Like any agricultural product, grain has its own quality characteristics that determine how suitable it is for human use. These parameters are approved by GOST and are evaluated in special laboratories. Grain analysis allows you to determine the quality, nutritional value, cost, safety and scope of a particular lot or variety.
The test results depend on three components:
- genetic characteristics of the crop from which the crop was harvested;
- growing conditions and transportation technology;
- storage.
The approved state quality assessment unit is the batch from which samples are taken for analysis.
Main analysis parameters
Parameters determined by laboratory analysis of grain are divided into 3 large groups:
- quality indicators - a set of physical, chemical and biological properties that characterize the degree of usefulness and suitability of grain for technical and agricultural use;
- indicatorssafety - assess the presence of harmful chemical impurities, characterize the environmental friendliness of grain;
- content of GMOs (genetically modified samples).
The first group is the most extensive and is an obligatory component of checking grain lots. There are 2 types of grain analysis indicators included in the quality assessment:
- organoleptic - evaluated using the human senses;
- laboratory or physico-chemical - determined using specific techniques and technical equipment.
Among the laboratory parameters there are basic (required for a particular culture) and additional. Each characteristic of grain quality has a specific name and method of determination.
| Parameter | Characteristic |
| Humidity | Percentage of water content in the grain. |
| Temperature | Measured at different points at the depth of the grain mass. Normal should not be too high or grow rapidly. |
| Nature | Characterizes the mass of one liter of grain, expressed in g/l. |
| Size | Determines grain size parameters. This group of indicators includes the weight of 1000 grains, specific gravity, as well as the length, width and thickness of the seed. |
| Vitreous | Characterizes the degree of grain transparency. |
| Chaffiness | Determined for cereal crops (oats, barley, rice, buckwheat, etc.). Characterizes the percentagefilms or shells in the grain mass. The higher the filminess, the lower the yield of finished cereals. |
| Clogging | Shows the percentage of impurities in the total grain weight. |
| germination | Ability to produce normal sprouts in natural conditions for a particular culture. |
| Sprouting Energy | Percentage of grains that sprouted within a given time frame. |
| Fall number | Characterizes the degree of grain germination (the higher the indicator, the lower the baking quality of the flour). |
| Ash content | Amount of mineral (inorganic) substances in grain. It is determined by weighing the mass remaining after the complete combustion of ground grain at a temperature of 750-850 ° С. |
| Evenness | Characterizes grain size uniformity. |
| Infection | The number of pests in the crop (turtle bugs, granary weevils, etc.), expressed as the number of live individuals per 1 kg of grain. |
For wheat, the grain is additionally analyzed for gluten and protein content.
Grain quality assessment is an integral part of the control of agro-industrial commodities and forms the basis of crop research that accompanies the development of new varieties or the study of the influence of various environmental factors on cereal plants (fertilizers, soil, pests, phytohormones, etc.).
Additional parameters of grain quality analysis include chemical composition, activityenzymes, microorganism content, etc.
Features of seed grain analysis
The abundance of the harvest largely depends on the quality of the seed grain. In this case, the key characteristics are size (the larger the seed, the better the growth will go), purity (the absence of weed impurities and crop parasites) and the results of the germination analysis.
To analyze grain for sowing qualities, 3 average samples are isolated from a batch by quartering, which are used to determine different indicators:
- sample 1 - purity, germination, weight of 1000 seeds;
- sample 2 - humidity and pest infestation;
- sample 3 - the degree of damage to seeds by diseases.
Based on the results of the analysis, a conclusion is made about the sowing qualities of the seeds, which is included in the corresponding inspection document.
Germination is determined by placing 100 seeds in suitable conditions for germination for 3 days. At the same time, the number and uniformity of seedlings are evaluated. For the rapid detection of dead grains, the Lecon method is effective, which gives results in a few hours. Live grains are identified by the color change that occurs when oxygen is absorbed from a tetrazolium s alt solution. Dead seeds do not breathe.
Organoleptic evaluation
The main organoleptic indicators are color, gloss, taste and smell, on the basis of which they conclude that the batch of grain is good quality and fresh. The color should be uniform, the surface of the seeds should be smooth andshiny. The presence of foreign odors (not characteristic of the culture) indicates deterioration or violation of storage technology.
