Corn seeds can be divided into the following nine types according to their morphology, endosperm structure and glume.
1. Hard grain type is also called flint type. The seeds are mostly square, the endosperm at the top and around is horny, and only the near embryo part in the center is silty, so the appearance is translucent, shiny, hard and full. The grain color is mostly yellow, and occasionally white, red, purple and other colors. Grain is of good quality and has a long history of cultivation in China. It is mainly used for eating.
2. Horse tooth shape is also called horse tooth shape. The grain is flat and rectangular, because the powder top dries faster than the keratin on both sides, so the middle of the top is sunken, which looks like a horse tooth, hence the name. Grain skin wrinkles are rough and opaque, mostly yellow and white, and a few are purple or red, so the edible quality is poor. It is the most cultivated type in the world and China, and is suitable for starch and alcohol or as feed.
3. Half-horse tooth type is also called intermediate type. It is a hybrid of hard corn and horsetooth corn. The depression at the top of the grain is shallower than that of the horse tooth type, and some are just white spots without depression. The silty endosperm at the top is less than that of horse-toothed type, but more than that of hard-grained type, and its quality is better than that of horse-toothed type, so it is widely cultivated in China.
4. Silt mold is also called soft mold. The endosperm is all silty, and the grain is milky white and dull. It can only be used as raw material for making starch, and it is rarely cultivated in China.
5. Sweet type is also called sweet corn. Endosperm is mostly horny with high sugar content and low starch content. Due to the evaporation of water at maturity, the grain surface shrinks and is translucent. Vegetables are widely used, but there are not many plants in China.
6. The upper part of sweet flour grains is horny endosperm; The lower half is silty endosperm. It is rarely cultivated in China.
7. Waxy type is also called waxy type. The endosperm of grain is horny, but opaque and waxy, and almost all endosperm is composed of amylopectin. It tastes like glutinous rice, sticky and palatable. China has only sporadic cultivation.
8. Bursting seeds are small, rice-shaped or pearl-shaped, the endosperm is almost all horny, the texture is hard and transparent, and the seed coat is mostly white or red. Especially suitable for processing puffed food such as popcorn. China has sporadic cultivation.
9. The seeds with barnyard grass are wrapped in a long barnyard grass shell, which is hard and difficult to thresh. It belongs to the primitive type and has no cultivation value.
China's national standards for corn quality are divided into four categories according to the grain color and grain quality of corn:
Yellow corn: Corn with yellow seed coat.
White corn: corn with white seed coat.
Waxy corn: corn rich in viscosity.
Miscellaneous corn: More than 5.0% of the above three types of corn are mixed with corn outside this category.
The history of maize planting and utilization
I. Planting history
Corn is also called "corn", "corn", "reed" and "pearl rice". According to research, corn originated in South America. 7000 years ago, American Indians began to grow corn. Because corn is suitable for dry land cultivation, western European colonists brought corn seeds back to Europe after invading America, and then planted them widely in Asia and Europe. /kloc-Around the middle of the 0/6th century, China began to introduce corn, and18th century spread to India. So far, corn has been planted on all continents in the world, with the largest corn planting area in North America and Central America.
Second, the classification of corn
There are two main ways to classify corn: by seed coat color and by quality. Details are as follows:
1, China's newly revised national standard and American standard divide corn into yellow corn, white jade rice and mixed corn according to the color of seed coat.
Yellow corn. The seed coat is yellow, including red and yellow corn. American standard stipulates that the content of other colors corn in yellow corn should not exceed 5.0%.
White corn. The seed coat is white, including slightly yellow or pink corn. According to American standards, light yellow means light straw color, and it is stipulated that the corn content of other colors in white jade rice should not exceed 2.0%.
Mixed corn. In China's national standards, it is defined as corn mixed with more than 5.0% of corn outside this category. The color expressed by American standard can neither meet the color requirements of yellow corn nor white corn, and it contains yellow corn with white top.
2. According to the quality classification, corn can be divided into conventional corn and special corn. The so-called special corn refers to various types of corn except conventional corn. Traditional special corn includes sweet corn, waxy corn and popcorn, and newly developed special corn includes high-quality protein corn (high lysine corn), high oil corn and high amylose corn. Special corn is called "high-value corn" abroad because of its higher technical content and greater economic value than ordinary corn.
Sweet corn. Usually divided into ordinary sweet corn, fortified sweet corn and super sweet corn. Sweet corn has strict requirements on production technology and harvest period, and its shelf life is short. China has mastered a set of breeding techniques and accumulated some germplasm resources, and all kinds of sweet corn types bred in China can basically meet the market demand.
