Where does sugarcane come from? Which part is the sweetest? An article on the history of sugarcane

Produced by: Science Popularization China

Author: Yang Changjialian, Yin Xin (Institute of Microbiology, Chinese Academy of Sciences)

Producer: China Science Expo

Editor's note: In order to decode the latest mysteries of life science, the China Science Popularization Frontier Science Project has launched a series of articles called "New Knowledge of Life" to interpret life phenomena and reveal biological mysteries from a unique perspective. Let us delve into the world of life and explore infinite possibilities.

October is the golden autumn season when sugarcane is about to mature.

From this season to April of the following year, you can see large tracts of bumper sugarcane fields in the southern sugarcane producing areas of Guangxi, Guangdong, Yunnan, Hainan and other places. You can buy a piece of fresh sugarcane, enjoy the scenery and feel the refreshing sweetness. It is simply a wonderful holiday enjoyment.

So, how can we make sugarcane more delicious? Today, we will take you to understand the unknown story behind this common fruit from the perspective of science and daily life.

The Mystery of Sugarcane's Origin

Speaking of sugarcane, many people may not know that sugarcane is a veritable "hybrid".

Why do I say so?

Because the main cultivated varieties of sugarcane are almost all obtained through hybridization. There are a total of 6 species in the genus Saccharum, including 2 wild species: large-stemmed wild species (S.robusfum) and thin-stemmed wild species (also known as cut-handed wild, S.spontaneum); 4 original cultivated species: tropical species (S.officinarum), Chinese species (S.sinense), Indian species (S.barberi) and edule species (S.edule) [1]. Different sugarcane species have different centers of origin. Among them, tropical species and large-stemmed wild species originated in the South Pacific island country of New Guinea; Indian species and thin-stemmed wild species originated in India; Chinese species originated in South China and Yunnan [2].

Since sugarcane is obtained through hybridization between different species, the origin of its "bloodline" is confusing and complicated. Therefore, the three mainstream hypotheses about the origin of sugarcane are the New Guinea origin theory, the India or Bangladesh region origin theory, and the China origin theory [3] .

The climate in these areas is suitable for the growth of sugarcane. As early as 4,000 years ago, the local indigenous people began to plant and use sugarcane. According to Ji Xianlin's research in "The History of Sugar", Indian sugarcane was introduced from India to Persia in the 6th century AD, and spread to the Mediterranean region due to the expansion of Arabia; in the 15th century, with the colonial expansion of Portugal and Spain, it spread to Madeira Island, Cape Verde Islands, São Tomé Island and West Africa; in 1493, during Columbus's second voyage, Indian sugarcane came to the New World, and later with the expansion of Portugal and Spain, it quickly spread throughout the New World, and the western end of the spread was Peru; although Australia and New Guinea (the birthplace of large-stemmed wild and tropical species of sugarcane) are separated by only a few hundred miles of Torres Strait, Indian sugarcane was not introduced to Australia until 1788 [4].

Later, different varieties of sugarcane gradually spread to other places with human migration and trade activities, and eventually became a widely planted sugar crop around the world.

The representative original species of the Chinese sugarcane (S. sinense) is bamboo sugarcane, which is mainly distributed in the three major sugarcane regions of South China, Central China and Southwest China. It was the main cultivated variety in China before 1953. Although there is a "bamboo" in bamboo sugarcane, sugarcane and bamboo have similarities in appearance, such as they both have node-shaped stems and belong to the tall grass family, but they are not members of the same family.

Sugarcane belongs to the genus Saccharum of the Poaceae family, and is a distant relative of crops such as rice, corn, and sorghum, while bamboo belongs to the subfamily Bambusoideae of the Poaceae family [7]. Although both belong to the Poaceae family, sugarcane and bamboo have significant differences in ecological habits, uses, and internal structures. The main feature of sugarcane is that its stems are rich in juice, which is rich in sucrose and is the core value of sugarcane as a sugar-making crop. The stems of bamboo, on the other hand, are mainly composed of fibers and lack rich juice. They are more often used as building materials, handicrafts, and even food (such as bamboo shoots). Therefore, although sugarcane and bamboo look like "relatives", they actually belong to different branches in terms of classification, and their functions and uses are completely different.

