展青霉素是由青霉属、曲霉属、丝衣霉属等真菌产生的一种聚酮类次生代谢产物,广泛存在于果品及其制品中,苹果及其制品是主要污染源,也是人类膳食中展青霉素最主要的来源.展青霉素有各种急性、慢性和细胞水平的危害.国际组织和不少国家均制定了果品及其制品中展青霉素限量.扩展青霉是最主要的产展青霉素真菌,能污染许多种果品及其制品.扩展青霉地域分布甚广,许多国家均分离到了其菌株.作为植物病原菌,扩展青霉往往通过果实上的伤口如受伤部位、害虫为害部位、病菌感染部位,以及果柄、开放的萼筒、皮孔等部位入侵.过熟和长期贮藏的水果更易感染扩展青霉.扩展青霉是一种好寒性霉菌,在0℃生长旺盛.展青霉素生物合成通路约由10步构成,棒曲霉和扩展青霉中展青霉素生物合成基因簇包含相同的15个基因,但两者基因序列差异很大.展青霉素的细胞毒性和遗传毒性归因于其与细胞中亲核物质的高反应活性,主要通过共价键与细胞的亲核物质,特别是与蛋白质和谷胱甘肽的巯基结合,从而发挥毒性、破坏染色体和致突变.在其反应通路中,1个展青霉素分子最多可与3个谷胱甘肽分子反应.采前措施、采后处理和贮藏条件对控制展青霉素污染及其产毒真菌至关重要.使用化学杀菌剂是重要的防控策略,但过度使用杀菌剂会导致抗性菌株出现.使用"低风险杀菌剂"则能降低产生抗药性的风险.生物防治是化学防治的替代方法或补充,可减少甚至避免使用杀菌剂.清洗、分选、整理等加工工艺有助于消减水果制品中的展青霉素污染.液液萃取和固相萃取是果品及其制品中展青霉素的经典提取方法,但液液萃取成本高、耗时、不适于固体样品.近年来,又研究建立了分散液液微萃取、盐析旋涡辅助液液微萃取、基质固相分散萃取、QuEChERS等提取方法.展青霉素通常用配紫外检测器或二极管阵列检测器的液相色谱仪进行定量,采用液相色谱串联质谱、气相色谱串联质谱等仪器进行定性.另外,PCR具有快速、专一的特点,可用于对潜在的产展青霉素真菌进行早期检测.%Patulin is a secondary metabolite of polyketide lactone mainly produced by species ofPenicillium, Aspergillus, and Byssochylamys. It was found as a contaminant in many fruits and fruit products, the major sources of contamination are apples and apple products, which are also the most important source of patulin in human diet. Patulin has various acute and chronic effects and others at the cellular level. Today, international organizations (Codex Alimentarius Commission and European Union) and many countries across the world have set maximum levels of patulin content in fruit and fruits products. Among the different genera, the most important patulin producer isP. expansum, it can contaminate a number of fruits and fruit products, and produce mycotoxin patulin. P. expansum distributes very extensively, its strains have been isolated from many countries. As a plant pathogen,P. expansum penetrates fruits typically through wounds or injuries produced during harvest and handling, it can also penetrate through stem end, open calyx tube and lenticels of fruits, and infection sites of other primary fruit pathogens. Overmature or long-stored fruits are more susceptible toP. expansum infection. P. expansum is a psychrophile, its growth is quite strong at 0℃. The biosynthetic pathway of patulin consists of approximately 10 steps. It has been clarified that both of the patulin biosynthetic gene cluster fromP. expansum and that fromA. clavatus composed of the same 15 genes, but their gene sequences differed greatly. The genotoxic and cytotoxic properties of patulin are due to its high reactivity to cellular nucleophiles. Patulin is believed to exert its toxic, chromosome-damaging, and mutagenic activity mainly by covalent binding to cellular nucleophiles, in particular to the thiol groups of proteins and glutathione (GSH). In the major reaction pathways, up to three molecules of glutathione can bind to one molecule patulin. To control the contamination of patulin and the growth of moulds producing it, pre-harvest measures, post-harvest treatments, and storage conditions deserve special attention. The use of chemical fungicides is an important strategy, but the overuse of fungicides will lead to the emergence of fungicide-resistant strains. Because their way of action reduces the risk of resistant population emergence, "low risk fungicides" are more suitable and efficient. Using biocontrol agents are alternative or complementary treatments that permit to decrease fungicide doses or even avoid the use of chemicals. Some stages of manufacturing process (such as washing, sorting and trimming) are highly efficient in reducing the levels of patulin in fruit products. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are classical methods to extract patulin in fruits and fruit products. However, LLE is expensive, time consuming, and unsuitable for the treatment of solid sample. In the last years, some other extraction measures have been studied and developed, including DLLME, IL-DLLME, BS-DLLME, salting out-VALLME, MSPD, and QuEChERS. LC-UV or LC-DAD procedure is routinely used for quantitative determination of patulin, and methods to confirm the presence of patulin usually include more specific detection techniques such as LC-MS/MS and GC-MS/MS. PCR method is a fast and specific method of early detecting the potential patulin producing fungi.
展开▼
