Family members, heating up fruits in winter is really amazing!

In the cold winter, people like to eat hot food to warm their bodies, and even heat up fruits. However, some people may worry: Can heated fruits still be nutritious?

In fact, the nutritional loss of fruit is not that great when heated, and it has a different flavor when eaten cooked.

Eating ripe fruit has a special taste

Under low-temperature cooking such as steaming, boiling, and stewing, the sugar, amino acids, vitamin C, carotenoids and other ingredients in fruits will be partially degraded, producing aldehydes, ketones, alcohols and other aromatic substances. Therefore, when we cook a bowl of pear soup, we can smell the unique aroma. In addition to the fruity aroma contained in the fruit itself, it is also related to heating. However, it is best not to cook the fruit for a very long time. In addition to the loss of heat-sensitive nutrients, the fruit's own fruity aroma is also lost. When cooking at high temperatures, such as baking, the glucose and fructose in the fruit will also undergo the Maillard reaction with amino acids. This reaction will not only give the fruit a brown color, but also produce various aromatic substances. This is the secret of the unique aroma of cooked fruit. In addition, when cooking fruit, some of the sugar and acid in the fruit will dissolve in the water. If you think some fruits are too sweet to eat directly, then this can make the sweetness become sweet and sweet, which is more suitable for your appetite, and you can also drink the sweet and sour fruit soup, which is another different taste experience. By the way, some fruits are more irritating when eaten raw, such as pineapple. The bromelain it contains will feel prickly when it comes into contact with the mouth. Calcium oxalate crystals can also prick the mouth like needles. You don’t have to be afraid of that if you cook them and eat them, because the enzyme can be destroyed at high temperatures and calcium oxalate crystals can be dissolved in water. So friends who are afraid of prickly mouths might as well cook the pineapple, grill it, or make it into pineapple fried rice.

Heating fruit: nutritional loss is not that great

——Don’t worry about the loss of these 7 nutrients. The nutrients that reach the gram level in every 100 grams of fruit include water, carbohydrates, protein, dietary fiber, and fat. The content of each 100 grams is at the microgram and milligram level for various vitamins, minerals, and phytochemicals such as beta-carotene, anthocyanins, lycopene, lutein, and zeaxanthin. If you don’t consider the effect of heating on the taste, and only consider nutrition, then the nutrients above can be easily obtained from other types of food besides fruit, so you don’t need to worry too much about whether they will be lost by heating.

1

water

The most abundant component in fruit is water, about 80 to 90 grams per 100 grams. However, eating vegetables, drinking milk, soy milk or drinking water directly can also replenish water well, so there is no need to worry about whether heating increases the loss of water in the fruit.

2

carbohydrate

The second most abundant ingredient in fruit is carbohydrates, which generally range from 10 to 20 grams per 100 grams. However, eating staple foods can supplement more carbon water. Some vegetables like carrots, garlic sprouts, fresh broad beans, edamame, wild rice stem, and lotus root can also reach more than 10 grams per 100 grams of carbon water, and they are also experts in supplementing carbon water. Therefore, when heating fruits, you don’t have to worry about whether carbon water will be lost.

3

Protein Wheel

When it comes to protein supplementation, fruit is far inferior to meat, eggs, milk and beans. Considering this point alone, there is no need to worry about whether protein is lost during heating. What's more, heating will hardly cause any protein loss. It will only break down a little bit of protein into amino acids. In addition, heating will denature the protein, making it easier to digest. Therefore, you don't need to worry about what will happen to the protein when heating fruit.

4

Dietary fiber

First of all, dietary fiber can be rotated, and whole grains, beans, and vegetables can also replace fruits. Secondly, heating can soften insoluble dietary fiber and reduce its irritation to the stomach and intestines, which is better for people with delicate gastrointestinal tracts. In addition, although heating will destroy the cell walls of the fruit and allow some soluble dietary fiber to dissolve in water, as long as you eat the fruit and drink the water used to cook the fruit, this part of the nutrition will not be wasted.

Image source: Pixabay

5

Fat

As for fat, there is usually only a few tenths of a gram per 100 grams, which is insignificant compared to nuts, meat, eggs, milk and beans. What's more, fat is also stable in low-temperature cooking such as steaming, boiling and stewing, so you don't need to worry about the fat when heating fruit.

6

Minerals

Minerals such as calcium, magnesium, and potassium are particularly resistant to high temperatures. How resistant are they to high temperatures? In the experiment, the ingredients are heated to about 500-900°C for 30 minutes, and then the remaining food residues are weighed to obtain the ash content of the food. This ash is the mineral. Such high temperatures can be tolerated, and steaming, boiling, stewing, stir-frying, and even frying, deep-frying, roasting, and baking are at most 200 to 300 degrees Celsius, which cannot destroy the minerals at all. A small amount of minerals will at most run from the fruit into the water, and if you drink the water used to boil the fruit, there will be no loss at all, so there is no need to consider what will happen to the minerals when heating the fruit.

7

Lutein

Lutein is not only heat-resistant, but also acid- and alkali-resistant, so it is not afraid of being heated with any kind of water. Therefore, from the perspective of lutein retention, it is completely fine to eat fruits rich in lutein, such as kiwi, grapes, and citrus fruits, when cooked.

