Fonterra has revealed what it claims is its "greatest ever" milk innovation - light-proof plastic bottles to keep milk fresher.

The giant dairy co-operative will roll out new matt white bottles across its entire Anchor-branded range of milk and cream from April 8.



Heat and light could both degrade milk quality and lead to the sour milk taste familiar to a generation of adults who drank warm milk in schools, Fonterra said.



While supermarket chillers and refrigerated trucking kept the temperature regulated, exposure to fluorescent lighting still took its toll.



It caused chemical reactions that could change the proteins and fats and create a range of unsavoury flavours, including cardboard, metallic, and burnt protein, Fonterra said.



Its response had been to design a 100 per cent light-proof milk bottle made of three layers of plastic - a white interior and exterior sandwiching a black sheet of plastic.



Managing director Peter McClure acknowledged it might not look like much, but reckoned the new bottle was a real game-changer.



He said that as far as Fonterra knew, the innovation was a world-first.



The company said its market research found that seven out of 10 people preferred the taste of the light-proof milk. (But Fairfax milk connoisseurs attending an Auckland launch event were not so sure. The normal milk tasted creamier and had a slightly stronger aftertaste, but was not necessarily unpleasant.)

Consumer reaction has been similarly mixed. Many people pointed out that the opaque plastic would lead to the harrowing situation of unwittingly running out of milk mid-coffee.



Others suggested a truly ground-breaking innovation would have been a return to glass bottles, perceived to be more sustainable.



Environmentalists will at least be pleased that the new bottle is made of the same HDPE recyclable plastic as the existing bottle.



The dairy giant also claimed the milk was more nutritious, as vitamins were often diminished after just two days of light exposure.



Fonterra's innovation manager for beverages Olaf van Daalen explained that light damaged vitamin B2, for example, which went on to react with proteins and fats and change the taste.



He said his finely tuned tastebuds could detect a difference in the space of minutes of sunlight exposure, or a couple of hours of artificial light.



A 2004 study from the United States found that measurable vitamin A losses occurred at two hours for non-fat milk, four hours for reduced fat and 16 hours for whole milk.



Van Daalen said Anchor would not change its recommended retail price for its newly packaged milk, and it was up to supermarkets to set final pricing.