生物发光快速测定生乳菌落总数的方法

为消除利用ATP生物发光法测定生乳菌落总数时非细菌ATP对测定结果的干扰,建立了一种样品前处理方法。利用ATP生物发光法对经过前处理的生乳样品进行检测,结果表明,生乳菌落总数对数值与生乳细菌ATP发光对数值呈现较好的线性关系(R2=0.982),相关程度为显著相关(P<0.01),说明该前处理方法能够有效排除非细菌ATP的干扰,有利于提高ATP生物发光法定量测定生乳菌落总数准确性。     

一种发酵乳中乳酸菌总数快速检测技术的研究

以还原法为理论基础,开发并建立一种应用于发酵乳饮料成品乳酸菌数指标的快速检测方法。本方法应用仪器记录了样品加入反应试剂后的颜色变化(RGB),通过数理统计分析,采用斜率法,以R值斜率表示样品颜色的变化速度。本研究对发酵乳样品进行了预处理,以符合刃天青还原法的反应条件。以GB 4789.35《食品安全国家标准食品微生物学检验乳酸菌检验》为标准,建立了R值斜率与乳酸菌菌落总数之间的标准方程,经验证本方法检测结果与GB 4789.35《食品安全国家标准食品微生物学检验乳酸菌检验》检测结果无显著差异。与现有标准方法相比,在时效性、运营成本等方面具有较大优势。     

流式细胞术快速检测生乳中细菌总数

研究了应用流式细胞术检测生乳中细菌总数的方法。实验对生乳采用酶法消化蛋白质颗粒、高速离心脱脂的方式来消除大颗粒物质对流式检测的影响。并对菌体进行热处理,使其能被荧光性染料碘化丙锭染色。经过前处理的乳液进入流式细胞仪分析、计数。结果表明,流式细胞术与平皿菌落计数法呈正的直线相关(P<0.01),相关程度为显著相关(r=0.9360)。该方法极大的缩短了检测时间,检出限为104/mL。     

ATP生物发光法快速测定生乳中微生物总数的研究

对ATP生物发光法应用于生乳中微生物检测进行了初步摸索,确定了加体细胞裂解液次数为三次;乳样最佳稀释倍数为20倍;用ATP生物发光法对大批乳样进行检测,同时用国标法进行了平皿菌落培养,结果显示,乳中微生物总数对数与光值对数呈正的直线相关(r=0.9485),相关程度为显著相关(P<0.001),二者回归方程为Y=1.0496x 2.4.     

氧含量对还原法检测原料乳细菌总数的影响

以还原法理论为基础,以刃天青作为氧化还原试剂,研制原料乳细菌总数快速检测仪器.原料乳中一些成分影响刃天青的颜色变化速度,干扰测定结果.对溶解氧的影响程度进行了判定,结果表明其影响程度较大,不容忽视.     

新乡市生乳中菌落总数和金黄色葡萄球菌及β-内酰胺酶调查

目的了解新乡市规模化奶牛养殖场生乳中菌落总数、金黄色葡萄球菌和β-内酰胺酶的基线数据,为生乳安全性风险评估及国家标准更新提供资料。方法以新乡市3家规模化奶牛养殖场(A、B、C场)为观测基地,2016年5月—2017年4月每月采集2家生乳样品各29份和1份混合样品。分别按照GB 4789.2—2010《食品安全国家标准食品微生物学检验菌落总数测定》和GB 4789.10—2010《食品安全国家标准食品微生物学检验金黄色葡萄球菌检验》测定菌落总数和金黄色葡萄球菌,胶体金法测β-内酰胺酶残留。结果 3家奶牛养殖场单份样品菌落总数的中位数分别为13 000、4 450、130 000 CFU/ml,明显低于GB 19301—2010《食品安全国家标准生乳》中的限量(2×10~6CFU/ml),差异有统计学意义(P0.01),3家奶牛养殖场的菌落总数之间差异有统计学意义(P0.05)。各奶牛养殖场单份样品的菌落总数与混合样品比较,仅B场差异有统计学意义(P0.05)。7~8月菌落总数较高。3家奶牛养殖场样品中金黄色葡萄球菌检出率分别为1.1%(4/360)、16.7%(30/180)和0.0%(0/180),计数结果为50~42 000 CFU/ml。3家奶牛养殖场的所有样品中均检出β-内酰胺酶,检出率为6.1%~10.6%。结论 GB 19301—2010生乳菌落总数限量远高于新乡市实际情况,建议修订标准;个别奶牛养殖场生乳中存在一定程度的金黄色葡萄球菌污染,需加强监管;筛查出的β-内酰胺酶需进一步鉴定其来源,同时要加强对β-内酰胺酶检测方法的研究。     

