Suggestions for classifying wheat by quality
Source: INTA of Marcos Juárez City
Classifying the wheat production by levels of protein and, whenever possible, by variety groups according to industrial quality, will contribute to improve the reliability of the producer and the silo owner. Further more, it will let us satisfy the industries’ demand and that of exportation, incrementing Argentina’s credibility and trustiness on the world’s market as a wheat exportation country.
On international markets, high quality wheat have a differential price due to the cost of adequate technology and production handling, to achieve a high quality grain.
To even think about achieving a correct classification, we must start by implementing a system that is as simple as it is easy for the producer and for the silo owner to apply.
How to classify wheat (for the producer)
- The producers knows the varieties that they have on their fields, that is a very important starting point to separate wheat of better generic quality, strong wheat, wheat of the corrective type with high stability in the dough. This quality wheat (Group 1) is on high demand by big bread makers in the Argentinean industry and countries like Brazil use, in many cases, our wheat as correctors to their own production.
- Other varieties (Group 2) are also of high quality. Without being corrective and having fermentation times over 8 hours, they are appropriate for traditional Argentinean bakery systems.
- There are also other varieties (Group 3) which are good performers but of a deficient quality. They are good for bakeries and preferably for direct and semi-direct methods. They have a shorter fermentation times.
This classification in three groups was consensus in the CONASE’s Winter Cereals Committee, and is the actual official classification based on the hectoliter weight, protein in the grain, performance in flour, ashes, humid gluten percentage, panification readyness or W of the alveolus report, flour stability and bread volume.
Due to the high interaction between genotypes and the environment for industrial quality and to the possibility of having to modify criterion, this classification is not rigid and will be updated annually.
Protein Content
To what is already mentioned, the producer has to add the determination
needed before the harvest of protein content on their lot.
Approximately 10 to 15 days before the harvest, the ears, leafs and stems start to turn
yellow, and this indicates that the plant has completed its physiological maturity. This
means that the grain is at a semi-hard state with about 40% humidity. After this, when the
grain has about 30% and 35% humidity (about a week before harvest time), the producer can
start to acquire samples by cutting between 300 and 400 ears from different spots in the
lot.
On its physiologic maturity, the grain completed its development, the protein has already formed and the wheat’s quality is already defined. It no longer needs to get its nourishment from the plant it self and it starts to lose humidity progressively until it reaches a commercial or harvest humidity. The amounts of days needed to get to commercial maturity are influenced by environment conditions and by the variety aspect.
The quality between pre-harvest and harvest must be very similar if adverse weather factors don’t intervene.
Samples from each lot must be sun dried or by using a heater at 40°C. The grain, properly labeled, must be taken to a laboratory so the content of protein and gluten can be analyzed, according to the requirements.
In these cases, it is possible to detect the "white belly" and "dotted" grains because they have not been washed by rains as it happens during its natural maturity on the field. A high percentage of "white belly" and "dotted" grains is indicative of a low level of protein and thus, from a soil with deficient nitrogen fertility. Vitreous grains and darker grains in general, contain higher contents of protein. The difference in protein on these grains can reach 4% and up to 10% in gluten. It does not make that much sense to analyze the samples when such starched or dotted aspect is evident.
Advantages
The advantage of analyzing the grain a few days before the harvest is that it allows the producer to know, ahead of time, the quality that each lot has and this, in turn, allows him or her to decide with enough time which silo is going to be used for grains with high or low content of protein.
Knowing the protein content and the variety in the lots, the producer would be able to separate those of better quality (Group 1), considered in the Special Wheat Class that has a protein level of 12% or better.
The variety of Group 1 that won’t reach 12% could be mixed with other varieties of Group 2 and 3 with protein levels of up to 11%, which is the base for commercialization, separating them from the lots that have less than 11% protein (low quality grain).
Any variety with les than 11% protein has a poor quality due to the lack of enough protein to form gluten. Gluten is responsible for the structure of the though during its use in bakeries. That is why is so important to sow in lots with a good fertilization, natural or artificial, and if is necessary, reinforce it with a good doses of fertilizer that has nitrogen, excellent time to improve performance and quality at the same time.
Possibilities for the silo owner
There is lots of equipment available in the market, some of them even use infrared technology, and others use chemical methods to determine the content of protein or that of gluten. The most adequate are NIRT which, in 30 seconds, they can determine these values, allowing the gatherer to quickly make a decision on which silo the grain belongs to depending on the protein content. This type of equipment is greatly put to use in countries such as United States, Canada and Australia. These countries have been classifying their production by protein content for many years now.
Is not an easy task for the gatherer to separate by variety, this is because they usually receive the production all mixed, thus, knowing the protein levels is enough to separate those grains that have more than 11%-11,5% of protein. This limit could vary according to the availability of high protein wheat on each harvest. During high performance years, protein levels might drop, achieving just a few batches of high protein grains, thus, in these cases the limit may drop to 11%.
The high protein batches should be superior to that of commercialization Group 3. In Canada, the protein bands are established for each grade. This system, which groups wheat of the same grade by its content of protein, minimizes the variation of it among shipments as well as in each one of groups.
Is very important that the gatherer has special care while the wheat with high humidity is drying, because if the temperature exceeds 65°C, the proteins that form gluten become damaged, losing its capacity to bind, thus, the wheat is no longer appropriate for flour making.
If we keep in mind all these, is possible to achieve a correct classification by wheat’s quality, thus, incrementing the possibility of higher prices for our product.
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