Cucumber Juice Loses 80% of Its Vitamin C
Firstly, even juice consumed immediately after being juiced will lose a significant portion of its nutrients. This is because fruits and vegetables have complex ultrastructures within their cells. Think of it as a building with many rooms, each with a specific function and containing different things that cannot be mixed. For instance, vitamin C must not come into contact with various oxidizing enzymes, or they will react with each other. However, when juicing, the high-speed blades completely destroy the cells, mixing all their contents together. As a result, vitamin C encounters multiple oxidizing enzymes and suffers heavy losses. An experiment conducted by my student showed that after being juiced, the destruction rate of vitamin C in cucumbers can be as high as 80%, with similar results for tomatoes, bok choy, and others.
In addition to vitamin C, antioxidant components like flavonoids and anthocyanins also suffer varying degrees of loss. As for insoluble fiber, it naturally does not end up in the juice. Insoluble elements like calcium are also left in the pulp. If possible, it's best to consume the pulp along with the juice. Blanching Before Juicing to Preserve Nutrients
Many people don't know that in commercial fruit and vegetable juice production, the produce is often blanched. This means the fruits and vegetables are briefly scalded in boiling water to "kill" the oxidizing enzymes and slightly soften the tissue before juicing. This not only reduces the loss of vitamins and increases the juice yield but also keeps the juice's color vibrant and prevents it from browning easily. This is especially important for vegetables without a sour taste, such as carrots, bok choy, celery, and sweet corn, which must be blanched before juicing.
As for the feeling of fullness that comes from eating whole fruits and vegetables, this cannot be retained no matter how you juice them. Therefore, for those trying to lose weight, it's better to eat them whole; juicing is not an ideal option. Freshly squeezed juice should be stored for no more than one day
If not blanched, juice should be consumed immediately after juicing and cannot be stored. You could say that with every passing minute, the loss of vitamins and antioxidant components increases. If the juice is made from blanched produce, the enzymes have been inactivated, so it can be sealed and stored in the refrigerator for one day.