New method for assessing trypsin inhibitor activity in plant-based food materials including soybeans, pulses, beans, cereals and their processed products.

 AOCS is the leading provider of methods and recommended practices critical to running a quality lab in the fats, oils and plant-protein industries, and recently approved a new method, Method Ba 12a-2020, for assaying trypsin inhibitor activity in plant-based food materials including soybeans, pulses, beans, cereals and their processed products.

Crystallographic structure of a Kunitz-type
trypsin inhibitor from Erythrina caffra seeds.

Trypsin inhibitors are found in a wide range of plants including pulses, beans and cereals. These proteins are thought to have evolved as part of the plants’ strategies to deter consumption by animals and irreversibly bind to enzymes involved in protein digestion. High levels of trypsin inhibitor activity in animal feed leads to decreased weight and has been linked to metabolic and digestive diseases. Humans have developed a range of approaches to disarm this defense, including denaturing by heating (processing or cooking), and selective breeding of plants. The ability to reduce, and, most critically, to accurately quantify, the trypsin inhibitor activity in plant material has been key to the development and production of new plant-protein based foods for animal and human consumption.

AOCS has had an official Method for measuring trypsin inhibitor activity since 1975. As part of the ongoing process of method revision, a new Method Ba 12a-2020 has recently been approved by the AOCS Uniform Methods Committee. Keshun Liu, a Research Chemist with United States Department of Agriculture, Agricultural Research Service (USDA-ARS), has led this effort. 

“The new method is easier to learn, requires smaller amounts of reagents and gives results with greater precision,” he says.

Keshun Liu

Method Ba 12a-2020 assesses inhibitor activity from the increase in light absorbance at 410 nm using Nα‐benzoyl‐DL‐arginine‐ρ‐nitroanilide as a synthetic trypsin substrate. It has an expanded scope, addressing the need for analytical methods for non-soy plant proteins. It also provides results using more meaningful units of measurement.

“Using AOCS Ba 12a-2020 analysts can now express results as the amount of trypsin inhibited, instead of using an arbitrary unit,” says Liu. “The new unit is standardized against a reference trypsin with a fixed value of specific enzyme activity.  If other methods adapt this new concept of standardization against the same reference trypsin, results will become comparable among reports.”

“The creation and validation of methods that encourage comparison of measurements from different laboratories is central to AOCS’s mission,” says Scott Bloomer, ‎Technical Services Director at AOCS. “The genesis of our society in 1909 was a collaborative effort among cottonseed producers to standardize analytical results.”

An international collaborative study of the new AOCS Ba 12a-2020 Method was recently conducted. Results are reported in a recent JAOCS article. You can purchase the Method at the AOCS Store.

A new AOCS Laboratory Proficiency Program (LPP) series has been launched in conjunction with AOCS Ba 12a-2020. For more information please contact Dawn Shepard dawns@aocs.org.