Sugarcane fields

(Photo source: veer photo gallery)

Sugarcane in Ancient Chinese Books

The history of sugarcane being introduced into China in ancient times can be traced back to the reign of King Xuan of Zhou during the Zhou Dynasty [3]. It was introduced into China mainly through trade and cultural exchanges in the south. The word "zhè" (pronounced zhè) in the pre-Qin era represented sugarcane. According to Li Zhihuan's research in "Draft History of Chinese Sugar Consumption", "zhèjiang" was mentioned in "Chu Ci·Zhao Hun" in the Warring States Period, "zhèjiang" in "Han Shu·Li Yue Zhi·Jiao Si Ge" in the Han Dynasty, and "zhuzhè" in "Zixu Fu" written by Sima Xiangru in the Han Dynasty are all evidence of sugarcane cultivation in my country [5]. In addition, sugarcane was no longer limited to chewing, but was processed into sugarcane juice; when the word "zhè" appeared in the Han Dynasty, it was the same as the word we use today [6]. In the "Shennong Bencao Jing" of the Eastern Han Dynasty, sugarcane was considered to have certain medicinal value and could moisturize and quench thirst.

The sweetness of sugarcane is not as obvious as that of fruit, because its skin is hard and must be peeled before chewing the juice. There is a speculation that people at that time may have accidentally chewed the exposed tender stems when cutting sugarcane stalks or using them as building materials, and then tasted the sweet juice.

Ban Gu of the Eastern Han Dynasty recorded in the Book of Han that "squeezing the juice and exposing it to the sun for several days makes it into candy". Ji Han of the Western Jin Dynasty said in his book Description of Plants in the South: "One of the sugarcanes is called sugarcane. The one grown in Jiaozhi is several inches in circumference and more than ten feet long, quite similar to bamboo. It is very sweet when cut and eaten. Squeeze the juice and expose it to the sun for several days to make candy. It melts in the mouth and people at that time called it rock honey." According to these documents, the ancients had mastered the methods of cultivating sugarcane and processing sugarcane products (syrup) very early [2].

As for when the production of sugarcane in China began, different scholars have different views. Mr. Ji Xianlin believes that it should have started in a period between the Three Kingdoms, Wei, Jin, Southern and Northern Dynasties and the Tang Dynasty, at least before the Later Wei Dynasty [6]. In the Tang and Song Dynasties, the cultivation technology of sugarcane was further promoted. Wang Zhuo of the Song Dynasty wrote the earliest Chinese sugar-making monograph "Sugar Frost Spectrum". Su Shi and Huang Tingjian also mentioned "sugar frost" and "sugarcane frost" in their poems. In the "Gan Shi" volume of "The Exploitation of the Works of Nature" in the late Ming and early Qing dynasties, Song Yingxing systematically introduced the entire process of sugarcane from "sugarcane seeds", "sugarcane varieties", "sugar making", "white sugar making", "animal sugar making", etc. However, it was not until later that sugarcane was truly used for large-scale industrial sugar production.

Sugarcane and sugar

(Photo source: veer photo gallery)

The structure of sugar cane: where is sweeter?

The main structure of sugarcane includes the husk, the stem nodes, and the pith. Each part plays an important role in the growth of sugarcane and when we taste it. The husk of sugarcane is very hard and plays a role in protecting the inside of the sugarcane. Although it looks shiny and bright, it cannot be eaten directly and usually needs to be peeled off with a knife. After peeling off the husk, we will see the stem nodes of sugarcane. The stem nodes of sugarcane are very obvious, and the relatively long part between each node stores a lot of juice, which is the most popular part for people to chew. Inside the stem node is the pith of sugarcane, which is the core part of sugarcane and is rich in water and sugar. When we chew sugarcane, we get sugarcane juice from the pith. Sugarcane juice is rich in sucrose, and it is these sugars that make sugarcane taste so sweet.

Interestingly, the sweetness of sugarcane is not evenly distributed.

Usually, the bottom of the sugarcane is sweeter than the top. This is because during the growth of sugarcane, sugar is generated through photosynthesis and transported and stored from the top to the bottom. Therefore, the bottom sugarcane near the root accumulates more sugar and tastes sweeter. Generally in production, when the sugarcane matures, relevant inspectors will use a hammer meter to measure the density of juice in different internodes of the upper, middle and lower parts of the sugarcane, and convert it into sugar content. If the upper part has much less sugar than the lower part, the sugarcane is not fully mature yet and needs to wait for some time; if the difference between the upper and lower parts is not big, the sugarcane has completed sugar accumulation and is fully mature and can be used for sugar production.

In addition, if sugarcane is not harvested in time after maturity, or if it is not processed in time after harvest, the sugarcane will also experience "sugar desaturation", that is, the sugar content of the sugarcane will decrease. This is because there are buds on the nodes of sugarcane, and each bud can grow into a new sugarcane seedling. This is also the main way of asexual reproduction of sugarcane. If it is not processed in time, the sugar stored in the sugarcane stem will be used for the growth of sugarcane buds, and the sugarcane stem will naturally not be as sweet as before.

