Lecture 2 – Level 4 Award in Managing Food Safety in Catering

Lecture 2 - Level 4 Award in Managing Food Safety in Catering



okay let's look at lecture two microbiology now the aim of this units to provide a detail understanding of microorganisms their effect on a food industry and how they can be effectively controlled and the learning outcomes by the end of this module you will be able to determine the requirements of bacteria understand the temperatures involved in the growth and death of bacteria identify specific bacteria define toxins and spores and the state which substances will stop the growth of bacteria so this will look at bacteria the size shape and structure first of all bacteria are living organisms the in animals the microscopic so you can't see them at the human eye you can only see them with a microscope you can see colonies of bacteria a million Salmonella for example would be about the size of a pinhead we have found everywhere so they're ubiquitous they are mostly harmless so it's only the minority really are what we call pathogens now remember the word pathogen comes from the Greek word pathos meaning illness so pathogen causes illness obviously we know the truth poison can kill but the actual definition for pathogen is causes illness now I say mostly harmless the studies have shown that we probably talking about more point naught naught 1 percent of all bacteria are pathogens or will cause harm now the they mostly pathogens because they start off as harmless bacteria in other words they good for the environment good for us they mutate into pathogens which then will cause us harm as I met there if you cause illness very small percentage some are essential in fact from a very technology point of view we need them in the soil to break down any dead and decaying vegetation and animals etc we use them in composting we use them as ecoli for example is used as the source for non human insulin which we use for injecting into people with type and diabetes for example other ones we use bacteria to dissolve oil spillages at sea there are a lot of uses of bacteria in the environment as they say some are essential some cause spoilage we look at spoilage bacteria later on now the shapes of bacteria they vary we've got a cocci of kaki these around a globular type bacteria Staphylococcus aureus for example this is the bacteria that inhabit our skin the slide behind the design behind this is actually Staphylococcus aureus looking under microscope so I've used this under a lot of slides and it does actually look like a bunch of grapes and Staphylococcus again is Greek for a bunch of grapes so these are the cocci so stuffer cups audience for example we've got once Ecola is an example of a rod-shaped now you will go on to other shapes you grow spider kites and lastly vibrios and what I want remember is very upon a hill perihelion it occurs so let's have a look at a bacterial cell so this is showing a rod-shaped cell and so look at the various components first of all you got the nuclear material this is a DNA scientists have found that DNA especially in e.coli which is studied quite substantially it's very similar to the DNA in human beings and other animals and as plants as well so therefore possibly show in the evolutionary similarities if you like between bacteria humans and vegetation so this is the if you like the bacterias identity the same with our identity is the DNA we got the cytoplasm this is the liquid part of the bacterial cell this is where all the action goes on this is where all the food is taken into dissolved and used up as nutrients and expelled accordingly as waste material the cell membrane this is very particularly in as much as what it will allow over the cell membrane and watch it will explore through the cell membrane it's a semi permeable membrane the cell wall very rigid cell wall which again protects the bacterial cell from destruction stops any liquids sort of seeping out and desiccated in the inside or in fact all of the bacterial cell and the capsule or the slime layer this actually gives it motivational properties in other words it can move through and on substances because of the slime layer the flagella gives it motivation if you've ever seen this in in in a slide in a video you will see it actually it's like like a person's swim in doing the breaststroke and these two flagella feel like alike arms that flap back and forth to project the back to yourself or backwards or whichever way you monster and the fimbria these used for adhesive properties these cause this cell to stick to animals animals gets on to other cells so these as I said this gives it these equalities and all the requirements of bacterial multiplication well we need nutrients first of all moisture content aw which is the moisture content needs to be between nor point nine nine naught point nine five anything lower than that then is too dry for the bacteria to survive warmth now the good different types of bacteria you've got cyclo files which prefer temperatures less than twenty degrees C we go Mesa files or masa files they prefer 20 to 50 degrees C and thermo files are greater than 45 degree C pathogens food safety pathogens fall and Misa files which is 20 to 50 degrees C some psycho files for example can go down to north degrees C some thermophiles can go up to hundred sixty degrees C these the ones that live and the senior thermal vents time oxygen we need a pH thus the alkalinity acidity value great and a four point five now the and I'll go through this later the scale of pH is from naught to fourteen seven is pH neutral