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55 Physical Tests Methods​

55-10.01 Test Weight per Bushel

Test weight provides an indication of grain soundness. In wheat, there is a positive correlation between test weight and milling performance and flour yield. Test weight is a criterion in the grading of grains, especially wheat among many wheat-producing countries. Most countries report test weight in kilograms per hectoliter (kg/hL). However, in the United States, it is reported as pounds per bushel (lb/bu). This method determines the weight of dockage-free grain required to fill a level Winchester bushel measure (2150.42 in³ or 35.24 dm³ [dm³ = liter]).

55-20.01 Corn Breakage Susceptibility

The breakage susceptibility test determines the potential for kernel fragmentation or breakage of a sample of corn subjected to impact forces when transported mechanically. Breakage susceptibility is closely correlated with the degree of stress cracks in the endosperm. In this method, a Stein breakage tester is used to test a representative sample of corn. The resulting material is then sieved and the amount of material remaining on the sieve (overs) is used to calculate the percent breakage susceptibility. This method is applicable to shelled corn containing less than 18% moisture but more especially to corn having moisture content at normal commercial average of 15.5% (wet basis).

55-30.01 Particle Size Index for Wheat Hardness

Wheat kernel texture has important implications for milling quality and for parameters such as damaged starch, water absorption, and gas production. This method determines the relative hardness of a wheat sample by determining the particle size index (PSI) through subsequent grinding and sieving. PSI results are expressed as a percentage with lower values indicating harder kernel texture and higher values indicating softer kernel texture. PSI values can be converted to a relative hardness classification through use of a table. As PSI results will differ based on the grinder used, the grinder used should be specified when PSI results are reported.

55-31.01 Single-Kernel Characterization System for Wheat Kernel Texture

Wheat kernel texture has important implications for milling quality and for parameters such as damaged starch, water absorption, and gas production. Using the Single Kernel Characterization System (SKCS), kernel texture (degree of hardness or softness) is determined by instrumental measurement of the average force required to crush 300 individual kernels and is reported as the hardness index (HI). The SKCS is calibrated to compute kernel texture by AACC Approved Method 39-70.02 or a modification of AACC Approved Method 55-30.01, using a cyclone (impeller-type) sample mill. Using the SKCS, higher HI values indicate harder kernel texture, while lower HI values indicate softer kernel texture. This method is applicable to all wheats and hulless barley.

55-40.01 Particle Size of Wheat Flour by Laser Instrument

The particle size of flour is related to the hardness of the wheat kernel and can affect flour quality including starch damage, water absorption and gas production. This method determines the particle size distribution of fine powders dispersed in alcohol using the Microtrac multi-channel laser light-scatter instrument and is applicable to wheat flour or similar materials in which maximum particle size is about 175 μm. It also can be used on larger particle size flours using instruments with a high upper range. Information on the particle size distribution of a sample can be reported as volume mean diameter, average mean diameter, specific surface area as well as other parameters.

55-50.01 Specific Volume

The amount of air incorporated during mixing into pastry creams, cake batters, and icings and thus the new volume they displace, is critical to the quality, functionality, and customer acceptance of these products. This method determines the specific volume (SV; SV = 1/specific gravity) using a calibrated volumetric cup filled with the product and weighed in order to calculate the SV and provide an indication of the aeration of the product. 

55-60.01 Guideline for Determination of Particle Size Distribution

This guideline applies to the determination of particle size distribution of powdered chemical leavening agents by mechanical sieving. Generally, the particle size distributions for these materials are defined by their respective specifications by using several screens with mesh sizes ranging from 60–325 U.S. Standard (250–44 µm). The intent of this document is to outline a general procedure, provide suggested values for key parameters where appropriate, and highlight controllable sources of error.

55-99.01 Glossary—Barley
These terms have been defined sp​ecifically for barley and may have different definitions when used in other contexts.