The popularity of fresh-squeezed juice is naturally inseparable from its rich vitamin content. However, there has been a lot of discussion recently about the nutritional content of fresh-squeezed juice. Some people strongly advocate for the rich Vitamin C in juice, while other scholars believe that Vitamin C is "severely depleted" after fruits are juiced, with losses exceeding 90%.
Meanwhile, industrially produced juices use preservation methods to solve the problem of Vitamin C loss, but other issues leave consumers confused. So, what is the nutritional value of fresh-squeezed juice? Is it good to drink regularly? Let's find out together.
A food analysis laboratory conducted an experiment to measure the amount of Vitamin C lost after juicing fruits and vegetables. The fruits and vegetables used in the experiment included cucumbers, pears, carrots, and watermelons.
The experimental results showed varying degrees of Vitamin C loss in the juices of fruits and vegetables, with the most severe cases losing over 90%. Such experimental results seem a bit unbelievable. Is the loss of nutrients in fruits so severe after juicing?
Experts explain that the loss of Vitamin C in fruits is mainly due to oxidation reactions. The scientific name for Vitamin C is ascorbic acid, which has antioxidant properties. When fruits and vegetables are juiced, the cells are destroyed, exposing the Vitamin C to the air where it can oxidize.
The amount of Vitamin C loss also varies after juicing different fruits. The Vitamin C content in 100 grams of cucumber, pear, and carrot is less than 1 mg, while the Vitamin C content in watermelon juice lost less than 20%. This is because watermelon is acidic and, compared to the first three fruits and vegetables, is less prone to oxidation.
Experts analyze that the juices currently sold on the market can be roughly divided into the following types:
1. Refrigerated and preserved juice: This type of juice is fresh-squeezed and generally contains no added sugar or sweeteners. This juice must be stored at low temperatures and consumed within a short period, generally not exceeding one week.
2. Pure juice: Can be stored at room temperature with a shelf life of more than six months. Most of this type of juice is made by reconstituting concentrated fruit juice from production areas with water to the original concentration, followed by instantaneous high-temperature sterilization.
3. Juice beverages: There are many varieties of carbonated and non-carbonated juice beverages, with varying juice content.
Experts explain that for high-concentration fresh-squeezed juices, a high-temperature heating method is often used to quickly kill bacteria and ascorbic acid oxidase in the juice. This ascorbic acid oxidase is the reason for the oxidation of Vitamin C, a process that homemade juices cannot achieve.
In addition, fresh-squeezed juices sold in supermarkets are sealed to isolate them from the air. In an environment without air, Vitamin C is not easily oxidized. Therefore, processed juices can guarantee a certain amount of Vitamin C content.
There are also many juice beverages on the market, with a juice concentration of only about 10%, making it difficult to guarantee their Vitamin C content. Therefore, Vitamin C is often added to these juices. Although the Vitamin C content is guaranteed, it is not yet clear how well the human body can absorb and utilize artificially added Vitamin C. Therefore, it cannot be determined how much Vitamin C will ultimately be consumed from drinking such juice beverages.
Whether it's juice made at home or fresh-squeezed juice bought from the supermarket, attention must be paid to storage conditions. Feng Shuangqing stated that juice is generally not recommended for storage and should be consumed as soon as possible. For larger packs of juice that cannot be finished all at once, they should be properly stored.
During the storage process, the fastest-depleting component in juice is vitamins. Generally, the more acidic the juice, the longer Vitamin C can be preserved.
This is because Vitamin C is most stable under acidic conditions, and microbial growth is also less likely. After opening, hawthorn juice, citrus juice, and grape juice can be stored in the refrigerator for 3 to 5 days, while less acidic juices like peach and pear juice are best consumed within 2 days of opening.
Additionally, many consumers believe that sealing juice and putting it in the refrigerator solves the storage problem. In reality, a refrigerator only slows the rate of nutrient loss; chemical reactions in the juice continue, and nutrients are constantly being lost.
The idea that children should drink more juice seems to have been deeply ingrained, but recently many scholars have questioned this. The Albert Einstein Medical Center in the U.S. conducted a retrospective survey of over 100 anemic children and found that more than 80% had a habit of drinking juice.
Experts explain that juice is rich in fructose, and excessive intake can affect the body's absorption of copper. The trace element copper is a component of many enzymes in the body and participates in iron metabolism. Therefore, a copper deficiency can also cause anemia. However, for Chinese children, a more significant problem with juice is its high calorie content.
Because the sugar content in juice beverages that children are exposed to in China is generally high, it leads to a high calorie intake. For some children, sufficient calories can lead to a decrease in appetite, affecting their normal diet.
If this situation persists for a long time, it will inevitably lead to insufficient intake of protein, minerals, and other trace elements. For children with a good appetite, drinking a lot of juice after meals will ultimately lead to an increase in obesity rates.
Many elderly people with poor teeth like to juice fruits and vegetables, believing it will aid digestion.
Experts explain that drinking fruits and vegetables as juice not only does not help digestion but can also cause constipation. This is because the juicing process loses a lot of essential dietary fiber. The insoluble fiber can prevent diseases of the gastrointestinal system, has the effect of stimulating intestinal peristalsis and promoting bowel movements.
In addition, dietary fiber can also affect blood sugar levels, reduce diabetics' dependence on medication, and has the effects of preventing excess calories, controlling obesity, preventing gallstones, and lowering blood lipids.
This situation is most common among the elderly, especially those with poor teeth. In fact, a large part of the cause of constipation is due to a diet that is too refined, leading to insufficient fiber intake. A refined diet is reflected not only in grains but also in beverages. Using fruit and vegetable juices as a substitute for whole fruits and vegetables is even more inadvisable.