Research On The Detection And Control Of Citrinin In Rice Wine

Citrinin, a secondary metabolite of fungus with nephrotoxicity and teratogenicity, is mainly produced by several filamentous fungi of the genera Penicillium, Aspergillus and Monascusby. Rice wine, as a kind of traditional food, uses wheat qu as saccharification and fermentation agent for brewing. There are many different kinds of germs in wheat qu, especially Aspergillus, which may result in the final wine being easily contaminated by citrinin. This paper mainly studied the method of extraction and detection of citrinin in rice wine, the effect of several materials on the adsorption of citrinin, the source of citrinin in rice wine, and also made a preliminary exploration on the control of citrinin in the process of brewing. The main conclusions are as follows:The wine sample after adjusting the pH to 2.5 is extracted by toluene: methanol(10:l, v:v) at liquid-liquid ratio of 1:2. After being extracted by ultrasonic wave for 20 min, the isolated organic phase is merged for rotatory evaporation to dryness and then reconstitutes with methanol for high performance liquid fluorescence detection. The column was Shimadzu Hypersil ODS2, (5 μm,250 mm×4.6 mm). The mobile phase composition was V(acetonitrile):V(H2O)=40:60(pH 2.5), fluorescence detector:λex=331 nm, λem=500nm. The recovery rate of using this method to extract and detect citrinin in rice wine is 93.06%.30 different brands of rice wine were detected, and the highest contents of citrinin reached 0.4653μg/mL.The citrinin in rice wine can be effectively adsorbed by Ca-alginate-activated carbon bean. The single-factor analysis and response surface analysis of adsorbent dosage, adsorption time and temperature were carried out.The results showed that the adsorption rate can reach a maximum of 78.23% at adsorbent dosage of 0.81 g, adsorption time of 3.10 h and adsorption temperature of 27.32℃ in 100 mL rice wine. Further research of the effect on the quality of wine showed that the alcohol content, pH, color, total sugars and amino nitrogen had no significant impact during the adsorption process. Ca-alginate-activated carbon bean is a safe and effective adsorbent, and can be used in rice wine to control the content of citrinin.Aspergillus flavus and Aspergillus which isolated from wheat qu have strong ability of producing citrinin. After cultured for 5 days, the content of citrinin in PDW and MSG medium inoculated with Aspergillus flavus is 6.40±0.26μg/mL,23.42±0.86μg/mL, respectively, and Aspergillus oryzae is 3.05±0.23μg/mL,11.46±1.32μg/mL. Water-soluble chitosan has inhibitory effect on these two fungi, the MIC of chitosan against Aspergillus flavus is 1.0%, while Aspergillus oryzae 0.5%. The MBC of chitosan against these two fungi is 4%. After adding 0.2%,0.5% chitosan for brewing, the final citrinin content reduced by 47.32%,58.82%, respectively. The further studies on the change of other physical and chemical indicators in the brewing process showed that being treated by 0.2% chitosan has a smaller effect on the quality of rice wine. On the 20th day of fermentation, the content of alcohol degree, total sugar, reducing sugar, and pH in the wine were 13.5 g/100g,11.58 g/L,10.26 g/L and 4.57, while that in control group were 14 g/100g, 10.82 g/L,9.24 g/L and 4.27 respectively. Flavor substances in rice wine were detected by head space-gas chromatography-mass spectrometry, and the same substances were found in chitosan treatment group and the control group. The further quantitative determination of n-butanol, isoamyl alcohol and phenylethyl alcohol showed that adding 0.2% chitosan for brewing had a promiting effect of generating n-butanol and isoamyl alcohol. On the 20th day of fermentation, the content of n-butanol and isoamyl alcohol in the wine were 0.99 mg/L and 77.54 mg/L, while that in control group were 0.95 mg/L and 72.54 mg/L respectively。...