Basic Food Microbiology

The Food Processing Center Author

03/27/2018 Added

1139 Plays

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This lecture provides an overview of food microbiology. It starts by describing the different groups of microorganisms associated with food, such as molds, yeasts, and bacteria. It then focuses on bacterial reproduction, spore formation and the factors that affect bacterial growth and survival. The last part of this lecture focuses on microorganisms that can cause food spoilage and those associated with foodborne diseases.

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[00:00:04.950]Thank you very much for coming,
[00:00:06.340]and welcome to the University of Nebraska.
[00:00:11.270]We are here today
[00:00:13.540]for another workshop that is part of our series,
[00:00:17.630]Science of Safe Food.
[00:00:19.440]Today we're gonna be focusing
[00:00:21.460]on food safety for farmer's market.
[00:00:23.810]And our first lecture is going to be
[00:00:26.440]Introduction to Food Microbiology.
[00:00:35.590]I am Andreia Bianchini.
[00:00:37.300]I am a professor here
[00:00:38.610]in the Food Science and Technology Department.
[00:00:41.360]And my area of expertise is working with food processes
[00:00:47.970]in how to make the food safer.
[00:00:49.790]So basically, I have a food engineering
[00:00:52.380]and microbiology background.
[00:00:56.090]So when we talk about microorganisms in foods,
[00:01:00.680]basically all raw agricultural commodities
[00:01:04.100]that you may work with or use as ingredients
[00:01:07.100]will contain microorganisms.
[00:01:08.760]There's nothing we can do about it.
[00:01:10.080]They grow in the environment,
[00:01:11.970]and they're exposed to the air, to the soil, to water,
[00:01:16.587]and all those things contain microorganisms.
[00:01:18.980]We can't grow them in a sterile environment.
[00:01:23.080]So they'll have microorganisms.
[00:01:24.780]Our duty is,
[00:01:27.750]or our task is to make sure
[00:01:30.240]that we prevent the bad ones from being present in the food.
[00:01:34.520]We wanna prevent the pathogens
[00:01:37.240]from being present in the foods.
[00:01:39.250]We wanna reduce the spoilage microorganisms
[00:01:42.070]to be able to preserve the food longer.
[00:01:44.800]And in some cases,
[00:01:46.140]we wanna promote the growth of the good ones,
[00:01:48.310]in case of you wanna do a fermentation, for example.
[00:01:51.256]In some cases, we may use a culture that we add,
[00:01:57.170]like you would, for example, to prepare yogurt
[00:02:00.420]or maybe a sourdough bread.
[00:02:02.500]You might add a culture to the product.
[00:02:04.550]Or in some cases, you just let the organisms
[00:02:07.160]that are present in that product
[00:02:09.350]to grow in a beneficial way.
[00:02:12.270]So our task is controlling that population.
[00:02:17.060]Killing the bad guys, reducing the spoilage ones,
[00:02:20.680]and promoting the growth of the good ones,
[00:02:22.770]if that's your goal,
[00:02:24.210]if you're doing a fermented product for example.
[00:02:26.630]The microorganisms that we're gonna be concerned of today
[00:02:30.010]will include molds, yeast, bacteria, and virus.
[00:02:32.820]And I'm gonna very briefly here introduce you
[00:02:36.730]to each of these different classes of microorganisms
[00:02:39.720]just to give you a little bit of background.
[00:02:42.640]And you're gonna see a lot of the regulations
[00:02:45.330]that Jane is gonna present to you in subsequent lectures,
[00:02:49.119]it's all tied back to basic food micro.
[00:02:52.900]So this is important, even if you're trying to think like,
[00:02:56.052]why is she explaining so much about this,
[00:02:58.460]or why should I care?
[00:02:59.700]Because all the regulations later on today,
[00:03:02.440]you're gonna see that it ties back to the basic micro.
[00:03:06.260]So basically,
[00:03:10.240]what we've done, scientists and regulators
[00:03:13.840]is we learned as much as we could about the microorganisms
[00:03:17.630]and we used those characteristics and that information
[00:03:21.070]to prevent foodborne illnesses and reduce the spoilage.
[00:03:25.440]So basically, we use what we know about them, against them.
[00:03:30.090]So that's the point here.
[00:03:32.330]So molds are multicellular organisms, meaning there's
[00:03:35.500]more that one cell that makes up the organism,
[00:03:38.050]just kind of like us.
[00:03:40.500]They reproduce by spores.
[00:03:42.050]You can think of the spores as little seeds,
[00:03:44.460]little plant seeds, so wherever this little seed lands
[00:03:48.470]a new organism can grow if the conditions are right.
[00:03:52.108]They're larger than bacteria and yeasts,
[00:03:54.947]and they're widely distributed in nature.
[00:03:57.110]There's not much that we can do about
[00:03:59.030]from preventing them from growing here and there,
[00:04:01.400]because they kind of move with the air.
[00:04:03.210]They're little spores.
[00:04:04.720]They kind of move with the air, and they can land anywhere.
[00:04:07.820]So it's kind of hard to control them in that way.
[00:04:10.640]They survive on many substances.
[00:04:13.020]How many times have you seen a drywall
[00:04:16.090]just turn black after a flooding, or after a water event?
[00:04:20.766]They don't need much to grow.
[00:04:22.250]If you give them a little bit of moisture
[00:04:24.470]and a little bit of food,
[00:04:28.930]be it carbohydrates or any other type of food,
[00:04:32.730]any type of cellulose or material
[00:04:36.400]that is like that, they will grow.
[00:04:38.310]They don't need much.
[00:04:39.520]They are very, very
[00:04:43.750]versatile in that way.
[00:04:45.200]They don't need much, they get very creative
[00:04:48.640]on how they can survive in the environment.
[00:04:52.780]So they're more tolerant to cold than heat.
[00:04:55.590]For us, that's a very good piece of information,
[00:04:58.230]because it means that they're gonna be very easily killed
[00:05:02.460]by any heating that we do in our food.
[00:05:04.420]Any heating process, pasteurization and all that
[00:05:07.600]will kill this microorganism, which is very good, right?
[00:05:10.810]So if you're baking your bread,
[00:05:13.050]the process of baking should kill them.
[00:05:15.430]If you're making any acidified foods,
[00:05:20.090]or any jams or jellies that require some cooking,
[00:05:23.890]the cooking should get rid of this microorganism.
