Wheat And Flour Testing Methods Pdf
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- US4262024A - Method for testing baking strength of flour - Google Patents
- Wheat and Flour Testing Methods Book
- Flour Analysis
US4262024A - Method for testing baking strength of flour - Google Patents
The quality control laboratory is an important part of the flour milling industry. It is important to use appropriate standard methods and procedures in the flour quality testing laboratory. Flour containing more than It is also necessary to know the moisture content of the flour in order to adjust flour test data to a constant moisture basis. Commonly used moisture basis varies by country so the basis used should also be reported. To convert to a constant moisture basis, minus the desired moisture content is divided by minus the actual moisture content of the flour which is then multiplied by the as-is actual moisture content value.
The example illustrates the importance of the moisture basis. Flour A contains Moisture can be measured using several direct or indirect methods. The direct methods use oven heating and assume that the loss in weight of the flour during heating is caused by the evaporation of water. The percentage of moisture in the four is calculated by dividing the weight of moisture lost by the weight of the flour prior to heating and multiplying by to convert to percentage. Oven heating methods take several hours to perform.
NIR methodology measures the absorption of electromagnetic energy at specific wavelengths in the near infrared region and plots it as a spectrum.
Peaks in the spectrum at different wavelengths correspond to different flour components such as water, protein, starch, fat, etc. The quantity of each of these components is calculated mathematically using a calibration or reference that is programmed into the instrument. The accuracy of the NIR data is only as accurate as the calibration equation that was programmed into the instrument.
It is extremely important to make sure the calibration is good and covers the whole range of values that occur in the product being tested. It is also a good practice to have the instrument serviced every 1 to 2 years to make sure the light source is fully functional as they tend to slowly burn out over time, causing incorrect readings. Most bench top moisture meters use the RF dielectric method which is also known as the capacitance method.
With this method, the sample is scanned with a radio signal at a specified frequency. The radio signal is changed by the dielectric constant as the water in the sample interacts with the radio wave. The change in the dielectric constant is used to calculate how much water is present in the sample. Several factors affect the dielectric constant, most commonly sample density and temperature. Consequently, these two factors are measured and corrected for in the more advanced moisture meters. As with the NIR, the calibration curve programmed into the instrument is critical and the results obtained are only as reliable as the calibration curve.
Protein Protein content is the basis by which wheat and flour are bought and sold and is one of the main factors controlling the price. In the hard wheat classes, price increases as protein content increases while in the soft wheat class, higher prices are paid for lower protein flours being used for specialty products. Protein content is one of the most important features because it affects many flour properties. Flour protein content is categorized as being low, medium or high, depending on the wheat class.
Within the hard winter wheat classes, low protein flours have less than In the spring and durum classes, low protein flours have less than In general, dough strength increases as protein content increases.
Doughs are referred to as being visco-elastic. This refers to the ability of the dough to be both viscous or extensible but also elastic or strong. The balance of extensibility and elasticity determine the best use for the flour.
Low protein flours have a weak dough strength characterized by high extensibility and low elasticity. Low protein flours work best in products that do not need a lot of strength such as cakes, cookies, some types of crackers, and all-purpose flour. Medium protein flours have a medium-high dough strength characterized by having moderate extensibility and moderate elasticity.
Medium protein flours work best in products that need an equal balance of extensibility and elasticity such as noodles, tortillas, and white pan bread. High protein flours have strong dough strength and are characterized by having moderate extensibility and high elasticity. High protein flours work best in products that need a highly elastic, strong dough like pasta, hearth breads and whole grain breads.
Protein content is measured by several methods including Kjeldahl, combustion and NIR. The Kjeldahl and combustion methods measure the nitrogen content of the sample which is then multiplied by a factor to calculate the crude protein content. The typical factor used is 5. As discussed above, it is important to report protein content on a constant moisture basis.
The moisture basis that is used should be reported as well. The Kjeldahl method, developed in , is the universally accepted traditional wet chemistry method. In the method, the sample is digested by heat and sulfuric acid which liberates reduced nitrogen as ammonium sulfate which is then distilled with sodium hydroxide to form ammonia. The level of ammonia is measured by back titration to determine nitrogen concentration which is used to calculate crude protein content.
Drawbacks of the method are that it takes longer than an hour to run a single sample, the operator works with harsh chemicals and high temperatures, and hazardous waste must be disposed of properly.
Combustion analysis is an automated and rapid method which is replacing the Kjeldahl method as the standard method of analysis for protein content in food and animal feeds. There are many different protein combustion instruments which all have the same basic operating principle. The carbon dioxide and water are absorbed and the nitrogen is separated out and quantified using special columns.
Nitrogen content is then used to calculate crude protein content using conversion factors. NIR can also be used to directly measure protein content. It is the fastest and easiest method to run.
An advantage of NIR is that the moisture and protein contents as well as many other properties of the flour can be measured simultaneously. Ash Ash is the inorganic or mineral content of the flour. It varies depending on soil and climate. The mineral distribution varies within the kernel but it is most highly concentrated in the bran. Wheat bran contains 30 times more inorganic matter than endosperm so even a small amount of bran in the flour can significantly affect the ash content.
