Abstract: Grain and oil products, the most basic materials for human survival, are subject to various factors such as temperature, moisture, oxygen and microorganisms, triggering a series of biochemical reactions which can cause the generation of off-flavors such as sour and rancid odor. Clarifying the types and formation mechanism of rancid odor compounds and regulating them can help greatly improve the quality of grain and oil products. This article summarizes the key volatile compounds contributing to rancid odor produced during the storage and processing of grain and oil products, and clarifies their formation mechanisms from three aspects: lipid hydrolysis and oxidation, protein oxidative aggregation and the interaction between volatile and non-volatile compounds. Furthermore, the control measures to remove or mask the rancid odor are reviewed. The removal methods mainly include biological breeding and improvement, new storage and preservation technologies, traditional and emerging processing techniques and chemical methods; the masking methods include encapsulation technology based on host-guest interaction, aroma enhancement with exogenous enzymes and the addition of exogenous aroma enhancing ingredients. This paper can provide a theoretical reference and technical support for rancid odor control and flavor quality improvement of grain and oil products.

Key words: grain and oil products; rancid odor; formation mechanisms; off-flavor removal; flavor masking