so really it most Mesa files most pathogens prefer about pH seven again the same as human beings and other animals the absence of competition pathogens are not very competitive in fact pathogens which are different from spoilage bacteria if spotted bacteria are pleasant then you will find that won't be any pathogens they're either going back to oxygen I figured well I will mention this later on but oxygen the bacteria cos I've with small amounts of oxygen medium amounts of oxygen and high amounts of oxygen I have the absence of preservatives any preservatives present obviously will stunt the growth or prevent the growth of bacteria so let's look at the different food types now first of all high-risk foods I've got a water content between nor point nine five and 0.99 so that ideal for bacterial growth and bacteria love high-risk foods if they can get access to high-risk foods and they're left in a warm environment they will multiply quite quickly in fact they can double in size from one to six billion within about six hours left and the right conditions because I saw bacteria and grow they grow by multiplication so high-risk foods include things like usually fuji find in a refrigerator that need to be kept cold and are already cooked and they've got a high protein content so we got some examples there of pâtés so-called cheeses seafoods i kept on saying our muscles already being cooked so Popeyes quiches sandwiches the ham sandwich perhaps we got a sausage roll again all these items usually a cold their common food vehicles in food poisoning usually protein ready-to-eat stored in a refrigeration and there's no further processing or reheat and required now roll foods there we've got vegetables meat and fish these are a major source of food poisoning organisms so in other words this is where we will find them in raw foods and if the raw foods come into contact with high-risk foods then we got a big problem that's called cross contaminate so if they're all foods cannot account or the highest foods either directly by touchnet or indirectly where there's a full night or something like a cloth or a hand touching the raw food then touching high-risk food you'll get cross-contamination if the highest food is left in warm conditions the bacteria started grow the person will eat that food they will get food poisoning are the ones low risk foods we call low risk because they will not support the growth of pathogens or other bacteria normally their acid foo are the curds only very different types of foods have different properties they could be acid foods such as pickles chutneys sources where they've got a pH of less than four point five so it's quite acidic where it's got a high sugar salt or fat content obviously these are good natural preservatives dry products where there's a low availability of water that's what the W stands for includes preserved foods not requiring refrigeration on anything held in ambient storage that's room temperature then ready to eat raw foods ready to eat raw foods such as fruit and salad vegetables should be thoroughly washed before consumption to minimize the risk from load those pathogens now load those pathogens which we find out later on our own will cause a foodborne disease rather than food poisoning now there are two different types of diseases food poisoning usually requires a high number of bacteria to cause food poisoning with food borne diseases they usually cry uh just from one to several bacteria in order to cause foodborne disease so let's have a look at temperatures what sort of temperatures the bacteria require so what I've got here is a thermometer on a Jumma meter and it will show you what happens to bacteria at certain temperatures so this thermometer goes from minus 18 degrees C up to an above 70 degrees C so everything is in Celsius obviously if you need to wake the cell in far tonight you'll need to use the formula I believe it's something like multiplying by 9 over 5 a 1932 and the reverse if on your from Fahrenheit Celsius so let's have a look at 18 degrees C bacteria are in hibernation they won't grow you won't kill them by freezing them they'll just remain dormant minus 18 all the way is the temperature in our freezer should be and then you've got 1 2 4 degrees C this is our fridge temperatures ideally vinca fridges below 3 degrees C but without freezing any solid items only great there's food safety bacteria and apart from Listeria won't grow below 3 degrees C so this temperature the bacteria still sleepy they weaken up this little bit too cold for them to multiply or to grow to any substantial size then we go from 5 degrees C to 63 degrees C this is called the temperature danger zone you must keep bacteria or food that might contain bacteria out of the temperature danger zone so in other words we either keep it cold in this zone yeah I'll keep the food hot in this zone here if we go onto the temptu danger zone this is very bacteria will multiply them they'll start to grow slowly at 5 degrees C very very slowly and they will increase in number the woman it gets as he gets warmer they wake up they start to multiply more readily the ideal temperature for multiplication is 37 degrees C which is body temperature anything high in the 37 degrees C then they will start to slow down they won't multiply any further around about 55 56 or bacteria killed but we go up to 63 as the top of the temperature danger zone although by then or bacteria killed anyway 63 is classed as a disinfection temperature it's also classed as the temperature at which if you keep in food hot it must be kept at 63 