Effect Of Exogenous Iodine Uptake By Vegetables On Biochemical Properties And Bioavailability

It has been well known that iodine deficiency can result in Iodine Difficiency Disorders (IDD), and this has become a global sanitation problem. In order to reduce the incidence of iodine deficiency disorders (IDD), the agricultural biofortification was used to increase iodine content in vegetable of human food chain to improve human nutrition. In our studies, the vegetable was cultivated as target crops and different forms of iodine (inorganic) including seaweed were chosen in hydroponic and pot experiment, which were carried out to elucidate the distribution, uptake and transprotation of iodine in plants, the effect of iodine on fruit quality and physiological and biochemical properties of vegetables. We studied the stability of iodine after cooking in comparison to iodized salt. A static in vitro gastrointestinal model was used to investigate the bioavailability of iodine in vegetables samples. The objectives of the studies are to provide theoretic basic for the breeding of iodine-enriched vegetable, and ultimately to seek an effective, safe and scientific approach to the prevention and cure of iodine deficiency disorders (IDD). The main conclusions obtained from our studies are as follows:The target crops could absorb and accumulate exogenous iodine, iodine uptake by vegetables was enhanced with the iodine addition, and the respective effects of iodine uptake by vegetables are:I->IO3-. The different plant has the different capability of accumulated iodine and which ranked as:leaf vegetable> fruit vegetable. The distribution of iodine in different organ of plants was showed as:root> leaf> stem> fruit.The application of exogenous iodine could affect the biomass of vegetable efficiently, the low levels of iodine can promote the biomass of vegetable; however, high iodine levels can inhibit the growth of vegetables. Nitrogen, phosphorus significantly affected the iodine-absorption of water spinach. Application of nitrogen, phosphorus and iodine in a proper range could increase the iodine content in plant, and promot the biomass.The application of different form and level iodine has influences on the Vc, soluble sugar, nitrate and total acid contents of cherry tomato fruit, strawberry fruit, pepper fruit. If cherry tomato, strawberry, pepper are treated with proper amount of iodine, fruits with high vitamin C and total soluble sugar content, low nitrate and total acid content will be obtained. Application iodine in a proper range could significantly increase the content of chlorophyll and activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and reduce the content of MDA.Our study indicated that iodine can both synergistically or antagonistically affect mineral nutrition absorption and transprotation of plant. It can be stated that iodine influence on plant uptake of macro-and micro elements as well as heavy metals and trace elements depends on numerous factors, including iodine dose, chemical form and application method, type of cultivation and genotype (cultivar), differences in plant preference (capability) towards mineral uptake.After stir frying,45.64-55.99%of iodine from iodized salt added the vegetable was lost, in comparison to the32.19-42.94%iodine loss rate of iodine-enriched vegetable treated under the same condition. The addition of vinegar causes a significant loss of inorganic iodine in iodized salt, but little affect the stability of iodine in iodine-enriched vegetable. After boiling only9.64%of the iodine from added iodized salt were retained in9.64%, whereas86.06%iodine retaining rate in iodine-enriched vegetable.A static in vitro gastrointestinal model was used to investigate the bioavailability of iodine in green stuff. The results showed that the bioavailability of iodine ranged from47.99%to74.08%in the simulated gastric solution, and from52.46%to68.28%in the simulated intestinal solution. The factors including pH values and digestion time of gastric solution, digestion time and liquid/solid (L/S) ratios of intestinal solution could affect the bioavailabitity of iodine in iodine-enriched vegetable.