School of Food and Nutritional Sciences, National University of Ireland, University College Cork, College Road, Cork, Ireland.
Int J Food Microbiol. 2012 May 1;156(1):32-43. doi: 10.1016/j.ijfoodmicro.2012.02.019. Epub 2012 Mar 1.
Barley infection with Fusarium species has been a long standing problem for the malting and brewing industries. In this study, we evaluate the impact of Fusarium culmorum infected raw barley on the final malt quality. Barley grains were infected for 5 days at optimum fungal growth conditions. Grains were fully characterized and compared to standard barley grains. Due to fungal infection, germinative energy of infected barley grains decreased by 45%; its water sensitivity increased dramatically, and grains accumulated 199 μg/kg of deoxynivalenol (DON). Barley grains were subsequently malted for 8 days, fully characterized and compared to standard malt grains. Fungal growth behavior was evaluated during malting using a PCR-based assay and mycotoxins were measured using HPLC. Fungal biomass increased in grains, during all stages of malting. Infected malt accumulated 8-times its DON concentration during malting. Kernel ultrastructure was evaluated using scanning electron and confocal laser scanning microscopy. Infected malt grains were characterized by extreme structural proteolytic, (hemi)-cellulolytic and starch deterioration with increased friability and fragmentation. Infected grains had higher protease and β-glucanase activities, lower amylase activity, a greater proportion of free amino and soluble nitrogen, and a lower β-glucan content. Malt loss was over 27% higher in infected malt in comparison to the control. The results of this study revealed that 20% F. culmorum infected barley kernels lead to a significant reduction in malt quality as well as mycotoxin formation.
大麦感染镰刀菌属真菌一直是麦芽和酿造行业长期存在的问题。在这项研究中，我们评估了感染镰刀菌的生大麦对最终麦芽质量的影响。大麦籽粒在最适合真菌生长的条件下感染 5 天。对感染的麦粒进行了全面的特征描述，并与标准大麦籽粒进行了比较。由于真菌感染，感染大麦籽粒的发芽能量下降了 45%；其水分敏感性显著增加，籽粒积累了 199μg/kg 的脱氧雪腐镰刀菌烯醇（DON）。随后，大麦籽粒经过 8 天的麦芽加工，进行了全面的特征描述，并与标准麦芽籽粒进行了比较。在麦芽加工过程中使用基于 PCR 的测定法评估真菌生长行为，并使用 HPLC 测量霉菌毒素。在整个麦芽加工过程中，真菌生物量在籽粒中增加。感染的麦芽在麦芽加工过程中积累了其 DON 浓度的 8 倍。使用扫描电子显微镜和共聚焦激光扫描显微镜评估了颗粒的超微结构。感染的麦芽颗粒的特点是极端的结构蛋白水解、（半）纤维素水解和淀粉降解，脆性和碎片化增加。感染的谷物具有更高的蛋白酶和β-葡聚糖酶活性、更低的淀粉酶活性、更高比例的游离氨基酸和可溶性氮以及更低的β-葡聚糖含量。与对照相比，感染麦芽的麦芽损失高出 27%。这项研究的结果表明，20%的感染镰刀菌属真菌的大麦籽粒会导致麦芽质量显著下降和霉菌毒素形成。
