Cốt Nhĩ 45 Đạm is a highly concentrated traditional fish sauce produced by Huỳnh Khoa on Phú Quốc Island. It is made from fresh anchovies caught in the waters around An Giang and Cà Mau provinces. Local varieties such as black, red, and striped anchovies are used in its production. The fish are cleaned and mixed with sea salt immediately after the catch to preserve their freshness. A traditional ratio of three parts fish to one part salt is used. Before use, the salt is aged for at least three months to reduce bitterness and the presence of undesirable impurities. The salted fish are transported to the production facility and placed in large wooden barrels reinforced with rattan hoops. Fermentation and maturation last between 12 and 15 months. The term cốt nhĩ refers to the first drops of concentrated sauce that are gradually extracted from the fully matured fish mixture. The product has a natural total nitrogen concentration of 45 grams per liter and is not diluted according to the producer. It contains no preservatives or flavor enhancers and is made exclusively from anchovies and sea salt. The finished sauce has a clear reddish-brown color, a mild fermented-fish aroma, and a pronounced salty flavor followed by natural umami sweetness. It is produced and bottled on Phú Quốc Island and carries the protected geographical indication of the region.