Air in packets - FGC media response
The Sunday Star-Times asked FGC about air in bags of chips, bagel crisps, cereals and other products: How much air is in the packets? Is there more air than food? Is there a ratio of air-to-food that packaging companies aim for? What is the reason behind the air in the packet? Is it misleading to consumers when they get a big packet/bag but most of it is air? why/why not?
They did not publish a story but Katherine Rich’s responses, using information gathered from members, were:
Air in packets
Air or spare capacity inside packets is part of the science of packaging and, as can be seen from the examples below, serves very definite but different purposes depending on the product. In some cases it’s to allow for expansion or settling, allow for the sealing and packing process, and even to help protect the product during transport and storage.
The “air” in fresh coffee packs is not air. It is either carbon dioxide or nitrogen. Oxygen is the enemy of coffee and makes it oxidise and go stale. When coffee is roasted if gives off water and carbon dioxide as part of the natural process. It then continues to give off carbon dioxide in the days following roasting. In order to pack coffee as soon as possible and keep it tasting as fresh as possible, most New Zealand roasters use packaging with one-way valves to allow excess CO₂ to escape in those early days (and shoppers like to give the packs a squeeze and smell the fresh coffee aroma). Companies also usually flush out the oxygen with either CO₂ or nitrogen before sealing the pack.
The powder is bulkier when packed, but settles over time. There are a range of variables that affect the filling of the laundry product and all these need to be taken into account when determining the optimal-size pack for a weight of powder. Powder is measured by bulk density which is a weight of powder for a specific volume. There are a few other significant reasons. In powder processing, the bulk density can vary slightly in manufacturing, so there needs to be allowances in the pack for this. With the design of the pack and tear strip for opening the pack, manufacturers need to ensure that powder does not spill out when the pack is opened. Powder does settle over time and during transportation, so the space can appear larger than at time of manufacture. The space also ensures that the powder does not interfere with the pack gluing process so they get a good seal on every pack.
There are a number of reasons for the gap in cereal boxes or packets. Cereals are bulkier at the time of packing and then settle over time. It depends on the type of cereal (light v muesli) as to how significant the settling process is. There’s another important reason: with automatic filling, manufacturers need some room at the top of the bag so loose flakes do not get caught in the sealing process, stopping the bag from being airtight. Manufacturers have looked extensively into this issue because if they can pack efficiently they can save additional packaging costs.
Chips are a very fragile product so the pack acts as protection. Packaging must fulfill its primary purpose for the consumer of preserving and protecting the quality of the snacks inside. This is quite a challenge when chip packs must be designed to be able to be automatically filled on a production line where chips can "stack" on top of each other, but whose contents can later settle during transportation. The "air" or "free space" contained in chips serves a very important purpose – acting much like an "air bag" in a car, providing protection for the chips inside the bag, and helping prevent them from being crushed. So some air around the chips is needed. Kiwis don’t like broken and crushed chips. Chips are sold by weight not volume and are filled to the weight printed on the outside of the packet.