The Effect Of High Pressure Cooking On Arsenic Speciation In Rice And Polysaccharide On Decreasing Arsenic Toxicity

Rice, as the primary staple in China, its safety is directly related to people’s livehood. Arsenic contamination has been one of the main issues of safety and quality in rice and attracts increasing attention. Arsenic in different chemical forms vary in toxicity. Different cooking method also can result in the change of arsenic species, so the determination of arsenic species in rice before and after cooking is not only benefit to assess its risk accurately, but also presents important references for people to cook correctly. As the complex systems and high safety requirements exist in food, the removal of arsenic in food seems to be difficult. Therefore, we can reduce the risk of arsenic by decreasing arsenic toxicity. Polysaccharide as endogenous substances, not only has nutritious, can also chelate heavy metals and have a certain research value to reduce arsenic toxicity.In this paper, a method was developed to determine arsenic in raw rice and cooked rice by optimization microwave extraction conditions, explored the effect of high pressure cooking on arsenic species(especially inorganic arsenic). The oxidation of As(Ⅲ) and its kinetic analysis in high pressure cooking model was need to ensure the mechanism of inorganic arsenic transformation.The effect of polysaccharide to arsenic toxicity was explored through the Caco-2 cell model and in-vitro gastrointestinal digestion model and respected to apply it to the detoxification of arsenic.The detailed results are as follow:1. The optimal conditions of microwave-assisted extraction were 80℃, 20 min and 600 W;2. Total arsenic content was decreased from 154.90 μg/kg to 141.28 μg/kg after high pressure cooking treatment, while the ratio of As(Ⅲ) was dropped from 58.41% to 56.55%;3. Under the high pressure cooking model, As(Ⅲ) oxidation rate constants of k120℃、k140℃、k160℃、k180℃were respectively 1.9×10-3 h-1、5.1×10-3 h-1、8.5×10-3 h-1、2.2×10-2 h-1 and food additives such as ClO2 and H2O2 have promoting effect on As(Ⅲ) oxidation, but Na2SO3 could inhibit the oxidation reaction;4. The molecular weight of purified cantharellus cibariu and Laetiporus sulphureus polysaccharides were respectively 336 kDa and 16 kDa;5. Under Caco-2 cell model, MTT results showed polysaccharides could depressed inorganic arsenic toxicity, moreover, the effect of Laetiporus sulphureus polysaccharide to arsenic toxicity reduction was better than cantharellus cibariu polysaccharide;6. Polysaccharide can stop arsenic pass through gastrointestinal tract and enter people’s tissue and blood by chelating arsenic. Mixed with cantharellus cibariu polysaccharide, As( Ⅲ)bioavailability was reduced from 85.8% to 75.1%, As( Ⅴ) from 80.3% to 78.9%; while the bioavailability of As(Ⅲ) and As(Ⅴ) were respectively dropped to 75.0% and 76.1% by mixed with Laetiporus sulphureus polysaccharide.