Why can the potato become a staple food while the sweet potato cannot?

At the very start of 2015, an ordinary agricultural news item caused a sensation like entertainment news. On January 6, the Chinese Academy of Agricultural Sciences, the National Food and Nutrition Advisory Committee, and the China Seed Association held the Potato Staple Food Development Strategy Seminar in Beijing, with the theme of potato staple food development and national food security, to deeply discuss the strategic significance, development ideas, goals and tasks, and promotion paths of making the potato a staple food. Vice Minister of Agriculture Yu Xinrong said at the meeting that technological innovation should lead the development of potato as a staple food, and efforts should be made to promote a new pattern of coordinated development of potatoes and grains. According to the introduction, the potato is expected to become the fourth major staple food crop after rice, wheat, and corn; the planting area will gradually expand to 150 million mu, and the annual output of fresh potatoes will increase by 200 million tons, which will significantly improve the level of national food security. Once the news came out, it immediately aroused attention from all sides, and the potato, which had long been neglected, suddenly gained much more popularity, but it also sparked some debate: why the potato and not the sweet potato? For example, the title of one report could well reflect this mood of doubt: "Potato Retires from the Vegetable World to Become a Staple Food: Sweet Potato and Yam Have Already Cried Themselves Unconscious." As an agricultural science and technology worker who once studied potatoes for 8 years, I became interested and prepared to answer this question: why did the potato win in the competition for the new staple food?

First, from the perspective of development trends, the potato has always been on the rise, while the sweet potato has always been on the decline. Compared with the sweet potato, after the adjustments of the 1970s and 1980s, China's potato area continued to increase in both area and output, reaching 83 million mu in 2012, with a total output of 18.55 million tons (already converted to grain at a 5:1 ratio; total fresh potato output 92.75 million tons), accounting for 62% of the national tuber crop area and 56% of total output respectively; while the sweet potato area, after reaching a historical maximum of 150 million mu in 1960, kept declining, with only about 50 million mu left by 2012, a decrease of nearly 2/3 from the peak; output was 14 million tons (already converted to grain at a 5:1 ratio; total fresh sweet potato output 70 million tons), a decrease of nearly 40% from the peak. It can be said that in recent decades the potato and the sweet potato have completely followed different fates, one rising as the other fell. This is obviously the result of a natural choice conforming to economic laws, and the sweet potato probably needs a little of the spirit of accepting defeat. For example, the dietary status of the sweet potato has clearly declined. It used to be a high-yield crop, was planted especially widely during difficult periods, and occupied an important position in dietary consumption for a long time, so much so that many people's stomachs developed a fear of sweet potatoes; nowadays very few people still treat sweet potatoes as a meal. Another example is feed: in the past, the status of sweet potato vines as feed could not be underestimated, but now corn has taken the leading role, and the growing period of sweet potatoes is basically similar to that of spring corn, so in many places corn is planted and sweet potatoes are not.

⟦NL> Second, from the perspective of market prospects, the potato is quite impressive, while the sweet potato is somewhat weak. If one sentence were used to describe it, the potato's market prospects can be called high-end, grand, and classy. Potatoes, corn, and wheat are known as the three major starch crops. Although corn starch has large output and low price, potato starch cannot be replaced by corn starch because of its unique properties, mainly shown in: high viscosity, much higher viscosity than ordinary wheat and corn starch; high degree of polymerization; containing natural phosphate groups; mild taste, basically non-irritating, without the typical grain flavor of wheat and corn. Therefore, although potato starch is somewhat more expensive, it is widely used in high-end industries such as food and medicine, with more than 2,000 kinds of derivatives. Its value-added processing space is equally astonishing: processing into ordinary starch can increase value by more than 1 times, processing into special starch can increase value by more than ten times, processing into water-absorbent resin can increase value by 8 times, producing cyclodextrin can increase value by 20 times, and producing biological gum can increase value by as much as more than 60 times. At the same time, the traditional potato crude starch food processing industry is also being transformed and upgraded, such as the transformation of traditional processing techniques for starch noodles and vermicelli, bringing new market space. In particular, processed potato foods are still an emerging market with huge potential. At present, 70% of the potato processing industry in developed countries is food processing, while China is still at the primary stage. Even more, some have developed potato biological batteries from potatoes, which is simply too much to handle!