——Although these 4 types of nutrients are easy to lose, they are harmless

1

Vitamin C

Vitamin C can not only promote the production of collagen, but also promote the absorption and utilization of iron, calcium, and folic acid, promote the production of antibodies, and participate in detoxification. It is of great significance to health. However, the intake of vitamin C by Chinese people does not reach the recommended intake. Because vitamin C is afraid of heat, it is better to eat fruits raw, but don’t be afraid to eat fruits cooked. The following table is the vitamin C retention rate of common fruits canned according to the data of the US Department of Agriculture. You will find that the vitamin C retention rate of three fruits with high vitamin C content, such as strawberries, oranges, and pineapples, is above 40%. Among them, the vitamin C retention rate of canned oranges is as high as 74%. This retention rate is quite impressive, so from the perspective of vitamin C, they are quite suitable for cooked eating. As for other fruits whose vitamin C content is not high, the vitamin C retention rate is slightly lower when they are canned, so don’t worry too much.

Vegetables and fruits rich in vitamin C Image source: Reference [3]

In order to adequately supplement vitamin C, we can also often eat raw fruits that are particularly rich in vitamin C, such as winter dates and kiwis. Eating two large winter dates or two small kiwis can meet an adult's daily vitamin C needs. In addition, we can also eat more vegetables that are as rich in vitamin C as fruits. For details, please refer to the table below. In this way, we don't have to worry too much about the loss of vitamin C when fruits are heated.

Vegetables and fruits rich in vitamin C Image source: Reference [1]

2

anthocyanin

Anthocyanins have poor thermal stability and will quickly degrade at temperatures above 60°C. They are also water-soluble, so they will be lost if cooked. Therefore, from the perspective of retaining anthocyanins, blueberries and mulberries rich in anthocyanins are not suitable for hot consumption. In addition, blueberries and mulberries are both berries with a very soft texture. They will become soft and mushy if cooked for a long time, and their taste is not good. Furthermore, if cooked with tap water, anthocyanins will turn blue, which is simply a dark dish. Therefore, fruits rich in anthocyanins are not suitable for hot consumption.

3

Beta-carotene

β-carotene is very sensitive to heat. In order to retain more β-carotene, fruits rich in β-carotene such as mango, papaya, and orange are naturally not suitable for hot food. However, vegetables such as spinach, radish tops, lettuce leaves, leeks, and wood greens are richer in β-carotene, about 3 times more than mangoes and more than 9 times that of papaya and oranges. We can completely consume more β-carotene from these vegetables, so we don't have to worry about β-carotene when heating mangoes, papayas and oranges.

4

Lycopene

Lycopene is unstable when exposed to heat, but after heating, the less active all-trans configuration of lycopene can be converted into a cis configuration with stronger antioxidant activity and higher bioavailability. That is to say, although heating will cause the loss of some lycopene, the antioxidant activity is stronger. Therefore, fruits rich in lycopene, such as guava, watermelon, papaya, and grapefruit, are completely suitable for eating cooked from the perspective of lycopene.

Fruits that are suitable and unsuitable for heating

Whether fruits are suitable for heating or not, in addition to considering the loss of nutrition, we also need to consider the texture and taste. For example, the berry fruits mentioned above, kiwi, blueberry, and mulberry, are not suitable for heating. This is because they are too soft and will easily become muddy if boiled, steamed, or baked. In addition, kiwi is particularly rich in vitamin C, and it is sweet and sour when eaten raw. It is a pity to cook it. Taking all factors into consideration, apples, pears, yellow peaches, plums, prunes, and pineapples are hard in texture and not rich in vitamin C. Apricots, tangerines, mangoes, oranges, and hawthorns are hard in texture and not rich in anthocyanins and lycopene. They are more suitable for heating. Boiling, microwave, and baking are all fine, but boiling will cause more loss of water-soluble vitamins, while baking will basically lose all heat-sensitive vitamins. Of course, we don't always heat fruits to eat, and there are other food sources to supplement various nutrients, so we don't need to care too much. Nutrition never requires eating a certain kind of food, but a balanced overall combination.

Image source: Pixabay

Fruits like blueberries, strawberries, kiwis, mulberries, dragon fruit, and watermelons are very soft and easily become mushed when heated, so don’t eat them cooked.

References

[1] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 1[M]. Peking University Medical Press, 2018

[2] http://down.foodmate.net/standard/yulan.php?itemid=49326

[3]https://fdc.nal.usda.gov/fdc-app.html#/?component=1162

[4]Xu Qing, Wang Daibo, Liu Guohua, et al. Research progress on factors affecting anthocyanin stability and improvement methods[J]. Food Research and Development, 2020, 41(7):7.

[5] Zhu Zhenbao, Wu Yuanfang, Yi Jianhua. Study on the stability of anthocyanin pigments in purple cabbage[J]. Grain and Oils, 2011(10):4.

[6] https://fdc.nal.usda.gov/fdc-app.html#/?component=1107

[7] Zhu Qian, Gao Ruiping, Lei Lin, et al. Research progress on the mechanism of lycopene thermal isomerization and its influencing factors[J]. Food Science, 2018, 39(15):6.

[8] Chan Jianquan. Food Chemistry (Second Edition)[M]. Beijing. China Agricultural University Press, 2008

Author: Gu Chuanling, Deputy Secretary General of Capital Health Nutrition and Gastronomy Association, Registered Nutritionist

Review | Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center