The California Wheat Commission wheat quality laboratory was built in 1990. Today, this laboratory has the equipment necessary for evaluation of grains including but not limited to wheat, rice, barley, and many other grain crops. The laboratory and its staff have gained respect in the domestic and international marketplace as a premiere source of technical information and assistance. The lab is available to work for customers in the area of quality assurance, problem solving, quality control training, and research.
The Commission laboratory is available for flour, semolina, milling, end-product, and new-product research. Technical expertise is available in hearth breads, pastries, pasta, Asian food products, standard loaf bread, and more. Tortillas and middle-eastern flat breads are also rapidly becoming an area of interest.
Private and public breeding programs play an important role in the development of new varieties available to California grain producers. The Commission analyzes over 1,000 samples each year to support these programs and encourages the release of new varieties that will meet the customers' needs.
Ranges from 10 to 20%, depending on variety, class, environmental conditions, and cultural practices during growth. Rainfall during kernel development results in low protein, whereas dry conditions during development usually results in high protein. 1.0 to 1.5% of protein is lost when the wheat is milled into flour.
Ranges from 5 to 12%. Water content in the wheat is inversely related to the amount of dry matter. Dry wheat can be kept for years if safely stored, but wet wheat may deteriorate dramatically.
A means of determining hard and soft wheat kernels. The higher the hardness, the higher the absorption.
Mineral content in the wheat. Bran has higher ash content than flour. Small or shriveled kernels have more bran on a percentage basis and therefore more crude fiber and ash than large, plump kernels and consequently yield less flour. Wheat usually contains 1.4 to 2.5% ash at 14% moisture basis.
Percentage of large, medium, and small kernels in a durum wheat sample. Ranges for large kernels are 80 to 100%, medium 0 to 20%, and small 0 to 2%.
Ranges from 55 to 75 lbs/bu. Wheat weight per unit volume. Most widely used and simplest criteria of wheat. Rough index of flour yield.
Function of kernel size, shape, dryness, purities, and density; also an index of potential milling yield. Ranges from 30 to 60 g.
Flour Moisture content is usually in the range of 12 to 15%. Under these conditions lipid degradation is not a problem in the short to medium term, but at higher moisture contents, rapid hydrolysis of lipids by proliferating molds seriously lowers flour baking quality.
1.0 to 1.5% of protein is lost when the wheat is milled into white flour. For whole grain flour, protein content remains the same as the grain protein content. Ranges from 10 to 20%.
A highly significant correlation is found between ash content and the brightness of semolina. For any given wheat, higher extraction produces darker semolina with higher ash content. Ranges from 1 to 3%.
A measure of the a-amylase activity (starch liquefied enzyme). With more a-amylase, degradation of starch is greater and starch viscosity decreases, giving a decreased falling number. A falling number of 300 and above is desirable. Note: Some grains inherently have low falling numbers due to its chemical composition related to starch.
10 g flour and 5 mL 2% salt solution are used to produce a wet gluten dough ball. The wet gluten is isolated by washing this dough with a sodium chloride solution. The residual water adherent to the gluten is removed by centrifugation and the remainder weighed. Ranges from 20 to 50%.
During centrifugation the gluten is forced through a sieve. The percentage of gluten remaining on the sieve is defined as the Gluten Index, which is an indication of gluten strength. A high Gluten Index indicates strong gluten. Ranges from 10 to 100.
A physical dough testing instrument is used to measure plasticity, or rheology, and mobility of dough when subjected to mixing action.
Percentage of water required to center the curve on the 500 Brabender Unit (B.U.) line at the maximum consistency of the dough. Because flours vary in "slacking out" during fermentation, this may not be the true absorption in the bakery. The preference is for higher absorption percentages.
The time curve takes to reach 500 B.U. line.
The time curve takes to drop below 500 B.U. line.
The time required for the curve to reach its full development or maximum consistency; long peak times usually associated with strong wheat.
Mixing Tolerance Index - Difference in B.U. from the top of the curve at the peak to the top of the curve measured at 5 minutes after the peak is reached.
Stability of Farinograph curve, Departure to Arrival
Difference in B.U. from the 500 B.U. line to the center of the curve calculated at 20 minutes from the addition of the water.
A numerical value based on a logarithmic function of the peak time in relation to the breakdown 12 minutes after peak time. Higher values indicate a stronger flour and lower values indicate a weaker flour.
The Alveograph determines the gluten strength in a specific dough by measuring dough elasticity, extensibility, and overall strength.
The force required to blow the bubble.
Balance between dough strength and extensibility. Ranges from 0.2 to 4.
P/L < 0.5 high extensibility. P/L = 1 balance extensibility/elasticity, P/L > 1 more elastic flour.
The extensibility before the bubble breaks.
The area under the curve and overall strength. Ranges from 60 to 400. W value < 80 low gluten strength (more suitable for pastries). W value > 150 strong gluten strength.
Mixes flour with water and generates a graph that records the force needed to mix. The mixograph is similar to the farinograph but is quicker and uses a pin mixer and a smaller flour sample. Peak height and peak time are common mixing parameters that are determined from mixogram.
Measures rapeseed displacement. Bread volume weight is measured immediately after bread loaf is out of the oven.
Volume of loaf divided by weight.
Grain texture is objective score using E, S, S-Q, Q, U.
1-5 based on prior factors in bake test. (5 is excellent)
The CWC Lab is developing standard methods for testing the quality of 100% whole grain flours. We will make this information available once finished. If you need assistance with developing 100% whole grain flour recipes, please contact us.
Alejandra Andrade is utilizing three whole wheat bread recipes for analyzing the overall baking quality of wheat varieties. CWC Whole wheat milling process: Hammer mill of screen mesh size of 0.8 mm.
To learn more about each method, please click below:
1. Straight Dough Method
2. Poolish Method
3. Sourdough Method (Monica Spiller's Test Loaf modified method)
Maya is a Plant Science student at UC Davis.
Christina is a third year undergraduate at UC Davis studying Clinical Nutrition and Design. Food scientists and nutritionists are commonly seen as having different and conflicting goals, but she recognizes each as an important player within our food system and aspires to bridge the gap between food science and nutrition. She values interdisciplinary collaboration and is excited to work with peers and professionals from different backgrounds and areas of expertise to bring awareness to the nutritional, societal, and environmental impacts of food.
Katie is a second year undergraduate at UC Davis pursuing a Food Science degree. While she enjoys learning about different food processes in the classroom, she is most passionate about learning directly from farmers and educating consumers in understanding the sources of their food. In her past time she plays the viola and is an active member of a vanilla bean co-op.