[00:05:26.620]So as long as you preserve that food,
[00:05:29.010]enclosed and in the right conditions,
[00:05:32.050]or preserve it from being exposed again
[00:05:34.790]to those spores that might be in the air,
[00:05:37.080]you might get a little bit of extension of shelf life.
[00:05:40.940]But they're very tolerant to cold,
[00:05:43.110]so what that means is that foods that we refrigerate
[00:05:47.320]tend to be spoiled by this microorganism.
[00:05:49.500]So if you bring from the store a piece of cheese,
[00:05:53.210]it looks beautiful, while it's packaged it will maintain
[00:05:57.400]its quality and the conditions.
[00:06:01.590]But as soon as you open that package of cheese
[00:06:03.580]and start eating from it and taking slices off of it,
[00:06:06.908]spores that are in the air may land on that cheese,
[00:06:09.920]and now you put it in the fridge,
[00:06:11.260]and slowly that mold will grow.
[00:06:13.210]And then that's when your cheese gets spoiled.
[00:06:15.830]So just to keep that in mind.
[00:06:18.612]Yeasts are unicellular.
[00:06:20.390]They're usually egg-shaped.
[00:06:21.610]They're smaller than molds, larger than bacteria.
[00:06:24.390]They reproduce themselves by budding,
[00:06:26.420]which basically again, if we can relate to plants,
[00:06:29.070]is a little bud of the plant that shoots off.
[00:06:31.780]Here it's very similar.
[00:06:33.260]You have a cell that's gonna shoot off another cell,
[00:06:37.010]and it's gonna kind of put inside there
[00:06:39.370]all the information and all the machineries
[00:06:42.190]that it needs to grow and reproduce itself later.
[00:06:45.970]So it basically makes a baby to the side of the cell,
[00:06:50.840]and then when that little daughter cell
[00:06:52.710]has everything that it needs to be on its own,
[00:06:59.433]it gets closed off from the mother cell and released.
[00:07:03.350]So here in this slide we can see that happening.
[00:07:06.120]So this is the daughter cell,
[00:07:07.420]and once the process is ready,
[00:07:09.570]this cell here is gonna close off this gate,
[00:07:13.720]or this bridge, and then this daughter cell
[00:07:16.000]is gonna be on its own and it's gonna be able
[00:07:17.830]to grow and reproduce itself as well.
[00:07:19.770]So one organism will give origin to two,
[00:07:22.920]two can give origin to four, and so on.
[00:07:25.640]So we have what we call the growth of the organism.
[00:07:30.210]They're associated with liquid foods
[00:07:32.187]that are very high in sugar and acid,
[00:07:35.420]so they might be an issue for jams and jellies.
[00:07:39.149]They can grow in those products and cause the spoilage.
[00:07:44.510]Bacteria are very important, or the most important
[00:07:47.860]of the three that we're gonna talk about today,
[00:07:49.860]because they're the ones
[00:07:50.950]that will cause illnesses, foodborne illnesses.
[00:07:53.730]And those are the ones that from a public health standpoint
[00:07:56.890]should concern us the most.
[00:07:59.000]They can produce enzymes or toxins
[00:08:01.880]and release those in the food as they grow.
[00:08:04.560]It's just part of their process.
[00:08:05.918]They produce those compounds,
[00:08:08.800]and some of their toxins can be very,
[00:08:14.800]cause very, very serious illnesses.
[00:08:17.930]So some of them may cause an intoxication
[00:08:20.900]and you end up with gastrointestinal issues.
[00:08:25.097]And some of them can also be neurotoxins,
[00:08:29.600]so they can affect our neural system,
[00:08:32.160]and then it can lead to death.
[00:08:35.077]And that's the case of the toxin produced
[00:08:37.380]by a bacteria called Clostridium botulinum.
[00:08:40.230]Which is very much a problem,
[00:08:42.720]or I should say a concern, for canned foods.
[00:08:46.020]So that's the organism that we're very interested
[00:08:49.590]when we talk about acidified foods and canned foods
[00:08:52.400]is Clostridium, because of this toxin
[00:08:54.680]that it can produce and then can lead to death.
[00:08:59.080]They're single-cell,
[00:09:00.330]and they come in several shapes and forms.
[00:09:02.970]Viruses are small infectious agents
[00:09:05.670]that replicates only when they're inside of living cells.
[00:09:09.280]While not inside, they will just exist,
[00:09:12.510]but they won't be able to replicate themselves.
[00:09:15.080]And they're very, very small.
[00:09:16.610]They're like 1/100 of the size of a bacteria,
[00:09:20.300]so they're very small.
[00:09:22.550]Now bacteria, because they're so important to us
[00:09:26.220]for the reasons I already mentioned
[00:09:28.180]regarding the public health concern and foodborne illnesses.
[00:09:31.690]We're gonna start now focusing more on them
[00:09:34.880]and discussing a little bit more about them,
[00:09:37.380]because all of the things we're gonna learn more
[00:09:41.640]later today will relate back
[00:09:43.580]to these characteristics of bacteria.
[00:09:46.000]So they're gonna reproduce themselves by division,
[00:09:48.950]and here we have a flowchart
[00:09:50.470]that kind of shows how that would work.
[00:09:52.780]So you have a bacteria that will start expanding itself
[00:09:56.950]and kind of duplicating everything that it has inside
[00:10:00.280]as we can see here, and there's a step.
[00:10:02.480]It's elongated, and everything,
[00:10:04.360]the DNA material is being replicated.
[00:10:06.580]And then they're gonna divide themselves into two organisms,
[00:10:11.130]and then once they're separated like that,
[00:10:13.620]they're independent and they
[00:10:14.740]can start the process once again.
[00:10:17.150]In optimal conditions, this whole process
[00:10:20.300]will take about 20 to 30 minutes,
[00:10:22.790]which is rather fast if you think about it, right?
[00:10:26.270]If you leave your milk sitting on the counter
[00:10:29.050]for a couple of hours, you allow the bacteria
[00:10:32.310]to multiply at least four times.
[00:10:35.895]But remember that one bacteria will give rise to two,
[00:10:39.800]two to four, so it's actually an algorithmic increase
[00:10:45.100]in the number of cells.
[00:10:46.690]So they get to very high numbers fairly quick.
[00:10:52.730]Different bacteria will get to, will have this
[00:10:56.860]generation time that I mentioned of 20 to 30 minutes.
[00:11:00.400]That's in optimum conditions.
[00:11:02.150]And it also varies with different bacteria.
[00:11:05.220]So here I have an example, a chart,
[00:11:07.740]that shows the growth curve for some different bacteria.
