Masala mixes smell sour in the rainy season due to increased humidity, which promotes the growth of mold and bacteria that produce acidic byproducts. These byproducts contribute to the sour odor.
During the rainy season, the air is saturated with moisture. This high humidity creates an ideal environment for microorganisms like mold and bacteria to thrive. Masala mixes, being composed of ground spices, contain organic matter that these microorganisms can feed on. As they consume the spices, they release metabolic byproducts, many of which are acidic. These acidic compounds, such as lactic acid and acetic acid, are responsible for the sour smell. Furthermore, the increased moisture can also lead to the clumping of spices, further encouraging microbial growth in the damp pockets. The spices most susceptible to this souring are those with higher oil content, as the oils can become rancid through oxidation and microbial action. Proper storage is crucial to prevent this.
Store your masala mixes in airtight containers with a desiccant packet (like silica gel) to absorb excess moisture and prevent microbial growth. Consider lightly toasting your spices before grinding them into a mix; this reduces moisture content and extends shelf life.