【作者】 张慧杰；

【导师】 王步军；

【作者基本信息】 中国农业科学院 ， 农产品质量与食物安全， 2014， 博士

【摘要】 真菌毒素是危害食品安全的重要污染物之一，为减少毒素对粮食的污染，同时为受毒素污染的小麦作为口粮食用的风险评估奠定基础，对受赤霉病（Fusarium head bligh，FHB）侵染的小麦中真菌毒素的含量进行了调查，深入研究了赤霉病发生程度与真菌毒素含量之间的相关性，同时对毒素在小麦磨粉、制品加工、贮藏环节的转化机制及降解规律，以及微生物对真菌毒素的清除机制和能力做了研究，主要结论如下：1．2012年对我国四个省份赤霉病小麦真菌毒素含量的调查结果显示，小麦赤霉病的发生通常都会伴随着真菌毒素的污染，同时，赤霉病的发生与毒素的产生受天气条件影响较大。此次调查的发病小麦中污染的主要是脱氧雪腐镰刀菌烯醇（Deoxynivalenol，DON）及其两种衍生物15-乙酰基脱氧雪腐镰刀菌烯醇（15-acetyldeoxynivalenol，15-ADON）、3-乙酰基脱氧雪腐镰刀菌烯醇（3-acetyldeoxynivalenol，3-ADON），以及玉米赤霉烯酮（Zearalenone，ZEN）和杂色曲霉素（Sterigmatocystin，SMC）等。DON超标率达67.11%，ZEN超标率为28.95%，无论是从毒素检出率、超标率还是含量水平，都以A省的污染情况最为严重。2．小麦赤霉病发生程度与DON及其代谢物脱氧雪腐镰刀菌烯醇-3-葡萄糖苷（Deoxynivalenol-3-glucoside，D3G）含量之间存在显著的正相关，线性回归方程分别为YDON=257.78XDI+2315.61（r=0.96）和YD3G=41.81XDI-43.79（r=0.96）。根据回归方程对赤霉病麦中DON和D3G的估测值分别比实测值高59%和低42%，这可能是由于自然条件下赤霉病的发生与产毒受小麦品种、镰刀菌菌种类型以及天气条件等一系列复杂因素的影响，因而难以根据赤霉病的发生情况准确预测真菌毒素的污染水平。3．小麦经磨粉加工后，粗麸皮中DON和D3G的含量分别达小麦籽粒的1.2～2.2倍和2.9～4.4倍，细麸皮中的毒素含量稍低于粗麸皮。与小麦籽粒相比，面粉中DON和D3G的含量分别降低了79～90%和23～39%。磨粉后DON总量降低，而D3G总量升高，粗麸皮、细麸皮、面粉中DON的量分别为小麦籽粒的35%、27%和9%，D3G的量分别为小麦籽粒的77%、58%和37%，这可能是由于DON在磨粉过程的高温和磨辊的摩擦力与剪切力作用下与淀粉结合，转化为D3G。4．经加工制作，馒头和面包中DON的含量比面粉增高了大约1倍，而D3G的含量显著降低，这可能是由于发酵过程中使用的酵母产生的水解酶作用于面粉中的D3G，使其释放出DON，导致馒头和面包中DON含量升高，而D3G含量降低。面条加工过程中，部分毒素向水中发生了迁移，因此熟面条中DON与D3G的含量仅分别约为面粉的50%和20%。5．小麦磨粉后，85%以上的ZEN残留在粗麸皮和细麸皮中，不到15%的ZEN残留在面粉中；粗麸皮和细麸皮中ZEN的含量达小麦籽粒的2倍以上，面粉中ZEN的含量比籽粒降低46～89%。面粉加工成馒头和面包后，ZEN的含量升高近1倍，而加工成面条后因ZEN在煮制过程中部分迁移至水中而降低50%以上。6．粮食状态对贮藏过程中DON和D3G的含量变化有显著影响，而贮藏温度、贮藏时间和包装材料等对DON及D3G的含量没有影响。小麦籽粒在不同的温度条件及包装材料中贮藏时，随着贮藏时间的延长，DON的含量呈降低趋势，贮藏30～90天时DON含量降低幅度最大，平均约为40%；面粉在不同的温度条件及包装材料中贮藏时，DON的含量随着贮藏时间的延长而逐渐升高。小麦籽粒在不同温度条件及不同包装材料贮藏180天后，绝大多数贮藏条件下籽粒D3G的含量有所升高，平均升高约31.76%；面粉在不同的温度条件及包装材料中贮藏时，D3G的含量基本随着贮藏时间的延长逐渐升高。7.乳酸菌对DON有清除作用，其作用机制是物理吸附，而非降解为其他代谢物。戊糖乳杆菌Lp23130、鼠李糖乳杆菌Lr23119和戊糖片球菌Pp23190对液体环境中DON的吸附率都达到了80%以上，脱毒效果明显。热处理及酸处理能够显著提高乳酸菌对DON的吸附能力，热处理后融合魏斯氏菌Wc23465对DON的吸附能力比活菌细胞提高40%以上，碱处理的作用不明显。更多还原

