菌落总数 英文.doc

Scope and field of application 适用范围 This LI describes routine methods for the detection of Aerobic Bacterial Count in foods. 本操作描述了食品中菌落总数的检验方法 Aerobic Bacterial Count is commonly used as microbiological indicator for contaminant evaluation in food. This method also can be used for evaluate the trend of bacteria increase in food and provide the evidence for hygiene evaluation of the test sample. 菌落总数主要作为判定食品被污染程度的标志，也可以应用这一方法观察细菌在食品中繁殖的动态，以便对被检样品进行卫生学评价时提供依据。 Definitions 定义 Under appropriate condition (media, temperature, time, pH and aerobic culture etc.), the total plate count of forming colonies in 1 ml (g) treated food sample. 食品检样经过处理，在一定条件下培养后（如培养基成分、培养温度和时间、pH、需氧性质等），所得1ml(g)检样中所含菌落的总数。 Principle of the method 原理 Aliquots of decimal dilutions of the sample are mixed with culture medium in Petri dishes. Colonies are counted after incubation at 36±1 OC for 48±2h and the number of microorganisms per gram or ml of the sample is calculated. 吸取样品稀释液，使之在平板内与培养基混合，36±1 OC培养48±2小时，然后计数。 Reagent and media 培养基和试剂 Nutrition Agar 营养琼脂 Procedure 步骤 Preparation of samples 样品准备 Weight 25g(ml) sample in 225ml sterilized buffer liquid, homogenized if necessary. 称25克（毫升）样品到225毫升缓冲液，如有必要将样品打匀。 Plating 接种和倒板 Aliquots of 1ml of the dilutions to be analyzed are placed into Petri dishes. Add about 15ml of liquid cooled to 46±1 OC in water bath) within 15 minutes after preparation of dilutions. Mix carefully inoculum and medium and allow the agar to cool and solidify. Test two parallel plates for each dilution. 吸1ml样品稀释液到平板中，然后倒15毫升营养琼脂（在水浴锅内冷却至46±1 OC)进去, 从样品稀释至倒平板不应 超过15分钟, 小心混匀, 待其凝固. 每个稀释度做两个平皿。 Incubation 培养 Plates are inverted and incubated for 48±2h at 36±1 OC. Do not stack more than 6 plates. 倒放于36±1 OC，培养48±2小时。把板垒成一叠时，一叠不要超过6块。 Reading 读板 After incubation colonies are counted. Examine the plates carefully, if necessary with a lens, to avoid mistaking particle or precipitates for pinpoint colonies. Count the weighted mean of each dilution. 板上所有菌落都数出来，如有必要可用放大镜。算出同稀释度的各平板平