakage during transportation.
Recommended Packaging Materials for Different Products
To facilitate purchasing decisions, we classify common products into dry goods and oily categories, providing reference structures:
Cookies and pastries: Aluminized PET + PE composite bag, or paper-aluminum-plastic composite; focus on moisture-proofing and stiffness. Nuts and roasted snacks: Pure aluminum foil composite bag + nitrogen filling/deoxidizer; focus on oxygen barrier and sealing performance. Tea and milk powder: Aluminum foil composite bag, balancing barrier properties and light protection. Edible oil and soy sauce: PET + AL + CPP or PET + PE oil-resistant structure; focus on oil resistance and seal strength. Spicy sauce and braised foods: PA + PE or PET + AL + CPP heat-sealable structure; balance puncture resistance and high-temperature resistance. Fried snacks: Aluminized composite + nitrogen filling; focus on oxygen barrier and print adhesion.
If your product contains both dry and oily ingredients (such as mixed nuts or meat floss cakes), it is recommended to select materials based on the oily standard, as oily requirements are generally more stringent. A high-grade option can meet the needs of both types.
Summary and Recommendations
Dry goods and oily food packaging materials should not be used together; this is the first principle in selecting food packaging materials. For dry goods, focus on moisture-proof and moisture-resistant properties, while for oily products, prioritize oil-proof, oxygen-proof, and puncture-resistant characteristics. Both types of products are recommended to prioritize the use of aluminum foil or metallized composite structures, combined with auxiliary methods such as nitrogen filling and oxygen absorbers to extend shelf life. When selecting materials, also consider printability, tear resistance, and cost, and conduct sample testing after achieving a balanced evaluation.
If you’re having trouble choosing materials for food packaging, feel free to contact Huashu Packaging. With over ten years of experience in producing food flexible packaging, we can provide free material selection advice and sample services tailored to your product characteristics. For customized packaging solutions, please contact us directly.Contact Us。
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