冲调谷物制品污染菌相的调查分析

Investigation and analysis of contaminated microflora in reconstituted cereal products

目的研究冲调谷物制品中的微生物污染情况及主要污染菌种类,探讨传统形态学鉴定法、分子生物学鉴定法和基质辅助激光解吸电离飞行时间质谱法(matrix assisted laser desorption ionization time off light mass spectrometry, MALDI-TOF-MS)鉴定微生物的适用效果。方法以流通领域抽取的冲调谷物制品为研究对象,采用GB 4789.2—2016《食品安全国家标准食品微生物学检验菌落总数测定》和GB 4789.15—2016《食品安全国家标准食品微生物学检验霉菌和酵母计数》对其菌落总数和霉菌进行计数,分离纯化不合格产品中的污染菌,以MALDI-TOF-MS结合16SrRNA序列分析方法对污染细菌进行鉴定,以MALDI-TOF-MS方法结合传统形态学鉴定方法对污染霉菌进行鉴定。结果 110批次冲调谷物制品的菌落总数不合格率为3.6%,霉菌计数不合格率为4.5%;分离得到的159株细菌可归于28个种,芽孢杆菌属(Bacillus)细菌为优势菌群,分离频率达到71.7%;分离得到的98株霉菌可划分至25个属,青霉属(Penicillium)和曲霉属(Aspergillus)为优势菌群,分离频率分别为12.4%和7.1%。污染菌中含有克罗诺杆菌(Cronobacter)等条件致病细菌和多种常见产毒真菌,存在一定的食品安全风险。结论冲调谷物制品的微生物污染情况较为严重。生产企业应重视生产加工过程中的微生物污染问题,相关部门应加强对冲调谷物制品的食品安全监管。MALDI-TOF-MS方法在鉴定细菌时具有较大优势,受限于真菌数据库的不足,其用于食品来源霉菌鉴定的准确率有待提高。

Objective To understand the microbial contamination and main types of contaminating microorganisms in the reconstituted cereal products,and explore the applicable effects of traditional morphological identification,molecular biology identification and matrix assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS) in identifying microorganisms.Methods The total bacterial colonies and moulds of the reconstituted cereal products extracted from the circulation field were detected according to GB 4789.2—2016 National food safety standard-Food microbiological examination-Aerobic plate count and GB 4789.15—2016 National food safety standard-Food microbiological examination-Enumeration of moulds and yeasts.The contaminated microorganisms in the unqualified products were isolated and purified,bacteria were identified by MALDI-TOF-MS and sequence analysis of 16 S rRNA,moulds were identified by MALDI-TOF-MS and traditional morphological identification methods.Results The unqualified rate of the total bacterial colonies of 110 batches of reconstituted cereal products was 3.6%,and the unqualified rate of moulds count was 4.5%;the isolated 159 strains of bacteria could be classified into 28 species,among which Bacillus were the dominant bacterial group,with the isolation frequency at 71.7%;98 strains of moulds could be classified into 25 genus,among which Penicillium and Aspergillus were the dominant mould groups,with the isolation frequency 12.4% and 7.1%.The contaminated bacteria contained some conditional pathogenic bacteria such as Cronobacter and common toxin-producing fungi,which posed a certain food safety risks.Conclusion The microbial contamination of the reconstituted cereal products is serious.Production enterprises should pay attention to the microbial pollution in the production and processing process,and relevant departments should strengthen the food safety supervision of the reconstituted cereal products.MALDI-TOF-MS method has great advantages in identifying bacteria,but due to the deficiency of fungal database,its accuracy in identifying molds from food sources needs to be improved.