Research On Methods Of Detecting The Sodium Formaldehyde Sulfoxylate Content In Wheat Flour

Sodium sulfoxylate formaldehyde (SSF) is a bleaching agent that is widely used in light industry for its reducibility. It decomposes and produces formaldehyde which can cause cancer when the temperature reaches above 60℃.Some illegitimate merchants mix it up with wheat flour for its bleach action and this may bring great danger to human and society. Therefore, to establish the determination method of SSF in wheat flour is needed.The methods for inspecting SSF are through detecing the content of formaldehyde and sulfur dioxide that SSF decomposes, however, there is no national standard method to detect it in wheat flour. The methods reported before were varied in sample treatments, which made the results inconsistent and restricted the supervision of SSF. The purpose of this thesis is to fix on the best detection conditions and help to establish the national standard method. The pretreatment and quantification methods of formaldehyde and sulfur dioxide were compared and verified, and the background values of the wheat flour were also investigated in this thesis.The main results are as follows:1 Research on pretreatment ways of detecting formaldehyde. Three pretreatment methods of steam distillation plant, aqueous thermostat and ultrasonic bath were compared for the detection of formaldehyde content in wheat flour using acetylacetone as chromogenic agent. The conditions of each pretreatment were discussed and optimized. It was found that the method of steam distillation and aqueous thermostat both gave good recoveries of different SSF contents added after distilling 200mL liquid or boiling 30 minutes at 80℃respectively, and the precisions were good, but the recovery of ultrasonic bath was not so good as that of aqueous thermostat and steam distillation, accordingly, the pretreatment methods of steam distillation and aqueous thermostat are recommanded for the determination of the SSF content in wheat flour.2 Research on quantification methods of formaldehyde. Spectrometry method and HPLC method for formaldehyde quantification were compared using steam distillation preteatment, and the instrumental setups were optimized. The results showed that when spectrometry was used, acetylacetone could react with formaldehyde thoroughly in 10 minutes, the maximum absorption wavelength of resultant of reaction was at 413nm, and the resultant could be stable for 10h, both recoveries and precisions were good; when HPLC was used, 2,4-dinitrophenylhydrazine could derive from formaldehyde completely after boiling 20 minutes at 60℃in aqueous thermostat, the maximum absorption wavelength of derivative was at 360nm, and the derivative coule be well separated from byproducts with the mobile phase of acetonitrile and water, but the recovery of formaldehyde was less than 50%.3 Research on methods of detecting the sulfur dioxide content. The content of sulfur dioxide was detected according to two methods of the China National Standard (GB/T5009.34-2003). The recovery of sulfur dioxide was good when using distillation method, thus, it is recommanded for determination the sulfur dioxide content in wheat flour. The recovery of sulfur dioxide obtained did not even reach 20% with the method of Hydrochloric acid Pararosaniline.4 Research on background values of formaldehyde in wheat flour. Wheat flour produces formaldehyde when it is pretreated and detected for SSF content, which forms the formaldehyde background value and influnces the determination of SSF. In this experiment, 107 wheat samples were milled by buhler 202 and pretreated using steam distillation, the formaldehyde background values were detected using the spectrometry method. Each of wheat sample showed formaldehyde background value and all of the values fit normal distribution, the average value was 3.72mg/kg with a confidence interval of 1.40 to 6.31 at the probability level of 95%.