A variety of intrinsic and extrinsic factors determine whether microbial growth will preserve or spoil foods, as shown in Table 3.3. EXTRINSIC PARAMETERS These are the properties of the storage environment that affect both the foods and their microorganisms. Although it is often convenient to examine the factors affecting microbial growth individually, some interact strongly, as in the relationships between relative humidity and water activity aw, and gaseous atmosphere and redox potential. humidity. Answer Now and help others. A single bacterium with a doubling time of 20 minutes (µ= 2.1 hr-1) growing in a food, or pockets of food trapped in equipment, can produce a population of greater than 107 cells in the course of an 8-hour working day. Welcome to BiologyDiscussion! Some of the micro-organisms introduced will be unable to grow under the conditions prevailing, while others will grow together in what is known as an association, the composition of which will change with time. Such factors are summarised in Table 1. The most important factors that affect microbial growth in foods can be summarized in the following categories: (i) “Intrinsic factors” related to the food itself which include (Nutrient content, water activity, pH value, and the presence of antimicrobial substances); (ii) “Extrinsic factors” related to the environment in which the food is stored, including (Temperature of storage, and the composition of gases and relative … Intrinsic and extrinsic factors that affect growth of microorganism and help us understand how to preserve food Accordingly, the slope of this portion of the curve will equal the organism’s specific growth rate µ, which itself will depend on a variety of factors (see below). As not all microorganisms are equal, a combination of various factors are utilized to influence the separate behaviors of bacteria, yeasts, and molds. This allows food to … Before sharing your knowledge on this site, please read the following pages: 1. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. water activity. Privacy Policy3. INTRODUCTION Microbial growth is defined as increase in number of cells, not the size of the cells. Intrinsic or food related parameters are inherent to the food product; they are the chemical and physical characteristics of food. For this reason, in the following discussion, we have not been over zealous in discussing individual factors in complete isolation. e.g., pH, water activity (a W ), oxidation-reduction potential (Eh), nutrient content, antimicrobial constituents and biological structures. Some of these changes, like those taking place during fermentation, are desirable, while others, like those resulting in food spoilage and food … The same exponential growth rule applies to filamentous fungi which grow by hyphal extension and branching since the rate of branching normally increases with hyphal length. The most important factors that affect microbial growth in foods can be summarized in the following categories: (i) factors related to the food itself, the “intrinsic factors,” which include nutrient content, water activity, pH value, redox potential, and the presence of antimicrobial substances and mechanical barriers to microbial invasion; (ii) factors related to the environment in which the food is … Extrinsic factors. freezing, drying, heating. Finally, changes in the medium as a result of exponential growth bring this phase to an end as key nutrients become depleted, or inhibitory metabolites accumulate, and the culture moves into the stationary phase. antimicrobial constutuents. Thus: An alternative way of representing exponential growth in terms of “the doubling time is: This can be simply illustrated by considering the case of a bacterial cell dividing by fission to produce two daughter cells. One common implicit … Temperature of storage. View food spoilage.pdf from PUPLIC HEA HSC 1104 at University of Guyana. Nutrient content • The concentration of key nutrients can, to some extent, determine the rate of microbial growth. One way of representing this overall process mathematically is to modify the basic growth Equation (3.1) so that the growth rate decreases as the population density increases. Factors affecting microbial growth in food. No public clipboards found for this slide. 6.1.1. You can change your ad preferences anytime. • The relationship between the two, known as Monod equation, is mathematically identical to the Michaelis-Menten equation of enzyme kinetics. 1. The doubling or generation time of an organism T can be obtained by substituting x- 2x0 in Equation 3.3. If you continue browsing the site, you agree to the use of cookies on this website. Like so, the type of nutrient content, pH, water activity, and oxygen are intrinsic factors that generally have greater influence on microbial growth in foods. These factors are temperature, irradiation, water activity, pH, acidity, organic acids, curing salts, antibiotics, gases, packaging, and cleaning systems. The word “factor” is extremely broad, and it means that practically anything can be an implicit factor. food Temperature. Why mitochondria is called as the power house of the cell? The exponential or logarithmic phase which follows is characterized by an increase in cell numbers following the simple growth law equation. You won't even know they're there until you start to feel nauseous or crampy or whatnot. Microbial growth is an autocatalytic process: no growth will occur without the presence of at least one viable cell and the rate of growth will increase with the amount of viable biomass present. For convenience they can be divided into four groups along the lines suggested 40 years ago in a seminal review by Mossel and Ingram (Table 3.1) physicochemical properties of the food itself (intrinsic factors); conditions of the storage environment (extrinsic factors); properties and interactions of the micro­organisms present (implicit factors); and processing factors. Risk factors affecting microbial safety of foods in catering establishments. Is growth rate an extrinsic, intrinsic or implicit factor for microbial growth in foods? Clipping is a handy way to collect important slides you want to go back to later. Jarmila Pazlarová, PhD. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. Factors Affecting Microbial Growth The key to a productive staff is creating and maintaining a safe and healthy work environment. Implicit factors are the result of mutual interactions in mixed microbial populations. A simple analysis of this curve can distinguish three major phases. In All Topics, Food Science 0 Comments. Minor fluctuations in these factors, either individual or multiple, can alter the stability of a food product and make them susceptible to the growth of spoilage or pathogenic microorganisms. Gaseous environment. How the vascular cambium is responsible for secondary growth? Content Guidelines 2. See our Privacy Policy and User Agreement for details. It is therefore, a prime concern of the food microbiologist to understand what influences microbial growth in foods with a view to controlling it. Although it is often convenient to examine the factors affecting microbial growth individually, some interact strongly, as in the relationships between relative humidity and water activity a w, and gaseous atmosphere and redox potential. Thus, the rate, of increase as well as the total cell number is doubling with every doubling time that passes. Implicit factors. Microbe-microbe interactions. Extrinsic or environ – mental, external factors are the properties of storage environments which affect both food as well as microorganisms. We can do so by understanding of intrinsic, extrinsic and implicit factors that affect microbial growth and their effects on the survival of food. Factors Affecting Growth of Bacteria. FOOD SPOILAGE AND FOOD PRESERVATION Intrinsic Factors Affecting Microbial Growth • pH • Moisture Content • Water Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If, however, we perform the experiment measuring microbial numbers with time and then plot log x against time, we obtain the curve shown as Figure 3.1 in which exponential growth occurs for only a part of the time. Which organelle is known as “power house” of the cell? Microbial growth is considered insignificant for practical purposes when Aw is lower than 0.7. Redox Potential (Eh): 4. Implicit factors can be difficult to detect; to pinpoint the factors affecting your sample, you really need to be familiar with your data and your data collection methods. This can be represented mathematically by the expression: where dx/dt is the rate of change of biomass, or numbers x with time t, and µ is a constant known as the specific growth rate. • It reflects the dependence of microbial growth on rate-limiting enzyme reaction. See our User Agreement and Privacy Policy. Hydrogen Ion Concentration (pH): All the microorganisms have a minimal, maximal and optimal pH for their growth, survival and activity of their ... 2. Factor affecting bacterial growth. 20. It is divided into 14 chapters that focus on the environmental factors affecting food microorganisms. or, taking natural logarithms and re-arranging: where xo is the biomass present when t = 0. understanding intrinsic, extrinsic and implicit factors can help to predict food spoilage, shelf life and food safety. These organisms don't produce any smell, discoloration, or any other changes you can detect with your senses. Intrinsic factors. Now customize the name of a clipboard to store your clips. These are: • Temperature of storage • Relative humidity of the environment • Presence and concentration of gases • Presence and activities of other microorganisms. The growth depends on the availability of nutrients and The Population Growth Curve of Cell (Explained With Graph), Heat Sensitivity of Micro-Organisms | Microbiology. ... (which can really affect the taste/texture of the food) because it may be possible to lower dosage of individual factors/hurdles. Factors affecting the growth and survival of microorganisms in foods 1.1 Types of factor 1.2 Intrinsic factors 1.3 Extrinsic factors 1.4 Implicit factors 1.5 Concluding remarks -earlier studies focused on the effects of one or two factors on microbial growth and survival while keeping the others optimal Share Your PPT File. Redox. Factors affecting microbial development. Temperature: All forms of life are greatly influenced by temperature. pH. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Growth of bacteria is affected by many factors such as nutrition concentration and other environmental factors. Time as a Factor. and so influence growth-Eg. 3 main temp groups of microbes (implicit factors of the microbes) Thermophiles: high temp - optimal 55 degrees (range 45-70) 1. A variety of factors determine whether microbial growth will preserve or spoil foods. Molds and yeasts can affect a wide range of products which have low pH or water activity (aw). Some of the important factors affecting bacterial growth are: Nutrition concentration. 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