Using fermentation to remove cadmium contamination in rice
A study published in the Journal of Food Science examines how to remove cadmium in rice by fermentation, the removal mechanisms, and the quality of fermented rice in order to utilize cadmium-contaminated rice.
A study published in the Journal of Food Science examines how to remove cadmium in rice by fermentation, the removal mechanisms, and the quality of fermented rice in order to utilize cadmium-contaminated rice. At present, the prevention and control of cadmium pollution in rice is mainly focused on reducing cadmium pollution, repairing cadmium-contaminated soil, and screening of rice varieties that have low tendency to accumulate cadmium. Microbial adsorption is often used to treat heavy-metal-contaminated wastewater, but fermenting the grain to remove heavy-metal ions from grains has not yet been attempted. This work studied a method of reducing the cadmium levels in rice without affecting the quality of the rice in order to provide technical support in the utilization of grain resources.
The researchers varied the fermentation time, temperature, liquid ratio, inoculant levels, and number of washes to optimize the efficiency of cadmium removal. The optimum fermentation process, in which the rate of cadmium removal from the rice is 80.84%, required an inoculant amount of 0.1%, a liquid ratio of 1:1, a period of 60 hr at 37°C, and subsequently washed with water four times.
The researchers also studied the physicochemical properties of raw cadmium-contaminated rice and fermented rice. They found that the pasting temperature of the fermented rice became lower, and temperature at which pasting starts dropped, but the endothermic enthalpy increased, implying that the protein content in the rice decreased during the fermentation. It suggested that the crystal structure of rice starch changed and fermentation did not result in the formation of new chemical bonds or functional groups in the rice.
The researchers concluded that the microbial fermentation method can effectively limit the cadmium content to within the food safety limits of the Chinese national standard. However, higher levels of cadmium in rice still require better approaches to their reduction.