Sweetness is the result of a long process of hard work: How hard will humans work for a taste of sweetness?

Produced by: Science Popularization China

Author: Xiao Bai (Institute of Botany, Chinese Academy of Sciences)

Producer: China Science Expo

Reviewer: Chen Wenli (Institute of Botany, Chinese Academy of Sciences)

For thousands of years, sweetness has been one of the most beautiful and precious tastes in human food culture. Whether it is to satisfy the appetite, to reconcile sourness and bitterness, or to be used as medicine, it is the most fascinating part.

When we think of sugar, we often think of it. Sugars are not uncommon in nature, but most of them exist in the form of polysaccharides such as starch, which cannot directly bring us sweetness. Sugars that can make people happy - usually monosaccharides and disaccharides - are very rare in nature. In the early days of human history, people could usually only get a glimpse of the beauty of sweetness from wild fruits and honey.

The structure of monosaccharides (glucose), disaccharides (maltose), and polysaccharides (starch)

(Image source: Reference [1], adapted)

Sugar Plants: An Early Source of Sugar

Today, sugar is no longer precious, or even dangerous to overdose. When we savor delicious candies, enjoy sweet snacks, or mix a glass of mellow drinks, few people would think that there is an ancient and sophisticated process behind these sweet enjoyments.

Key players in this process are sugar plants, which are refined to sweetness. They play a vital role in human food history.

From ancient malt to sugar cane in Asia, sugar beets in Europe, and corn in the Americas, the diversity of sugar-producing plants is astonishing. They are cultivated and processed in different ways, but they all contribute to one of the world's most popular foods: sugar.

These plants not only provide a sweet taste, but also have a profound economic, cultural and social impact.

Sugar in life

(Photo credit: Pexels, photo by Pavel Danilyuk)

Chinese maltose is considered the earliest sugar in the world. The Book of Songs, Da Ya, contains the line "The Zhouyuan is fertile, and the violets and chicory grown there are as sweet as molasses." This line praises the fertile land of the Zhou Dynasty, where violets and chicory grown there are as sweet as molasses.

The "Yi" here refers to maltose. People mix starchy ingredients with malt and soak them, use the amylase produced when the wheat germinates to partially hydrolyze the starch into maltose and glucose, and then boil and concentrate it into a viscous state to become "Yi". To this day, maltose is still a favorite food of many people.

Maltose

(Photo credit: Flickr, photo by Robin)

The rise of sugarcane

Sugarcane (Saccharum officinarum) is considered one of the earliest sources of sugar. Its high yield and sucrose content are the reasons why it was chosen as a sugar plant, which is also due to its sophisticated photosynthesis system.

The main types of photosynthesis in plants can be divided into three types: carbon three (C3), carbon four (C4) and Crassulacean acid metabolism. About 95% of plants are C3 plants. The latter two types have evolved based on the C3 pathway to adapt to the climatic characteristics of tropical regions.

C4 plants can use less water and fix CO2 in the air more efficiently. Although this requires extra energy, the strong sunlight in tropical areas is enough to make up for this, and the photosynthesis products are greatly improved compared to C3 plants. Common C4 plants include sugarcane, corn and sorghum.

sugar cane

(Image source: Reference [2])

C4 Plant Photosynthesis

(Image source: Wiki)

The history of using sugarcane to make sugar can be traced back to the fourth century BC, when sugarcane cultivation flourished in the Indian subcontinent. Ancient Indian texts mentioned the method of extracting sugar from sugarcane juice. Soon after, the sugarcane sugar production method spread to China, Persia and the Mediterranean region, and developed independently in each place, and sugar became a valuable resource.

The yellow mud water sugar clarification method recorded in Tiangong Kaiwu

(Image source: Reference [3])

For a long time afterwards, sugar was a luxury item among the rich and powerful. Its production process was quite cumbersome, requiring the juice to be extracted from sugar cane, and then boiled, crystallized and dried many times. Therefore, the price of sugar during this period was extremely high, and only a few people could enjoy it.

The voyages of European explorers led to the spread of sugarcane cultivation in the New World. In the Americas, especially in the Caribbean, sugar production became a key factor in the slave trade. Slaves were forced to do the hard work of sugarcane planting and sugar production on colonial plantations, supplying large quantities of sugar to Europe.

During this period, the route from Europe through Africa to America and finally back to Europe was called the "triangular trade", in which European manufactured goods, slaves and sugar constituted three important trading elements .

Black slaves and sugarcane cultivation

(Image source: Wiki, photo by Henri Georgi)

Triangular trade

(Image source: drawn by the author)

In the 18th century, with the rise of the Industrial Revolution, sugar production became more modern and efficient. The development of mechanical sugarcane juice pressing and chemical sugar refining technology reduced the cost of sugar production, which led to the gradual rise of the sugar industry and the popularity of various candies and desserts among ordinary people.

