Not too hot, and still chewy, are cold Yuanxiao so delicious? I advise you not to eat it this way!

Happy Lantern Festival! Is it time to eat Yuanxiao (or Tangyuan, not the focus of this article, anyway, it is the thing eaten during the Lantern Festival hahaha) again? Nowadays, many friends pursue novelty and do not eat ordinary things. It is not found on a certain social APP that many people post: Yuanxiao tastes good when it is cooled down... Maybe you have eaten cold Yuanxiao, which is not hot in the mouth, and has a hard and chewy texture. It is delicious and intoxicating! Little do you know that eating like this will not only satisfy your taste, but also increase the burden on the digestive system and cause indigestion!

Netizens commented that the cooled Yuanxiao was "delicious" (Image source: screenshot from Xiaohongshu)

01 Why is it so annoying? When it gets cold, it becomes old.

Indeed, Yuanxiao will become hard when it is cooled. If you haven't noticed it, you can also save a Yuanxiao and try it. In fact, not only Yuanxiao, but also bread, steamed buns, rice and even qingtuan will become hard when they are cooled. If you look closely at their ingredients, you will find that they have something in common: the main ingredient is starch .

Yuanxiao wrapped in glutinous rice flour (copyright image from the gallery, reprinting may cause copyright disputes)

The outer skin of Yuanxiao is mainly made of glutinous rice flour, which is mainly composed of starch. Here we have to talk about one of the characteristics of starch: aging and regeneration .

The main component of glutinous rice flour is starch, which accounts for about 75%-77% , and is mainly amylopectin . When the glutinous rice flour is put into water and cooked, the starch will swell and split to form a paste solution. This process is called starch gelatinization . During the gelatinization process, the structure of the starch will be destroyed, becoming soft and easy to chew and digest. After cooling, part of the amylopectin will turn back into a neatly structured straight-chain starch , which will make people feel hardened. This is the aging and regeneration of starch.

Amylose polysaccharide polymer (copyright image from the library, reprinting may cause copyright disputes)

Even if you reheat it, it will be hard for the food to return to its previous soft state. The cold Yuanxiao will not only be hard, but also difficult to digest, which has to do with the body's digestion of starch.

02 Every step is not easy

The human body's digestion of starch is divided into two categories: mechanical digestion and chemical digestion .

Mechanical digestion refers to tearing and grinding , such as when starch enters the mouth, it is bitten and chewed into pieces by the teeth. Gastrointestinal peristalsis also belongs to mechanical digestion.

Chemical digestion is the chemical reaction between various digestive enzymes in the human body and starch . For example, amylase in saliva and intestines digests starch. The more and more fully the food comes into contact with enzymes, the more it can be broken down by enzymes and then digested.

When we say that a certain food is easy to digest, we mean that it is easy to grind, can be fully mixed with enzymes, and can form small enough nutrient molecules after digestion to be absorbed by the intestines. When starchy foods are just cooked, they are relatively soft and easy to be ground by teeth. Compared with the rope-like straight-chain starch, the branch-like amylopectin can be more fully mixed with the amylase in the saliva, so it is easy to digest. After entering the small intestine, it is also easy to be absorbed. Therefore, compared with other grains, cooked glutinous rice foods are easily digestible foods.

Illustration of the starch digestion process (copyright image from the library, reprinting may cause copyright disputes)

But the glutinous rice food after aging is different. First of all, because the food becomes hard, it is difficult to fully chew in the mouth, and it is ground into pieces, and sometimes even swallowed in large pieces. This leads to insufficient contact area and degree between the food and the amylase in the saliva , and the digestion process in the mouth is not completed well. Then the glutinous rice food enters the stomach. But there is no amylase in the human stomach. In the stomach, starch can only be neutralized with gastric acid, and continue to be ground into chyme under the peristalsis of the stomach . But because the food itself is large and sticks together, it takes longer to decompose. If the food stays in the stomach for a long time, people will feel full and feel bloated and difficult to digest. After entering the small intestine, the glutinous rice food will be further decomposed by the action of amylase, and then digested and absorbed.

The March 2023 article "Biological factors controlling starch digestibility in human digestive system" in the Journal of Food Science pointed out that if starch passes through the small intestine into the colon, this part of starch is usually called resistant starch . This starch can potentially be used as a prebiotic, that is, an indigestible food ingredient. Under anaerobic conditions in the large intestine, this type of starch is mainly fermented into hydrogen, carbon dioxide, methane and hydrogen sulfide. If too much gas is produced, it is inevitable that people will feel bloated. This is also the reason why some people think that glutinous rice foods are difficult to digest and easy to cause bloating.

03 Why are some glutinous rice foods soft even when they are cold?

There are always exceptions to everything, and the same is true for glutinous rice foods. Although Yuanxiao is soft when hot, it becomes hard when cold. But there are some glutinous rice foods that are naturally cold but still soft, such as donkey rolls, cold-eaten Yuanxiao and rice cakes. In fact, this is because their methods are very different. When making foods such as donkey rolls, the ratio of glutinous rice flour and sticky rice flour is controlled. In addition, in order to prevent hardening, more oil, sugar, salt and other materials are added , and the starch is also beaten and kneaded more to increase its toughness and delay the aging process of starch. Therefore, donkey rolls and cold-eaten glutinous rice balls can be kept for a longer time, but they will still become hard if they are too long.

Various types of cold-eaten Yuanxiao (dry-eaten glutinous rice balls) (Image source: screenshot from Xiaohongshu)

04 Even if you have good teeth, you can’t eat too much

In fact, whether glutinous rice foods are easy to digest does vary from person to person. Some people have good teeth and can chew and grind them, and their gastrointestinal motility is sufficient, so digestion and absorption are not delayed. But this is not a good thing. In his 1992 article "Classification and measurement of nutritionally important starch fractions", British scholar Dr. Ingrist divided starch into rapidly digestible starch and slowly digestible starch. Rapidly digestible starch can be quickly digested and absorbed in the small intestine, raising blood sugar and causing large fluctuations in blood sugar after meals. Soft and chewy glutinous rice foods, especially Yuanxiao that is cooked just right, belong to this category. This is why people with high blood sugar should not eat too much glutinous rice foods such as Yuanxiao.

(Copyrighted images from the gallery, reprinting may lead to copyright disputes)

As for Yuanxiao, not only is the glutinous rice skin easy to raise blood sugar, but the fillings are high in oil and sugar, which are not friendly to blood sugar. Even healthy people with normal blood sugar should not eat too many Yuanxiao at one time. The sticky starch mixed with oil and sugar will reduce its contact area with amylase, making it more difficult to digest than pure glutinous rice food.

Therefore, even if you love soft and chewy Yuanxiao, remember to control your diet for the sake of your health.

References

1.Englyst HN, Kingman SM, Cummings J H. Classification and measurement of nutritionally important starch fractions [J]. European Journal of Clinical Nutrition, 1992.

2.Cheng Li, Yiming Hu. Biological factors controlling starch digestibility in human digestive system[J]. Food Science and Human Wellness, 2023.

3.Zhenlei Yang, Yuyang Zhang, Factors influencing the starch digestibility of starchy foods: A review[J]. Food Chemistry, 2023.

4. Li Xuehong, Chen Zhijing, Factors affecting starch digestibility and characterization methods [J], CNKI, 2015.

Author: Jiuyi Popular Science Creator

Reviewer: Liu Zhengxin, Chief Physician, Department of Gastroenterology, Beijing Chaoyang Hospital, Capital Medical University

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.