This allows food to … No public clipboards found for this slide. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. It ranges from 0–1. Nutrient content • The concentration of key nutrients can, to some extent, determine the rate of microbial growth. In the course of growth, harvesting/slaughter, processing and storage, food is subject to contamination from a range of sources. 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. Bacteria and fungi are the most common group of microbes that are implicated in food spoilage; and these spoilage organisms make use of nutritive factors or … See our User Agreement and Privacy Policy. Such factors are summarised in Table 1. Hygienic food handlers` practices. 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. How the vascular cambium is responsible for secondary growth? RNDr. Therefore, it’s important to have an understanding of the conditions that aid microbial growth. Microbe-microbe interactions. 6.1.1. 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. Microbial growth is considered insignificant for practical purposes when Aw is lower than 0.7. As x increases and approaches K, the growth rate falls to zero. Thus, the rate, of increase as well as the total cell number is doubling with every doubling time that passes. For this reason, in the following discussion, we have not been over zealous in discussing individual factors in complete isolation. A continual challenge that we have in the food industry is keeping microbial contamination and growth under control. Welcome to BiologyDiscussion! Stress responses. Answer Now and help others. Temperature of storage. Factors such as temperature of storage, relative humidity, age of eggs, and level of surface contamination will influence internalization. The Population Growth Curve of Cell (Explained With Graph), Heat Sensitivity of Micro-Organisms | Microbiology. Temperature of storage is highly important parameters that affect the spoilage of highly perishable food. Which organelle is known as “power house” of the cell? TOS4. Food may be plant or animal origin. Molds and yeasts can affect a wide range of products which have low pH or water activity (aw). 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). 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. Disclaimer Copyright, Share Your Knowledge 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. If you continue browsing the site, you agree to the use of cookies on this website. The significance of exponential growth for food processing hardly needs emphasizing. Microbial growth is dependent on the “water activity” (Aw) of foods. What are the characters Mendel selected for his experiments on pea plant? Hydrogen Ion Concentration (pH): All the microorganisms have a minimal, maximal and optimal pH for their growth, survival and activity of their ... 2. Share Your PDF File 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. 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. One common implicit … 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. Intrinsic or food related parameters are those parameters of plants and animal tissues which are inherent part of the tissue. Factors affecting microbial growth in food Implicit factors • Implicit factors: • Specific growth rate / μ • Synergism • Antagonism • commensalism 42. Some of these changes, like those taking place during fermentation, are desirable, while others, like those resulting in food spoilage and food … Extrinsic factors. ... (which can really affect the taste/texture of the food) because it may be possible to lower dosage of individual factors/hurdles. Before sharing your knowledge on this site, please read the following pages: 1. Factors Affecting Microbial Growth August 20, 2018. understanding intrinsic, extrinsic and implicit factors can help to predict food spoilage, shelf life and food safety. Temperature. or, taking natural logarithms and re-arranging: where xo is the biomass present when t = 0. A variety of intrinsic and extrinsic factors determine whether microbial growth will preserve or spoil foods, as shown in Table 3.3. Each type of food has its own characteristic constituents which may affect the growth of microbial cells. Redox. Intrinsic and extrinsic factors that affect growth of microorganism and help us understand how to preserve food Jarmila Pazlarová, PhD. and so influence growth-Eg. 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. The exponential or logarithmic phase which follows is characterized by an increase in cell numbers following the simple growth law equation. You can change your ad preferences anytime. Gaseous environment. Intrinsic factors. 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. The situation is complicated by the fact that the microflora is unlikely to consist of a single pure culture. Share Your Word File We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. The factors that affect microbial growth in foods, and consequently the associations that develop, also determine the nature of spoilage and any health risks posed. It is therefore, a prime concern of the food microbiologist to understand what influences microbial growth in foods with a view to controlling it. Water Activity or Moisture Content (aw): 3. In time π, a single cell will divide to produce two cells; after a further doubling time has elapsed four cells will be present; after another, eight, and so on. Factors Affecting Growth of Bacteria. 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. Temperature. Growth rate. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? Redox Potential (Eh): 4. 1. You won't even know they're there until you start to feel nauseous or crampy or whatnot. 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. 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 See our Privacy Policy and User Agreement for details. -earlier studies focused on the effects of one or two factors on microbial growth and survival while keeping the others optimal The growth of microorganisms in the body, in nature, or in the … water activity. Some of the important factors affecting bacterial growth are: Nutrition concentration. 