Waxy corn. Its production technology is much simpler than sweet corn. Compared with ordinary corn, it has almost no special requirements, flexible harvest period and long shelf life, and does not need special storage and processing conditions. Waxy corn is not only fresh, but also an important raw material for starch processing industry. The breeding and production of waxy corn in China have developed rapidly.
Popcorn.
High oil corn. The oil content is high, especially the content of unsaturated fatty acids such as linoleic acid and oleic acid reaches 80%, which has the functions of lowering serum cholesterol and softening blood vessels. In addition, the protein of high-oil corn is higher than that of ordinary corn by 10- 12%, lysine is higher by 20%, and vitamin content is also higher, so it is a multifunctional corn with both grain, feed and oil.
High quality protein corn (high lysine corn). The yield is not lower than that of ordinary corn, but the lysine content of whole grain is 80- 100% higher than that of ordinary corn. In some areas of China, the combination of high yield and high quality has been achieved.
Purple corn. It is a very rare corn variety, which is a special product of our country. It is called "black pearl" because its particles are shaped like pearls. Although the quality of purple corn is excellent and single-minded, there are few sticks and small grains, and the yield per mu is only about 50 kg.
Other special corn and improved corn varieties. Including high starch special corn, silage corn, edible corn hybrid varieties and so on.
Third, use history.
1, overview of maize utilization
As far as the utilization of corn is concerned, it has generally experienced three stages as human rations, livestock feed and raw materials for industrial production.
Ration consumption accounts for about 5% of the total corn consumption, but with the development of the times, this proportion has a downward trend. Corn is one of the three major grain varieties, which plays a great role in solving the problem of food and clothing for human beings. Today, corn is still an indispensable food on people's tables all over the world: in Mexico, the hometown of corn, the annual consumption of "national grain" tortillas is as high as120,000 tons, which people like very much, regardless of wealth; In developed countries and regions, corn is also widely eaten as a source of iron, magnesium and other minerals necessary for human body. In some poor countries and regions, corn is still a cheap thing for people.
Feed consumption is the main consumption channel of corn, accounting for about 70% of the total consumption. This kind of consumption can be regarded as a function of the change of living standard and population with time: in the initial stage of the improvement of people's living standard, Engel's coefficient is high, and people's strong demand for meat, eggs, poultry and milk has promoted the great development of animal husbandry and feed industry, which has greatly increased the demand for feed corn and become the main driving force for increasing corn production; When the living standard reaches a certain level, the Engel coefficient will decrease, and the demand for meat, eggs, poultry and milk will remain stable. At this time, the consumption of feed corn will only be proportional to the population.
Being used as industrial raw materials is also the main channel of corn consumption. Corn is not only the "king of feed", but also the most widely used industrial raw material in grain crops, with the most exploitable products and the largest consumption. Using corn as raw material to produce starch can obtain products with the best chemical composition and the lowest cost, and the added value is dozens of times of the original value of corn, which is widely used in papermaking, food, textile, medicine and other industries. Alcohol produced by corn starch is a clean "green" fuel, which may be widely used in 2 1 century instead of traditional fuel.
Inventory is also a form of corn demand. For the sake of food security, countries always reserve some food. World corn stocks generally account for about 20% of consumption. In recent years, China's corn stock is about 6-7 million tons.
2. Current situation of maize utilization in the world
The overall situation of corn utilization is that corn is used as feed in industrialized countries, while corn is used as rations in developing countries.
With the great development of animal husbandry and feed industry in the world, the demand for feed corn in the world is increasing. In developing countries, the consumption of industrial feed corn is increasing, and the consumption of feed corn fed to livestock and poultry in the traditional way is also increasing. In developed countries and regions, a large number of corn grains are processed into industrial feed.
Judging from the trend of corn consumption all over the world, in the past 15 years, whether in developing countries or developed countries, corn used as feed increased year by year, the amount used as rations decreased, and corn used as industrial raw materials and food processing increased. Take China as an example: In the early 1990s, the feed industry and animal husbandry developed rapidly. 193 The consumption of feed corn reached 62 million tons, accounting for 67% of the total consumption of corn. 1995, this index quickly reached 77%, and the increase of total corn consumption was almost entirely reflected by the increase of feed corn consumption.
In 1980s, there were 264 million tons of corn used as industrial feed, 66 million tons of corn used as rations and 44 million tons of corn used as industrial raw materials. In the 1990s, the above three indicators were 352 million tons, 59 million tons and 56 million tons respectively.
