Kafirins

Kafirins are a class of cereal storage proteins found in the seeds of sorghum (Sorghum bicolor). They belong to the prolamin family, alcohol-soluble storage proteins located in the endosperm. Kafirins are analogous in function to gluten proteins in wheat in being proline- and glutamine-rich, but they are genetically and biochemically distinct from gluten.

The kafirin family comprises several subtypes, including alpha-, beta-, gamma-, and delta-kafirins. Alpha-kafirins are the dominant fraction, forming roughly the majority of the kafirin pool. Molecular weights for alpha-kafirins are typically in the 18–22 kDa range, with gamma- and delta-kafirins present in smaller amounts. Kafirins are encoded by a gene family on sorghum chromosomes and accumulate in protein bodies within the endosperm, where they can form networks via disulfide bonds.

As storage proteins, kafirins serve as a nitrogen and amino acid reservoir during germination and early seedling growth. Their amino acid profile is relatively low in lysine and tryptophan, which affects the overall protein quality of sorghum. Processing techniques and breeding strategies aim to improve lysine content and digestibility. Processing, milling, and food formulation can influence kafirin digestibility and the bioavailability of amino acids.

Health and dietary notes: sorghum-based products are generally considered gluten-free and are widely consumed by people with celiac disease or gluten intolerance. Kafirins are not gluten proteins, and sorghum is typically regarded as safe for those following a gluten-free diet, though individual tolerance can vary.

Breeding and biotechnological efforts include approaches to reduce kafirin content or alter its composition to improve nutritional quality and protein digestibility in sorghum.