Sugarcane structure

(Photo source: veer photo gallery)

“Same sugarcane, different fates”: the difference between fruit cane and sugar cane

Sugarcane is divided into two categories: one is the fruit cane that we eat directly, and the other is the sugar cane used to extract sugar. Fruit cane is tall and strong, with a crisp and delicate taste, relatively low fiber content, rich juice, and moderate sweetness. It is mainly eaten as a fruit and is not suitable for sugar production. Sugar cane is more "slender" than fruit cane, with coarse and hard fibers, strong resistance to lodging, and high sugar content, making it suitable for refining sugar. This "same sugarcane but different fates" is the result of the combined effects of natural differentiation and artificial breeding of sugarcane [8]. Sugarcane originated in tropical regions. After a long period of natural evolution, different variants have emerged under different climate and soil conditions. With the development of agriculture, humans discovered the differences in the characteristics of different sugarcanes, and through hybridization, screening, breeding and other means, they specially bred two types of sugarcane that are more suitable for eating raw and making sugar.

Sugarcane is versatile

In addition to being used as a fruit and for making sugar, sugarcane has many other uses. The tops of sugarcane can be used as seeds for cultivation, the leaves can be crushed and returned to the fields to improve the soil, and the roots of sugarcane are cool in nature and can be used as medicine.

Bagasse is the main byproduct of the sugar industry. Every ton of sucrose produced produces 2-3 tons of bagasse, and 40%-50% of bagasse is cellulose, 25%-30% is hemicellulose, and there are also lignin, protein and other components, which are valuable resources that can be recycled. In recent years, with the advancement of science and technology, bagasse has achieved high-value comprehensive utilization in animal feed production, biodegradable product production, pulp and paper making, biomass fuel development, etc. [9].

Molasses, another by-product of sugar production, can also be used to make alcohol, feed additives, etc. Internationally, the distilled liquor produced with sugarcane juice or molasses as raw materials is named "rum".

Sugarcane can also be used as a raw material for the production of ethanol, becoming a biofuel energy source, and helping the bioenergy industry. Sugarcane is not only delicious, but also provides many conveniences in our daily lives.

Bagasse

(Photo source: veer photo gallery)

How can you pick sugarcane that is sweet and delicious?

First of all, when choosing sugarcane, you should look at its husk. Good sugarcane has a smooth husk with bright colors, preferably black or turquoise.

Secondly, pay attention to the length of the sugarcane internodes. Sugarcane with longer internodes usually has more juice.

Finally, gently pinch the sugarcane. If the skin is hard but not shriveled, it is fresh. If the sugarcane has moldy or black spots on the skin, or the cross section is yellow or liver-colored, emits a musty smell, and tastes sour or wine lees, be careful, because such sugarcane is likely to have deteriorated and may contain toxins, so remember not to eat it.

Take these tips for picking sugarcane and enjoy the sweet taste of nature! While enjoying the deliciousness of sugarcane, you are also meeting science unexpectedly and feeling the convenience and good life brought to us by the progress of agricultural technology.

(Note: Latin parts in the text should be italicized)

References:

1. Dong Guangrui, Shi Jiaxian, Hou Ailing, Zhang Jisen. (2018). Research progress on sugarcane genome. Biotechnology, 28(3): 296.

2. Que Youxiong et al. (2023). Things about Sugarcane and Sugar. China Agriculture Press.

3. Zhang Jisen, ed. (2024). Sugar and Civilization: How Sugarcane Shaped Our World. Science Press.

4. Ji Xianlin. (1998). Ji Xianlin's Collected Works: History of Sugar (II). Jiangxi Education Press.

5. Li Zhihuan. (1990). A Draft History of Sugar Consumption in China. Beijing Agricultural Press.

6. Ji Xianlin. (1998). Ji Xianlin's Collected Works: History of Sugar (I). Jiangxi Education Press.

7. Soreng, RJ, Peterson, PM, Romaschenko, K., Davidse, G., Zulonga, FO, Judziewicz, TS, Filgueiras, TS, Davis, JI & Morrone, O. 2015. A worldwide phylogenetic classification of the Poaceae (Gramineae). Journal of Systematics and Evolution 53: 117–137.

8.James, GL (2004). Sugarcane. Blackwell Publishing.

9.Rein, P. (2012). Cane Sugar Engineering. Bartens.