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ID:59392509
大小:2.97 MB
页数:30页
时间:2020-05-29
《侦测食品中之微生物.doc》由会员上传分享,免费在线阅读,更多相关内容在工程资料-天天文库。
1、DetectingMOinFoodsAims1.Tounderstandthetraditionalmethodsandrapidmethodsfordetectingmicroorganismsinfoods2.Tounderstandtheprinciples,advantages,limits,andapplicationforeachdetectingmethod3.Tounderstandtheissuesofthemetabolicallyinjuredmicroorganisms(MO)andthevia
2、blebutnon-cultivableMO(VBNC)Outline1.Homogenizationmethods2.Standardplatecount(SPC)3.Spiralplatecount4.Membranefiltrationmethods5.Microscopeplatecount6.Petrifilm7.MPN8.Directmicroscopiccount9.Dyereductiontest10.DetectingMOonsurfaces11.Metabolicallyinjuredmicroor
3、ganisms12.Viablebutnon-cultivablemicroorganisms(VBNC)13.Phisical,chemical,molecular,andimmunologicalmethods§均質法(Homogenizationmethods)WaringBlendorvs.StomacherWaringBlendor為廣泛使用方法(除了有刺、尖銳之食品外),優點:1.免於清洗、殺菌操作2.正常操作時間內(≦2min)不生熱,不影響菌數3.噪音低4.均質液易貯藏5.不會引起食品組織(細胞)之高度
4、破碎,容易吸取樣品,而且,降低來自食品組成份之干擾(尤其在非SPC偵測法)9-1§標準平板法〔StandardPlateCount(SPC)〕,活菌數1.計數:25~250cfu(或30~300cfu)2.假設:(1)各培養皿中之菌落源自單一菌體。(2)所提供之條件(營養、溫度等)足以使食物中所有菌生長,而產生菌落。3.方法:(1)混稀法(pourplatecount)(2)塗抹法(spreadplatecount,surfaceplatecount)塗抹法優缺點(與混稀法比較)(a)無熱傷害(b)有利好氧菌快速生長(
5、c)容易計數(d)可自動化操作(e)菌落易分離§螺旋平板法(Spiralplatecount)1.所用培養基、平板、稀釋液、吸管均較少2.快速,50~60plate/h3.易受食物顆粒阻塞1.設備費用高9-2§膜濾法(Membranefiltrationmethods)l適用於水、飲料、或空氣等菌數低者l可能需預濾,以去除食物顆粒,或添加酵素、介面活性劑等以利過濾1.直接螢光過濾法(DirectEpifluorescentFilterTechnique,DEFT)留於濾膜上之菌株,以螢光染劑,如acridineoran
6、ge染色,再以螢光顯微鏡計數操作:Foodhomogenate↓5μmnylonfilter↓filtrate,+2mlTritonX-100&0.5mlTrypsin↓0.6μmNucleoporepolycarbonatefilter↓filterstainedwithacrineorange↓count2.Microcolony-DEFTFiltrationlMicrocolonymethod:Sample→filter→plate,incubatefor3~6h→microscopiccountlMicroco
7、lony-DEFTmethod:(nucleoporemembrane)Sample→filter→plate,andincubated→acridineorangestain→fluorescencemicroscopiccount9-33.疏水性格膜過濾法(HydrophobicGridMembraneFiltration,HGMF)(1)1600waxgrid/membrane(2)減少稀釋操作(2)已有分析項目totalcoliformsfecalcoliformsSalmonellaeE.coliO157:H
8、7§顯微鏡菌落計數(Microscopecolonycounts)0.1mlsample+2mlnutrientagar→mix→spreadovera4cm2areaonaglassslide→incubated3~8hinawarmmoistchamber→airdried,flame-fixed,stainforcountw
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