School of Chemistry and Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom.
Anal Chem. 2012 Jul 17;84(14):5951-8. doi: 10.1021/ac300582d. Epub 2012 Jun 13.
Microbiological safety is one of the cornerstones of quality control in the food industry. Identification and quantification of spoilage bacteria in pasteurized milk and meat in the food industry currently relies on accurate and sensitive yet time-consuming techniques which give retrospective values for microbial contamination. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), a proven technique in the field of protein and peptide identification and quantification, may be a valuable alternative approach for the rapid assessment of microbial spoilage. In this work we therefore developed MALDI-TOF-MS as a novel analytical approach for the assessment of food that when combined with chemometrics allows for the detection and quantification of milk and pork meat spoilage bacteria. To develop this approach, natural spoilage of pasteurized milk and raw pork meat samples incubated at 15 °C and at room temperature, respectively, was conducted. Samples were collected for MALDI-TOF-MS analysis (which took 4 min per sample) at regular time intervals throughout the spoilage process, with concurrent calculation and documentation of reference total viable counts using traditional microbiological methods (these took 2 days). Multivariate statistical techniques such as principal component discriminant function analysis, canonical correlation analysis, partial least-squares (PLS) regression, and kernel PLS (KPLS) were used to analyze the data. The results from MALDI-TOF-MS combined with PLS or KPLS gave excellent bacterial quantification results for both milk and meat spoilage, and typical root mean squared errors for prediction in test spectra were between 0.53 and 0.79 log unit. Overall these novel findings strongly indicate that MALDI-TOF-MS when combined with chemometric approaches would be a useful adjunct for routine use in the milk and meat industry as a fast and accurate viable bacterial detection and quantification method.
微生物安全是食品工业质量控制的基石之一。在食品工业中，巴氏杀菌牛奶和肉类中腐败菌的鉴定和定量目前依赖于准确、敏感但耗时的技术，这些技术提供微生物污染的回溯值。基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF-MS）是一种在蛋白质和肽鉴定和定量领域得到验证的技术，可能是快速评估微生物腐败的一种有价值的替代方法。在这项工作中，我们因此开发了 MALDI-TOF-MS 作为一种新的分析方法，用于评估食品，当与化学计量学结合使用时，可以检测和定量牛奶和猪肉腐败菌。为了开发这种方法，对巴氏杀菌牛奶和生猪肉样品进行了自然腐败，分别在 15°C 和室温下孵育。在腐败过程中定期收集样品进行 MALDI-TOF-MS 分析（每个样品需要 4 分钟），同时使用传统微生物方法计算和记录参考总活菌计数（这些方法需要 2 天）。主成分判别函数分析、典型相关分析、偏最小二乘（PLS）回归和核 PLS（KPLS）等多元统计技术用于分析数据。MALDI-TOF-MS 与 PLS 或 KPLS 结合的结果为牛奶和肉类腐败提供了极好的细菌定量结果，测试光谱中典型的预测均方根误差在 0.53 到 0.79 个对数单位之间。总的来说，这些新发现强烈表明，MALDI-TOF-MS 与化学计量学方法相结合，将成为牛奶和肉类工业常规使用的有用辅助手段，作为一种快速准确的活菌检测和定量方法。
