Panorama highlighted two methods that some chicken processors in Holland use to bulk up their products.

These processes of "adulterating chicken" were secretly filmed by two journalists working undercover for Panorama.

Both of the methods involve adding water and additives to the product.

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Tumbling

A tumbling machine

In this process, the chicken fillets are pounded with water in large drums until they are bloated and heavy.

They are spun in these washing machine like drums for between an hour and an hour and a half, together with additives.

The process means that the chicken fillets absorb the water and the additives and are removed from the drums looking rather like a thick chicken fillet soup.

These watery fillets are then placed on the production line and scooped into bags.

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Injecting

Water being squeezed out of a chicken fillet

The other method is not quite as subtle as tumbling - and basically involves injecting water and additives into the chicken.

The chicken moves along the production line and large needles attached to tubes full of a water fluid are plunged into the meat as it goes past.

It is thought that both water and proteins are pumped into the chicken during this process, which leaves the product dripping wet, and sometimes blistered.