预测食品微生物学

预测食品微生物学是食品微生物学的一个新兴分支学科,是在微生物学、数学、统计学和计算机应用学的基础上建立起来的新学科.预测食品微生物学研究和设计一系列描述和预测微生物在特定条件生长和衰亡的模型,因而一种防止病原微生物对食品污染的有效的预警工具.     

Predictive microbiology and food safety

The evaluation of risk in food safety requires knowledge of the probability that microbial population sizes will not exceed defined levels. This probability is evaluated assuming that the growth of the microbial population can be described by the Gompertz equation with the variance of growth depending on the population size. It is shown that the probability density associated with this phenomenon is skewed, so that the risk of a high microbial population is greater than that which would be estimated using a symmetrical probability distribution such as the Gaussian. Maximum likelihood estimates of the parameters of the Gompertz equation based on the derived probability density are calculated using data published by Zwietering et al. [23] for the growth of Lactobacillus plantarum under different temperatures. The probability that a microbial population of a given size will exceed an unacceptable level within a given time is calculated for growth at two temperatures, 10 and 25 degrees C. The implication of these theoretical results for the management of risk in food safety and in the design of hazard analysis critical control point procedures is discussed.     

预测微生物学与食品质量安全

预测食品微生物学利用数学模型定量地分析不同环境条件下食品中病原菌和腐败菌的生长和存活，对食品的货架期作出合理的预测。该文简要介绍了预测模型的3个水平及其在预测货架期中的应用，并展望了预测微生物学未来的发展趋势。     

Predictive microbiology: providing a knowledge-based framework for change management

This contribution considers predictive microbiology in the context of the Food Micro 2002 theme, "Microbial adaptation to changing environments". To provide a reference point, the state of food microbiology knowledge in the mid-1970s is selected and from that time, the impact of social and demographic changes on microbial food safety is traced. A short chronology of the history of predictive microbiology provides context to discuss its relation to and interactions with hazard analysis critical control point (HACCP) and risk assessment. The need to take account of the implications of microbial adaptability and variable population responses is couched in terms of the dichotomy between classical versus quantal microbiology introduced by Bridson and Gould [Lett. Appl. Microbiol. 30 (2000) 95]. The role of population response patterns and models as guides to underlying physiological processes draws attention to the value of predictive models in development of novel methods of food preservation. It also draws attention to the paradox facing today's food industry that is required to balance the "clean, green" aspirations of consumers with the risk, to safety or shelf life, of removing traditional barriers to microbial development. This part of the discussion is dominated by consideration of models and responses that lead to stasis and inactivation of microbial populations. This highlights the consequence of change on predictive modelling where the need is now to develop interface and non-thermal death models to deal with pathogens that have low infective doses for general and/or susceptible populations in the context of minimal preservation treatments. The challenge is to demonstrate the validity of such models and to develop applications of benefit to the food industry and consumers as was achieved with growth models to predict shelf life and the hygienic equivalence of food processing operations.     

Predictive microbiology: Quantitative science delivering quantifiable benefits to the meat industry and other food industries

Predictive microbiology is considered in the context of the conference theme "chance, innovation and challenge", together with the impact of quantitative approaches on food microbiology, generally. The contents of four prominent texts on predictive microbiology are analysed and the major contributions of two meat microbiologists, Drs. T.A. Roberts and C.O. Gill, to the early development of predictive microbiology are highlighted. These provide a segue into R&D trends in predictive microbiology, including the Refrigeration Index, an example of science-based, outcome-focussed food safety regulation. Rapid advances in technologies and systems for application of predictive models are indicated and measures to judge the impact of predictive microbiology are suggested in terms of research outputs and outcomes. The penultimate section considers the future of predictive microbiology and advances that will become possible when data on population responses are combined with data derived from physiological and molecular studies in a systems biology approach. Whilst the emphasis is on science and technology for food safety management, it is suggested that decreases in foodborne illness will also arise from minimising human error by changing the food safety culture.     

