Key Techniques for Analysis of Crop Seed Clarity

Clarity analysis is the determination of the percentage by weight of the different components (net seeds, other plant seeds, and impurities) of the test sample and the characteristics of the sample mixture, and the composition of the seed batch is deduced accordingly. The purpose is to understand the true weight of the clean and available seed in the seed lot and the types and contents of other plant seeds and inanimate impurities by analyzing the three components of the net seed, other plant seeds and impurities in the sample. Particle sizer or automatic counting instrument) provides basis for evaluating seed quality.

In 1996, the standard values ​​of grain quality of crop seeds such as cereals, fiber, oil, etc. were too low. Many seed companies and even quality inspection agencies paid insufficient attention to it, and the phenomenon of unclearness in the actual work was widespread. To the extent that it infringes the interests of consumers, it is also not conducive to international integration. To this end, AQSIQ and the National Standards Supervision Commission revised and reissued the quality standards for cereal seeds such as cereals, fiber, and oilseeds on April 14 and June 28, 2008, and on September 1, 2008. It is implemented on December 1. The new quality standards revise individual terms, quality characteristics and inspection rules. The greatest change in the quality characteristics is the value of the cleanliness characteristics, including the main grain crops of wheat and corn in our province. The cleanliness value of most crops has increased by one percentage point. Because of the increase in the value of the cleanliness values ​​in the quality standards, the requirements for seed quality have also been correspondingly increased. The analysis of the degree of purity should be caused by the seed companies and inspection agencies in future seed testing. Enough attention. Clarity analysis is more complex in the operation and calculation of the four major seed quality inspection items (clarity, purity, germination rate, and moisture). Now it is combined with years of practice and theoretical experience in the analysis and training of cleanliness. Problems that are prone to occur, and put forward the technical requirements for the successful completion of this test for the reference of the seed inspection personnel.

1 Accurately understand the criteria for identifying net seeds, other plant seeds, and impurities

The key to the correctness of the Clarity Analysis lies in the ability to accurately determine the criteria for identifying net seeds, other plant seeds, and impurities. The main principles for the identification of net seeds are stipulated in the General Principles of Distinction, but for different genera or species, specific problems should be specifically analyzed. Therefore, the definition of net seed definitions has been formulated for each genera or species. Since the net seeds are significantly different from other plant seeds, the key to the clarity analysis is to distinguish net seeds from impurities, other plant seeds and impurities. In order to better grasp the criteria for distinguishing between net seed, other plant seeds, and impurities, it is necessary to fully understand the meaning of the two main principles of net seed and the detailed definition of net seeds. It can be judged from this: (1) The damaged seed unit is larger than half of the original seed itself. Although there is no embryo, it is still a net seed, and the other half is less than half the size of the original seed. Although there are embryos, it should be classified as impurities. (2) Net seeds of grass seeds must have endosperm; (3) Structures not described in the net seed definition are classified as impurities, such as peanut husks are classified as impurities; (4) The separation is separated, such as rice, barley When it exceeds the length of the floret, it should be removed as impurities; (5) The damaged seed that has not apparently injured the seed coat or pericarp, whether empty or enriched, is used as a net seed or other plant seed; (6) It must be judged promptly to stay Whether the seed unit exceeds half of its original size, if it cannot make a quick decision, the seed unit is classified as a net seed or other plant seed.

2 Correct selection of scales

Since the clarity analysis requires the determination of the weight of the components of the test sample, correct selection of the balance is critical. Weighing the balance consists of weighing the test sample, the cleanliness test sample, and the 3 components (net seeds, other plant seeds, and impurities) after analysis. The balance used and the number of decimal places after weighing should be Table 1 Requirements.

From Table 1, it can be seen that if the weight after weighing is 4 significant figures, the selection of the balance is correct.

3 Defining the weight of the sample (test sample and clarity test sample)

The sent sample is the sample sent to the laboratory and the clarity test sample is the sample used for the item of the test clarity. The minimum weight of the two samples shall be in accordance with the provisions of the GB/T3543.2-1995 standard for the “Agronomic Seed Inspection Regulations” (hereinafter referred to as the "Regulations"). It should be noted that the weight of the test samples and the cleanliness test samples specified in the "Regulations" are the minimum weight and cannot be lower than this weight. If the test sample weight does not meet the required weight, it shall be filled or re-weighed. Comparing the weights of the test samples and the cleanliness test samples in the “Procedure”, it can be seen that the two are very different, generally more than 10 times. The reasons are: (1) The sample size is too small, the sample is inaccurate, and the representativeness is not strong. (2) There must be sufficient samples to meet the detection of other items, such as germination tests; (3) sometimes need to do a second test, such as excess error; (4) "Procedure" provides for the determination of the number of seeds of other plants The required amount of sample is large; (5) The test sample needs to be separated from a certain number of seeds, retaining a growing season for review. In addition, the "Regulations" also mention that if the determination of the number of other plant seeds is not carried out, the sample submitted shall at least meet the weight of the test sample specified in the "Clarity Analysis" of the "Regulations" and be described on the result report form.

