Do you know how to distinguish corn grades? With this in mind, you have a pretty good idea of how much corn will sell for.
Characteristics of new maize and corresponding control points
1、Water is high and uneven. The moisture content of newly harvested corn is generally 15%-20% in North China, and more than 20% in northeast China and Inner Mongolia. Excessively high moisture is liable to mildew and fever, which is not conducive to storage. Will improve the moisture of feed products at the same time, undermining the feed diet in the diet with vitamins and other active ingredients, to reduce the metabolic energy and crude protein levels, breaking the balance relationship between the nutrients in the diet, such as corn moisture 1%, protein energy than 0.5% difference, the energy of amino acids than 0.5% difference, namely the nutritional value is 0.5%. So according to the warehouse storage corn turnover storage situation reasonable formulation of the acquisition of moisture standards.
5 points method can be used for sampling and mixed detection during acceptance, and separate sampling can be used for detection if local moisture is suspected. It can also be taken and measured during unloading.
Sensory detection method: the moisture content of maize embryo is generally higher than 14% or even 16% when pinched with nails, but lower when it is hard dried or not pinched. If you bite corn with your teeth, it has low moisture, but high moisture if you bite corn with your teeth.
Instrumentation: The general use of grain moisture detector. Pay attention to the temperature difference between morning and night as well as indoor and outdoor temperature when the grain moisture tester measures corn water. When the temperature difference is too high, the instrument error is very large, so the indoor return temperature can be placed for testing when sampling. At the same time, the testing data of grain moisture meter were measured and calibrated by oven method 2-3 times a week to update the data.
2. More broken grains and high impurities. New corn has short drying time, high humidity, and corn kernels and kernels are easy to break into the corn during mechanical threshing. In addition, impurities such as sand can reach about 5% or even higher. The destruction of the tyre roller forklift in transportation also leads to more broken grains. The impurities mixed with corn occupy the active ingredients of corn, and the impurities filled in the cracks of corn affect ventilation, and the broken part will increase the chance of mildew.
Note: Broken particles and impurities will generally deposit in the car bottom, sampling bit is difficult to get, can be taken in the unloading process for the average number of times. Most of the corn kernels are sifted by the corn roller into large or small kernels. Don't throw them away, don't throw them away, don't throw them away (important thing three times)! It is an excellent feed for ruminants, has a high economic value, and can also be fed to poultry.
3. Low mildew. At present, the mildew rate detected in the acceptance of new corn is relatively low, generally not more than 2%. Mildew not only occurs during storage, but can be infected in large fields, so it is divided into storage mold and field mold.
Before checking mildew, mix the samples and sample them in four parts. After sieving and removing impurities, spread them on a white enamel plate and select them from left to right. Don't look down on this white plate. The corn grains are very clear against a white background, showing mildew and broken grains, and they don't roll out easily. After testing, the corn samples can be poured directly from the porcelain plate corner for centralized processing.
At present, there are two methods of mildew detection: grain method and weighing method.
Several grain method: corn sample particles should not be too small, according to the corn 1000-grain weight of about 300-400g, small make up recommendations for 500g, not less than 400g.
Weighing method: than normal grain mildew grain and the average grain weight per spike (or), the same amount of particle we found that the mould size is lighter, the proportion between 0.7 0.8, mildew after weighing method is the blending of corn grain weighing to miscellaneous spread in white enamel, pick out the mildew grain of weighing, divided by the total weight and 0.75, as the rate of mildew.
Sensory detection method: randomly grab a handful of corn (a handful of corn is usually less than 100 grains), count the number of mildew, more than two mildew grains can be returned directly. This method can also be applied to the corn self-test of retail suppliers.
4. Large difference in bulk density. Regional differences, variety differences and planting season differences of corn in China lead to a large bulk density gap, while the full grain bulk density of spring corn is relatively large due to its full maturity.
The grain cylinder should be clean and free of debris before use. Zero load should be adjusted before use. The sample can only be scraped flat when full, not pressed.
In the measuring cylinder method, it should be noted that the corn sample should be put into the measuring cylinder at a constant speed. When approaching 1000ml, the sample should be put several times until the total amount of the sample is adjusted to the scale line. The test error can be reduced by averaging multiple tests.
How to distinguish corn grade?
There are three national corn quality standards in China, which are the most basic corn national standard, feed corn national standard and industrial corn national standard. These three standards are interrelated and have their own characteristics. Corn national standard is the general standard of bulk corn, widely applicable to the acquisition, storage, transportation, processing and marketing of commodity corn. And feed corn standard and industrial corn standard are more targeted, on the basis of corn national standard, there are some changes and adjustments. These three standards have in common water, impurities, imperfect grains, mildew grains and so on as the main indicators to measure the quality of corn; The difference lies in that in addition to the main indexes such as bulk density of feed corn, crude protein is added as the technical index, while industrial corn abandons bulk density.