平板显色法同时计数生乳中的大肠菌群和菌落总数

为提高大肠菌群和菌落总数的计数效率，选用2-硝基苯基-β-D-吡喃半乳糖苷作为平板培养基中的显色底物，利用大肠菌群lacZ基因编码的β-半乳糖苷酶将其分解产生黄色化合物，使得大肠菌群菌落区分于其他菌株，实现大肠菌群和菌落总数的同时计数，优化该培养基配方，评估培养基的特异性、准确性以及在生乳中的应用效果。最终确定该培养基配方：胰蛋白胨12.5 g/L、酵母浸粉2.5 g/L、磷酸氢二钾2.75 g/L、磷酸二氢钾1.75 g/L、氯化钠5.0 g/L、琼脂15.0 g/L，2-硝基苯基-β-D-吡喃半乳糖苷0.1 g/L，pH值为7.0。在此基础上，添加0.05 g/L异丙基-β-D-硫代半乳糖苷或2.0 g/L乳糖均能够增强菌落显色效果，而葡萄糖则会抑制黄色化合物生成。特异性实验中，仅大肠菌群菌落颜色呈黄橙色，其他菌株则呈乳白色。在生乳样本中，该培养基与国标方法对于大肠菌群和菌落总数的计数结果基本一致。因此，该复合显色培养基能够大大提高大肠菌群和菌落总数的计数效率，降低检测成本，为生乳的卫生指标检测提供一种可行方案。     

对GB 19301-2010《生乳》中蛋白质和菌落总数的指标验证和建议

目的完成"GB 19301-2010《生乳》跟踪评价项目"。方法 对陕西省7家乳企使用的原料生乳进行了7次采样,样本量为111份,其中夏季51份,冬季60份,采用GB 5009.5和GB 4789.2分别对样本中的蛋白质和菌落总数进行了测定。结果 所有样本的蛋白质含量都是合格的,冬季、夏季生乳蛋白质含量分别均不低于3.6 g/100 g、2.8 g/100 g,其中16%的夏季生羊乳蛋白质检测值为2.8 g/100 g,是"生乳蛋白质指标"的界限值。所有样本中,只有夏季4份样本的菌落总数超过了2.0×106CFU/m L的指标界限值,冬季、夏季生乳菌落总数平均值分别低于1.0×105CFU/m L、1.0×106CFU/m L。结论 GB 19301规定的生乳蛋白质、菌落总数指标值是科学合理的,建议将夏季生羊乳的蛋白质指标修订为≥2.6 g/100 g。     

应用流式细胞技术快速检测液态商品中的细菌总数

建立应用流式细胞技术(flowcytometry,FCM)快速检测液态商品牛奶、果汁中的细菌总数的方法。采用膜过滤、离心技术对果汁样品进行前处理,去除影响FCM检测的基质颗粒,使样品达到FCM可检测状态,检测限达到101CFU/mL数量级。对液态商品牛奶进行重复性和验证实验,检测结果经Q检验法和方差分析,在一定范围浓度下,FCM检测液态商品中的细菌总数与平板法成线性相关。FCM是一种比平板法检测细菌总数更加快速、准确的方法。     

电阻抗法快速检测鲜牛奶中细菌总数

采用阻抗法监控鲜牛奶中的细菌总数,建立了利用阻抗法检测供港鲜牛奶中细菌总数的标准曲线及计算方程。同传统平板计数方法相比,阻抗法检测鲜牛奶中细菌总数不仅快速、准确,且操作简便。     

