Explain its significance. Factors affecting microbial growth in water activity. Disclaimer Copyright, Share Your Knowledge We can do so by understanding of intrinsic, extrinsic and implicit factors that affect microbial growth and their effects on the survival of 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. 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. Content Guidelines 2. What are antibiotics? The significance of exponential growth for food processing hardly needs emphasizing. EXTRINSIC PARAMETERS These are the properties of the storage environment that affect both the foods and their microorganisms. An equation that does this and gives us a closer approximation to the observed microbial growth curve is the logistic equation: where K is /the carrying capacity of the environment (the stationary phase population) and µm, the maximum specific growth rate. Factor affecting bacterial growth. 6.1.1. These are: • Temperature of storage • Relative humidity of the environment • Presence and concentration of gases • Presence and activities of other microorganisms. A variety of intrinsic and extrinsic factors determine whether microbial growth will preserve or spoil foods, as shown in Table 3.3. A simple analysis of this curve can distinguish three major phases. If you continue browsing the site, you agree to the use of cookies on this website. Name the types of nitrogenous bases present in the RNA. Factors affecting microbial development. Share Your PPT File. The growth of microorganisms in the body, in nature, or in the … Implicit factors. The word “factor” is extremely broad, and it means that practically anything can be an implicit factor. Factors affecting microbial growth in food Implicit factors • Implicit factors: • Specific growth rate / μ • Synergism • Antagonism • commensalism 42. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? 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 Intrinsic or food related parameters are those parameters of plants and animal tissues which are inherent part of the tissue. Time as a Factor. 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. Each type of food has its own characteristic constituents which may affect the growth of microbial cells. 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. It is therefore, a prime concern of the food microbiologist to understand what influences microbial growth in foods with a view to controlling it. For this reason, in the following discussion, we have not been over zealous in discussing individual factors in complete isolation. Before sharing your knowledge on this site, please read the following pages: 1. 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. FOOD SPOILAGE AND FOOD PRESERVATION Intrinsic Factors Affecting Microbial Growth • pH • Moisture Content • Water Microbial growth is considered insignificant for practical purposes when Aw is lower than 0.7. No public clipboards found for this slide. 1. Nutrients. Some of the important factors affecting bacterial growth are: Nutrition concentration. 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. food Temperature. One common implicit … Stress responses. It ranges from 0–1. • It reflects the dependence of microbial growth on rate-limiting enzyme reaction. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. 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. What are the characters Mendel selected for his experiments on pea plant? This last group of factors (subsumed under intrinsic properties by Mossel and Ingram) usually exert their effect in one of two ways: either they change an intrinsic or extrinsic property, for example slicing a product will damage antimicrobial structures and increase nutrient availability and redox potential, or they eliminate a proportion of the product microflora as would occur in washing, pasteurization or irradiation. understanding intrinsic, extrinsic and implicit factors can help to predict food spoilage, shelf life and food safety. Clipping is a handy way to collect important slides you want to go back to later. Privacy Policy3. or, taking natural logarithms and re-arranging: where xo is the biomass present when t = 0. Hydrogen Ion Concentration (pH): All the microorganisms have a minimal, maximal and optimal pH for their growth, survival and activity of their ... 2. 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). INTRODUCTION Microbial growth is defined as increase in number of cells, not the size of the cells. 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. 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. As x increases and approaches K, the growth rate falls to zero. RNDr. Temperature: All forms of life are greatly influenced by temperature. Water Activity or Moisture Content (aw): 3. Composition of Nutrients: 5. Factors affecting microbial growth in food. The doubling or generation time of an organism T can be obtained by substituting x- 2x0 in Equation 3.3. Temperature of storage. This allows food to … Hygienic food handlers` practices. humidity. See our Privacy Policy and User Agreement for details. Our mission is to provide an online platform to help students to share notes in Biology. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. 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. antimicrobial constutuents. ___ factors which affect microbial growth & survival in foods relate to the makeup of the specific bacterium itself. For example, conditions such as high humidity and wet and dirty shells, along with a drop in the storage temperature will increase the likelihood for entry of bacteria. In the course of growth, harvesting/slaughter, processing and storage, food is subject to contamination from a range of sources. 