[00:11:11.870]So Geobacillus stearothermophilus,
[00:11:14.040]which is this blue line here,
[00:11:15.500]you can see it takes about 20 minutes
[00:11:17.510]for that cycle to happen.
[00:11:19.750]E. coli takes about 30 minutes in optimum conditions.
[00:11:23.947]And some other bacteria, like Neisseria,
[00:11:26.720]will take about 40 minutes.
[00:11:28.490]So it's very specific to each different genus in the species
[00:11:34.100]but the time, or the generation time,
[00:11:38.540]can be as short as 20 minutes,
[00:11:40.560]and we need to keep that in mind.
[00:11:42.860]Another thing that is very important for us,
[00:11:45.290]and it's gonna come up again later in our lectures
[00:11:50.100]is about the ability of some bacteria to form spores.
[00:11:53.630]So the bacterial spores, they're basically a time capsule,
[00:11:57.840]or like a safety measure, that is used by the bacteria
[00:12:03.310]when it senses that it could die.
[00:12:05.680]So instead of just letting the environment destroy it,
[00:12:10.400]and say perhaps eliminate that organism, it's gonna say,
[00:12:15.900]I am gonna make sure that my species can survive.
[00:12:19.370]So I'm gonna pack it up in this little capsule
[00:12:22.360]that is really, really hard,
[00:12:24.000]everything I would need to survive.
[00:12:26.430]And then it's gonna put in there all the information
[00:12:28.321]and the DNA and everything that it needs to survive.
[00:12:32.250]And then even if the environment ends up killing
[00:12:35.170]this organism, that little capsule will survive,
[00:12:39.090]because it's made to do so.
[00:12:40.990]Nature was very smart that way, and it's made to survive.
[00:12:45.789]So when the conditions now are right again,
[00:12:49.270]and are optimum again, that little capsule
[00:12:52.540]will germinate and turn into a vegetative cell.
[00:12:56.720]So here we have two terms to learn.
[00:12:58.820]The vegetative cell and the spore.
[00:13:01.330]The vegetative cell, it's kind of like the mother cell,
[00:13:06.971]and when it feels the need,
[00:13:09.700]it's gonna produce a spore inside of that cell,
[00:13:15.070]and then even if this vegetative cell,
[00:13:17.090]the mother cell gets killed,
[00:13:19.020]the spore is gonna be released into the environment,
[00:13:22.120]and it's gonna survive.
[00:13:23.540]Once the conditions are right, that spore
[00:13:26.400]is gonna turn again into a vegetative cell
[00:13:29.010]that can multiply itself, one turning into two,
[00:13:32.440]like we talked about a minute ago,
[00:13:34.600]or it can go ahead and make a spore again.
[00:13:37.490]So it can choose what it's gonna do next
[00:13:40.470]depending upon the conditions in the environment.
[00:13:42.730]Why is that important?
[00:13:44.335]Because the bacteria that can produce a spore,
[00:13:48.780]they take a little bit more work to get rid of,
[00:13:52.180]because that spore is more resistant.
[00:13:55.870]So now if I could kill this bacteria here
[00:13:59.390]by simply boiling my product or cooking my product,
[00:14:04.540]to kill that spore, I'm gonna require pressure cooking.
[00:14:08.730]So that's where things start to,
[00:14:11.090]like we need to know about this
[00:14:13.290]to make sure that we process our foods in the correct way.
[00:14:19.850]So the vegetative cell is gonna be eliminated
[00:14:22.600]or killed by simple pasteurization,
[00:14:25.170]while the spore is gonna require higher heat.
[00:14:29.360]Or we can use other means
[00:14:31.320]that I'm gonna talk about a little later here,
[00:14:33.290]other means of preventing that spore
[00:14:35.470]from growing and creating issues.
[00:14:37.340]Okay, so keep that in mind.
[00:14:40.300]Here's just a few pictures for you to see
[00:14:42.940]how that spore can be inside of the cell.
[00:14:45.460]So here we have an under-the-microscope picture
[00:14:48.010]of a bacteria, it could be perhaps a clostridium
[00:14:52.760]that has a spore inside.
[00:14:54.719]This one here is germinating,
[00:14:56.680]so we can see that the spore is kind of breaking itself
[00:14:59.750]and a vegetative cell is coming out of it.
[00:15:02.620]So that's kind of like what would happen
[00:15:05.560]given the right conditions.
[00:15:08.620]So now we're gonna talk about the factors
[00:15:10.540]that affect the bacteria growth and their survival,
[00:15:13.060]because these are the tools.
[00:15:14.620]You can see this or look at this as our little toolbox
[00:15:19.250]that we can pull out and say, in this case
[00:15:21.820]I'm gonna use this to prevent bacteria from growing.
[00:15:24.450]In this other product, I'm gonna use this other tool.
[00:15:27.740]So it's our toolbox that we can use for preserving foods.
[00:15:33.050]So this first thing we're gonna talk about
[00:15:34.720]is nutritional requirements.
[00:15:37.870]Every bacteria has a nutritional requirement,
[00:15:41.020]and they kind of like us, some prefer some flavors,
[00:15:45.610]so to speak, some nutrients than others.
[00:15:48.580]So in that case, they always will need
[00:15:51.690]a carbon source, a nitrogen source,
[00:15:54.597]and some other trace elements and vitamins.
[00:15:58.000]In our case, because we are processing and making food,
[00:16:01.690]it's kind of hard to get rid of this,
[00:16:03.430]or do something about it,
[00:16:05.930]because our food is full of nutrients
[00:16:08.700]so it's hard to use this particular
[00:16:12.330]requirement against the bacteria.
[00:16:14.541]In some cases, what we can do is add preservatives.
[00:16:18.790]And that preservative can prevent the bacteria from growing.
[00:16:22.710]So we can tweak a little bit,
[00:16:24.990]and use preservatives to help us.
[00:16:29.070]Other things that we can do are related to moisture.
[00:16:33.410]For example, so moisture is something
[00:16:36.417]that's extremely for bacteria,
[00:16:39.150]and any other microorganisms.
[00:16:41.220]They can't grow if moisture is not available.
[00:16:44.107]And the reason why, I have some complicated pictures here,
[00:16:48.070]but the message I wanna give it to you is
[00:16:51.680]this is the bacterial cell.
[00:16:53.710]This is what surrounds a bacteria.
[00:16:56.240]It's a layer that looks like this.
