That may sound obvious but many fruit juices are available that do not require to be put in the fridge until they are opened. Although they do not go bad before their best before date, they are probably losing their anthocyanins.
So what are anthocyanins? They are water soluble natural pigments responsible for the colour in berries, currants and purple coloured vegetables such as purple cabbage. Research suggests they have potential health effects against a range of diseases such as cancer, diabetes, age related neurological problems and bacterial infections.
In a paper published in the upcoming August edition of the Journal of Food Composition and Analysis, Finnish scientists looked at anthocyanin content in juices of blackcurrant, crowberry and chokeberry. Some juices were prepared in the lab and some were bought. They found that the anthocyanin content in lab made juices kept at 9°C had a three-fold increase in the half life, i.e. it took three times as long at 9°C for half of the total anthocyanin content to have degraded compared to juice kept at room temperature. The anthocyanins took even longer to degrade at 4°C as would be expected.
Looking at the commercial fruit juices stored at room temperature, one had lost 85% of its anthocyanin content by the end of its shelf life of 35 weeks. Another had a shelf life of almost one year and had only 11% of its original anthocyanin content left. Other components in the fruit juice remain relatively unchanged suggesting the juices were stable.
So keep it cold to keep it fresh.