3 main temp groups of microbes (implicit factors of the microbes) Thermophiles: high temp - optimal 55 degrees (range 45-70) 1. Intrinsic and extrinsic factors that affect growth of microorganism and help us understand how to preserve food • The relationship between the two, known as Monod equation, is mathematically identical to the Michaelis-Menten equation of enzyme kinetics. Temperature of storage is highly important parameters that affect the spoilage of highly perishable food. A continual challenge that we have in the food industry is keeping microbial contamination and growth under control. Intrinsic Parameters in Food: 1. 1. and so influence growth-Eg. Growth rate. The Population Growth Curve of Cell (Explained With Graph), Heat Sensitivity of Micro-Organisms | Microbiology. Jarmila Pazlarová, PhD. The real danger stems from certain bacteria called pathogens, which are the ones that cause food poisoning. Is growth rate an extrinsic, intrinsic or implicit factor for microbial growth in foods? Processing factors. In All Topics, Food Science 0 Comments. Why mitochondria is called as the power house of the cell? These organisms don't produce any smell, discoloration, or any other changes you can detect with your senses. Microbe-microbe interactions. Factors such as temperature of storage, relative humidity, age of eggs, and level of surface contamination will influence internalization. Extrinsic factors. Thus, the rate, of increase as well as the total cell number is doubling with every doubling time that passes. Factors Affecting Microbial Growth August 20, 2018. View food spoilage.pdf from PUPLIC HEA HSC 1104 at University of Guyana. Looks like you’ve clipped this slide to already. Which organelle is known as “power house” of the cell? 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. Food may be plant or animal origin. Share Your Word File Gaseous environment. Intrinsic factors. Nutrient content • The concentration of key nutrients can, to some extent, determine the rate of microbial growth. (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. Anything that can alter the Aw of the food will affect microbial growth -Level of moisture in atmosphere in contact with the food will influence Aw . Risk factors affecting microbial safety of foods in catering establishments. 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 … e.g., pH, water activity (a W ), oxidation-reduction potential (Eh), nutrient content, antimicrobial constituents and biological structures. Micro-Organisms are reported to grow between -34 0 c to 100 0 c and each organism exhibit a minimum, optimum and maximum temperature for growth and these are known as cardinal temperature. As not all microorganisms are equal, a combination of various factors are utilized to influence the separate behaviors of bacteria, yeasts, and molds. freezing, drying, heating. 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. The exponential or logarithmic phase which follows is characterized by an increase in cell numbers following the simple growth law equation. The situation is complicated by the fact that the microflora is unlikely to consist of a single pure culture. Spoilage caused by molds and yeasts is often manifested by their visible growth on the surface of foods such as cheese and meat, as well as by fermentation of sugars in liquid and semiliquid products. 13.7.2014 2 Factors affecting microbial growth/behaviour in foods Intrinsic factors Nutrients pH and buffering capacity Redox potential Water activity Antimicrobial structures Extrinsic factors Implicit factors Processing factors Factors affecting microbial growth/behaviour in foods Some of these changes, like those taking place during fermentation, are desirable, while others, like those resulting in food spoilage and food … You can change your ad preferences anytime. Implicit. TOS4. These factors are temperature, irradiation, water activity, pH, acidity, organic acids, curing salts, antibiotics, gases, packaging, and cleaning systems. 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. Factors affecting microbial growth in food Processing factors • Processing factors: • Slicing • Washing • Packing • Irradiation • Pasteurization 43. When microorganisms grow in food they cause varying degrees of change in the food's characteristics as a result of metabolic activity. In the first, the lag-phase, there is no apparent growth while the inoculum adjusts to the new environment, synthesizes the enzymes required for its exploitation and repairs any lesions resulting from earlier injury, e.g. Such factors are summarised in Table 1. In fact, the microorganisms … Answer Now and help others. Share Your PDF File Redox. Therefore, it’s important to have an understanding of the conditions that aid microbial growth. Microbial growth is dependent on the “water activity” (Aw) of foods. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. 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. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Welcome to BiologyDiscussion! Aw is the ratio of the vapor pressure of water in the product to the vapor pressure of pure water at a certain temperature. Maintaining work equipment and the physical state of a building is important, but there are potential threats lurking in a company’s infrastructure that are too small for the naked eye to see. 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