Third, in terms of adaptability, the potato can be said to make its home everywhere, while the sweet potato is much more delicate. Although both potato and sweet potato are called "potatoes," their natures are quite far apart. The potato is a cool-climate crop and does not like heat; it can sprout above 3°C; while the sweet potato is a heat-loving crop, especially afraid of cold, and can suffer freezing damage below 9°C. The potato is especially drought-tolerant, disaster-resistant, and tolerant of poor soil, and generally will not completely fail, hence the nickname "life-saving egg"; it can be planted in mountains, rivers, plains, and dams, and it does not matter much whether the soil is a bit acidic or alkaline. Even more remarkable, potatoes can be planted in spring, summer, autumn, and winter; the fastest can be harvested two months after emergence, and generally three months is enough, so fresh potatoes can be eaten nationwide in all four seasons. In the south, large areas of idle winter rice fields have in recent years been widely planted with potatoes, which does not affect rice production, allows crop rotation, and adds another season of harvest. Of course, if because of the potato's strong stress resistance you think its yield is low, then you are out of date. As long as suitable conditions are given, the potato's yield can exceed your imagination. Scientific research shows that the potato's yield potential is 16 tons per mu. At present, fields in China have already created a yield of more than 6 tons per mu, a yield level sufficient to make Mr. Yuan Longping feel humbled--after more than 30 years of continuous hybrid rice research, what can currently be achieved is only about 1 ton per mu in small areas! Compared with the potato, the delicate sweet potato is somewhat embarrassing: seedlings must be raised in hotbeds, and in the past the filling material for hotbeds even had to be horse manure; thankfully this has now changed, otherwise where would horse manure be found? After seedling raising, they still have to be transplanted into the field, buried one by one in the soil, and then given life-saving water, which is truly time-consuming and labor-intensive. Except outside the Tropic of Cancer, other places can basically only transplant around Qingming and harvest after National Day, so the crop slot is very inflexible. Therefore, "potatoes all over the city" can also be regarded as survival of the fittest!

Fourth, from the perspective of nutrition, the potato is almost divine, while the sweet potato seems to have a much smaller reputation. The potato belongs to the Solanaceae family, which can be called humanity's closest friend: tomato, eggplant, chili pepper, and potato, these four major Solanaceae crops, are the four common household vegetables of Chinese people, and tobacco is even the lifeblood of many men. The potato inherits the excellent genes of Solanaceae crops. Its nutrition is comprehensive; in addition to carbohydrates, it contains large amounts of protein, minerals, and vitamins, and is called the "second bread" abroad; it contains lysine, tryptophan, and vitamin C that general grain crops lack, and is also praised as the "underground apple"; it also has carotene, which neither wheat nor rice has. A study in the United States showed that whole milk powder and potatoes alone can meet human nutritional needs. Potatoes are low in fat and low in calories; carbohydrate content is only 1/5 that of rice and flour; energy content is less than 1/4 that of rice, flour, and beans; fat content is only 1/4 that of rice and 1/8 that of flour. Rich in dietary fiber, listed by nutritionists as the "seventh nutrient," it can reduce the incidence of chronic constipation and lower blood lipids, blood sugar, and cholesterol levels in the body; from the perspective of food therapy, it harmonizes the stomach and regulates the middle burner, strengthens the spleen, and boosts qi. Scientists' research also shows that the potato is a future food; currently astronaut space food includes potatoes, and in the future, as humanity moves to other planets, the potato will be the most ideal crop along the way. How nutritious is the sweet potato? Similar to the potato, because it grows underground it is also rich in vitamins and dietary fiber, but its starch and sugar content are somewhat higher.

