Bacteria reproduce by splitting into two. This process is known as binary fission and the time taken between each division (generation time) varies considerably depending on, among other things, temperature and the nutrients (food) available. In optimum (ideal) conditions some food poisoning bacteria can split in two every ten minutes, although at temperatures of around 10°c it may take up to ten hours or they may stop multiplying. Show
The average generation time of the common food poisoning bacteria under optimum conditions is usually considered to be around 20 minutes. When food bacteria are growing and multiplying this is described as the vegetative state. If food is contaminated a common level of contamination may be around 1,000 bacteria per gram of food. Is this food provides optimum conditions then within one hour 40 minutes, these bacteria could double every 10 minutes and become 1,000,000. This number of bacteria is likely to cause food poisoning. The multiplication of pathogens in food is a hazard. Nutrients Food poisoning bacteria obtain their essential basic nutrients from amino acids, fats, vitamins and minerals. which are usually provided high protein food such as meat, fish and dairy produce. Foods with high sugar and salt content are usually unsuitable and therefore are unlikely to support bacteria multiplication. Moisture Bacteria required water to transport nutrient into the cell and take away waste products. The water activity of food is the measure of the available water. With the expectation of dehydrated products such as milk powder, most foods contain sufficient moisture to enable bacteria to multiply. How ever, some bacteria can survive dehydration and when liquid is added to the dried food it once again becomes a high-risk food and must be stored under refrigeration. Acidity and alkalinity (PH) The pH of a food is measured on a scale of 1 to 14 (hydrogen ion concentration.) Acid foods have pH values below 7, alkaline foods about 7 and a pH value of 7 is neutral. Most bacteria will not multiply in pH below 4.0, i.e. an acid food such as fruit juice. However, if a large number of food poisoning bacteria are introduced into an acid food it may take some time for the bacteria to die. For this reason we must protect acid food from contamination at all times. Temperature Bacteria have a maximum and minimum temperature for multiplication as well as an optimum temperature when multiplication is the most rapid. Most food poisoning bacteria grow best at around 37 ºC (body temperature) although clostridium perfringens prefers 46°C. The common food po  Some food spoilage bacteria multiplying slowly under refrigeration, which is one of the reasons for food becoming unfit if stored longer than the recommended shelf life.
Presence of oxygen Some bacteria can only multiply in the presence of oxygen and other can only multiply when there is no oxygen. The former bacteria are known as aerobes and the latter anaerobes. Many bacteria can multiply with or with out the presence of oxygen and these are called facultative anaerobes, for example, Salmonella. Oxygen is normally present in food except in the case of liquids which have been thoroughly boiled. Cooking, for example, joints of meat, also drives off oxygen and the centre then provides ideal conditions for anaerobes, such as clostridium perfringens. Toxin production Food poisoning bacteria produce toxins (poisons) which cannot be detected by visual inspection. Toxins may be either exotoxins or endotoxins. Exotoxins are produce as waste products during multiplication or sporulation of bacteria. Quite often Exotoxins are released into the food and many are heat resistant, so that even if cooking destroys the bacteria, the toxin may remain and cause illness if the food is eaten. This result in a short onset time. Toxins will usually not be produced if the food is kept below 5°C or above 63°C and at the time ambient temperature is kept short. Enterotoxins are Exotoxins that affect the gastrointestinal tract. Endotoxins form part of the bacteria cell wall and are released on the death of the bacteria, usually in the intestines of persons consuming contaminated food. If the toxin is produced in the intestines, the onset period, for the first symptoms to appear, will usually be longer than if the toxin is in the food. Spore formation Some food poisoning bacteria, such as Clostridium Perfringens, Bacillus cereus and Clostridium Botulinum are able to form spores which are capable of surviving unfavourable conditions such a high temperatures, dehydration and the use of disinfectants. Spores are round protective bodies which form inside the bacterial cell and may allow survival for many years without food and water. They cannot be detected by visual inspection. Spores survive normal cooking and germinate during long, slow cooling. The vegetative bacteria released will then start multiplying and may produce toxins. Temperatures in excess of 100°C are often required for long periods (as much as five hours) to destroy spores. The temperatures used to ensure the safety of low-acid canned food, by destroying spores of Clostridium botulinum, is the equivalent of 121°C for three minutes. BACTERIAL SPORES DIAGRAM Competition When there are many different bacteria present, they will compete for the same food. Fortunately, most