[00:16:58.800]They don't have mouths and arms like we do,
[00:17:01.360]so how are they gonna search and get the nutrients
[00:17:04.670]from the environment and bring inside of the cell?
[00:17:08.100]The only way they can do that is by using water
[00:17:11.500]to move things, to flow things in and flow things out.
[00:17:15.630]And they have different mechanisms.
[00:17:17.260]Some are simply by permeation, just permeating that cell.
[00:17:22.269]Some require a little bit more energy,
[00:17:25.810]so those are facilitated diffusion.
[00:17:27.960]They have mechanisms or sometimes enzymes,
[00:17:31.530]or compounds that are present in that bacterial cell,
[00:17:38.610]or that bacterial layer here, that is gonna help
[00:17:41.900]the nutrients to go from outside to inside.
[00:17:44.520]And that's gonna require some energy,
[00:17:46.380]and that's what it's showing on this one here.
[00:17:48.830]The nutrients are not gonna move by themselves,
[00:17:52.170]but they're gonna be helped by this mechanism
[00:17:55.310]at the cell wall, and that's gonna require energy.
[00:17:58.890]So we have different types of mechanisms
[00:18:01.950]to move things from inside out or outside in.
[00:18:06.280]It goes both ways, and in all of those, we need water.
[00:18:10.380]If water's not present, things can not flow back and forth.
[00:18:16.170]So how can we use that characteristic now,
[00:18:19.350]to preserve foods and prevent pathogens
[00:18:23.470]from being an issue in food?
[00:18:26.490]We're gonna remove the water.
[00:18:28.890]If we take that water away, we can preserve the food
[00:18:32.920]and we can prevent the microorganisms from growing.
[00:18:36.000]There're different ways that we can do that.
[00:18:38.640]We can simply dry the food,
[00:18:41.260]but not all the foods that we consume are dried.
[00:18:44.520]But if you dry, you are physically removing that water.
[00:18:47.560]There are other ways that we can remove the water,
[00:18:50.910]or prevent it from being available to microorganisms,
[00:18:55.430]and that's the concept of water activity
[00:18:57.700]that I'm gonna introduce to you.
[00:18:59.600]So basically, water activity is a term that we use
[00:19:03.970]to describe how much water
[00:19:06.680]can move in and out of that produce.
[00:19:10.320]If you have a product that a lot of water can move
[00:19:13.580]in and out, you have a product with a high water activity,
[00:19:18.090]and do you think it's gonna be easier
[00:19:21.040]or more difficult for microorganisms to grow in that case?
[00:19:25.210]Easier, exactly, so the higher the water activity,
[00:19:28.607]the easier it is for microorganisms to grow,
[00:19:31.800]because they need that water,
[00:19:32.690]and they need that water to be free.
[00:19:35.490]The water cannot be bound.
[00:19:37.315]However, we can influence, we can use this knowing all this.
[00:19:43.440]We can use it in our favor, and we can use ingredients
[00:19:46.910]in our products that actually bind water,
[00:19:49.380]making them less available to microorganisms from growing.
[00:19:53.420]And that's what I have here in the picture.
[00:19:55.230]So basically, let's pretend that this is our product,
[00:19:59.210]and you have all these different molecules
[00:20:01.830]that are part of the ingredients inside of that product.
[00:20:06.810]The water likes certain ingredients,
[00:20:11.150]so it's gonna hold on to it, kind of like give hands to it.
[00:20:15.400]And in some other cases, there're other ingredients
[00:20:18.670]that the water doesn't like very much,
[00:20:20.910]so it's not gonna hold hands with it.
[00:20:23.700]So what we do is basically, we add,
[00:20:26.840]and in this case here I'm adding as an example salt.
[00:20:30.680]Just sodium chloride, as an example.
[00:20:33.910]If I add an ingredient like sodium chloride,
[00:20:36.620]it really likes water.
[00:20:38.720]So now it's gonna hold that water down.
[00:20:41.730]So as long as that water's being held down by an ingredient,
[00:20:46.000]it cannot move in and out of the product,
[00:20:49.170]and it can not be used by microorganisms for growing.
[00:20:53.180]Ingredients that help us a lot
[00:20:55.350]in this regard, salt and sugar.
[00:20:58.480]So when we work with our preserves and we make preserves
[00:21:02.190]and jams and jellies, we're adding some sugar to the product
[00:21:05.680]or we're cooking the product
[00:21:07.650]to concentrate the sugars that are naturally present.
[00:21:11.190]By doing that, by cooking the product down,
[00:21:14.330]we're eliminating some water by evaporation,
[00:21:17.080]so we're physically removing some water,
[00:21:19.467]and we are letting the water that is there bind
[00:21:22.722]to the sugars that are present, either naturally
[00:21:25.660]by the fruit or because we added sugar to it.
[00:21:29.000]Now we're reducing the water activity of the product a lot,
[00:21:32.350]and that's what helps us preserve those products.
[00:21:38.030]So just as an example, the water activity of water,
[00:21:42.140]it would be one, because that's how we measure it.
[00:21:45.320]Basically the water activity measurement
[00:21:47.810]is a comparison between completely free water.
[00:21:51.490]And you would have completely free water
[00:21:53.900]in a glass of water, right?
[00:21:55.690]So the glass of water has a water activity level of one.
[00:22:00.340]A cookie will have a water activity level of 0.3.
[00:22:07.430]Bread will have a water activity 0.92.
[00:22:13.630]Where do you think, don't look at your book,
[00:22:16.980]because the answer's there, don't look at your book.
[00:22:19.760]And then everybody looked.
[00:22:21.990]Don't look at it, tell me where do you think a jam
[00:22:25.550]or a jelly would fall in that line?
[00:22:28.980]Do you think it would have more water
[00:22:31.460]available than bread, or less?
[00:22:33.890]Where do you think jam would be?
[00:22:36.010]Think about how it spreads on the bread and such.
[00:22:40.710]You think it would have more water?
[00:22:42.640]It would be over here?
[00:22:44.960]Let's see.
[00:22:49.460]It's actually on the other side, why?
[00:22:52.680]The sugars, it binds that water.
[00:22:55.910]So it actually falls right here in the line,
[00:22:59.250]so that's how we get them to be preserved,
[00:23:02.040]is because that water is there but it's not available.
[00:23:07.430]So that's the trick.
[00:23:08.740]It's to have the water there to have a moist product,
[00:23:11.970]but the water not being available for growth.
[00:23:14.870]Okay, so sugar is a great, it's great at water binding.
