Extending the shelf life of fruit juices

In practice pasteurization is virtually the only procedure used to give fruit juices a longer shelf life. 

Bottles which immediately after hot-filling are stacked in large storage containers (e.g. pallet boxes) retain the heat for a very long time. Although such juices have a fairly reliable shelf life, there is a significant loss of quality because of the prolonged action of the heat. 

Faults in pasteurization are the main reason for deficient keeping quality of fruit juices. Simple thermometers can show divergences of up to 4°C. If the temperature out of the pasteurizer falls, these thermometers still indicate the higher temperature. 

Immediate cooling after bottling is also a problem. Since the cap (and also any air present) has to be pasteurized, it is advisable to turn the bottles over after filling and not to start cooling until after that. 

The volume of the juice decreases in the course of cooling, and a partial vacuum is created in the bottle. If the cap is not airtight or if the bottle is chipped, this partial vacuum draws air into the bottle. Microorganisms in the air come into contact with the cold juice and can spoil it. For this reason new caps should always be used and bottles should be checked before use. 

---