This is how much air is taking up your favourite crisps packets (including the brand that is 72 per cent EMPTY)

MANY hungry shoppers will know the sinking feeling of opening up a crisp packet only to find it is half empty – but which brands are the biggest culprits?

Researches put 15 well-known brands to the test and found the worst offender was 71 per cent air.

The , which was commissioned by appliance manufacturers CDA Appliances, used water displacements to determine the amount of air compared to crisps in each packet.

Providing shoppers with the worst deal was Popchips Barbecue, which only had 28 per cent of crisps per packet.

This was followed by McCoys, which was 59 per cent air, Kettle Chips at 55 per cent and Mini Cheddars at 53 per cent.

Popular brand Walkers was also full of more air than crisps, at 53 per cent.

On the flip side, one of the best packets for getting more crisps was Wotsits which contained just 18 per cent air - the lowest amount of any crisp brand they tested.

This was followed by Wheat Crunchies, which contained 39 per cent air.

While it may seem like a rip off to get a bag with a large amount of air, manufacturers claim there is a good reason for increasing this.

They say that many crisps have a best before date of 55 days before they go stale, and Nitrogen gas in packets helps to prolong this.

Crisps makers claim that bags that contain the most air last for longer, even without artificial preservatives.

Popchips – the bags that contained the most air in the study – last for 290 days, which is well above the average length of best before days.

Many crisp creators aim to get a balance of making crisps last longer, without ripping off the customer in the process.

The issue of crisp bags being full of large amounts of air was also explored in Channel 4’s Supershoppers.

In that study a 55g bag of Doritos, was almost three-quarters air.

At the time a Doritos spokesperson said: “Our crisp packets are filled by weight (and not by volume).

"To help us deliver this consistently, state of the art weigh heads make sure the right amount of product is filled into the bags as they are produced and each pack passes over a ‘check-weigher’ which is designed to stop any under-filled packs from leaving our factory.

"As our snacks are susceptible to a level of breakage, we try to eliminate any damage by filling the packs with air just prior to sealing so that this acts as a ‘cushion’ during transit.”

Earlier this year we tested Britain’s top snacks to see if Walkers, Hula Hoops or Mini Cheddars fail the ‘empty bag’ challenge.