[00:23:22.290]So now let's look at the minimum water
[00:23:24.690]activity for growth of different microorganisms,
[00:23:26.913]so that we get familiar with them
[00:23:28.910]and we can understand how it works.
[00:23:32.070]So here we have the pathogen.
[00:23:34.380]This is Staphylococcus aureus is a pathogen.
[00:23:37.900]It needs 0.85 of water activity for growing.
[00:23:43.180]Salmonella, Clostridium,
[00:23:44.927]the other two pathogens, they need 93.
[00:23:47.630]So if we wanna try and keep our foods
[00:23:51.840]free from pathogenic growth, or bacteria,
[00:23:55.220]pathogenic bacteria and their growth,
[00:23:58.310]I need to have my water activity below what?
[00:24:03.913]0.85, if I don't want those guys to grow,
[00:24:07.310]I need to have my water activity below 0.85.
[00:24:10.570]Keep that in mind, because part of our regulations
[00:24:13.280]is that 0.85, that's where it's coming from.
[00:24:16.340]To prevent pathogenic bacteria from growing,
[00:24:19.200]we need to keep the water activity below 0.85.
[00:24:22.930]Yeast and molds, they require somewhat less
[00:24:27.460]water for growing.
[00:24:28.810]So that's why sometimes they are the ones
[00:24:31.450]spoiling our jams and our jellies, because remember,
[00:24:34.930]what was the water activity of the jam in my example?
[00:24:37.743]0.75, how much molds need to grow?
[00:24:41.223]0.75, so they can grow there.
[00:24:45.250]So sometimes that's how those products get spoiled.
[00:24:51.440]Another characteristic that is extremely important for us
[00:24:55.360]is the ability of microorganisms to either use oxygen
[00:25:00.490]for growing, as respiration, or not.
[00:25:03.940]So some organism are called aerobes,
[00:25:07.190]or aerobic microorganisms.
[00:25:09.700]Those microorganisms need oxygen.
[00:25:11.700]If you remove oxygen, if you vacuum package your food,
[00:25:15.780]they can't grow anymore.
[00:25:17.970]Some other microorganisms are anaerobe,
[00:25:22.320]they're called anaerobes
[00:25:23.660]and they are anaerobic microorganisms.
[00:25:25.870]They only grow if the oxygen is taken away.
[00:25:29.550]So now your vacuum packaged food would allow them to grow.
[00:25:34.190]Or if you have a canned product,
[00:25:36.380]inside of the can do we have lots of oxygen,
[00:25:39.220]or no oxygen at all?
[00:25:41.320]No oxygen, so the anaerobic microorganisms
[00:25:44.483]could grow in there without no problem.
[00:25:47.820]We have pathogenic bacteria that falls
[00:25:50.280]in either of those two groups.
[00:25:52.410]So we need to be aware and know about them.
[00:25:55.360]Clostridium botulinum, which is the microorganism
[00:25:58.660]that we're very much concerned in acidified foods
[00:26:01.240]and canned foods, is anaerobic.
[00:26:05.270]Which means that if we don't do something else,
[00:26:08.490]what happens?
[00:26:10.560]They'll grow just fine inside of that can, okay?
[00:26:13.790]So keep that in mind as well.
[00:26:17.520]So what we do to preserve
[00:26:19.110]the foods based on oxygen requirements,
[00:26:21.670]we can do a modified atmosphere packaging.
[00:26:25.010]You can do vacuum packaging as I mentioned
[00:26:27.630]by removing the oxygen or changing that atmosphere
[00:26:32.320]to prevent organisms that need oxygen for growing,
[00:26:37.270]so that's what we can do.
[00:26:38.900]Now we're gonna talk about temperature,
[00:26:41.600]because again, it's another very important characteristic
[00:26:45.200]that if we know about the behavior of the microorganisms
[00:26:49.400]we can then use somewhat against them.
[00:26:52.450]So there's some microorganisms that really like
[00:26:54.890]low temperatures, and this is a chart in Celsius degrees.
[00:26:59.135]So I'm gonna try and correlate with Fahrenheit.
[00:27:02.020]So this would be basically your refrigeration temperature
[00:27:08.190]maybe in the 35 to 40ish, right, 42 maybe?
[00:27:13.070]It would be in this area.
[00:27:14.560]Then your mesophiles here,
[00:27:16.530]they would be in your room temperature,
[00:27:19.030]maybe 60 to 75 Fahrenheit would be in this area.
[00:27:24.890]Thermophiles here would be a little bit higher,
[00:27:28.120]maybe in the hundreds, and then hyperthermophiles,
[00:27:32.320]they're higher than that.
[00:27:34.860]So just for you to have an idea.
[00:27:36.340]So if you think about looking at this,
[00:27:38.670]this would be your refrigeration concern,
[00:27:42.130]like microorganisms that can grow under refrigeration.
[00:27:45.620]These ones would be the ones that can grow
[00:27:47.530]under ambient temperature.
[00:27:50.690]And these are the ones that can grow in your food
[00:27:53.660]if the food is not maintained in the right temperature.
[00:27:58.080]So sometimes when we are processing foods,
[00:28:02.740]we're gonna cook it to a high temperature
[00:28:05.130]to kill microorganisms, but then after cooking,
[00:28:08.160]we need to chill the food down.
[00:28:10.620]Not if you're gonna serve it.
[00:28:11.680]If you're gonna serve it, you keep it hot,
[00:28:13.740]but if you're not gonna serve it right away
[00:28:15.680]we need to cool it down.
[00:28:17.180]And what we're trying to do is get away from the area
[00:28:20.330]where microorganisms that like the heat
[00:28:22.979]grow and spoil that product before you can even serve.
[00:28:26.670]So that's why restaurants, they have that danger zone.
[00:28:30.660]So if they are preparing the food,
[00:28:32.600]they have to cook it at what, 165 Fahrenheit
[00:28:36.340]and then keep it there until it's consumed,
[00:28:39.620]or if they're not gonna serve it right away,
[00:28:42.680]they need to chill it quick and then keep it refrigerated.
[00:28:47.133]Then we jump from kind of like all the way here,
[00:28:50.910]we jump all the way here and preserve
[00:28:53.610]the microorganisms that would grow in this area
[00:28:56.890]from the spoiling and causing issues in the food, okay?
[00:29:03.440]And how do we use the temperature
[00:29:06.010]then for food preservation?
[00:29:08.020]We can chill the food.
[00:29:10.450]We can freeze foods, right?
