implicit factors affecting microbial growth in food

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