Predictive microbiology models vs. modeling microbial growth within Listeria monocytogenes risk assessment: what parameters matter and why

Predictive microbiology models are essential tools to model bacterial growth in quantitative microbial risk assessments. Various predictive microbiology models and sets of parameters are available: it is of interest to understand the consequences of the choice of the growth model on the risk assessment outputs. Thus, an exercise was conducted to explore the impact of the use of several published models to predict Listeria monocytogenes growth during food storage in a product that permits growth. Results underline a gap between the most studied factors in predictive microbiology modeling (lag, growth rate) and the most influential parameters on the estimated risk of listeriosis in this scenario (maximum population density, bacterial competition). The mathematical properties of an exponential dose-response model for Listeria accounts for the fact that the mean number of bacteria per serving and, as a consequence, the highest achievable concentrations in the product under study, has a strong influence on the estimated expected number of listeriosis cases in this context.     

Food microbiology: the challenges for the future.

Food microbiology has become a mature science in the twentieth century and has made great advances. While recognising these achievements, it is also necessary to consider how the science may need to change. This paper addresses this by reference to three areas. These are possible changes in foodborne diseases of concern and the impact of molecular and genetic techniques on our current methodology. The recognition of the role of food and associated microbial contaminants in chronic diseases could become a major concern. New developments in our understanding of microbial genetics could affect our concepts of bacterial taxonomy. The current methodologies we use, based upon genotypically identical populations, may need to be addressed. If the trends indicated here are realised, they indicate a major challenge and opportunity for the food microbiologist.     

Impedance microbiology: applications in food hygiene

Impedance microbiology is a rapid method that enables qualitative and quantitative tracing of microorganisms by measuring the change in the electrical conductivity. With direct impedance technology, the change in the conductivity of a liquid culture medium serves as a measuring parameter, whereas with indirect impediometry, the change in the electrical conductivity of a reaction solution, which occurs through the absorption of gases from the inoculated bacterial culture, is measured. Most investigations concerning the applicability of impediometry in food microbiology deal with the impedimetric detection or enumeration of Enterobacteriaceae, especially the detection of Salmonella. However, impediometry has been applied to other bacterial groups or species as well. Furthermore, a great number of published findings concern the impedimetric determination of the total bacterial count. The successful application of this fast method on further areas of food hygiene, such as tracing antibiotics and testing additives for their antimicrobiological effect, has also been described. In general the use of impediometry for the application areas stated has been judged positively. However, the time and expense required by the user to optimize the method, the deficits when testing slightly contaminated sample material or determining the bacterial count in those cases in which the microorganisms are sublethally damaged, and the necessity of performing individual calibration for each food category limit the applicability of impediometry.     

Winemaking biochemistry and microbiology: current knowledge and future trends

The fermentation of grape must and the production of premium quality wines are a complex biochemical process that involves the interactions of enzymes from many different microbial species, but mainly yeasts and lactic acid bacteria. Yeasts are predominant in wine and carry out the alcoholic fermentation, while lactic acid bacteria are responsible for malolactic fermentation. Moreover, several optional winemaking techniques involve the use of technical enzyme preparations. Considerable progress has been made recently in understanding the biochemistry and interactions of enzymes during the winemaking process. In this study, some of these recent contributions in the biochemistry of winemaking are reviewed. This article intends to provide an updated overview (including works published until December, 2003) on the main biochemical and microbiological contributions of the different techniques that can be used in winemaking. As well as considering the transformations that take place in traditional winemaking, the production of special wines, such as sparkling wines, 'sur lie' wines, and biologically aged wines, are also studied.     

On the microbiology of Serra da Estrela cheese: geographical and chronological considerations

Serra da Estrela cheeses, produced following artisanal practices from raw ewe's milk in two consecutive years in five selected dairies, were sampled throughout a 60-day ripening period. The viable numbers of the major microbial groups (Enterobacteriaceae, staphylococci and yeasts, as well as such lactic acid bacteria as lactobacilli, lactococci and enterococci) were determined and statistical significance of the results was assessed. Significant differences in the viable counts of lactococci, lactobacilli, enterococci, Enterobacteriaceae and staphylococci were found for the various geographical locations, whereas the year of manufacture played a significant role only upon the viable numbers of yeasts and staphylococci. These data back up the claim that those microbial families usually implicated with health hazards are prone to a wide variability, which reflects the intrinsic heterogeneity associated with production and handling of raw milk in traditional cheesemaking.     

Rapid methods and automation in food microbiology: A review

Abstract

Rapid methods and automation in microbiology are dynamic fields and are constantly moving forward in helping to solve applied microbiology and food safety issues. This article is a review of the current development of this field in the areas of sample preparation, alternative methods for viable cell counts, new methods for estimation of microbial populations and biomass, and new and novel techniques. This article should be of interest to all scientists concerned with the current development of rapid methods and potential application of these techniques in their daily work. The article addresses the basic principles of rapid methods and specific applications of methods, and provides an updated reference list for further investigations by readers.     