20. If you continue browsing the site, you agree to the use of cookies on this website. Looks like you’ve clipped this slide to already. Processing factors. Factors affecting microbial growth in 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. Each chapter explores the scientific principles of the specific environmental factor; methods of measurement; and effects on growth and … Factors affecting microbial development. Privacy Policy3. The doubling or generation time of an organism T can be obtained by substituting x- 2x0 in Equation 3.3. Why mitochondria is called as the power house of the cell? Clipping is a handy way to collect important slides you want to go back to later. Content Guidelines 2. 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. freezing, drying, heating. Temperature: All forms of life are greatly influenced by temperature. 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 . Our mission is to provide an online platform to help students to share notes in Biology. Implicit factors. 3 main temp groups of microbes (implicit factors of the microbes) Thermophiles: high temp - optimal 55 degrees (range 45-70) 1. Intrinsic Parameters in Food: 1. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. The word “factor” is extremely broad, and it means that practically anything can be an implicit factor. Name the types of nitrogenous bases present in the RNA. These are: • Temperature of storage • Relative humidity of the environment • Presence and concentration of gases • Presence and activities of other 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. 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 … Factors Affecting Microbial Growth The key to a productive staff is creating and maintaining a safe and healthy work environment. Factors affecting microbial growth in food Processing factors • Processing factors: • Slicing • Washing • Packing • Irradiation • Pasteurization 43. 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. Now customize the name of a clipboard to store your clips. These organisms don't produce any smell, discoloration, or any other changes you can detect with your senses. food As not all microorganisms are equal, a combination of various factors are utilized to influence the separate behaviors of bacteria, yeasts, and molds. Microbial cells obtain all required nutrients from food nearby. In All Topics, Food Science 0 Comments. Explain its significance. 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. It is divided into 14 chapters that focus on the environmental factors affecting food microorganisms. 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. In fact, the microorganisms … e.g., pH, water activity (a W ), oxidation-reduction potential (Eh), nutrient content, antimicrobial constituents and biological structures. (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. 1. 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. Share Your PPT File. 3.1.1 Nutrients The more or less contents in proteins, sugars and other nutrients are going to determine what type of microorganisms are, preferably, able to grow on that food. These factors are temperature, irradiation, water activity, pH, acidity, organic acids, curing salts, antibiotics, gases, packaging, and cleaning systems. The growth depends on the availability of nutrients and 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 … 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. Aw is the ratio of the vapor pressure of water in the product to the vapor pressure of pure water at a certain temperature. View food spoilage.pdf from PUPLIC HEA HSC 1104 at University of Guyana. Intrinsic or food related parameters are inherent to the food product; they are the chemical and physical characteristics of food. Is growth rate an extrinsic, intrinsic or implicit factor for microbial growth in foods? INTRODUCTION Microbial growth is defined as increase in number of cells, not the size of the cells. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Factor affecting bacterial growth. Factors affecting microbial growth in food. FOOD SPOILAGE AND FOOD PRESERVATION Intrinsic Factors Affecting Microbial Growth • pH • Moisture Content • Water Implicit factors are the result of mutual interactions in mixed microbial populations. EXTRINSIC PARAMETERS These are the properties of the storage environment that affect both the foods and their microorganisms. Implicit. • The relationship between the two, known as Monod equation, is mathematically identical to the Michaelis-Menten equation of enzyme kinetics. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. When microorganisms grow in food they cause varying degrees of change in the food's characteristics as a result of metabolic activity. ___ factors which affect microbial growth & survival in foods relate to the makeup of the specific bacterium itself. • It reflects the dependence of microbial growth on rate-limiting enzyme reaction. Growth of bacteria is affected by many factors such as nutrition concentration and other environmental factors. Time as a Factor. Composition of Nutrients: 5. Risk factors affecting microbial safety of foods in catering establishments. Nutrients. What are antibiotics? Extrinsic or environ – mental, external factors are the properties of storage environments which affect both food as well as microorganisms. A variety of factors determine whether microbial growth will preserve or spoil foods. pH. humidity. 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. antimicrobial constutuents. 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 The real danger stems from certain bacteria called pathogens, which are the ones that cause food poisoning. 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. 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. 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