Gas flushing vs vacuum exchange

It’s a recurring focus for food manufacturers: finding the best way to extend shelf life, reduce food waste and maintain the quality of perishable goods. 

However, it doesn’t have to be an impossible conundrum to solve. The ability to tailor gas mixtures makes modified atmosphere packaging (MAP) a flexible and particularly effective solution. MAP is a well-established technology that has been proven to safely extend shelf life, by creating a protective atmosphere that helps inhibit the growth of bacteria that leads to food spoilage. 

MAP is achieved either manually or automatically by replacing the atmospheric air in food packaging with specific quantities of carbon dioxide, nitrogen and/or oxygen before sealing. In turn, MAP helps maintain the quality and safety of food.

There are two ways of introducing a specific gas mixture to a MAP-packaged product: through the process of gas flushing or a vacuum process followed by gas injection (gas exchange). With either method, the objective is the same: to have the product surrounded by the appropriate gas mixture to extend shelf life. From dairy products to vegetables, the way in which that gas mixture is introduced will differ depending on the type of product being packaged and specific gas consumption depends on the type of packaging machine used.

So, what are the key differences, and how are they best applied?

As the name suggests, gas flushing involves removing the existing air in packaged goods by flushing the desired gas mixture, until the air is completely replaced, and the product is surrounded by the chosen MAP gas. 

For example, snacking goods such as crisps are often packaged in nitrogen, achieved using MAP via gas flushing. The bag is flushed with the desired volume of nitrogen until all the existing air in the bag is pushed out. Then, it is tightly sealed using a packaging material highly resistant to oxygen to slow down decay and extend shelf life. Using nitrogen in this way also helps preserve freshness and quality, particularly for oven-baked crisps. 

Gas flushing is often best used for snacks, crisps and dry fruit that may be more fragile, as well as minimally processed foods such as broccoli, salads and baby greens.

Gas exchange differs from flushing, in that the air is first totally removed from the packaging instead of being flushed out. In the gas exchange method, the air is extracted from inside the packaging, before the resulting vacuum filled with the desired gas mixture. Although this two-step process is slower than gas flushing, it is more efficient in reducing residual oxygen levels because the air is almost completely removed. As with gas flushing, a packaging barrier resistant to oxygen is then used as a sealant.

With gas exchange, it is possible to remove as much or as little oxygen as needed from the packaged product, making it an effective tool in tailoring specific volumes and mixtures of gas for different products. It is best suited for products such as meat, ready meals and cheese.

MAP is a highly effective packaging technique mainly due to its use of carbon dioxide, an important gas that contains key properties against microbes. Alternative packaging techniques such as vacuum packaging, which is more recently being used for red meat, are effective in removing air in a packaged product, but still lack the presence of carbon dioxide. Carbon dioxide is crucial in preventing the growth of food-spoiling bacteria, which is why MAP can significantly extend the shelf life of packaged goods by creating an environment where microbes cannot thrive. 

As the food industry increasingly looks to extend shelf life in both a safe and sustainable way, considering the effectiveness of techniques like gas flushing or gas exchange in MAP to prevent food waste and preserve the integrity of produce will be key. Understanding the different methods of application in MAP can help food businesses uncover the solutions that work best for their customers and the planet.

At Air Products, we’ve been offering food grade gases and technical expertise to the food industry in the UK for over 60 years. Our Freshline® food solutions offer high-purity gases and equipment, international supply capability and, most importantly, unmatched industry experience to help tailor the right solutions for your business. 

Our online Food Waste Calculator helps customers discover which types of packaging are the best solutions to minimising food waste and reducing carbon footprint. This uses data taken from independent sustainability studies to compare the various impacts of either MAP packaging, packaging in air or no packaging, based on the type and amount of food.  

If you would like to speak to us at Air Products about how we can support your production processes and work together to choose the right solutions for your business, please get in touch at 0800 389 0202, via email at apukinfo@airproducts.co.uk, or fill in the request form below.