Sugarcane supply bottleneck and sugar beet production

Sugarcane is a good plant, but it is very demanding on climate. When global commodities are in normal circulation, its excellent yield and relatively simple production methods make it the first choice of the global sugar industry. But in certain special periods, the long distance between the main production areas and the main consumption areas of sugarcane has become an insurmountable gap.

In the early 19th century, the relationship between Britain and France became tense, and the sugar produced in overseas colonies could not be shipped. As the transportation of sugar became difficult, the entire European continent fell into a "sugar shortage". Europe had to develop new plants to produce sugar, an important strategic material.

Thus, sugar beet production came into being.

Beet (Beta vulgaris) is a biennial plant of the genus Beta in the family Amaranthaceae, native to Europe. It was first cultivated in the eastern Mediterranean region. Unlike sugarcane, which is adapted to tropical growth, beet is a C3 plant and is more suitable for cultivation in the cooler native European climate.

At the end of the first year of vegetative growth, beets grow tubers that store sugar. After selective breeding, the sugar content of beets is close to that of sugarcane when mature, making them an excellent raw material for sugar production. The production principle and method of beets are very similar to those of sugarcane, so they are developing rapidly in Europe.

As a result, sugar production from beets has been successfully retained and developed, and remains the main source of sucrose in temperate regions.

beet

(Image source: Wiki, photo by Evan-Amos)

Development of corn sugar production

However, Europe's beet sugar industry was hit hard later, and the trade routes for cane sugar were no longer smooth. The world once again sought new sources of sugar, and this time the plant that emerged was corn (Zea mays).

corn

(Image source: Reference [2])

By the end of the 19th century, American companies had developed a method of producing corn syrup using acid hydrolysis of corn starch, and it gained a place in the market with its low price. However, due to process reasons, the corn syrup at that time had low sweetness, more impurities, and poor flavor.

At that time, the shortage of sugar cane caused the profits of corn processing to soar. Stimulated by money, producers continued to expand production, invest, and improve technology. The corn processing industry achieved considerable development and maintained its expansion momentum.

American corn syrup advertisement (1917)

(Image source: Wiki)

In 1967, High Fructose Corn Syrup (HFCS) was successfully commercialized in the United States. Initially, its fructose content was only 15%, but it was successfully increased to 42% the following year. The product was called HFCS-42, and its sweetness was comparable to that of sucrose.

By the 1970s, new technologies had been used to successfully produce corn syrup with a fructose content of up to 90%. The most widely used HFCS-55 is a blend of these two products. Today, you can taste its delicious taste in various beverages.

Other sugar-producing plants

In addition to beets and corn, some regions also use other plants to make sugar. Sugar coconut (Arenga pinnata) is a traditional sugar-making plant in Southeast Asia. It is a plant of the genus Arenga in the palm family (Arecaceae). The method of using it to make sugar is very unique. The locals cut its immature inflorescence axis, and brown syrup will flow out of it, which can be directly used to make coconut sugar. Some other palm plants can also use similar methods to make coconut sugar.

Sugar Coconut

(Image source: Reference [4])

Workers cut open the inflorescence axis of the sugar palm to obtain syrup

(Image source: Reference [17])

In addition, the use of sweet sorghum (Sorghum bicolor 'Dochna') to make sugar is also a research direction that has gradually emerged in various countries since World War II. However, impurities in sweet sorghum syrup are difficult to remove and crystallize, and it is currently mainly used as a raw material for making downstream products such as alcohol.

Sweet sorghum

(Image source: Wiki)

Sweet Burden

As sugar production continues to rise, people in many countries and regions are gradually suffering from excessive sugar intake. Sugar is a godsend for our taste buds, but excessive intake of sugar leads to health problems such as obesity, diabetes and cardiovascular disease.

World sugarcane production (2019) Unit: tons

(Image source: AtlasBig.com)

In order to find a substitute that can satisfy taste needs without causing negative effects on health, sugar substitutes have become a highly researched and widely used food ingredient.

At first, most sugar substitutes were obtained by chemical synthesis, such as saccharin and acesulfame potassium. However, the flavor of these sugar substitutes is often not very natural. In order to improve the flavor, natural sugar substitutes in plants have become an important direction of sugar substitute research, such as xylitol, erythritol, steviol glycosides and allulose.

Conclusion

From a luxury item enjoyed exclusively by the rich and powerful to a favorite of ordinary people; from a good medicine for curing diseases and saving lives to a source of health risks, the relationship between sugar and humans is complex and close, and the fate of sugar-producing plants has also changed accordingly.

Whether it is wild fruit honey, maltose, or corn syrup, human beings' understanding, development, and utilization of plant endowments have a profound impact on the spread, growth, and distribution of plants.

The story of sugar-making plants and humans runs through history and the present, and is written behind every bite of sweetness. It will surely continue to unfold. Perhaps in the future, humans will get new inspiration from some plants, refine them into sweetness, and create new legends.

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