Capacity building: beyond state and market

This article considers what happens to education under the impact of twin dynamics of neo-liberal reform and globalisation in an Australian Institute of Technical and Further Education (TAFE) located in the state of Victoria. The pattern of policy reform in TAFE is documented in order to emphasise the significant extent of marketisation, commercialization and decentralisation in the vocational education and training sector. The responses by TAFE teachers and managers to these reforms are illustrated. The analysis indicates that while some teachers and managers either actively resist or espouse these reforms, most work out innovative ways of reconciling their old educational commitments with new entrepreneurial demands. These hybrid practices or capacity-building strategies are described and theorised. The article suggests that capacity-building entails a renorming of educational practice, but questions the political significance of these emergent practices given the contested image of the capacity builder - as teacher or as soft-skill manager.     

Kombucha, the fermented tea: microbiology, composition, and claimed health effects

Kombucha is a slightly sweet, slightly acidic tea beverage consumed worldwide, but historically in China, Russia, and Germany. Kombucha is prepared by fermenting sweetened black tea preparations with a symbiotic culture of yeasts and bacteria. Potential health effects have created an increased interest in Kombucha. Yet, only a few research studies have shown that Kombucha has in vitro antimicrobial activity and enhances sleep and pain thresholds in rats. Furthermore, Kombucha consumption has proven to be harmful in several documented instances.     

Food engineering and predictive microbiology: on the necessity to combine biological and physical kinetics

Predictive microbiology is mainly applied in the area of risk assessment, but unusually regarded as a tool for the optimisation of processes, which needs the implementation of food engineering. Combination of predictive microbiology and food engineering allows both the assessment of a process in relation to risk and its optimisation. Intrinsic comparison between processes in relation to risk, on one hand, and the development of process optimisation tools on the other hand, necessitates the implementation of new concepts and the involvement of simplified and standard calculations based upon reference target strains and environmental conditions. Some conventional concepts related to heat treatments are extended, while some new ones related to bacterial growth are derived from the gamma concept of Marcel Zwietering.     

The microbiology of DFD fresh meats: A review

Muscle which is deficient in glycogen because of exercise or stress prior to slaughter produces dark, firm, dry (DFD) meat. Such meat is characterized by a high ultimate pH (>6·0) and deficiencies in glucose and glycolytic intermediates. These factors can result in bacterial spoilage becoming evident at an early stage of growth of the meat flora. Spoilage becomes apparent when bacteria attack amino acids. This does not occur under aerobic conditions until bacteria exhaust the glucose at the meat surface. However, since glucose is absent in DFD meat, amino acids are utilised without delay and spoilage becomes evident at lower cell densities than in normal meat. The absence of glucose also allows the anaerobic flora to produce spoilage odours at an early stage. Additionally, the high pH of DFD meat allows growth of potent spoilage organisms which are inhibited at the usual ultimate pH of meat. Early aerobic spoilage can be prevented by the addition of glucose, but prevention of early anaerobic spoilage requires the addition of a citrate buffer which reduces the surface pH, as well as providing a carbohydrate substrate which is utilised in preference to amino acids. Comparisons can be made between spoilage of DFD red meat and spoilage of white meats from poultry and fish, which normally have a high ultimate pH.     

The microbiology and historical safety of margarine

The microbiology and safety of margarine are reviewed from the perspective of its material composition and the historical absence of foodborne illness incidents associated with the consumption of this product. Intrinsic factors limit the growth of most micro-organisms, including pathogens. Margarine is a water-in-oil emulsion with a high fat content that limits the growth of most prokaryotic and eukaryotic micro-organisms. The size of the aqueous phase droplets and the inability of micro-organisms to move between droplets also reduce the ability of margarine to support microbial growth. In addition, depending upon the formula, up to 2% salt may be added which further reduces the ability of most micro-organisms to grow. The addition of preservatives such as sorbates can reduce spoilage problems. Spoilage, when it is observed, is typically caused by molds which can extend mycelia into the oil phase. The use of raw material specifications and the implementation of a Hazard Analysis Critical Control Point system can be effective in enhancing the microbiological quality of margarine. The safety of margarine is documented by the lack of any verified incidences of foodborne illness resulting from the consumption of margarine.