[00:29:12.860]If we freeze them, we go way below
[00:29:16.010]that refrigeration temperature
[00:29:17.890]so nothing can grow under frozen conditions.
[00:29:20.670]No microorganisms will grow under frozen conditions.
[00:29:23.810]So to preserve foods, we can either refrigerate them
[00:29:26.850]or freeze them, and that's the reason why we do so.
[00:29:30.530]It's to get away from that growth zone.
[00:29:34.300]We can also use very high temperatures
[00:29:37.286]like I mentioned the cooking temperatures,
[00:29:39.710]to kill the microorganisms.
[00:29:41.750]And what I wanna point out in this chart
[00:29:44.430]is just how you have the number of bacteria
[00:29:47.900]that could be present in the product,
[00:29:49.510]and let's say that you're starting with
[00:29:51.080]extremely high number like here in this chart.
[00:29:54.260]And then you apply temperature for two, four,
[00:29:57.410]six, eight, 10, 12, 14, 16 minutes.
[00:30:00.580]As you apply that temperature to the product,
[00:30:03.030]the number of bacteria and bacterial cells
[00:30:06.220]in the product is gonna be reduced.
[00:30:08.350]So that's important, that's something
[00:30:10.210]that we use a lot in food processing, right?
[00:30:12.970]Another thing to consider is that,
[00:30:16.270]so here for example,
[00:30:18.780]if I have 10,000 cells it might take
[00:30:23.594]12 minutes to achieve that.
[00:30:26.560]Let me see if I have another comparison, yes.
[00:30:29.230]And to get to 1,000, so to go from 10,000 to 1,000,
[00:30:33.870]it took me two minutes.
[00:30:35.640]So in this case we're gonna way that
[00:30:37.480]it takes two minutes to reduce my population by 90%.
[00:30:43.070]That's important for us in science and regulations,
[00:30:46.816]because we call this the 90% reduction,
[00:30:51.200]we call it a decimal reduction.
[00:30:53.400]We're reducing the population by 1/10, right?
[00:30:57.670]So this decimal reduction here in this case
[00:31:01.130]takes me two minutes.
[00:31:03.100]So if I wanna reduce the population by 99%,
[00:31:08.199]how long do I need to cook?
[00:31:11.520]Four minutes, right, it's two for 90,
[00:31:14.810]four minutes for 99.
[00:31:16.330]If I wanna add another tenth or another decimal reduction,
[00:31:20.660]99.9, I need to cook for six minutes.
[00:31:25.160]Each of these reductions that we're calling,
[00:31:28.848]we call it a log reduction.
[00:31:31.627]So one log reduction in this case
[00:31:34.590]takes two minutes.
[00:31:36.600]Two log reductions, four minutes.
[00:31:39.720]Three log reductions, six minutes, and we can add up.
[00:31:44.000]So why is this important?
[00:31:45.250]Because sometimes the regulation might say
[00:31:47.430]that when you cook your product,
[00:31:49.040]you need to have a five log reduction.
[00:31:51.750]So you need to first find out
[00:31:53.830]how long does it take to get one?
[00:31:56.210]And then you need to multiply that by five,
[00:31:58.930]and that's the time of cooking.
[00:32:00.880]Sometimes that work is already done for us,
[00:32:04.090]and they provide us with tables and charts
[00:32:07.610]that tell us, at this temperature you need to cook
[00:32:10.690]for this long to get your internal temperature
[00:32:14.440]of a roast, for example, safe.
[00:32:18.070]If you have chicken, then you're gonna have to cook
[00:32:20.040]at this temperature for this long.
[00:32:21.510]So those tables, guess what?
[00:32:23.570]They were all made based on a chart that looked like this.
[00:32:28.690]That's where the science is coming from.
[00:32:31.020]So those times and temperatures are not
[00:32:33.210]necessarily pulled out of a hat.
[00:32:35.530]They are all science-based, okay?
[00:32:39.750]So this was all done at a temperature
[00:32:42.100]of 60 celsius degrees, as an example.
[00:32:46.610]If I use a higher temperature,
[00:32:48.550]what do you think is gonna happen with my times?
[00:32:52.750]Exactly, I don't need to cook as long,
[00:32:55.220]but if I reduce my temperature, I need to cook longer.
[00:32:58.590]And that's what this chart is showing us.
[00:33:01.030]As you go down in value, now you need to cook longer.
[00:33:04.850]As you go higher in value, you can achieve the same
[00:33:08.440]log reduction in a much shorter amount of time.
[00:33:12.550]So keep that in mind when we talk
[00:33:14.870]about those log reductions and temperatures.
[00:33:19.540]And we also need to be aware that vegetative cells
[00:33:24.301]will be killed much faster than the spores.
[00:33:28.370]So the vegetative cells are much easier
[00:33:31.130]to be reduced than the spores.
[00:33:34.560]And when we talk about canned foods,
[00:33:36.710]what we are trying to kill there
[00:33:38.392]is the spore of Clostridium botulinum,
[00:33:41.130]so it's a very hard task to achieve.
[00:33:45.150]That's why we need so high temperatures
[00:33:47.430]and pressure cookers and that sort of thing.
[00:33:49.660]Another characteristic, pH.
[00:33:51.783]It refers to the degree of acidity
[00:33:54.810]or alkalinity in a product.
[00:33:57.330]The more acid, the lower the pH.
[00:34:00.860]And a low pH is inhibitory to certain microorganisms,
[00:34:05.290]and especially to spore germination.
[00:34:08.730]So if we put our puzzles, you start to think about it,
[00:34:13.190]so it's hard to kill the spore.
[00:34:15.400]But maybe I don't need to kill it.
[00:34:17.130]Maybe I just need to prevent it from growing, what can I do?
[00:34:21.080]Reduce the pH.
[00:34:22.850]Where do we do that in our food processing?
[00:34:26.090]With fermentation and acidified foods.
[00:34:28.970]You don't need to pressure cook those,
[00:34:31.660]but you need to make sure that the pH is very low
[00:34:35.490]to prevent the spore from germinating.
[00:34:37.520]So here's where things start
[00:34:39.180]to kind of come together, right?
[00:34:41.210]The organisms, they have the most favorable pH for growing.
[00:34:45.760]Usually yeast and molds like lower pH,
[00:34:48.500]and bacteria likes neutral pH.
[00:34:51.010]So if we go away from the neutral,
[00:34:53.010]if we go to low pHs, then the bacteria starts not liking it,
[00:34:57.540]not growing in those conditions.
