the present invention relates to a biopolymer based barrier coating composition wherein said biopolymer based barrier coating composition comprises a plasticizer , a nano - sized clay and a biopolymer comprising a native starch and / or a de - graded starch and / or a chemically modified starch . the present invention also relates to a method for preparing the biopolymer based barrier coating composition as well as to a method for coating a cellulose based substrate with the biopolymer based barrier coating composition . finally , the present invention relates to a cellulose based substrate coated with said biopolymer based barrier coating composition .