Estimated also:
- shape and size;
- homogeneity of the batch;
- weediness;
- shell state.
The color, smell and taste of the beans are checked for compliance with a specific biological variety. Organoleptic analysis is superficial and approximate, but may reveal serious deviations from the norm. The parameters of the test sample are compared with the standards available in the laboratory.
Assessment of weediness and infestation
Impurities are divided into 2 large groups: grain and weed. The latter is divided into 4 types:
- mineral - particles of inorganic nature (pebbles, sand, dust, pebbles, etc.);
- organic - third-party particles of organic origin, to a greater extent - vegetable (pieces of spikelets, leaves, etc.);
- weed - seeds of foreign crops;
- harmful - fruits or seeds that contain substances that are poisonous to humans.
Defective (other than normal) seeds of a batch are called grain impurities. They can also be used for technological processing, although they give a lower quality product. To reduce the content of weed impurities, the grain is cleaned on production machines.
The weight of average samples for grain analysis for weediness is 20-25 grams. The proportion of impurities is determined as a percentage.
Infection may beexplicit and hidden. In the first case, pests are separated from the sample using a sieve, and in the second case, each grain is split and examined (sample size - 50).
Chemical analysis
This analysis belongs to the category of additional and involves the study of the chemical composition of the grain. At the same time, the percentage of the following components is determined:
- proteins;
- lipids;
- carbohydrates (including starch and fiber);
- vitamins;
- minerals (macro-, micro- and ultramicroelements).
The chemical analysis of grain also includes the determination of ash content.
These parameters show the nutritional value of a particular variety, and sometimes technical usefulness. For example, a large amount of lipids in sunflower seeds indicates the high suitability of raw materials for oil production.
Determining some of the components of the composition is a key fatcore of quality. So, when analyzing wheat grain, the percentage of protein is necessarily determined. This indicator characterizes not only nutritional value, but also baking properties, as it correlates with vitreousness and gluten quality.
Equipment
There are a huge number of instruments for grain analysis, among which are specialized (designed for laboratory evaluation of grain products) and general. The latter include instruments for physical and chemical measurements, equipment for working with reagents.
To the standard laboratory kit for grain analysisincluded:
- high precision scales;
- weights;
- devices for determining the properties of gluten;
- watch glasses and Petri dishes;
- sieves with cells of different diameters;
- porcelain mortars;
- desiccator;
- mill;
- moisture meters;
- temperature measuring device;
- laboratory glassware (flasks, bottles, etc.);
- drying chamber;
- chemical reagents.
The kit may also contain narrow-profile devices, for example, peelers, with the help of which filminess is determined. The presence of metal-magnetic impurities is detected using milliteslameters.
Some instruments replace manual methods for determining some parameters. For example, vitreousness can be established using a diaphanoscope. Automation of grain analysis significantly reduces the subjective factor and saves time.
There are also devices for complex analysis, which replace the multi-stage process of determining various parameters, which requires a whole set of instruments and reagents. However, the functionality of such devices is still limited.
Currently, the assessment of the quality of grain products is a combination of manual and automated methods of grain analysis, the ratio of which is determined by the technical support of a particular laboratory and a set of indicators to be verified.
Determination of humidity
Moisture is one of the key parameters of grain quality, which determines not only its nutritional value, but also conditionsstorage.
There are 2 ways to analyze grain moisture:
- using an electric drying cabinet (ESH) - consists in drying the ground grain sample and comparing the weight before and after the procedure;
- using an electric moisture meter - determining the degree of moisture by electrical conductivity, a grain sample is placed in the device under the press.
The second method is time-saving, but less accurate. In case of too high humidity (more than 17%), the test sample is pre-dried.
Depending on the percentage of water, 4 degrees of grain moisture are distinguished:
- dry (less than 14%);
- medium dry (14-15.5%);
- wet - (15.5-17%);
- raw - (more than 17%).
The percentages shown are acceptable for major cereals (rye, oats, wheat, etc.).
Moisture above 14% is considered high and undesirable, as it leads to a decrease in the quality and germination of grain. Each crop has its own water content standards, developed taking into account the characteristics of the chemical composition of the seeds.
Chaffiness
Estimation of filminess includes 2 stages:
- counting the number of casings or films;
- determination of the percentage mass fraction of shells.
