Fermentation affects heavy metal bioaccessibility in Chinese mantou

Effect of different fermentation methods on heavy metal bioaccessibilities in wheat flour is undetermined. In this work, gastric and gastrointestinal heavy metal bioaccessibility in wheat flour products (control-wheat dough, T1-mantou made with normally fermented dough, T2-mantou made with over-fermented dough and T3-mantou made with over-fermented dough +Na2CO3) made from two wheat flour samples (NX and QD) was assessed via a modified physiologically-based extraction test. Cadmium, Zn and Mn bioaccessibility in the gastric phase (GP) was greater than in the gastrointestinal phase (GIP), yet the opposite was observed for Cu (p < 0.05). Lead bioaccessibility in the GIP of the QD sample was 1.37-4.08 times greater than that in the GP, while only the control had greater bioaccessibility in the GIP than that in the GP (p < 0.05) for the NX sample. Treatments T2 and T3 had greater Cd, Cu, Zn and Mn bioaccessibilities than the control and T1 in the GP (p < 0.05). In the GIP, however, only T3 had greater Mn bioaccessibility than the control for the NX sample. Enhanced degradation of the heavy metal-phytate following over-fermentation may have led to greater heavy metal bioaccessibility. Results should help food processors reduce human absorption of excessive heavy metals present in wheat flour foods.

Automated summary

The effect of different fermentation methods on heavy metal bioaccessibilities in wheat flour is uncertain. This study assessed the gastric and gastrointestinal heavy metal bioaccessibility in wheat flour products, and found that cadmium, zinc, and manganese bioaccessibility was higher in the gastric phase than in the gastrointestinal phase, while copper showed the opposite pattern. Lead bioaccessibility in the gastrointestinal phase was significantly greater than in the gastric phase for the QD sample, and only the control had higher bioaccessibility in the gastrointestinal phase than in the gastric phase for the NX sample. The over-fermented treatments showed higher bioaccessibilities of cadmium, copper, zinc, and manganese in the gastric phase compared to the control and normally fermented treatment. However, in the gastrointestinal phase, only the over-fermented dough with Na2CO3 showed higher manganese bioaccessibility compared to the control for the NX sample. The enhanced degradation of heavy metal-phytate following over-fermentation may contribute to the increased bioaccessibility of heavy metals.