Determination of total oxalate contents of a great variety of foods commonly available in Southern China using an oxalate oxidase prepared from wheat bran

• Oxalate contents of foods reliably determined with new oxalate oxidase method.
• New method uses oxalate oxidase prepared from wheat bran.
• Some commonly available foods in Southern China have high oxalate levels.
• Chinese wolfberry, dragon and abalone fruit, Chinese torreya fruit: high in oxalate.
• Water spinach, black rice, rice bean, are also high in oxalate.

The total oxalate contents of various vegetables, legume seeds, cereals, fruits and nuts commonly available in Southern China were determined using an improved enzymatic method. Spinach, xeric water spinach (grows on moist soil), amaranth, bamboo shoot, ginger, Chinese wolfberry, rice bean and black glutinous rice contained more than 100 mg oxalate/100 g FW, but leaf mustard, white radish, broccoli, cauliflower, cabbage, onion, gourd except bitter melon, tomato, pepper, chufa, kelp, mushroom, soybean sprout and cowpea contained less than 10 mg oxalate/100 g FW. The oxalate contents of star fruit and dragon fruit were 111.4 and 97.1 mg/100 g FW, respectively, and those of other fruits except strawberry and black plum were less than 20 mg/100 g FW. Almond, cashew, hazel, pine nut and abalone fruit contained more than 150 mg total oxalate/100 g FW, and the oxalate levels in Chinese torreya fruit, peanut, pistachio and walnut ranged from 54.1 to 83.1 mg/100 g FW. Based on the results obtained, water spinach, Chinese wolfberry, black glutinous rice, dragon fruit, rice bean, abalone fruit and Chinese torreya fruit should also be considered as high oxalate-foods. The enzymatic method used in the present study enabled us to perform a large-scale quantitative investigation of oxalate contents of different foods.