Title : Facts of Heating and Oxidation of Juice  Previous | Next

You may heard or read following claims from one or the other sources like :

1. The higher RPM's of the centrifugal juicers causes more heat and more oxidation (foaming action) to the food being crushed, which decreases the nutrients in the food.
2. As the food is pushed through the chute, the slower crushing action of a masticating juicer provides a more effective crushing action than a centrifugal juicer, creating less heat resulting in less damage to the food being crushed.
3. This process of crushing and squeezing extracts more juice and also has less heat build up than from the high speed at which centrifugal juicers work, which destroys the enzymes and other vital nutrients.
4. ... It's specially designed to be quiet while at the same time preserving vital nutrients and enzymes often destroyed by friction, heat and oxidation caused by other juicers.
5. Because Twin Gear juicers operate at a lower speed they also tend to produce less heat.
6. Centrifugal juicers run at higher speeds and produce more heat than the twin-gear or single auger juicers and introduce more oxygen into the juice.
7. We are all aware these days that cooking kills essential vitamins and enzymes in food. Are you aware that fast high-speed juice extractors have the same destroying effects, because high speed and friction = heat.
8. Since there is no heat generated, all of the enzymes are preserved for a fresh and 'live' tasting juice.

These statements would lead a person to believe that certain juicers are really bad, and produce a juice that is no good.   To clear all these points let’s discuss the process of juicing in detail.  First, we would need to define the nutrients in juice to see if they would be affected by the juicing process.

• Purified Water
• Vitamins
• Minerals
• Enzymes
• Phytochemicals including Antioxidants
• Proteins
• Carbohydrates
• Fats
• Fiber
• Other Unknown Nutrients

Of all these nutrients, Phytochemicals (including Antioxidants and some vitamins) are  the most sensitive nutrients in juice.  

The two main factors that effect juice quality are: Heat and Oxidation.

Heat can affect the juice mainly  by causing enzyme deactivation.  Enzyme deactivation occurs only when temperatures exceed 118 degrees fahrenheit.  In addition to the heat, there is a time component associated with enzyme deactivation.  For example you could probably heat juice to 130 degrees for 1 nano-second with no enzyme deactivation.  Passing your finger over a flame is a similar example (this is not advised).  

Oxidation occurs when you break open cell walls of the produce and expose it to oxygen.  Oxidation occurs when you cut open an apple and it turns brown. In general, oxidation does affect the quality of the juice. Many of the nutrients in the juice are not affected by oxidation, but some are.  Oxidation is a natural process.   Its best  to minimize oxidation. 

Oxidation occurs with all juicers.  Some juicers create less oxidation in the process of juicing. Oxidation increases, the longer the juice is sitting around.  So instead of thinking about that my juicer produce more initial oxidation, drink it immediately when it is made.  If you cut open an apple, oxidation is created (it turns brown). You never see the brownining occur if you eat the apple as soon as you cut it!