Rapid Determination of Protein Digestibility in Sorghum Before and after Cooking

Quantifying the digestibility of proteins in cereal grain is important for assessing and improving the nutritional quality of the grain after ingestion. This trait is particularly important for sorghum since the grain protein is known to be less digestible after wet cooking compared to other cereals. The reduced digestibility contributes to malnutrition in regions where sorghum is consumed as a staple food. We describe here a modified, high-throughput protocol to quantify pepsin-digestible proteins in sorghum grain before and after cooking. The protocol includes three basic steps: • grinding and cooking the sorghum into a small porridge for 20 min, • digesting the porridge with pepsin for at least 2 h, • extracting and assaying the protein extract.This method closely resembles the reality of sorghum usage as food and feed, can be scaled to process large numbers of samples and can be adapted for use with other cereal crops. This protocol requires only basic lab equipment and expertise, and one person can easily process 280 samples (140 accessions) in 7-8 h.