The antiradical properties of hydrolysates and hydrothermal extracts of bivalve mollusks (Anadara broughtonii) from the Far Eastern Region of Russia and their influence on lipid oxidation in mayonnaise were investigated. The radical binding activity of hydrolysates and extracts of A. broughtonii varies from 55% to 89%. The maximum radical-binding activity was observed for acid hydrolysates. The antiradical efficiency of acid hydrolysates is 35%-41% of the BHT (butylhydroxytoluene) index. The antiradical activity depends on the (method of) technological and biotechnological processing of raw materials. Acid and enzymatic hydrolysates and hydrothermal extracts of A. broughtonii in mayonnaise slow down the process of oxidation of lipids and hydrolysis of triglycerides. Acid hydrolysates reduce the speed of oxidation and hydrolysis of lipids in mayonnaise more efficiently than the enzymatic hydrolysates.Foods 2020, 9, 304 2 of 13 high antioxidant capacity: Extracts from Crassula aequilatera, Mactra murchisoni, and Paphies donacina, which were reported to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals [14]; Paphia malabarica extracts, which were evaluated in relation to DPPH and ABTS + radical [15] crude extracts and fractions of alcohol extracts from Mactra veneriformis [16]; and oligopeptides from Meretrix meretrix [17].The clams Anadara broughtonii, Spisula sachalinensis, Mactra chinensis, and others can be found in the coastal zone of the Sea of Japan [18]. The tissues of bivalve mollusks are rich in amino acids and specific carbohydrates [19][20][21][22][23][24][25]. A. broughtonii belongs to the family Arcidae and is a rather common type of Mollusca, in the Bivalvia class. It is found in the upper-sublittoral in subtropical areas of the Asian Pacific, with commercial stocks at depths of 2-15 m. The maximum lifespan of A. broughtonii is 65 years; the total mass of individuals varies from 80 to 380 g, and the shell length is 65-80 mm. A. broughtonii inhabits muddy and sandy bottoms, burrowing to depths of 10-25 cm. It is found in the Yellow Sea and the Sea of Japan [26].Acid and enzymatic hydrolysates and hydrothermal extracts are products of technological and biotechnological processing of bivalve mollusks. They are sources of biologically active substances with potential health benefits [27,28].Their antioxidant properties may be the basis for use as ingredients in lipid-containing emulsion products in order to reduce the rate of oxidation of lipids. Nowadays, various synthetic substances that perform the function of antioxidants are used for lipid stabilization of vegetable oils-potassium diethyl dithiophosphate or 2,4,6-tris-(dimethylamino) phenol or antioxidant mixtures containing BHT, naphthols, propyl gallates, and others. The disadvantages of these stabilizers are that they are not devoid of toxic properties [29]. Natural antioxidants are safer at stabilizing the quality of lipid rich foods [30].The purpose of the present study was to investigate the antiradical properties of acid and enzymatic hyd...