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Scientists have learned a lot about the kinds of food people need. They say that there are several kinds of food that people should eat every day. They are: (1) green and yellow vegetables of all kinds. (2) citrus(柑桔) fruits and tomatoes; (3) potatoes and other fruits and vegetables; (4) meat of all kinds, fish and eggs; (5) milk and foods made from milk; (6) bread or cereal(谷类), rice is also in this kind of food; (7) butter, or something like butter.

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People in different countries and different places of the world eat different kinds of things. Foods are cooked and eaten in many different kinds of ways. People in different countries eat at different times of the day. In some places people eat once or twice a day; in other countries people eat three or four times a day. Scientists say that none of the differences is really important. It doesn’t matter whether foods are eaten raw(生的) or cooked, canned or frozen. It doesn’t matter if a person eats dinner at 4 o'clock in the afternoon or at eleven o'clock at night. The important thing is what you eat every day.

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There are two problems, then, in feeding the large number of people on earth. The first is to find some ways to feed the world’s population so that no one is hungry.

The second is to make sure that people everywhere have the right kinds of food to make them grow to be strong and healthy.

Technology is always trying to meet our needs and demands. There’s a new frontier in 3D printing that’s beginning to come into focus: food. Recent development has made possible machines that print, cook and serve foods on a mass scale. And the industry isn’t stopping there.

With a 3D printer, a cook can print complicated chocolate sculptures and beautiful pieces for decoration on a wedding cake. Not everybody can do that — it takes years of experience, but a printer makes it easy. A restaurant in Spain uses a Foodini to “recreate forms and pieces” of food that are “exactly the same,” freeing cooks to complete other tasks. In another restaurant, all of the dishes and desserts it serves are 3D-printed, rather than farm to table.

The global population is expected to grow to 9.6 billion by 2050, and some analysts estimate that food production will need to be raised by 50 percent to maintain current levels. Sustainability is becoming a necessity. 3D food printing could probably contribute to the solution. Some experts believe printers could use hydrocolloids (水解胶体) from plentiful renewables like algae (藻类) and grass to replace the familiar ingredients (烹饪原料). 3D printing can reduce fuel use and emissions. Grocery stores of the future might stock “food” that lasts years on end, freeing up shelf space and reducing transportation and storage requirements.

Future 3D food printers could make processed food healthier. Hod Lipson, a professor at Columbia University, said, “Food printing could allow consumers to print food with customized nutritional content, like vitamins. So instead of eating a piece of yesterday’s bread from the supermarket, you’d eat something baked just for you on demand.”

Despite recent advancements in 3D food printing, the industry has many challenges to overcome. Currently, most ingredients must be changed to a paste (糊状物) before a printer can use them, and the printing process is quite time-consuming, because ingredients interact with each other in very complex ways. On top of that, most of the 3D food printers now are restricted to dry ingredients, because meat and milk products may easily go bad. Some experts are skeptical about 3D food printers, believing they are better suited for fast food restaurant than homes and high-end restaurants.

Guilin rice noodles have a history of more than 2, 300 years. It is said that Oin Shi Huang, the founder of the Qin Dynasty (221 B C-206 B. C), took his army to southern China to wage war, aiming to unify southern China. However, the soldiers are from northern China and got used to eating wheat. They could not adapt to eating rice, which is the staple food in southern China, and couldn't digest it. In order to solve this problem. The chef had the idea to combine rice with wheat. They first inflated the rice and ground (把……磨成粉) it into rice syrup .After filtering the water from the rice syrup the chef smashed the rice into rice dough and steamed it, and then pulled it into noodles. The noodles were cooked with some special brine made from traditional Chinese medicine that cured the soldiers' digestive problems. The soldiers regained their energy after eating the cooked rice noodles, and finally unified southern China, according to reports .

Spring rolls

The spring roll is rolled from a thin pancake made of rice and filled with meat and vegetables. The rolls are very crispy after being deep fried.

The spring roll, a kind of traditional snack in northern China, is well known all over the world. Traditionally, the spring roll is very small.

According to reports, a man from the Song Dynasty (960-1279)studied very hard and often forgot to eat meals. His wife reminded him to eat meals on time but he failed. So she came up with the idea to make rice into a pancake, and filled it with meat and vegetables. By doing this, her husband could eat food from an entire meal in one roll, which was very convenient and nourishing.