degrees or above the cooking temperature we tend to go for is 75 degrees C these this comes from recommendations from environmental health departments and the Food Standards Agency although from a quality point of view there's nothing to the food it's probably best to cook your food whether it's chicken meats or any other products to roundabout between 60 and 63 degrees C this is where you get minimum shrinkage you'll get moist products and it's gonna be safe because all the bacteria that are killed anyway but if questions do come up in the exam from a food safety point of view at 75 degrees C that we need to attain and the point of water is 100 degrees C that in all bacteria survive in at that temperature so let's have a look at the bacterial growth curve a lag phase where we go several phases like phase log phase stationary phase on a decline phase the lag phase really there's no multiplication the temperature there is props the ideal temperature but the bacteria are still using app nutrients and enzymes in order to get a large enough number so they can multiply quickly which they will do which is called the log phase this is where they a multiply in the doubling in size between every 10 minutes are between 10 and 20 minutes now the stationary phase really is where they don't grow any further this is because they might have run out of nutrients the temperature might be okay other conditions might be okay but it might be a reason from not growing any further or there might be so many that the competition is too high and after the stationary phase is working all the decline phase is where they start a reducing number so there's no multiplication in the land phase is rapid multiplication in the log phase the numbers are bacteria remain constant as the number of reduce is equal to the number dying the numbers of bacteria decrease in the decline phase so also look at the oxygen requirements of bacteria we've got different types of bacteria we got anaerobic bacteria is a bacterial that will happily survive without oxygen and so you'll see them in liquid for example where they'll survive because there is no oxygen all the oxygen is on the surface of the food obligate aerobes you'll find on the surface of food obligate must means that they must have oxygen in order to survive facultative anaerobes can live with or without oxygen and obligate anaerobes means they must not have any oxygen the bacteria that springs to mind there are the clostridia Clostridium perfringens Clostridium botulinum they are obligate anaerobes so it's a look at water activity limits for microbial growth so we go from one to door by six where one is for water filet and 0.6 is dry and it shows the different types of bacteria and the types of water they require in order to survive and grow Pseudomonas they need a lot of water between 0.95 at NOAA pine 9/8 Ecole des and Chris tritium orchestra dr vis to their roundabout nor point five two nor point three Salmonella we could bacillus staph aureus Staphylococcus aureus most East's most mold Zarafa lake was more filling zero philic and I was woefully East's require very small amounts of water indeed so you see on the bottom the legend says 8 w is distilled water and no point on all water particles who completely burned but he will find even dried products such as dried rice or powders do have a water content albeit very small not enough for any bacteria to grow so I mentioned earlier the pH scale goes from 1 to 14 where 1 is acid 7 is neutral and 14 is alkaline bacteria prefer neutral conditions although II coli have been known to grow in acidic conditions around about four point five five so we got low acid food its classes four point five when I said it would be one alkaline we tend to hear cleaner materials tend to our alkalinity around about the 1214 volume how do we destroy bacteria well we can do it through pasteurization thus the temperature I mentioned a 63 degree scene above this destroys pathogens sterilization is attempted it's really difficult to achieve in a normal kitchen because it's hundred and twenty one degrees C or in excess of that for a period of time but if you achieve that temperature it destroys all bacterial spores and toxins that's not a temperature you'll see or all you see of use in autoclaves and heat and the pressure now Canon is classes commercially sterile Canon actually use the sterilization process where it's heated 421 degrees C and above for a period of time and effective cooking will kill bacteria I've already mentioned that bacteria start dying around about 5 55 to 56 degree C but anything up to 75 degrees C and he can be assured that it's very safe to eat but I've already mentioned anything from I've explained him a to myself with temperatures from 57 up to 63 it's safe if you use a sous-vide process for example this is very you vacuum-packed foods and cooking for an extended period of time at lower temperatures such as sixty degrees C in fact the 60 degree C will penetrate all the food can and all pathogens but it doesn't coagulate the proteins as much as over cooking to attempt a 75 degree C does we can use chemicals to kill bacteria salt sugar nitrates nitrites for example what's on of sugar tend to do is draws moisture out of foods so it makes it less desirable for pathogens to grow and nitrates and nitrites actually act as preservatives chemical preservatives so the bacteria won't grow irradiation is a process which is used throughout several continents but only spices the license radiation in the UK ultraviolet light is used in quite a few industries especially in the