It is well-known that trypsin inhibitors are an important anti-nutritional factor in soybean meal (SBM). Fortunately, these trypsin inhibitors are inactivated by heating or cooking. However, either under cooking or overcooking can have deleterious effects on the protein quality of SBM. Actual direct measurement of trypsin inhibitor has historically been difficult. Thus, several different indirect methods that are easier to conduct have been developed. One of the first useful assays was the urease test. It was found that heat inactivation of trypsin inhibitor and urease enzyme in SBM were highly correlated. Thus, a rapid urease pH change assay was developed and has been used extensively for more than 75 years. The ideal or most desirable range for urease pH change has evolved and been modified over many years. Eventually, it was generally accepted that the urease pH change is a good basic method of detecting underprocessing of SBM but is of little or no value for assessing overprocessing or excessive heating of SBM. Therefore, a method based on protein solubility in KOH was later developed and evaluated and was shown to be a good method of detecting overprocessing of SBM for poultry. There is, however, considerable interlaboratory variability for the KOH protein solubility assay and recent research is being conducted to better standardize the assay to reduce interlaboratory variation so that results are more repeatable and consistent across labs. Recent research has also been underway to evaluate the KOH assay to better define its critical limits for in vivo amino acid digestibility of commercial SBM since most of the earlier research was conducted using laboratory autoclaved SBM and also did not determine amino acid digestibility. There has been considerable recent work and advances for laboratory assays to analyze trypsin inhibitors in SBM. For example, a new official AOCS method was established in 2020 and a new rapid and cost-effective method has been recently developed.