Processing of Fruit Juices
Fruit juices are processed mainly by three methods to increase the shelf life:
1.) By concentration
These products are mainly preserved by high concentration of solids. Above 70% solids by volume, bacteria and other food spoilage micro-organisms are unable to grow. However, the negative side is the product needs to be diluted to drink. They may also be too sweet, and juice content may be too low because of all the sugar that needs to be added to reach 70% solids content. Cordials and fruit based mixers fall into this category.
2.) Preservatised ready to drink fruit juices
these juices are preserved via addition of preservatives and must be kept chilled at 4c to 10c. Chilled storage is necessary since preservatives by themselves cannot control bacteria growth. The negative side of this method is that even with chilled storage and preservatives the shelf life is restricted to around 60 days. If you check your typical chilled ready to drink juice at a supermarket, check the labels – ingredients like sodium benzoate and sorbic acid are commonly used preservatives. there may be chilled products without preservatives, but these products will have even shorter shelf life, perhaps 15 days to 30 days under chilled storage
3) Heat treated long shelf life ready to drink juices
with this method, the bacteria and other food spoilage organisms are destroyed using heat, making chilled storage or presevatives unneccessary. The product can have a shelf life of up to two years low sugar, high juice content is also possible. The negative side of this method is loss of some of the flavours in the juices. However, losses in flavour can be minimised by careful control of the heat treatment and addition of additonal flavours to compensate.