Assessment of the application of an automated electronic milk analyzer for the enumeration of total bacteria in raw goat milk

Automated electronic milk analyzers for rapid enumeration of total bacteria counts (TBC) are widely used for raw milk testing by many analytical laboratories worldwide. In Ontario, Canada, Bactoscan flow cytometry (BsnFC; Foss Electric, Hillerød, Denmark) is the official anchor method for TBC in raw cow milk. Penalties are levied at the BsnFC equivalent level of 50,000 cfu/mL, the standard plate count (SPC) regulatory limit. This study was conducted to assess the BsnFC for TBC in raw goat milk, to determine the mathematical relationship between the SPC and BsnFC methods, and to identify probable reasons for the difference in the SPC:BsnFC equivalents for goat and cow milks. Test procedures were conducted according to International Dairy Federation Bulletin guidelines. Approximately 115 farm bulk tank milk samples per month were tested for inhibitor residues, SPC, BsnFC, psychrotrophic bacteria count, composition (fat, protein, lactose, lactose and other solids, and freezing point), and somatic cell count from March 2009 to February 2010. Data analysis of the results for the samples tested indicated that the BsnFC method would be a good alternative to the SPC method, providing accurate and more precise results with a faster turnaround time. Although a linear regression model showed good correlation and prediction, tests for linearity indicated that the relationship was linear only beyond log 4.1 SPC. The logistic growth curve best modeled the relationship between the SPC and BsnFC for the entire sample population. The BsnFC equivalent to the SPC 50,000 cfu/mL regulatory limit was estimated to be 321,000 individual bacteria count (ibc)/mL. This estimate differs considerably from the BsnFC equivalent for cow milk (121,000 ibc/mL). Because of the low frequency of bulk tank milk pickups at goat farms, 78.5% of the samples had their oldest milking in the tank to be 6.5 to 9.0 d old when tested, compared with the cow milk samples, which had their oldest milking at 4 d old when tested. This may be one of the major factors contributing to the larger goat milk BsnFC equivalence. Correlations and interactions between various test results were also discussed to further understand differences between the 2 methods for goat and cow milks.     

乳与乳制品中细菌总数的检测技术

对各种常用检测乳与乳制品中细菌总数方法的原理、操作、优缺点及应用作了一个较详细的介绍，并对快速检测技术的要求进行了总结。     

贮存时间对酿造酱油中菌落总数的影响

为了研究贮存时间对酿造酱油中菌落总数的影响,检测了同批酱油在不同贮存时间条件下的菌落总数变化.经试验发现,酱油中的菌落总数随着贮存时间的延长呈现降低趋势.该试验旨在为酿造调味品的质量安全性提供一些参考.     

不同乳酸菌在毛酸浆发酵中的特性研究

为比较嗜热链球菌（Lactobacillus plantarum）（L1）、保加利亚乳杆菌（Lactobacillus bulgaricus）（L2）、瑞士乳杆菌（Lactobacillus helveticus）（L3）、植物乳杆菌（Lactobacillus plantarum）（L4）、短乳杆菌（Lactobacillus brevis）（L5）和干酪乳杆菌（Lacbobacillus casei）（L6）在毛酸浆发酵中的特性,研究发酵过程中总酸含量、活菌数和色泽的变化。结果表明,发酵过程中,6种乳酸菌活菌数均能维持在8.0 lg（CFU/mL）以上,生长良好,其中乳酸菌L4、L5和L6在毛酸浆中产酸能力较好,最高总酸含量分别为11.85 g/L、10.95 g/L、10.45 g/L,并均能很好地保持发酵液本身的颜色,色差值均＜54.51;当乳酸菌L4、L5和L6按不同接种比例复合发酵毛酸浆果汁时,各处理间活菌数和发酵液颜色变化基本一致,当乳酸菌L4∶L6为3∶2（V/V）进行复合发酵时,最终所得毛酸浆发酵液的总酸含量（17.91 g/L）最高。     