shellfish industry it destroys bacteria in water destroys bacteria membrane and it destroys microorganisms in the atmosphere you might have seen as an example I think it's the new hand dryers you find I think the name from now Dyson's I think they are but other ones aren't available of course for advertising peer says but when you press a start but there's a bright blue light if you like that is ultraviolet light that's actually helping destroy any pathogens and there might be wrong hands after you wash them so you're drying them but the ultraviolet light helps to give it a double whammy if you like and spores now only two families of bacteria produce spores on the tritium and the cell s of the study are and bacilli these are the only two pathogens that produce spores so what are spores it's called the resistant rest in phase of these two bacterial families where most bacteria are killed through heat through radiation through chemicals or disinfection Christian Christian bacillus will not die they'll turn into spores but more precisely the spool is really already present inside of the bacterial cell and so what happens under unfavourable conditions the bacterial cell dies off and the spore comes into being now spores can survive high temperatures for example up to 2,000 degrees C and rocket taking off and minus 20 degrees C from liquid nitrogen they can survive chemicals such as disinfectants they can survive dehydration so under unsuitable conditions with a bacterial cell a spore forms in the sound as I already mention it's already in the cell but it starts to develop in earnest when the conditions become unsuitable the cell disintegrates releasing the spore under suitable condition suitable conditions rather the sporty ominous turns back into a bacterial cell and then the cell will multiply so a bacterial spoiled our bacterial spores are our for all intensive purposes harmless we ingest spores on a daily basis from the atmosphere they go down through our digestive system I would ask sorry our stomach is very acidic so stops the spores from germinating but if they do germinate and they started to grow all this when we can the problem so spores per se do not cause food poisoning but the bacterial cells that Joomla from them do spit on a psychological process the the bacterial cells tell its false walls to back in the cells etc etc and toxins are organic poisons produced by animals plants and bacteria the first one is called with bacterial cells and exotoxin these are toxins poisons which are produced when the cell multiplies or grows in food so Staphylococcus aureus for example if he cough or sneeze over food we've released Staphylococcus aureus because we are the depository supposedly flight for Staphylococcus aureus they're on our skin and in a nose and mouth so freely sauce back to you on the food and it's high-risk food and the food is at warm temperatures they will start to grow it's the bacteria grow they give off me as products called exotoxins Wiese materia micro me grow for example we give off feces in urine they are poisons to other animals these are poisons to us an extra toxins from stuff aureus excuse you another one is Endor toxin Endor meaning within again a Greek word from them this is when the bacteria already in the colon or the small intestine and they start to die and as they die the toxins are released from the cell walls so you can see the the cell starting to dissolve in this diagram here I'm releasing the toxins on the LDS as we call them into the system the body system and these toxins will affect our immune system in as much as our immune system will sell send its immune cells to the point where the toxins are and it will start to absorb the toxins but this is not an easy process there is a lot of pain and discomfort involved in a living system actually tackling the toxin cleanup if like this is where we start to get pains like abdominal cramps etc now how do identify bacteria well we could use a macroscopic examination this is large-scale examination if you like by seeing them growing colonies on agar agar on petri dishes microscopic examination obviously used a microscope uses something called the Gram stain this is we can tell if it's gram negative or gram positive grams a scientist that invented this process where you use a certain stain for bacteria certain bacteria will hold onto the stain and other ones will not hold onto the stain so we tell there's different colors biochemical reactions obviously bacteria will react to certain chemicals given certain gases or different reactions serological type in again use in for example salmonella it's got about 2,000 different types of strains so using this we can find out which type of strain it is phage type in again similar to cell logical type in and use in things called immunoassay for more details on the Gram stain the reactions type in and we wanna say if you look at the notes of II provided it'll give you some further info so the key points for lecture 2 food poison bacteria common in all food businesses they require fluid moisture time suitable pH to multiply most pathogenic bacteria prefer 20 to 50 degrees C and they called meso files on miso files excuse me they can double number in 10 minutes temperatures above 75 degrees here used to destroy them some toxins and spores can survive boiling for several hours most food poison bacteria do not grow below 5 degrees C high acids salt and sugar stop multiplicate multiplication of bacteria on the various methods of identification of specific bacteria

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