Understanding transmission rates in food packaging films is crucial for maintaining product freshness, safety, and shelf life. Here’s how each rate affects food packaging:
Water Vapor Transmission Rate (WVTR) in Food Packaging
Direct Water Protection: Packaging with a low WVTR is essential for products that must stay arid. Such as, dry snacks, powders, and cereals, as exposure to water could lead to spoilage or contamination.
Barrier Layers: Materials with low WVTR are often used as outer layers in packaging. This provides a barrier against external moisture (e.g., rain, condensation, or accidental spills).
Applications: Used for products that need a watertight seal, like vacuum-sealed foods, canned goods, and liquids. This prevents water from leaking in or out of the packaging.
Moisture Control: For many foods, controlling internal humidity is essential. A material with the right WVTR allows moisture to escape. Essentially, reducing condensation and preventing microbial growth, mold, and spoilage.
Breathability: Fresh produce, for instance, releases moisture. Packaging with a carefully balanced WVTR allows the produce to “breathe” without trapping excess humidity inside, which could lead to rot or decay.
Shelf-Life Extension: Many snack foods and non-perishable packaged goods benefit from packaging with a specific WVTR. This keeps them crisp and fresh by balancing internal and external humidity levels.
Examples of Food Packaging Needs Based on WVTR
Dry Foods (Cereals, Chips): Require packaging with very low WTR to keep external water out and low VTR to maintain crispness.
Fresh Produce: Requires packaging with a moderate WVTR to allow moisture to escape and reduce condensation. Meanwhile, maintaining the freshness.
Ready-to-Eat Meals: Often use multi-layer packaging with both low WTR and a controlled VTR. This protects against outside water while managing internal humidity.
Oxygen Transmission Rate (OTR) in Food Packaging
OTR measures the rate at which oxygen passes through a material over time. Oxygen can lead to food spoilage, oxidation, and the growth of aerobic (oxygen-dependent) bacteria and molds, affecting flavor, color, and nutritional value.
Sensitive Foods: Foods high in fats, like nuts, chips, and oils, are prone to oxidation, which causes rancidity. Packaging with low OTR helps prevent oxidation, maintaining the taste and quality of the product.
Color Preservation: Oxygen exposure can cause color changes in foods like fresh meats and vegetables. As such, can make the product appear less fresh to consumers. Low OTR packaging helps maintain appealing colors and lock in freshness.
Fresh and Processed Foods: Packaging with low OTR can significantly extend the shelf life of perishable foods by limiting oxygen exposure. This slows down spoilage and maintains product quality.
Ready-to-Eat and Snack Foods: Foods like chips and snacks are packed in materials with low OTR to keep them fresh and crisp longer.
Spoilage Prevention: Many spoilage organisms require oxygen to grow. Packaging that limits oxygen can reduce the growth of bacteria and molds. This helps preserve the food’s safety and quality.
Vacuum and Modified Atmosphere Packaging (MAP):
By using low OTR materials in combination with techniques like vacuum sealing or MAP (replacing oxygen with nitrogen or carbon dioxide), manufacturers can create an oxygen-free environment. Of which, is ideal for extending the freshness of meats, cheeses, and produce.
Examples of Food Packaging Based on OTR
Snack Foods (Chips, Nuts): Packaged in materials with very low OTR to prevent staleness and oxidation, maintaining freshness and flavor.
Fresh Meats and Cheeses: Often packed in vacuum-sealed or MAP environments with low OTR packaging to limit oxygen. This keeps the product fresh for longer.
Coffee and Spices: Oxygen-sensitive products like ground coffee and spices are often packaged in low OTR materials to prevent flavor loss and degradation over time.
Balancing OTR and WVTR
For many foods, packaging design must balance Oxygen and Water Transmission Rates to optimize freshness and ultimately – FOOD SAFETY.
Examples to consider are:
Fresh Produce: May need breathable packaging with a certain WVTR and a moderate OTR to allow the release of ethylene gas and some moisture, extending freshness without trapping excess oxygen.
Dairy Products: Often require low OTR to prevent spoilage but also a low WVTR to keep out moisture, maintaining a controlled environment.
The OTR in food packaging is critical for maintaining quality, shelf life, and freshness, particularly for products prone to oxidation or spoilage.
Testing WTR, VTR, and OTR
Standardized units of measure are used to test and quantify Water Transmission Rate (WTR), Vapor Transmission Rate (VTR), and Oxygen Transmission Rate (OTR) in food packaging. Such testing methods allow manufacturers to reliably compare materials and ensure they meet specific requirements for preserving food quality.
WTR: Typically measured in grams per square meter per hour (g/m²·hr) or grams per square meter per day (g/m²·day).
VTR: Measured in grams per square meter per day (g/m²·day).
OTR: Usually measured in cubic centimeters per square meter per day (cc/m²·day) at specified temperature and humidity.
Why Standard Units and Methods Are Important
Consistency: Standard units and methods ensure consistent, comparable data across different materials, manufacturers, and countries.
Quality Control: Such Testing helps manufacturers meet regulatory and consumer expectations for food quality, shelf life, and safety.
Material Selection: Packaging engineers can compare WTR, VTR, and OTR data to select materials that meet specific preservation needs for different food products.
Each of these standardized tests plays a vital role in ensuring that packaging materials provide the necessary protective barriers for food products, extending shelf life and maintaining freshness.
Contact PennPac to discuss your product needs and we will be able to determine the best film to use to maximize your product’s shelf life.