[00:35:00.310]And if we are going to have a spoilage issue,
[00:35:03.070]it's gonna be with yeast and molds.
[00:35:04.970]So those are the ones that might grow
[00:35:07.410]in products that have been either fermented or acidified,
[00:35:10.770]like a tomato sauce.
[00:35:12.370]You may have mold growing in the top of it,
[00:35:14.640]because they don't mind too much the pH.
[00:35:17.210]But it's safe regarding pathogenic bacteria,
[00:35:20.270]because the pH is low.
[00:35:23.460]So that's how we use that tool in terms of food safety.
[00:35:28.820]So we can ferment products and reduce the pH,
[00:35:33.180]or we can acid foods that are either
[00:35:35.860]naturally acidic or acidified.
[00:35:40.700]And we're gonna talk more about it later today.
[00:35:43.180]We're gonna have a lecture
[00:35:44.500]that is all about acidified foods.
[00:35:47.836]So the microorganisms, just to kind of close up here,
[00:35:52.920]they have different behaviors, right?
[00:35:54.433]They have the good ones that we can use for producing food,
[00:35:59.420]and fermenting foods and they're beneficial.
[00:36:01.820]The bad ones that will spoil our products,
[00:36:04.030]and we have the ugly ones that will cause disease.
[00:36:07.260]So the good ones, we add them intentionally to foods,
[00:36:10.770]or we provide the conditions in the food for them to grow.
[00:36:15.640]And we wanna do that to develop flavors and textures
[00:36:21.140]that we like, and that also helps
[00:36:23.320]with preservation, extension of shelf life.
[00:36:25.770]Examples could be yogurt, cheeses,
[00:36:27.900]sour cream, pickles, and bread.
[00:36:32.250]The good ones will enhance the preservation.
[00:36:34.620]They'll give us a longer shelf life.
[00:36:37.150]Sometimes they'll enhance the nutritional value
[00:36:39.550]by making some nutrients more available.
[00:36:43.080]They can enhance functionality, organoleptic properties,
[00:36:46.430]which means the flavors and textures.
[00:36:48.690]And in most cases they will increase
[00:36:51.490]the economic value of that product.
[00:36:53.160]You can sell it for a higher price.
[00:36:56.540]The bad ones will change the food
[00:36:58.370]and cause them to go bad, or spoil,
[00:37:01.770]and they're gonna lead to economic losses, of course,
[00:37:04.860]and that's what we're trying to prevent here,
[00:37:07.510]and issues with food security.
[00:37:10.240]The ugly ones are the ones that can make us sick.
[00:37:12.800]Those are the pathogens.
[00:37:14.250]Those are the ones that we want zero in our food.
[00:37:17.180]They can't be there.
[00:37:18.170]If they're present, the food is adulterate,
[00:37:20.370]and can't be consumed or sold.
[00:37:22.880]Illnesses can range from very mild to life-threatening.
[00:37:27.240]And I have a laundry list here
[00:37:29.360]of bacterial foodborne illnesses,
[00:37:31.710]and the organisms that can cause them.
[00:37:34.040]And the list is quite large,
[00:37:36.130]and it's not even perhaps complete.
[00:37:38.460]There's more organisms that can also
[00:37:40.240]cause foodborne illnesses,
[00:37:43.420]but here we have the main ones listed.
[00:37:46.020]And like I said, some of them will cause
[00:37:48.480]gastrointestinal issues,
[00:37:50.200]some may lead to more serious diseases.
[00:37:54.380]Just as an example, E. coli,
[00:37:56.650]depending on the type of E. coli,
[00:37:59.120]it can cause issues with your kidneys.
[00:38:04.900]Listeria monocytogenes,
[00:38:06.940]if the individual that is affected by the organism
[00:38:12.670]is pregnant, for example,
[00:38:15.090]if it's a woman that is pregnant,
[00:38:18.050]it can move into the fetus,
[00:38:22.080]it can cross the placenta barrier,
[00:38:24.200]and it can cause death of the fetus, it can cause abortion.
[00:38:28.710]So those are microorganisms that are very serious.
[00:38:31.560]You don't want that in your food,
[00:38:33.070]you don't want to have to deal with those.
[00:38:37.610]Clostridium botulinum is the one that I mentioned
[00:38:40.250]that can make spores, and it can be an issue
[00:38:43.440]in canned foods because it's anaerobic.
[00:38:46.600]It likes that closed environment.
[00:38:49.180]It has the spores that is really resistant to heat,
[00:38:52.370]so we need to take precaution in those cases.
[00:38:56.300]Staphylococcus aureus is an organism
[00:38:59.330]that is very commonly associated with poor hygiene,
[00:39:02.730]so if we keep hygiene in the kitchen and employee hygiene,
[00:39:06.810]usually we can prevent issues with that microorganism.
[00:39:11.780]Salmonella and Campylobacter are very much
[00:39:14.090]associated with poultry products.
[00:39:16.100]It's common in that product,
[00:39:18.900]in that raw agricultural product,
[00:39:20.650]so we need to make sure that the food is properly cooked,
[00:39:25.690]and if we apply the heat appropriately,
[00:39:28.260]then it shouldn't be an issue.
[00:39:29.950]So it's a matter of knowing the microorganism,
[00:39:32.700]knowing what to do to eliminate
[00:39:35.840]or prevent it in our products.
[00:39:38.900]Here I just have a list of total cases from the CDC.
[00:39:45.080]This is on an annual basis.
[00:39:47.230]The number of total cases, the number of hospitalizations,
[00:39:50.690]and that's caused by different microorganisms,
[00:39:52.980]just so you understand which are the ones
[00:39:55.320]that we are most concerned about.
[00:39:57.080]So if you look at norovirus, which is a virus,
[00:40:01.130]it causes the majority of the disease.
[00:40:03.710]So we're very much concerned about it, and it also,
[00:40:07.170]it's very much transmissible by poor hygiene.
[00:40:11.420]By not washing your hands properly,
[00:40:15.280]using the restroom and not washing your hands.
[00:40:18.760]So if you take those precautions,
[00:40:21.930]you can reduce the number of cases in that regard.
[00:40:28.790]Another organism that is important is Salmonella,
[00:40:31.900]Clostridium perfringens causes issues in food.
[00:40:36.224]The Salmonella is associated, perhaps,
[00:40:40.260]with not proper cooking.
[00:40:42.530]The Clostridium perfringens would be associated
[00:40:45.040]with not holding the food following that guideline
[00:40:50.410]for temperature in food service.
