PROBLEM TO BE SOLVED: To provide a dry composition exhibiting properties such as water retention, shape retention and thickening by absorbing water and swelling and having heat resistance where it is not dissolved even by heating, a water absorption swelling gent and food containing the same.SOLUTION: There are provided a dry composition which has an average particle diameter of 5 μm to 2 mm obtained by gelatinizing a mixture solution containing agar and alginate and then drying it, has a weight ratio of the agar and the alginate of 1:1 to 1:20 where the alginate contains salt of a monovalent cation and salt of bivalent cation with the bivalent cation of 0.04 to 0.30 times mole and the monovalent cation of 0.10 to 0.70 times mole to a monomer unit of the alginate and molar ratio between the bivalent cation and the monovalent cation of 1.0:0.35 to 1.0:8.70, absorbs distilled water at 20°C and distilled water at 90°C and swells and becomes gel having the weight of 30 to 200 times of the dry composition during either water absorbance and swelling when an average molecular weight of 300 μm, a water absorption swelling gent and a food containing the same.COPYRIGHT: (C)2016,JPO&INPIT【課題】吸水膨潤して保水、保形、増粘などの機能を発揮し、さらに、加熱しても溶け出さない耐熱性を付与された乾燥組成物、吸水膨潤剤及びそれを含有する食品を提供する。【解決手段】寒天及びアルギン酸塩を含む混合溶液をゲル化させ、その後乾燥させて得られる平均粒子径が5μm~2mmの乾燥組成物であって、前記寒天及びアルギン酸塩を重量比率1:1~1:20で含み、前記アルギン酸塩には、1価カチオンの塩と2価カチオンの塩とが含まれ、アルギン酸塩のモノマー単位に対し、2価カチオンが0.04~0.30倍モルであり、さらに1価カチオンが0.10~0.70倍モルであり、2価カチオンと1価カチオンとのモル比が1.0:0.35~1.0:8.70であって、20℃の蒸留水及び90℃の蒸留水に吸水膨潤し、平均粒子径が300μmの場合において、いずれの吸水膨潤でも乾燥組成物の30~200倍の重量を有するゲルになることを特徴とする乾燥組成物、吸水膨潤剤及びそれを含有する食品である。【選択図】なし