4 Correctly identify heavy blends

Heavy-duty contaminants refer to those that are significantly different in size or weight from the test sample (or at least ten times the weight of the sample for clarity analysis) and that seriously affect the results, such as clods, pebbles, Large seeds and the like are mixed in the seeds or small seeds. Therefore, heavy-duty hybrids must have the following two conditions: First, the volume or weight is significantly different from the tested seeds; second, it is different from the severity of the impact analysis results. It should be noted that the provocation of heavy-duty hybrids should be preceded by a degree of clarity before the analysis of the sample. The reasons are: (1) The volume or weight of the heavy-duty hybrid is large. When using the sample splitter, it is easy to block the sample splitter and cause confusion. (2) The number of heavy-duty hybrids is small, and if they are not provoked, they may be assigned to a clean degree analysis sample at the time of sampling, and the clarity analysis result will be significantly lower than the actual result; In degree analysis samples, the clarity analysis result will be higher than the actual result; both cases are unfair to the enterprise and the consumers.

5 Independently allocated test samples

The test sample used for the clarity analysis shall be separated from the test sample by a specified method (slicer or freehand). Clarity analysis can be performed with one sample (full sample) or two half samples (half the sample weight) of the specified weight. Take wheat seeds as an example to separate the methods as shown in Table 2.

A first set of any 62.5 g can be combined with a second set of any 62.5 g to form a set of half samples. The same group cannot be combined.

6 Reasonable selection of sieve

After the sample is weighed and weighed, the sample can be separated by sieving, so as to objectively separate out the impurities and other plant seeds and reduce the analysis workload. The set of sieves used for screening seeds is generally composed of upper and lower two layers. The upper layer is a large-hole sieve, auxiliary hand-picking, separating net seeds and large crushing particles and impurities; the lower layer is a small-hole sieve, separating small particles, lean particles and dust Impurities. The sieve holes are divided into two kinds: round holes and long holes. The round hole sieves are separated according to the seed width and used for round or similar sieve seeds, such as rapeseed, corn, etc. The long hole sieve is separated according to the seed thickness. For long or similar to long seed seeds, such as wheat. The mesh size and shape should be determined according to the seed size and shape. When using, press the screen size from top to bottom, and the long-hole sieve screen holes should be parallel to each other. Pour the sample into the upper screen, cover and manually conduct the electric screen or sieve. The long hole screen should follow the direction of the screen hole. Screening.

7 Carefully separate, analyze and identify

The screened samples are laid on a cleanliness analysis table (or a cleanness analysis tray), and the sample can be analyzed by the identification criteria of the net seed, other plant seeds, and impurities using a certain instrument, and then classified and loaded accordingly. The container, because other plants seeds and impurities are generally lighter and smaller, do not lose these substances during operation, so as not to affect the analysis results. In addition, the skinny seed of the bottom sieve is a complete seed unit and should be culled as a net seed or other plant seed.

8 Correct Calculation and Expression

The results of the clarity analysis use more formulas, are more complicated than the other three indicators, and are relatively cumbersome to express. They can be performed in the following order: (1) The weight of the three components of net seeds, other plant seeds, and impurities after calculation and analysis And (2) comparing the sum of the weights of the three components with the weight of the original sample, checking whether the loss of the substance during the analysis exceeds 5% of the weight of the original sample, which exceeds that of the redo; (3) Calculating the weight percentage of the three components The calculation shall use the sum of the weights of the three constituents as the denominator. The full sample shall be calculated to one decimal place. The half sample shall be calculated to two decimal places. The final result shall be one decimal place; (4) The final result of the three components shall be retained. For fractional numbers, the sum is 100.0%, and less than 0.05% is expressed as “trace”, and is eliminated in the calculation. The result of zero is represented by “-0.0-”. If the sum of the three components is 99.9% or 100.1%, increase or decrease 0.1% from the maximum component of the net seed component. If the rounding value is greater than 0.1%, check for errors in the calculations; (5) The test results for the netity analysis include the weight percentages of the three components of net seeds, other plant seeds, and impurities. When determining the weight percentage of a certain kind of impurity or a certain other plant seed reaching or exceeding 1.0%, the type should be indicated in the result report.