干酪凝乳酶代用品研究

针对干酪凝乳酶供应短缺 ,为寻找凝乳酶的最适代用品 ,采用L16 ( 4 5)正交实验设计 ,研究加入不同水平的小牛皱胃酶、乳猪胃酶、育肥猪胃酶对干酪生产的影响 ,结果表明 :乳猪胃酶能以50— 66.7%的比例替代小牛皱胃酶 ,育肥猪胃酶不能用来替代。三种凝乳酶对干酪特性好坏影响的排序是小牛皱胃酶 >乳猪胃酶 >育肥猪胃酶。     

Risk‐Based Approach for Microbiological Food Safety Management in the Dairy Industry: The Case of Listeria monocytogenes in Soft Cheese Made from Pasteurized Milk

According to Codex Alimentarius Commission recommendations, management options applied at the process production level should be based on good hygiene practices, HACCP system, and new risk management metrics such as the food safety objective. To follow this last recommendation, the use of quantitative microbiological risk assessment is an appealing approach to link new risk‐based metrics to management options that may be applied by food operators. Through a specific case study, Listeria monocytogenes in soft cheese made from pasteurized milk, the objective of the present article is to practically show how quantitative risk assessment could be used to direct potential intervention strategies at different food processing steps. Based on many assumptions, the model developed estimates the risk of listeriosis at the moment of consumption taking into account the entire manufacturing process and potential sources of contamination. From pasteurization to consumption, the amplification of a primo‐contamination event of the milk, the fresh cheese or the process environment is simulated, over time, space, and between products, accounting for the impact of management options, such as hygienic operations and sampling plans. A sensitivity analysis of the model will help orientating data to be collected prioritarily for the improvement and the validation of the model. What‐if scenarios were simulated and allowed for the identification of major parameters contributing to the risk of listeriosis and the optimization of preventive and corrective measures.     

Stochastic, Compartmental, and Dynamic Modeling of Cross-Contamination During Mechanical Smearing of Cheeses

Cheese smearing is a complex process and the potential for cross-contamination with pathogenic or undesirable microorganisms is critical. During ripening, cheeses are salted and washed with brine to develop flavor and remove molds that could develop on the surfaces. Considering the potential for cross-contamination of this process in quantitative risk assessments could contribute to a better understanding of this phenomenon and, eventually, improve its control. The purpose of this article is to model the cross-contamination of smear-ripened cheeses due to the smearing operation under industrial conditions. A compartmental, dynamic, and stochastic model is proposed for mechanical brush smearing. This model has been developed to describe the exchange of microorganisms between compartments. Based on the analytical solution of the model equations and on experimental data collected with an industrial smearing machine, we assessed the values of the transfer parameters of the model. Monte Carlo simulations, using the distributions of transfer parameters, provide the final number of contaminated products in a batch and their final level of contamination for a given scenario taking into account the initial number of contaminated cheeses of the batch and their contaminant load. Based on analytical results, the model provides indicators for smearing efficiency and propensity of the process for cross-contamination. Unlike traditional approaches in mechanistic models, our approach captures the variability and uncertainty inherent in the process and the experimental data. More generally, this model could represent a generic base to use in modeling similar processes prone to cross-contamination.     

民航管制员“错、忘、漏”发生原因分析及对策

空中交通管制是国家交通运输事业的重要组成部分,是保障国家领空安全和航空事业发展的重要基础.空中交通管制的目的是防止航空器与航空器相撞,防止航空器与障碍物相撞,维持并加速空中交通的有秩序的活动.管制员的"错、忘、漏"可能直接导致飞行冲突,甚至带来更严重的后果.随着民航的飞速发展,航班量急剧增加,飞行密度加大,管制间隔缩小,管制员的"错、忘、漏"造成严重后果的风险越来越大.本文首先从人为因素的角度分析了"错、忘、漏"的特点和产生原因,结合民航工作实际,提出相应的应对措施,以及一些针对性的管理办法.