On the whole, bulk density, impurities, moisture, imperfect grains and moldy grains are the most basic and important indexes to measure the quality of corn, which are widely representative and authoritative.
There are the following differences in the quality of maize from different producing areas in China:
(1) unit weight
In normal years, the bulk density of northeast Inner Mongolia corn is the highest. The quality of Tongliao and Chifeng corn is basically above the second class, with the first class accounting for 90%. More than 70% of Jilin corn is second-class; The quality of Heilongjiang corn is general, 60%-70% can reach the third class; In Liaoning, 50% of corn can reach the second grade and 80% can reach the third grade. But the bulk density of corn is greatly affected by the year, for example, due to the weather, the corn moisture is larger, bulk density decreases.
In normal years, the corn in Shandong and Hebei in North China is basically above the second class, especially in the north of Shanxi, Hebei Xingtai north of the corn quality is good.
(2) moisture
In normal years, the moisture content of corn harvest in northeast China ranges from 28% to 30%, while in bad years, it can reach as high as 35% to 40%. The moisture content of inner Mongolian corn is slightly lower, generally around 24%, sometimes up to 27%-28%.
Due to the cold weather in winter in northeast China, the proportion of natural drying corn is relatively small. Except for Tongliao in Inner Mongolia and southwestern Liaoning, drying corn is mostly used. Drying is mainly used in two ways, one is direct drying to 14.5% left and right, in the process of storage, moisture gradually lost to 14% below; The second is to air to about 20% moisture, and then drying. The first method is mainly used for the corn listed before the Spring Festival in northeast China. Due to the large precipitation range, it is easy to cause the corn grain to shrink and the bulk density to be low. And the Spring Festival after the market of corn is mainly used in the second way, natural drying time in advance for a long time, so full grain, generally high bulk density. In general, the grain depot will only reduce the water content to 14.5%, so in October, November and December, it is difficult for the northeast corn to reach 14% of the water content. Only after several months of natural water loss in April and May of the next year, can the corn reach 14% of the water content. Moisture may sometimes decline further during transportation from the producing area to the selling area. However, the moisture content of corn purchased as national reserve grain is basically less than 14% after drying and no more than 14.5% at most. Also some grain storehouse root will decide drying effect according to the requirement of buyer, moisture index is decided by buyer oneself, differ from general 13%-15%.
Compared with corn in northeast China, corn in North China has a lower moisture content during harvest, about 18% to 20% in most cases, and the temperature is higher than that in northeast China. Generally, it can reach less than 15% after 5-6 days of drying, so natural drying method is almost adopted for precipitation. In normal years, the water content of Hebei corn is about 16%-18%, and that of Shandong corn is about 14%-16%.
(3) impurity
Northeast corn due to the use of machine drying, less impurities, generally not more than 1%, some areas even less than 0.5% impurities. Natural drying is adopted for corn in North China, and a large number of impurities will be added in the drying process. Therefore, there are too many impurities in corn in North China, sometimes exceeding 1%, requiring additional sieving and finishing.
(4) unsound kernel
In the drying process of corn in northeast China, the precipitation is too fast to be broken easily, and the mechanical operation also leads to the increase in the proportion of broken grains. Meanwhile, drying leads to the increase in the number of heat-damaged grains, so the broken grains are generally higher than 5%. After a series of links, such as storage, delivery, port transfer, loading and unloading, loading and unloading, loading and unloading, loading and unloading, loading and unloading, loading and unloading, loading and unloading, loading and unloading, loading and unloading, etc., the broken grains of dried corn will increase to some extent, resulting in the incomplete grains generally reach 8%.
Natural drying is adopted in North China maize, and the broken grain is less, basically controlled within 5%, and the quality is a little better than 2%. In the spot purchase, the general provisions shall not exceed 5% of the total imperfect grain.
(5) moldy kernel
The moisture of northeast maize is very high in harvest period. If there is much rain in harvest period and the maize is not properly stored after harvest, it is very easy to have maize mildew phenomenon. In bad years, most corn mildew grains can exceed 2%, and some can even reach more than 5%. Due to the limitation of storage environment and storage technology, small farmers cannot store and ventilate in strict accordance with the standard. Therefore, the proportion of mildew grains in northeast China's corn is very small before April, and will increase greatly after April. The mildew content of Inner Mongolian corn was low, almost no, no more than 2%. Liaoning's is a little higher; The moisture content of Heilongjiang corn is uneven, mildew grain is highest.
