Yes, curd should be refrigerated immediately after setting to slow down bacterial activity, prevent it from becoming too sour, and maintain its desired texture and flavor.
Curd, also known as yogurt, is a dairy product created through bacterial fermentation. The bacteria, typically *Lactobacillus* species, convert lactose (milk sugar) into lactic acid. This lactic acid is what gives curd its characteristic tangy flavor and thick texture. The fermentation process continues even after the curd has set. If left at room temperature, the bacteria will continue to produce lactic acid, causing the curd to become increasingly sour and potentially develop an undesirable texture. Refrigeration significantly slows down the metabolic activity of these bacteria, effectively halting the fermentation process. This allows you to preserve the curd at its optimal stage of flavor and consistency. Refrigerating also helps to prevent the growth of undesirable microorganisms that could spoil the curd.
If you prefer a slightly tangier curd, allow it to sit at room temperature for a shorter period after setting before refrigerating. Experiment to find the perfect balance of tanginess for your taste. However, never leave it at room temperature for extended periods, especially in warm climates, as this can lead to spoilage.