1996 The production of industrial feed in the United States consumes1270,000 tons of corn, accounting for 53% of the total corn output. Europe consumes 66 million tons of feed corn, China consumes 34.98 million tons of industrial feed, Japan consumes 6.5438+0662 million tons, Brazil consumes 6.5438+0520 million tons of feed corn, France consumes 6.5438+0326 million tons of feed corn, and South Korea consumes 8.52 million tons of feed corn.
American corn production accounts for 40% of the world's total output. Looking at the consumption trend of American corn market for decades, we can see that in 1950s, American corn products accounted for 85.7%, industrial raw materials and food accounted for 8.08%, and exports accounted for 5. 17%. In 1960s, feed corn accounted for 8 1.76%, industrial raw materials and food accounted for 8.23%, and export accounted for 12.38%. In 1970s, feed accounted for 66.02%, industrial raw materials and food accounted for 8.77%, and export accounted for 25.2 1%. From 1980s to early 1990s, corn used as feed accounted for 59.36% (1223,700 tons), industrial raw materials and food accounted for11.65% (240100000 tons), and exports accounted for 28.63% (59000 tons). It can be seen that although the proportion of corn used as feed in the United States is decreasing, feed is still the industry that consumes the most corn, and the export volume is growing rapidly, and the consumption of corn used as industrial raw materials and food processing is relatively stable.
Since China's reform and opening up, with the great development of animal husbandry, the improvement of people's living standards and the development of corn industry, corn has become a multi-purpose crop of grain, feed, industrial raw materials and export commodities.
In the 1980s, the proportion of corn consumption in China was 38% in rations, 25.88 million tons in corn consumption, 48% in feed corn (industrial feed and traditional feed), 32.69 million tons in corn consumption, 654.38+065.438+0% in exports, 7.49 million tons in exports, 3% in industrial raw materials and food processing, and about 2.05 million tons in corn consumption.
In the 1990s, the proportion of corn directly consumed by people was declining. The corn consumption in the national rations accounts for about 19% of the total corn production, and the corn consumption is about18.7 million tons; There are two kinds of corn feed consumption in China. First, it is processed into compound feed. In recent years, the output of compound feed in China is about 48 million tons, and the annual consumption of corn is 28.8 million tons at the rate of 60%. Second, traditional corn is directly used for feed consumption. In rural areas, corn is mainly fed directly to large livestock, pigs and poultry. According to experts' estimation, this traditional feeding method consumes about 35 million tons of corn every year, and these two items consume about 63.8 million tons of corn every year, accounting for 68% of the total corn output.
Corn is an important industrial raw material and can also be processed into refined corn food. At present, corn used in industrial raw materials and food industry in China accounts for about 5% of the total corn output and consumes about 2.5 million tons of corn every year. From 1990 to 1994, China exported an average of 8.2 million tons of corn, accounting for about 8% of the total corn output. 1995 and then turned to a large number of imported corn. In recent 10 years, the trend of corn consumption in China is that the number of corn used for producing compound feed has soared, while the number of corn used for rations has decreased year by year. Corn used for industrial raw materials and food processing grew slowly, changing from a corn exporter to a corn importer.
3. The new trend of maize utilization in China.
Since the 1980s, China has begun to attach importance to and develop the corn deep processing industry, introduced technology and equipment successively, and built a number of corn deep processing enterprises with a production scale of over 654.38+10,000 tons. Jilin Province has implemented the "Million Tons of Corn Deep Processing Project", taking the corn deep processing industry as the pillar industry. A joint venture between Ji Fa Group and Hong Kong businessmen, with an annual corn processing capacity of 400,000 tons, is the largest corn processing enterprise in Asia. Although China's corn deep processing industry has made initial progress, there is still a big gap compared with advanced countries in the world. Take Jilin Province as an example: from 1979 to 1998, the grain processing and transformation volume in Jilin Province increased from1590,000 tons to 6 million tons (including 4.4 million tons for livestock and feed processing), with an average annual increase of 230,000 tons. In the same period, the main corn output in Jilin Province increased from 9.03 million tons to 25.06 million tons, with an average annual increase of 80,000 tons. Compared with the two, the former is only 28% of the latter, and the output is far greater than the consumption. Compared with the United States and other countries, there are more than 4,000 kinds of corn deep-processed products with an output value of hundreds of billions of dollars, and the gap is obvious. However, the production of modified starch and high fructose corn syrup in China has just started, and the alcohol output is not high, so the prospect of corn deep processing is very broad.