With the approach of the apple harvesting season, Transition Bath’s energy group were wondering which was the most efficient way of preserving apple juice?
For domestic juicers there seems to be three alternative approaches: pasteurisation and freezing. Both require energy:
- pasteurisation incurs energy heating the juice up to 80C (fast pasteurisation method)
- freezing incurs energy reducing the temperature of the juice to 0C, freezing the liquid and then cooling the frozen solid to -18C, and if you put the frozen apple back into your fridge to thaw then you get back the energy used freezing the liquid
- as above, but defrost the apple juice in your fridge, so you get back the energy you used to freeze the juice
Our brief analysis suggests that freezing followed by defrsoting in the fridge might be the most efficient
|Method||Energy Requirement (kWh/litre)||Cost (pence/litre)|
|Freezing (defrost in kitchen)||0.0403||0.6|
|Freezing (defrost in fridge)||0.00583||0.1|
So if you put your frozen apple juice back in the fridge then it uses 16 times less energy than pasteurisation.
If you have apples to spare this year, Transition Bath has an apple press and pasteuriser available for loan and we run training courses in their use. If you are interested in making use of this equipment, please contact us firstname.lastname@example.org .
Freshford Village also have an apple pressing day on Sunday 16th October 2015.