Analysis of Sulfite Content in Mung Bean Sprouts using the Distillation (with a Nitrogen Flow)–Ortho-phthalaldehyde Fluorescence Method
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Abstract:
A new method was established for the determination of sulfite (SO2) content in mung bean sprouts. Mung bean sprouts were distilled with a nitrogen flow, and the volatilized SO2 was absorbed by sodium hydroxide solution. At room temperature, the absorbed sulfite, ammonium salt and ortho-phthalaldehyde (OPA) could react to generate compounds with strong fluorescence in a medium with a pH of 6.6. The fluorescence intensity and concentration of SO2 showed good linearity in the range of 0 to 9.60 mg/L, and the regression equation was y = 403.1x – 147.41, with a correlation coefficient of 0.9996. This method for determination of SO2 content in mung bean sprouts was simple, sensitive, and selective, and the results obtained showed no significant differences from those using the national standard method (the distillation-distillation method). Furthermore, appropriate methods for removal of sulfite in mung bean sprouts were studied. Additionally, the effects of water, acetic acid solution, salt solution, sodium carbonate solution, and rice washing water on removal of SO2 from mung bean sprouts were investigated. The results showed that the sulfite in mung bean sprouts could be effectively removed with rice washing water and sodium carbonate solution. At 65°C, mung bean sprouts were soaked in 150.00 g/L rice washing water and 2.00 g/L sodium carbonate solution for 1.5 h, and the removal rates of SO2 reached 66.41–72.83% and 67.07–80.12%, respectively.
