Milling new crop wheat
November 01, 2004
by World Grain Staff
by Mark Fowler
Every year flour millers are faced with the challenge of adjusting to the differences that occur with each new wheat harvest. These subtle changes can significantly affect flour extraction and consequently the profitability of the milling companies.
The question that millers and bakers alike must work together to answer each year is when to begin adding new crop wheat into the mill grist.
In an ideal situation, many millers would prefer to store the grain for three months and make the change over to new crop wheat after the crop has sufficient "sweat" or aging to the grain. However, physical grain storage restrictions and the cost of carrying the wheat for such a long period of time prohibit this perfect scenario in most cases.
Importers of wheat have the benefit of the time it takes to transport the grain, in most cases 60-90 days, for the wheat to sweat before arriving at its final destination.
The next alternative for millers is to begin incorporating the new crop wheat into the mix in small quantities, immediately as it begins to arrive at the mill. Blending the new wheat into the mill mix in increments of 5% to 10% depending on blending capabilities of the mill, and then gradually increasing this percentage each week until the old crop wheat stocks have been exhausted is the most common practice to transition from old crop to new crop each year. This practice also allows maximum aging of the new crop wheat within existing storage and logistical restrictions. However, this strategy does have drawbacks for bakers, which have to adjust to new flour characteristics each week as the percentage of new crop wheat increases.
Some of the changes that millers will see in the performance of the new crop wheat include the granulation of break system passages, including changes in the amount of sizing stock produced and increased difficulty in flour bolting of break and reduction passage stock.
In a wheat quality study done by Dr. E. S. Posner and Dr. C. Deyoe in 1986, some evidence suggested the bonds in the gluten-containing protein in hard wheat continued to develop during the sweating period of wheat. Also, the maturation of wheat kernels continues for a period of time after they are harvested, changing the kernel hardness and amount of vitreous kernels. These changes in the properties of hard red winter wheat during the sweating period help to explain why new crop wheat tends to mill similarly to soft wheat.
Milling new crop "softer" wheat during the first few months after harvest requires the miller to make small adjustments to his mill and milling practices during the transition period from old crop to new crop. Typically, millers will find it necessary to open up slightly the head end flour clothing of the mill. The softer wheat does not bolt or sift as efficiently as harder wheat.
Increasing the micron size of the flour clothing in the head end break passages helps to reduce the carry over of fine material to the reduction and sizing passages of the mill.
Adjusting the grinding of their break rolls to balance the sizings production from the break system in the mill is also necessary to maintain a good operating balance of the mill.
Well-maintained rolls in the mill are always important to maximize extraction and the operation of an efficient mill, however freshly cut corrugated rolls in the break system when introducing new crop wheat are especially important. Changes in the physical properties of the wheat may cause a reduction of the running capacity of a mill for the first few weeks after harvest. Making the necessary adjustments to the mill will help to maximize mill capacity and efficiency during this time of transition.
WORKING WITH THE CUSTOMER
Some of the changes in the flour that bakers will experience relate primarily to changes in the percent of water absorption and mixing tolerance of the flour. Studies have shown that for the first three months of storage the percent of water absorption as measured by farinograph tests tend to increase, changing the dough mixing properties of the flour. Regardless of what changes occur in the wheat for the first 90 days after harvest, bakers are faced with the challenges of baking with a changing raw material each harvest. Millers and bakers have to work together to determine the best quality of flour for the next season. The qualities of wheat available after each harvest weigh heavily on the decisions for milling and blending of wheat and flour each year. Typically, a miller produces flour according to the specifications agreed to with his customers. As the properties of the wheat change each harvest, the blend of wheat required to meet the customers’ requirements also changes. Protein content and protein quality of the wheat is always the first topic of discussion each harvest. Test weight, 1000 kernel weight and other physical characteristics of the wheat kernel are other top concerns for millers.
Protein content and protein quality are important when making wheat selection decisions. Changes in protein characteristics not only affect flour quality but the economics of determining what type of wheat to purchase and blend in order to meet customer needs. If the protein of U.S. Hard Red Winter (HRW) wheat crop had a lower than average protein, for example, it may be necessary to add Spring Wheat (HRS) to the mill grist to improve the performance of the flour to meet the needs of the customer. A higher than average protein from the HRW wheat harvest may allow the miller to incorporate some soft wheat flour into his mill grist or reduce the amount of HRS that he uses to meet protein and perfor- mance requirements of the customer.
However, it is just as likely to find that the functionality of the new crop wheat may differ slightly at similar protein levels from the previous year due to the different growing condition and varieties grown.
A wheat with a protein content of 11.5% at a 12% moisture basis, may perform the same as a 12% protein wheat from the previous year or a 11% protein wheat depending on changes in the dominant variety and growing conditions. The miller and baker must work closely together to make the necessary adjustments to the mill grist and flour
improvers used each year to produce a quality product that meets their needs from a performance as well as a cost position.
WATCH THE WEIGHT
Other measurements that millers watch closely each year are test weight and 1000 kernel weight results. Although, some question the relationship between these measurements and flour yield, they remain important characteristics in determining the quality of wheat is available each year.
For millers who have the ability to source wheat from specific areas, lower than average test weight or 1000 kernel weight are reasons to adjust the contract parameters to assure the quality of wheat received is adequate for your needs. This year, buyers of U.S. HRW wheat may be concerned about weather related damage due to wide spread rain during the harvest period. These concerns can be managed easily enough by including a minimum Falling Number specification as well as requesting U.S. number 2 HRW or better to assure receiving wheat with a test weight of 58 pounds per bushel or greater.
Early testing and good communication between millers and bakers will help to better manage the challenges and opportunities of new crop wheat. WG
Mark Fowler is the flour milling specialist for the International Grains Program at Kansas State University. He has a BS in Milling Science and Management. He may be contacted at: firstname.lastname@example.org