The effect of rice cooking method in reducing heavy metals
The researchers found that using a combination of three washes and six hours of soaking was the most effective way to reduce heavy metals. Also, phloem cooking is more effective in reducing the concentration of these contaminants than cat cooking.
Rice is one of the most widely consumed grains in the world, especially in Asia. One of the concerns about rice is its contamination with heavy metals.
Heavy metals do not decompose in nature, so they accumulate in different parts of plants. The presence of these pollutants is mainly due to human activities such as irrigation with sewage, manure, chemical fertilizers, pesticides, sewage sludge, etc.
Due to the importance of this issue, the researchers measured the level of heavy metal contamination of Hashemi rice samples and then evaluated the effect of pre-cooking rice soaking and cooking method on the level of this contamination.
For this study, three farms were randomly selected from three areas of Masal, Shanderman and Soomehsara in the west of Gilan province and five samples were randomly taken from each farm.
After measuring the amount of heavy metals in the samples, the researchers examined the effect of washing frequency, soaking raw rice, as well as the effect of cooking type and drainage on the amount of heavy metals.
The results of this study showed that the samples had a significant difference in the concentration of heavy metals. The observations showed that the highest concentrations belonged to chromium and the Shanderman region, which was higher than the standard of the World Health Organization and the Food and Agriculture Organization of the United Nations (FAO). Nickel concentrations were also higher than allowed in Shanderman and Soomehsara. The amount of lead in all samples was lower than the allowable level and there was no trace of cadmium in the samples.
The researchers in this study say that irrigation with sewage water, the proximity of paddy fields to busy highways and the excessive use of phosphate fertilizers seem to be the main causes of high nickel concentrations in the samples.
Findings obtained from the effect of washing and soaking on the concentration of heavy metals in raw rice samples showed that rice soaking generally reduces the amount of heavy metals and this decreasing trend continues with increasing soaking time.
In this study, it was found that cooking generally reduces the content of heavy metals. However, the drainage cooking method is more effective in reducing heavy metals than the kiln cooking.
The researchers of this study; The combined method of three washes and six hours of soaking and cooking in both methods is suggested as the most effective method to reduce the concentration of heavy metals in rice.
These researchers believe that due to the significant share of rice in the diet of our society, as well as the effect of washing and cooking methods in reducing the concentration of heavy metals, it is necessary to take an effective step in reducing the intake of heavy metals through food. This issue is more sensitive due to the high level of nickel and chromium in the study area.
In conducting this research, Azar Abbasi and Mandana Taifeh; Researchers of Food Engineering Department, along with Seyed Mostafa Sadeghi; Researcher of Department of Agriculture and Plant Breeding of Islamic Azad University, Lahijan Branch, participated.
The findings of this study were published in the winter of this year in the form of a scientific research article entitled The effect of cooking method and soaking time on the concentration of heavy metals (lead, cadmium, nickel and chromium) in rice in the Journal of Food Hygiene Has been.