Study On The Changes Of Ochratoxin A Content And Its Influencing Factors In Xinjiang Wine Brewing Process

The quality control of Ochratoxin A(OTA)in Xinjiang wine was studied in this paper.71 wines were collected from four major regions of Xinjiang.The content of OTA in Xinjiang wines was analyzed by ELISA.The OTA-producing bacteria were screened and their OTA-producing properties were studied.The variation of OTA during wine brewing and storage was monitored to explore the effect of OTA on the quality of Xinjiang wines.It provides a theoretical basis for improving the safety control system of Xinjiang wine industry and reducing OTA content of Xinjiang wine.The main conclusions are as follows:(1)A rapid laboratory ELISA method for the determination of OTA in wine was established.The precision of this method was between 1.35%and 9.75%.The recovery of standard addition was 97.07%-111%.The precision met the requirements and could meet the quantitative analysis of OTA.The OTA content of 71 wine samples from four major regions in Xinjiang was determined by this method.The results showed that the average OTA content of Xinjiang wine was 0.53 ?g/L and the detection rate of OTA was 73.24%.There were significant differences in the average OTA content of red and white wines.There were also differences among wines from four regions in Xinjiang,and among wines from different vineyards from the same region.The average OTA content of Chardonnay wine was only 0.07 ?g/L.(2)Twelve strains of mould were isolated from grape,soil and wine.The OTA production of two strains on the medium was identified and one strain was high-yielding.Molecular biological identification of OTA-producing strain was carried out.The strain with high OTA production is Aspergillus carbonarius and the other is Aspergillus niger.(3)The OTA production performance of Aspergillus carbonarius on wine grapes under different conditions was studied.The results showed that temperature,humidity,inoculation amount,illumination and wine grapes had no damage to the OTA production performance of wine grapes infected by Aspergillus carbonarius to varying degrees.Among them,inoculation amount,temperature and wine grapes had no damage to the OTA production performance of Aspergillus carbonarius on wine grapes.The peak OTA content of mature Chardonnay grape infected by Aspergillus carbonarius was 1.77 ug/L on average,which was higher than that of infected Cabernet Sauvignon grape(2.41 ug/L).(4)To monitor the changes of OTA during wine brewing and the effects of different conditions on OTA content during the storage of standard-added wine.The results showed that the OTA content of white wine decreased significantly in industrial production,from 0.0476 ug/L to 0.0014 ug/L before the end of fermentation,with a decline rate of 89.08%,while that of red wine increased first and then decreased.Grapes infected with Aspergillus carbonarius were used for wine-making experiments.The OTA content of grapes in the process of removing stalks and crushing samples and cold impregnation was higher than 2 ug/L stipulated by the national standard.Grape picking,pressing and cold impregnation are the key control points for controlling OTA in grape wine.During the storage of standard-added grapes,OTA content showed a downward trend.