不同储存温度下鸡蛋表面和内部真菌动态研究

Study on the Dynamics of Fungi on the Surface and Inside of Eggs at Different Storage Temperatures

试验旨在通过检测商品鸡蛋在不同储存温度和时间蛋壳表面和内容物中真菌的数量和类别,了解真菌污染的动态变化,为改善鸡蛋储存条件并延长保鲜期提供参考。采取冀南某养殖小区不同养鸡场180枚新鲜鸡蛋,分别在25和4℃无菌环境下储存42 d,每7 d进行一次蛋壳和蛋液的真菌数量和类别检测。真菌数量检测参照国家标准GB 4789.15-2016;真菌种类鉴定采用形态观察结合rDNA-ITS序列分析法。试验结果显示,鸡蛋内外真菌检出率和数量均随储存时间延长而显著增长;蛋壳比蛋液真菌检出时间早、检出率高,蛋液处理组真菌检出率在21~28 d快速增长;在相同时间点,25℃处理组真菌数量(菌落数)显著高于4℃处理组,蛋壳处理组显著高于蛋液处理组(P<0.05);在蛋壳和蛋液中共分离鉴定了168个真菌菌株,分属于18个种(属),其中优势属为青霉属(Penicillium sp.),优势种为草酸青霉(Penicillium oxalicum);蛋液与蛋壳处理组的总菌落数和分离株数分别呈显著(P<0.05)和极显著相关(P<0.01)。综上,在采样养殖场环境下,鸡蛋的真菌污染普遍存在;样品真菌检出率和菌落总数均随储存时间延长呈明显上升趋势;冷藏(4℃)是防止鸡蛋真菌污染扩展的有效方法;蛋液的真菌污染可能主要来自蛋壳表面的真菌污染;样品鸡蛋污染真菌的多样性较高,其优势种属多为环境常在菌,但污染真菌中也有部分致病或产毒种类。

By detecting the amounts and kinds of fungi in surface and content of the table eggs at different storage temperatures and time,the dynamic changes of fungal contamination were understood,which provided reference for improving the storage conditions and prolonging the preservation period of eggs.180 fresh eggs from several chicken farms in Southern Hebei were stored respectively at 25 and 4℃for 42 days.The amount and kind of fungi in eggs were detected every 7 days.The national standard GB 4789.15-2016 was consulted for the fungal count detection.The fungi species were identified by morphological observation combined with rDNA-ITS sequence analysis.The results showed that the detection rate and quantity of fungi in eggs increased significantly with time.The detection time of fungi in eggshell was earlier and the detection rate was higher than that in egg liquid,and the detection rate of fungi in egg liquid increased rapidly from 21 to 28 days.At the same time point,the amount of fungi(colony number)of 25℃condition was significantly higher than that of 4℃(P<0.05).168 fungal strains were isolated and identified,belonging to 18 species(genera),of which the dominant genus was Penicillium sp.,and the dominant species was Penicillium oxalicum.There was significant correlation between eggshell and egg liquid in the total number of colonies(P<0.05)and the number of isolated strains(P<0.01).In conclusion,fungal contamination of eggs was frequent in the environment of the farms sampled,the fungal detection rate and total number of colonies in samples increased significantly along with the storage time,refrigeration(4℃)was an effective method to prevent spread of the fungi in eggs,the fungal contamination of egg liquid might mainly come from that of the eggshell surface,the diversity of fungi in egg samples was high,and most of the dominant species(genera)were common in the environment,but some pathogenic or toxigenic kinds were also found in the contaminating fungi.