The Detection Of Deoxynivalenol And Its Evolution In The Soy Sauce Fermentation

Soy sauce is the traditional condiment in China, which was tasty and has strong aroma. Now, soy sauce is one of the indispensable condiments in international market. Deoxynivalenol (DON), belonging to trichothecene group B, is frequently detected in wheat, barley and maize. In mycotoxin pollution, DON contamination severity is only second to aflatoxin. An analytical method for determination of DON in soy sauce was developed by solid phase extraction and gas chromatography-mass spectrometry in this paper. The DON variations of raw materials and fermentation progress were also been monitored. All of these will be used to improve the safety of soy sauce and provide theory principle for fermentative regulation.The paper established the determination method of DON in soy sauce by solid phase extraction and gas chromatography-mass spectrometry (SPE-GC-MS). Samples were extracted with acetonitrile-water mixture, and then defatted by petroleum ether. After that, extracts were dried by nitrogen gas stream and cleaned up with SPE C18column. Finally, the residue was derived with TMSI-TMCS before GC-MS. Under the optimal conditions, linear range was 0.025-8.0μg/mL for DON. The limit of detection (LOD) and the limit of quantification (LOQ) were 5 ng/mL and 16.67 ng/mL, respectively. At the spiked levels of 0.05, 1.00 and 8.00μg, the average recoveries were 82%-106%. The proposed method has high yield of extraction, good cleaning efficiency and high sensitivity, which was suitable to detect DON in soy sauce.The established method has been successfully applied to determine DON in 39 commercial soy sauce samples. The results showed that concentration of DON were mainly in the range of 0.005-0.10μg/mL. Overall, the contamination level of DON in Chinese senior high-salt diluted soy sauce and Japanese soy sauce is almost the same. The higher the level of Chinese soy sauce, the higher the concentration of DON is. The concentration of DON is higher in high-salt diluted soy sauce than in low-salt soy sauce, in terms of the same level.The influence of pretreatment of raw materials and fermentation to DON had been illustrated. Results indicated that water treatment could reduce the content of DON significantly (P<0.05), but no obvious effects had been observed after 125℃high temperature treatment. The process of koji could decrease the concentration of DON dramaticlly, which reduced 32.53% in soybean koji and 21.25% in defatted soy flakes koji respectively. The process of soy sauce mash fermentation enhanced the level of DON, but the growth rate varied with raw material. The concentration of DON increased faster in soybean soy sauce than defatted soy flakes soy sauce.The relationship between environment conditions, microbiology, microenvironment of microorganism and DON had been analyzed. The results showed that, there was no correlation between DON level and average temperature, average humidity and degree of severe weather. Negative Correlation between lactic acid bacteria, yeast and DON level had been found, but the correlation was not significant (P>0.05). The DON level had a significant negative correlation with pH (P<0.05) and significant positive correlation with saltless soluble solid material content. However, no significant correlation between DON level and salt concentration had been observed.