Fifth, from the current dietary status, the potato is for the poor and also for the rich, while the sweet potato is more like the poor person's food. The edible value of the potato was discovered by hungry poor people through brave attempts, because when they found that pigs in pigsties used their noses to root out some magical lumps from underground and ate them safely, the poor no longer hesitated; in recent years, the changing world potato pattern shows that the area and output in Asia and Africa are increasing year by year, and the potato continues to provide food and economic income support for the people of developing countries. In this sense, the potato is for the poor. But observing the world distribution of the potato industry, we can also surprisingly find that the industrial distribution of potatoes is mainly in the Northern Hemisphere, and the world's most developed regions, Europe and North America, are also the areas with the most concentrated potato cultivation; the potato was originally the favorite of nobles, and even today, McDonald's French fries are to some extent a symbol of American culture. In this sense, the potato is also for the rich. Therefore, the world eats potatoes together, and the potato industry has spring. At present, per capita annual consumption in European countries is stable at 50-60 kg, Russia's per capita consumption reaches more than 170 kg, while China's is only about 30 kg, so there is indeed room for growth. Because of growth habit issues, the sweet potato is mainly planted in areas south of 40°N, and Asia, mainly China, accounts for 80% of world output, so it cannot yet be called a world staple food.

Of course, after saying so much, making the potato a staple food is not something that can be done just by saying so; people must be willing to eat it as a staple food, which still requires some changes in attitudes. For a long time, when the potato is mentioned, people's first impression is that it has high starch content and that eating more makes one fat. This is actually a serious misunderstanding: ordinary potatoes have a starch content of only 15%-18%, indeed much less than rice and flour. In production, starch processing factories have long urged scientists to develop potatoes with higher starch content, but unfortunately the results have not been satisfactory. Not only that, the potato has also suffered unjust cultural grievances. For example, Marx once used a sack of potatoes to describe French peasants in the 19th century, and in Northeast China there is a saying, "No matter how you dress up a potato, it is still a potato." Another example: eating a baked or steamed potato every morning may be something Russians are used to, but Chinese people certainly cannot stand it for a while. To make the potato a staple food, it is necessary to remove rusticity and prejudice, which requires long-term publicity and guidance.

There are also technical problems. For example, for more people the potato is more like a vegetable, and the transition from vegetable to grain requires good recipes; potato starch and protein content are low, so it cannot be made into noodles and can only be mixed into flour to make flour products, which destined the future method of eating potatoes as a staple food to be blending rather than standing alone; the variety of potato staple food products developed is still very monotonous, with poor selectivity. Products mature abroad, such as potato fast food, mashed potatoes, potato bread, potato instant noodles, potato chips, potato preserves, and potato beverages, are still rare in China, especially frozen products, which occupy more than 50% of the potato products market in the United States and Japan, and mixed beverages, which occupy more than 10%, are still quite unfamiliar in China; fried potato products such as French fries and potato chips increase the intake of oil and salt, are not conducive to health, are junk food that nutritionists try hard to stop, and there is also doubt about carcinogens produced by changes during frying.

As for expanding the planting area according to local conditions in the future, expanding to 150 million mu without crowding out the three major staple grains, raising the potato yield per mu to 2 tons, and producing about 300 million tons of fresh potatoes annually, market benefits are even more needed to guide farmers to be willing to plant, and scientific research and extension need to be more effective, combining excellent varieties and scientific agronomy to achieve both increased production and increased income.

But no matter what, from the day it was announced that the potato would enter the staple food category, the Chinese people's rice bowl will begin another revolutionary change, which concerns everyone's dietary structure and nutritional health, also concerns the country's food strategy adjustment, and will moreover bring profound evolution in food culture. It is worth looking forward to!