Study On Effect Of Processing On Sulfur Dioxide Residues And Dietary Exposure Assessment In Zizania Latifolia

A method for the determination of sulfur dioxide in zizania latifolia by ion chromatography was established in this study. The existing situation of sulfur dioxide was investigated in postharvest zizania latifolia after using fenaminosulf and potassium sulfate compound fertilizer in the growth process. Then the color-protecting effects of zizania latifolia in the sodium pyrosulfite solution of different concentrations were preliminarily studied. In addtion, the effects of washing and cooking modes on the elimination of sulfur dioxide were also investigated to achieve the processing factors. Meanwhile, the changes of total sugar after washing and cooking modes were studied. Finally, the dietary exposure assessment of sulfur dioxide was conducted by the point estimates in zizania latifolia from laboratory. The main conculsions are as follows:1. The ion chromatography method for determination of sulfur dioxide was applied to oil sample and oil-free sample. The results indicated that this method has a good linearity in the range of 0.1～10 mg/Lfor sulfur dioxide. The linear equation is y=0.1034 x 0.0074, with correlation coefficient(r) of 0.9998. For two kinds of samples, the recovery in zizania latifolia was in the range of 85.32%-91.65%, and the RSD was in the range of 2.9%～4.4%. The detection limit was 0.5 mg/kg.2. The results indicated that residue of sulfur dioxide was not detected in the postharvest zizania latifolia, when we had used fenaminosulf and potassium sulfate compound fertilizer in the growth process.3. The sodium pyrosulfite solution of different concentrations had color-protecting effects for zizania latifolia. The effects for cross section were obviously better than that for skin. The changes of pH were not significant (p>0.05). The sodium pyrosulfite solution could delay free phenol content to decrease rapidly. After 24 h of storage, pH has negative correlation with colour, and free phenol content has positive correlation with colour.4. The effects of different cleaning fluid on the elimination of sulfur dioxide in zizania latifolia from laboratory were developed. Four kinds of cleaning fluid such as tap water, detergent solution, acetic acid solution and NaCl had certain removal effect for sulfur dioxide residues. The acetic acid solution was the best cleaning liquid. And the best washing conditions were as fllows:1% acetic acid solution cleaning for 30 min.5. The effects of different cooking modes on the elimination of sulfur dioxide in zizania latifolia from laboratory were developed. Three kinds of cooking modes such as blanching, frying and microwave had certain removal effect for sulfur dioxide residues. The removal effect was in order:blanching(add lid)> frying (160℃)> blanching (not add lid), frying (210℃)> microwave (medium, medium-high heat). The best way of cooking was blanching (add lid) for 3 min, frying (210℃) for 3 min, and microwave(medium-high heat) for 1 min.6. The total sugar content did not lose after deal with tap water, acetic acid solution and NaCl. But the total sugar content dcreased after detergent solution. The total sugar content decreased under blanching. After frying and microwave, the total sugar content did not decrease obviously.7. The results of dietary exposure assessment without processing factors were as follows:the %ADI (234.21～423.6) was not acceptable for zizania latifolia of 2.5% sodium pyrosulfite solution with different age-sex groups, as it was far more than 100. The %ADI (101.84) was not acceptable for zizania latifolia of 1% sodium pyrosulfite solution with 2-7 age-sex groups, as it was more than 100, but the %ADI (56.30～80.92) were acceptable with other age-sex groups.8. The results of dietary exposure assessment with processing factors were as follows: the %ADI (120.61) were not acceptable for zizania latifolia of 2.5% sodium pyrosulfite solution after blanching (add lid) with 2-7 age-sex groups, as it was far more than 100, and the %ADI (66.68～95.83) were acceptable with other age-sex groups, as it was less than 100. The %ADI (138.79～251.05、116.17～248.06.158.70～289.28) were not acceptable for zizania latifolia of 2.5% sodium pyrosulfite solution after blanching (not add lid), frying, microwave with different age-sex groups, which was far more than 100. The %ADI (8.03～21.44.12.82～27.95.19.03～38.19) were acceptable for zizania latifolia of 1% sodium pyrosulfite solution after blanching, frying, microwave with different age-sex groups, as it was less than 100.9. The specification for the application of sodium pyrosulfite in zizania latifolia, under the results of dietary exposure assessment was as follows. At room temperature (25℃), 1% sodium pyrosulfite solution immersion for 60 min. The ratio of sodium pyrosulfite solution volume (mL) and quality (g) of zizania latifolia was 5:1, then followed by 1% acetic acid solution washing for 30 min. The ratio of acetic acid solution volume (mL) and quality (g) of zizania latifolia was 10:1. Finally, used by blanching (add lid, not add lid), frying (160℃,210℃) cooking for 3 min or microwave (medium, medium-high heat) cooking for 1 min.