Ash content is often used as a measure of the grade or type of flour because it shows how much bran is present in the flour. Flours milled using a low extraction rate are premium products with low ash contents that can be sold for a higher price than flours milled with a high extraction rate that includes more bran and higher ash.
Ash also indicates the completeness of separation of the bran and endosperm during milling or how much bran was removed during sifting. The bran from red wheat affects the color of the flour. The higher the extraction, the darker the color of the flour. Flours milled from red wheat will also have a dull or darker color compared to flours milled from white wheat due to the presence of the red colored bran. The most accurate way to measure ash is using the muffle furnace method; however, the method takes many hours.
In this method, the flour is combusted and burned overnight. The following day, the burned samples are cooled in a desiccator and the residue ash is weighed. Ash content is calculated as the weight of the residue divided by the original weight of the sample times to convert to percentage.
As discussed above, ash content should be reported on a constant moisture basis. Many manufacturers and distributors advertise that NIR instruments measure ash. Because the NIR measures the bonds in organic materials and ash is inorganic, NIR does not actually measure ash content.
Much of the fiber in wheat is concentrated in the bran layers and flour ash correlates highly with flour fiber content so it is highly likely that the NIR is measuring fiber rather than the mineral ash. This instrument allows the user to adjust the bias and slope in the NIR calibration so the measured values are more accurate. The adjustments are calculated by analyzing a reference set of flours using both the NIR and the muffle furnace ash method.
Falling Number The Falling Number FN is a hot paste viscometer that is used to measure the alpha amylase activity of wheat and flour. One use of the FN is to determine whether the wheat experienced any pre-harvest sprouting. This is especially important in areas that received excessive rain at harvest time. Once grain reaches maturity, sprouting can occur when the moisture and temperature are right. If these conditions happen at harvest, the kernels can sprout in the field.
When sprouting occurs, enzymes in the kernel become active; amylases break down the starch, lipases break down the oil and proteases break down the proteins. The enzymes can become active and influence the functionality of the wheat even before the sprout is visible on the kernel.
The impact of sprouting depends on the activity of the enzymes and the degree of breakdown to the components of the kernel. FN values of seconds or less are an indication that the flour has excessively high amylase activity and is unfit for use in most baking applications.
Malt malted barley is a flour additive made by the controlled germination and drying of barley. It is often added to flours used for bread making because the alpha amylase in the malt has positive effects on dough handling and machinability, increases oven spring and extends shelf life of the bread. FN is used to verify that the flour meets the customer specifications and was not over or under malted. FN of to seconds are typical values that are specified for bread flours.
Wheat or flour with FN values greater than seconds are sound, meaning that they have no amylase activity and were not sprout damaged or malted. In the FN scale , values higher than seconds i. However, there are great differences in performance when the FN values are less than seconds. It is the best practice for a mill to purchase wheat with a FN near or above seconds and then add malt as needed to produce flours with different FN values. Flour Color Flour color can be measured by several methods, most of which use older instruments that report color in various instrument specific units of limited value.
The Chroma Meter Konica Minolta is a recommended modern instrument that utilizes a granular materials attachment for the measurement of flour. The scale ranges from 0 for pure black to for pure white. Bran or other extraneous materials in the flour will decrease the color value. Yellowness is caused by natural pigments in the endosperm which lighten during aging or can be chemically lightened with benzoyl peroxide.
Wheat and Flour Testing Methods Book
Wheat and Flour Testing Methods: A Guide to Understanding Wheat and Flour Quality provides an introduction to the analysis of wheat and flour in a clear and concise format. Basic information is presented on standardized testing procedures for wheat and flour quality characteristics as well as dough properties. Results from these tests are explained and applied to processing performance and end product quality. Laboratory testing of a variety of wheat-based finished products is also included. The finished product formulations and processes described are laboratory testing protocols that are used to evaluate flour quality. They are model systems that may be used to predict commercial production for common uses of wheat flour worldwide.
Basic infor- mation is presented on standardized testing procedures for wheat and flour quality gov/reference-library/handbooks/grain-insp/grbook2/wheat.pdf.
Scope of Appointment Form Medication Form. Late December Early December November
The production of uniform bakery products require control over the raw materials used in their formation.
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In general, a farinograph is used to determine the water absorption, but this method requires large amounts of wheat flour g. In this study, water absorption in a small amount of wheat flour 10 g was determined using a mixograph. The water absorption measured using the mixograph was very similar to that measured using a farinograph and g of wheat flour. Thus, the water absorption in a small amount of wheat flour can be accurately measured using a mixograph. Eliasson, A.
The quality control laboratory is an important part of the flour milling industry. It is important to use appropriate standard methods and procedures in the flour quality testing laboratory. Flour containing more than It is also necessary to know the moisture content of the flour in order to adjust flour test data to a constant moisture basis. Commonly used moisture basis varies by country so the basis used should also be reported.
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