food poisoning bacteria are not as competitive as the normal flora found on food and unless present in high numbers, will usually die. Destruction of bacteria Food poisoning bacteria can be destroyed by using high temperatures for sufficient time. The higher the temperature, the shorter the time required. However, the type of bacteria (whether or not they produce spores), the number of bacteria present and the type of food also affect the time needed to kill bacteria and make food safe. Bacteria will start to die at around 55°C. However, a core temperature of greater then 75°C is required when cooking food to be reasonably confident that most harmful bacteria will have been destroyed. Unfortunately, much higher temperatures are required to destroy toxins and spores produced by some food poisoning bacteria. Spores are much more resistant to drying, boiling, disinfectants and other conditions, which usually destroy vegetative food poisoning bacteria. The survival of bacteria, spores or toxins is a hazard. Bacteria can also be destroyed by irradiation, chemicals such as nitrates, salt or sugar, u/v light, ste It is essential to keep work surfaces and fridges clean to prevent the spread of bacteria. You should also wash and dry your hands carefully to avoid spreading germs and bacteria.… Preventing the spread of germs
See also what happens when short day plants receive flashes of light Bacterial growth slows down or stops in food that is kept at temperatures colder than 5°C or hotter than 63°C. Most bacteria can survive cold temperatures though (in a fridge or freezer) and resume multiplication when they are back in the Danger Zone. Why it matters: Bacteria are among the fastest reproducing organisms in the world doubling every 4 to 20 minutes. Some fast-growing bacteria such as pathogenic strains of E. How do bacteria grow?Bacteria are all around us. Given good growing conditions a bacterium grows slightly in size or length new cell wall grows through the center and the “bug” splits into two daughter cells each with same genetic material. If the environment is optimum the two daughter cells may split into four in 20 minutes. Can bacteria grow at 4 degrees Celsius?Both extreme cold and hot temperatures require evolutionary adjustments to macromolecules and biological processes. Psychrophiles grow best in the temperature range of 0–15 °C whereas psychrotrophs thrive between 4°C and 25 °C. Mesophiles grow best at moderate temperatures in the range of 20 °C to about 45 °C. What are the 6 conditions necessary for bacteria to grow?FATTOM is an acronym used to describe the conditions necessary for bacterial growth: Food acidity time temperature oxygen and moisture. Foods provide a perfect environment for bacterial growth due to their provision of nutrients energy and other components needed by the bacteria. Bacteria have these same needs they need nutrients for energy water to stay hydrated and a place to grow that meets their environmental preferences. The ideal conditions vary among types of bacterium but they all include components in these three categories. What temperatures can bacteria survive in?Most bacteria thrive in temperatures of 40°F to 140°F or what the United States Department of Agriculture (USDA) refers to as the ‘danger zone’. This is when bacteria grow multiplying by two every 20 minutes. How do pathogens multiply?Once you’re infected viruses invade host cells within your body. They then use the components of the host cell to replicate producing more viruses. After the replication cycle is complete these new viruses are released from the host cell. This usually damages or destroys the infected cells. How the pathogens grow and reproduce?Bacteria reproduce primarily by binary fission an asexual process whereby a single cell divides into two. Viruses on the other hand are produced by the host cell that they infect but are not capable of self-reproduction. … These conditions include temperature moisture pH and environmental oxygen. Understanding the optimal conditions for bacterial growth can potentially help you reduce your risk for bacterial infections and food poisoning. What is the process of bacteria multiplying called?
Bacterial growth is proliferation of bacterium into two daughter cells in a process called binary fission.
See also what is used to clean up oil spills Why do bacteria multiply quickly?When the conditions are right with warm temperatures moisture and the nutrients in food then bacterial contamination can spread quite quickly.
According to the Certified Food Safe Professional (CFSP) program there are three ways time-temperature abuse can occur:
The USDA Food Safety and Inspection Service (FSIS) has determined that it is just as safe to cook pork to 145°F with a 3-minute rest time as it is to cook it to 160°F with no rest time the agency said. … The agency noted that cured pork such as cured ham or pork chops will remain pink after cooking. What is food holding temperature?Take Temperatures Hot foods should be kept at an internal temperature of 140 °F or warmer. Use a food thermometer to check. Microbiology – Bacteria Growth Reproduction ClassificationWhat do bacteria need to survive and multiply?The science of skin – Emma Bryce |
What is needed for most bacteria to multiply in food
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