Small-scale screening the SDS gel test incorporating a swinging bucket rotor and small sample size (wheat meal or flour) is a robust technique that can clearly distinguish wheats with diverse quality and genotype. However, when comparing samples of similar quality, the discrimination is poor, which is a logical result as this test essentially measures protein quality for breadmaking. Compared to the SDS sedimentation volume test, the advantage of the SDS gel test is in the utilization of a much smaller sample size, higher sample throughput and lower influence by the operator on test results as the test requires only minimal sample handling. The SDS gel test appears to provide better discrimination of wheats with relatively uniform breadmaking quality. The main disadvantage of the SDS gel test is the requirement of a relatively expensive ultracentrifuge. SDS gel rheology and dough mixing characteristics were found to be closely related to a single biochemical factor, i.e. the content or concentration of insoluble glutenin (largest polymers) in flour. The biochemical nature of the SDS gel test for loaf volume prediction appears to be related to two independent factors, (1) insoluble glutenin content of flour, and (2) the disaggregation rate of glutenin during SDS gel extraction. (Abstract shortened by UMI.)