Chỉ Dẫn Địa Lý Phú Quốc 40 Độ Đạm is a traditional fish sauce produced by Thanh Quốc on Phú Quốc Island. It is made from fresh anchovies caught in the waters surrounding the island and sea salt from the Bà Rịa–Vũng Tàu region. The fish and salt are combined in a weight ratio of approximately three to one. The mixture undergoes natural fermentation for 12 to 15 months in large traditional wooden barrels. During maturation, the fish proteins gradually break down and form natural amino acids responsible for the sauce’s depth and umami character. The 40N designation indicates that the product contains approximately 40 grams of total nitrogen per litre. It contains no preservatives, flavour enhancers, artificial colours or artificial flavourings. The finished sauce has a natural reddish-brown to dark amber colour and a pronounced flavour of fermented anchovies. Its taste is intensely savoury and rich in umami, with natural depth and a mildly sweet finish. The product bears the Phú Quốc geographical indication, which is protected in Vietnam and the European Union. This designation confirms the origin of the ingredients and that fermentation, extraction and bottling are carried out on Phú Quốc Island. It can be served directly as a dipping sauce or used to season cooked dishes, marinades and dressings.