Within 2 hours. Bitter vegetable soup should usually not be left at room temperature for too long because room temperature is a breeding ground for microorganisms, which can easily lead to food spoilage and food poisoning, so you should limit the time you leave the food at room temperature to less than 2 hours. The leftover bitter vegetable soup should be cooled down quickly and stored in the refrigerator. At low temperature, microorganisms in the food cannot multiply and hence the freshness of the food can be prolonged. Bitter vegetable soup can be stored in the refrigerator for 2-4 days, but it is best to consume it within 48 hours to ensure the safety and quality of the food.