Pressure. Temperature. Micro-organisms. And why cold pressed juices are cold pressed.
Why are cold pressed juices cold pressed? Why not just put them into a blender?
One reason is that using a blender or any rotary cutting mechanism breaks up the fruits and vegetables. It also generates heat. The combined effect is to speed up the oxidation and enzymatic browning of fruits and vegetables. If sustained, it can even cook them, changing their taste and look. A second reason is blenders and rotary cutters are unable to fully extract the juices and nutrients.
Cold pressed juices avoid these. After being cut up into sawdust-like pulp by a machine, the fruit and vegetable pulp is put into a bag (see video above). The bag is then subject to pressure of 600 MPa or 87,000 psi gradually (that’s almost 6000x more than sea-level atmospheric pressure, which is 101 kPa or 14.7 psi!), until all the juices and nutrients are mostly extracted.
Micro-organisms such as molds, yeast and bacteria cannot survive such high pressure. Eliminating them thus prolongs the shelf life of the cold pressed juices. Moreover, the entire operation is usually done in a low temperature environment (5-15ºC), slowing down any micro-organism activity to begin with.
To increase shelf life further, some companies use high pressure a second time. They put the bottles of cold pressed juices in cold water, and subject it to high pressure for several seconds. This additional process is called high pressure pascalization (HPP – see video above). While this costs more and requires more work, the shelf life is extended from several days to up to a month.
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