The second indicator is the most important. To determine it, the grains are first freed from the shells using a peeler or manually, and then the cereals and the film mass are weighed separately. At the endcompare the weight of cleaned and uncleaned samples.
Vitreous
The degree of transparency depends on the ratio of protein and starch. The higher the content of the latter, the more powdery (starchy) and cloudy the grain. Conversely, a large amount of protein increases the transparency of the seed. Therefore, the glassiness value reflects the nutritional value and baking quality of the grain. In addition, this indicator is associated with the mechanical and structural properties of the endosperm. The higher the vitreousness, the stronger the grain and the more energy required for grinding.
There are 2 methods for determining this parameter: manual and automated. In the first case, transparency is assessed by eye or using a diaphanoscope. A sample of 100 grains is subjected to analysis. Each seed is cut in half and assigned to one of three vitreous groups:
- mealy;
- partly vitreous;
- vitreous.
The total number of grains from the last two categories is the total glassiness (only half of the number of partially glassy seeds is included in the total). The check is carried out 2 times (the discrepancy between the results should not exceed 5%).
There are also automated diaphanoscopes that simultaneously determine the vitreousness of seeds placed in a cuvette. Some devices do not even require pre-cutting the grains.
Fall number
The falling number is an indirect indicator of the degree of germination, determined on the basis of the level of autolytic activity of the grain. The latter is the result of an actionalpha-amylase enzyme, which breaks down the starch of the endosperm into simple sugars, which are necessary for the development of the seed embryo. Naturally, this leads to a significant reduction in baking quality.
Autolytic activity is determined using special equipment (Falling Number, ICHP, PChP, etc.). The method is based on the enzymatic liquefaction (by the action of alpha-amylase) of a flour suspension gelatinized in a boiling water bath.
GOST grain analysis
All components of product analysis are strictly regulated and prescribed in the relevant standards. GOST contains quality standards, equipment requirements and methods for determining each indicator. The results of the analysis of grain are recognized as reliable only if obtained in accordance with established instructions.
According to GOST, classes of grain crops are defined, for each of which the corresponding values of quality parameters (the so-called restrictive norms) are prescribed. Soft wheat has 5 classes.
| Indicator | 1 | 2 | 3 | 4 | 5 |
| Mass fraction of protein, not less than | 14, 5 | 13, 5 | 12 | 10 | no limit |
| Amount of raw gluten, not less than | 32 | 28 | 23 | 18 | no limit |
| Number of falls | 200 | 200 | 150 | 80 | no limit |
| Nature, g/l, not less than | 750 | 750 | 730 | 710 | no limit |
The class defines the nature of processing and use, features of storage and market value of grain.
Quick grain analysis with IR spectroscopy
With the help of IR spectroscopy, you can quickly and accurately determine:
- humidity;
- protein and gluten content;
- amount of starch;
- kind;
- density;
- oil content;
- ash content.
For the main parameters of grain analysis, the error does not exceed 0.3%.
The operation of complex analyzers is based on the diffuse reflection of light with a wavelength within the near infrared region. At the same time, time is significantly saved (analysis of several parameters is carried out within a minute). The main disadvantage of the express method is the high cost of equipment.
Gluten content and quality analysis
Gluten is a dense and viscous rubbery mass formed after water-soluble substances, starch and fiber are washed out of the ground grain. Gluten contains:
- proteins gliadin and glutenin (from 80 to 90% dry matter);
- complex carbohydrates (starch and fiber);
- simple carbohydrates;
- lipids;
- minerals.
Wheat contains from 7 to 50%raw gluten. Readings over 28% are considered high.
In addition to the percentage, when analyzing grain for gluten, four parameters are evaluated:
- elasticity;
- extensibility;
- elasticity;
- viscosity.
The most important indicator is elasticity, which characterizes the baking properties of wheat. To determine this parameter, a gluten deformation index (DIC) instrument is used. The sample for analysis is a ball rolled from 4 grams of the test substance and pre-soaked in water for 15 minutes.
Gluten quality is a hereditary trait of a particular variety and does not depend on growing conditions.
Analysis of wheat grain for gluten content is carried out strictly in accordance with the standard, since the slightest error can greatly distort the result. The essence of the method is to wash the analyte from the dough, mixed from wheat meal (crushed and sifted grains). Laundering is carried out under a weak water jet at a temperature of +16-20 ° С.
