Phytate, calcium, iron, and zinc contents and their molar ratios in foods commonly consumed in China.

A total of 60 food samples commonly consumed in China were analyzed for phytate using the anion-exchange method and for calcium, iron, and zinc using atomic absorption spectrophotometry. The foods analyzed included those based on cereal grains and soybean. Phytate contents expressed on a wet weight basis ranged from 0 for foods made from starches to 1878 mg/100 g for dried stick-shaped soybean milk film. The calcium contents were between 2.08 mg/100 g for ground corn and 760.67 mg/100 g for diced fried soybean curd. The lowest values of iron and zinc were 0.04 mg/100 g for Panjin pearl rice cooked with discarding extra water and 0.08 mg/100 g for potato and bean starches, while the highest values of iron and zinc were observed in dried stick-shaped soybean milk film. Although many foods were relatively rich in calcium, zinc, and iron, many also contained a higher level of phytate. Of the 60 food samples, 34 foods had a phytate/calcium molar ratio >0.24, 53 foods had a phytate/iron molar ratio >1, 31 foods had a phytate/zinc molar ratio >15, and only 7 foods had a phytate x calcium/zinc >200. Phytate in foods impair the bioavailability of calcium, iron, and zinc, which to some extent depends upon food processing and cooking methods.