A trade-off between shelf-life mitigation and nutritional retention: a persistent challenge in pearl millet

Pearl millet serves as a vital cereal crop for ensuring food and nutritional security, particularly in arid and semi-arid regions known as "Grains of God," due to its remarkable tolerance to drought and other adverse environmental conditions. In addition to its climate resilience, pearl millet possesses superior nutritional quality, being enriched with essential amino acids, dietary fiber, iron, zinc, and several health-promoting bioactive compounds, thereby making it an important component of sustainable and nutritious food systems. However, a major limitation associated with the commercial utilization of pearl millet is its susceptibility to rancidity during storage. Rancidity primarily results from the oxidative degradation of lipids, leading to the formation of free fatty acids, hydroperoxides, aldehydes, and other volatile compounds responsible for undesirable off-flavors and reduced sensory acceptability. This deterioration is largely attributed to enzymatic reactions involving polyunsaturated fatty acids, which adversely affect the shelf life and consumer preference of pearl millet-based products. In addition to the limited long-term efficacy of conventional stabilization approaches, these strategies are often associated with nutrient loss, deterioration of quality attributes, reduced scalability, and increased processing costs. Recent advances in "Omics" approaches, such as genomics, transcriptomics, lipidomic, and metabolomics, have substantially enhanced our understanding of the molecular mechanisms underlying rancidity development in pearl millet. Several candidate genes, including PgTAGLip1, PgTAGLip2, LOX, phospholipases, and lipid metabolism regulators, have been implicated in flour stabilization and lipid degradation pathways. Nevertheless, significant challenges remain, including the effective integration of multi-omics datasets, the lack of standardized phenotyping protocols for storage-related traits, and difficulties in temporal transcriptomic analyses due to RNA degradation during flour storage. This review provides a comprehensive synthesis of the current biochemical, nutritional, molecular, and omics-based insights into pearl millet rancidity, with particular emphasis on future breeding strategies aimed at developing varieties with enhanced storage stability and improved end-use quality.