By Michelle Dickinson 07/08/2015


New nanosilver containing milk bottles extend the shelf of life of milk up to 15 days (source)
New nanosilver containing milk bottles extend the shelf of life of milk up to 15 days

We have already seen milk bottles get a nanotechnology upgrade with the titanium dioxide filled Lightproof bottles used to extend the life of UV sensitive vitamin B2 in the milk. 

Now Brazil is solving the problems of the low shelf life of fresh milk through nanotechnology of a different kind – Nanosilver. Fresh milk has a relatively short shelf life of only a few days which can cause issues in rural areas where the transport times from dairy to customer are long.  For this reason, most of the milk sold in Brazil is UHT milk also known as long life milk which is sterilised using temperatures around 150˚C to kill most of the bacterial spores.  Anyone who has tried UHT milk will know its unique taste and I personally find it quite unpalatable!

Schematic showing how silver nanoparticles could cause cell death (Image source)
Schematic showing how silver nanoparticles could cause cell death (Image source)

A Brazilian company called Nanox has found a solution by combining the antimicrobial and bactericidal properties of nanosilver and mixing them with polyethylene to make antibacterial plastic milk bottles!Although the exact mechanism for how nanosilver kills bacteria is still not fully understood, it is thought that the nanoparticles anchor to the bacterial cell wall causing structural changes to the cell membrane and also that silver ions interact with thiol groups inactivating vital bacteria enzymes.

Schematic of silica core with nanoparticles attached around the surface to prevent them migrating into the milk.

To remove the fear of the silver nanoparticles leaving the bottle and entering the milk, core miscospheres of silica ceramic were used as a central material base which are much larger than the nanoparticles and less likely to move out of the plastic. The silver nanoparticles were then attached to the silica to create a larger cluster of nanoparticles with a strong central core, and these were then added to the polyethylene pellets before they were heated up and blow molded into bottle shapes. Nanox have also been able to transfer the technology to flexible milk bags which a packaging type that some dairies use in southern regions of Brazil.  These bags have shown an extended shelf life from four to ten days and now have FDA and EPA approval for overseas use.