【Abstract】 Mycotoxin is one of the most important contaminants hazarding food safety, to minimize thecontamination on grains, and set a foundation for the safety risk assessment of wheat contaminated withmycotoxins, mycotoxins levels in wheat infected by Fusarium head blight (FHB) were investigated, andthe relationship between severity levels of FHB and mycotoxin levels was studied. In the meanwhile,the transformation mechanism and degradation rules of mycotoxins in wheat milling, wheat-basedproducts processing and storage, and the mechanism and ability of microorganism on mycotoxinsclearing were studied, and the main conclusions are as follows:1. The investigation of mycotoxin levels in wheat infected by FHB in four provinces in2012demonstrated that, the occurrence of FHB was generally accompanied by the contamination ofmycotoxins, and the occurrence of FHB and production of mycotoxins were influenced by weathercondition. Deoxynivalenol (DON),15-acetyldeoxynivalenol (15-ADON),3-acetyldeoxynivalenol(3-ADON), Zearalenone (ZEN) and Sterigmatocystin (SMC) were the main mycotoxins detected in thisinvestigation, and the over-limit rates of DON and ZEN were67.11%and28.95%, respectively. Wheatcollected from A province was the most severely mycotoxin-contaminated in relation to the detectionrate, over-limit rate and contamination levels.2. There were distinct linear correlations between the severity levels of wheat infected by FHBand DON, deoxynivalenol-3-glucoside (D3G) contents, and the linear regression models werecalculated as YDON=257.78XDI+2315.61(r=0.96) and YD3G=41.81XDI-43.79(r=0.96). According to themodels, the predictive contents of DON when compared with the measured contents were overestimatedby59%whereas the predictive contents of D3G when compared with the measured contents wereunderestimated by42%, when predicting mycotoxin levels of wheat infected by FHB. This may beexplained that the occurrence of FHB and production of mycotoxin in the filed influenced by wheatvarieties, Fusarium species, and epidemiological conditions, thus it is difficult to accurately forecastmycotoxin contamination levels.3. Concentrations of DON and D3G were1.2to2.2times and2.9to4.4times higher in bran thanthat in wheat grain，and they were slightly lower in shorts compared to bran. Reductions of79to90%for DON and23to39%for D3G in flour were observed, respectively, compared to wheat grain. Withrespect to wheat grain, the distribution of DON was35%in bran,27%in shorts, and9%in flour, andthe distribution of D3G was77%in bran,58%in shorts, and37%in flour. Milling decreased the totalamount of DON but increased the amount of D3G, which may be explained that, wheat grains weresubjected to extrusion and shear forces of the grinder roll during milling, and the temperature becameincreasingly high as milling time continued, thus modification of mycotoxin structure by interactionwith wheat components may occur, and DON bound to starch.4. DON levels approximately doubled when flour was processed into Chinese steamed bread (CSB)and baked bread, whereas D3G levels were significantly lower. This may be explained by the conversion of D3G to DON under the influence of hydrolase released by yeast during CSB and bakedbread processing. DON and D3G concentrations in noodles decreased after cooking due to leaching ofthe mycotoxins into the cooking water. Retention levels of DON and D3G from flour to cooked Asiannoodles were nearly50%and20%, respectively, of the original levels.5. More than85%of ZEN in wheat remained in bran and shorts and less than15%in flour afterwheat was milled. ZEN concentrations doubled in bran and shorts and decreased by46～89%in wheatflour as compared to that in wheat. ZEN levels approximately doubled when flour was processed intoCSB and baked bread, while decreased about50%when flour was processed into noodles and cookeddue to ZEN leaching into the cooking water.6. Storage might exert significant influences on the concentrations of DON and D3G. As theincreasing of storage time, DON contents in wheat stored under different temperatures and in differentpackaging materials deceased, and DON levels decreased averagely by40%during storage30～90days.DON in wheat flour stored under different temperatures and in different packaging materials increasedgradually as time increasing. After storing for180days, D3G contents in most wheat samples storedunder different temperatures and in different packaging materials increased, which increased averagelyby31.76%; D3G contents in wheat flour samples stored under different temperatures and in differentpackaging materials increased as the storage time extension.7. Lactic acid bacteria has the ability of clearing DON, and the mechanism was physical binding,rather than degrading DON to other metabolites. The binding rate of Lactobacillus pentosus23130,Lactobacillus rhamnosus23119, and Pediococcus pentosaceus23190to DON in liquid were all higherthan80%. Heat treatment and acid treatment were able to increase the binding ability of LAB to DON.After heat treatment, the binding ability to DON of Weissella confuse23465increased by more than40%comparing with viable LAB, while alkali treatment had no significant impact.更多还原