"Lemon Star" is a brand name for high-purity, food-grade Citric Acid Monohydrate, a white crystalline powder naturally found in citrus fruits, widely used as a sour flavoring, preservative, and pH adjuster in foods, drinks (like soft drinks and candies), cosmetics, and cleaning products, valued for its antioxidant properties, excellent water solubility, and ability to control metal buildup