大肠菌群测量审核结果与分析

目的通过测量审核提升食品中大肠菌群检测能力和实验室质量管理水平。方法以测量审核作业指导书、GB 4789.3-2016《食品安全国家标准食品微生物学检验大肠菌群计数》第二法平板计数法为依据,采用平板计数法、PetrifilmTM大肠菌群测试片法同时检测样品。运用配对t检验法评价2种不同方法对乳粉中大肠菌群计数结果一致性的影响。结果平板计数法与PetrifilmTM大肠菌群测试片法检测结果无明显差异,样品|Z|2,结果满意。结论可根据实际情况来选择相应方法检测食品中大肠菌群以提高检测效率和质量。     

Effect of mastitis-related bacteria on total bacterial count of bulk milk supplies

Seven hundred and fifty-four bulk milk samples from a total of 9,066 tested by the Aberdeen and District Milk Marketing Board in 1984 had total bacterial counts greater than 45,000 per ml. Of the failed samples, 43.8% had more mastitis-related bacteria present than non-mastitis types. More than a quarter of the failed samples had almost pure cultures of Streptococcus agalactiae, Str. dysgalactiae, Str. uberis, Staphylococcus aureus or coagulase-negative staphylococci. No relation was found between the failed samples resulting from subclinical mastitis infections and the somatic cell count of the bulk milk. Seventy-five per cent of the financial penalties imposed on producers were attributable to mastitis bacteria in bulk milk samples .     

Evaluation of calf milk pasteurization systems on 6 Pennsylvania dairy farms

Waste milk has been fed to calves for many years, but concerns with bacterial contamination as well as possible transmission of diseases have discouraged widespread use of this feed. Pasteurization of waste milk is one option to reduce management risk while utilizing a valuable, low-cost, liquid feed source for calves. However, many farms currently pasteurizing waste milk lack a system to adequately monitor the efficiency of the process. A study was carried out to evaluate 6 on-farm pasteurization systems, including high-temperature, short-time pasteurizers and low-temperature, batch pasteurizers. Milk samples were taken pre- and postpasteurization as well as from the calf buckets and immediately frozen for later bacterial culture. Samples were collected twice daily for 15 d. Milk samples were examined for standard plate count (SPC), coagulase-negative staphylococci count, environmental streptococci count, coliform count, gram-negative noncoliform count, Streptococcus agalactiae count, and Staphylococcus aureus count. Before pasteurization, 68% of the samples had SPC <20,000 cfu/mL, and 39% of samples contained <100 cfu/mL of coliform bacteria. After pasteurization, 96% of samples had SPC <20,000 cfu/mL, and 92% had coliform counts <100 cfu/mL. Bacteria counts were significantly reduced by pasteurization, and pasteurized milk contained acceptable numbers of bacteria in >90% of samples. These results indicate that pasteurization can be very effective in lowering bacterial contamination of milk. However, bacteria numbers significantly increased after pasteurization and, in some cases, bacteria counts in milk fed to calves were similar to prepasteurization levels. Milk handling after pasteurization was identified as an important issue on the farms studied.     

Rapid estimation of psychrotrophic and proteolytic bacterial counts from total bacterial counts in cooled raw milk

Cooled raw bulk milk samples were examined for total bacterial count after 3 days at 30°C, and the numbers of psychrotrophs and proteolytic psychrotrophs after 10 days at 7°C. Positive correlations were found between the total bacterial count and the numbers of psychrotrophs, enumerated on standard plate count (SPC) agar (r = 0.88, n = 65), and between the numbers of psychrotrophs counted on SPC agar and on milk agar, respectively (r = 0.89, n = 59). Only 30.4% of the bacteria were psychrotrophs but the regression shows that the percentage of psychrotrophs increases when the total bacterial count rises. On average only small differences were found between the counts of psychrotrophs on SPC agar and milk agar, suggesting that in most samples the same organisms were probably enumerated on both media. The numbers of proteolytic bacteria were less well correlated with the numbers of psychrotrophs (r = 0.65, n = 56), as wide variations occurred between the samples. It is suggested that the total bacterial count at 30°C can be a useful estimate of the number of psychrotrophs.