[00:40:52.610]If you keep it hot enough, and if you're gonna cool it,
[00:40:55.270]you cool fast enough, you shouldn't have issues
[00:40:58.680]with this microorganism.
[00:41:00.440]When you serve it, if you reheat it
[00:41:02.770]to the right temperature you shouldn't have issues.
[00:41:05.800]You see there that Clostridium botulinum is not even showing
[00:41:09.790]which is a good thing, because it means
[00:41:12.080]that the number of cases per year is very small.
[00:41:15.140]And we wanna keep it that way,
[00:41:16.580]because that organism is extremely,
[00:41:21.636]it terms of fatality, it's a much higher rate
[00:41:24.940]than any other that you see in here.
[00:41:27.240]So the industry, the FDA, the inspectors,
[00:41:30.840]all work together with the industry
[00:41:33.030]and the food processors to keep the numbers
[00:41:35.100]as low as possible by providing training
[00:41:37.870]and making sure that everybody is doing what they need
[00:41:41.546]to keep Clostridium botulinum away from our food supply.
[00:41:49.900]So with that, we finish
[00:41:51.870]our Introduction to Food Microbiology.
[00:41:53.840]I'll take any questions that you may have,
[00:41:55.880]or any curiosity or concern
[00:41:58.880]about anything that we discussed so far.
[00:42:03.820]Listeriosis,
[00:42:05.646]what are the high risk foods that carry it?
[00:42:08.747]That's a very good question,
[00:42:11.560]because traditionally and historically,
[00:42:13.880]and I'll give my perspective and then the inspectors
[00:42:17.110]can jump in later and maybe add to that.
[00:42:20.144]But basically, historically we always associated them
[00:42:23.830]with deli meats and products,
[00:42:28.110]like meat products that are refrigerated
[00:42:31.510]and maintained refrigerated like hot dogs
[00:42:33.930]and that sort of thing.
[00:42:35.730]However, over the years the industry
[00:42:41.020]have taken precautions to reduce those problems,
[00:42:44.210]and I explain why.
[00:42:45.450]Listeria is an organism that it's very easy to kill.
[00:42:49.940]Temperature will kill it very easily, it's not a problem.
[00:42:53.600]However, it lingers in the environment a lot.
[00:42:57.370]So it's an environmental problem.
[00:43:00.180]So if you have a product that you cooked,
[00:43:03.290]and then you exposed to the environment,
[00:43:05.230]it can get recontaminated.
[00:43:07.040]And that's what happened with the deli meats,
[00:43:08.950]because they would cook the ham,
[00:43:10.840]but then what do you do after you cook?
[00:43:13.490]You slice it.
[00:43:14.500]During the slicing is when you would have the contamination.
[00:43:17.670]So historically, they have been associated
[00:43:20.090]with deli meats and hot dogs and things of the sort.
[00:43:23.160]However more recently, we have had cases
[00:43:26.410]of produce being associated.
[00:43:30.090]I think the last outbreak, was it cantaloupe with listeria?
[00:43:34.440]And I think there was even a lady in Iowa
[00:43:36.910]that lost a baby because of it.
[00:43:39.030]And I remember very well, because at the time
[00:43:40.690]I was pregnant, and so I'm like,
[00:43:41.820]oo, I'm staying away from cantaloupe,
[00:43:43.117]and I really like cantaloupe.
[00:43:45.600]So the issue was that
[00:43:49.900]the contamination was in the environment.
[00:43:52.400]Like I said, this organism is lingering in the environment,
[00:43:55.800]and they were not doing a proper job
[00:43:57.820]of washing and sanitizing those fruits
[00:44:00.530]as they were being picked up.
[00:44:01.970]So they were getting to the store
[00:44:03.520]with contamination on the outside.
[00:44:05.560]And then when people were cutting in,
[00:44:07.550]that contamination that was on the rind ended up inside.
[00:44:11.100]So because of that, we learned our lessons,
[00:44:13.300]and now we have a lot more procedures
[00:44:15.150]for food service as far as washing and sanitizing
[00:44:19.440]the rinds of melons before they cut it.
[00:44:23.530]So I don't know if you guys want to add to that,
[00:44:25.750]if you have any?
[00:44:27.760]Where does seafood fall in that?
[00:44:30.693]You know, like deli meats or is it
[00:44:32.943]on a higher end for risk, or--
[00:44:36.930]I would say it's on the higher end
[00:44:41.430]because in terms of keeping it fresh,
[00:44:44.140]if you keep it fresh and you keep it iced,
[00:44:46.970]you should be okay, but it's a very perishable food.
[00:44:50.500]It was growing in the environment,
[00:44:51.960]it was in the water, so there's,
[00:44:53.970]imagine the water activity of those products.
[00:44:56.870]It's really high, right?
[00:44:58.600]That's how they, the shellfish, it's a filtering organism.
[00:45:04.500]It filters water, so water has to be there in and out
[00:45:07.460]to bring nutrients and take things out of that organism,
[00:45:10.380]so in terms of being perishable, it's really high.
[00:45:14.090]But if you keep it refrigerated,
[00:45:15.880]you keep it iced, then you might be able
[00:45:18.180]to maintain that shelf life and safety of that product.
[00:45:22.790]Anybody wants to add to that?
[00:45:25.100]Any of the ready-to-eat products that are refrigerated
[00:45:27.890]are ones that we're most concerned about,
[00:45:29.897]and that's why the sanitation step
[00:45:32.430]within our coolers and stuff is so important,
[00:45:34.470]because you can have listeria that grows.
[00:45:36.420]And that's where our date marking regulation comes from,
[00:45:39.090]the seven day requirement,
[00:45:41.060]because we know that after seven days at 40 degrees,
[00:45:45.850]listeria is happy to grow to a log
[00:45:49.940]where it can cause issues.
[00:45:51.500]And so that's why we want refrigerators
[00:45:54.430]to be kept sanitized and clean,
[00:45:56.300]racks to be cleaned and stuff like that.
[00:45:58.840]Thank you.
[00:46:03.020]Question?
[00:46:04.600]Please do.
[00:46:07.070]What about biltong or jerkies
[00:46:08.680]or anything like that?
[00:46:10.110]How does that process work?
[00:46:14.555]Cured meats?
[00:46:15.690]So cured meats, can you tell me what you do
[00:46:18.295]when you are in the process of making it?
[00:46:21.230]And we're gonna,
[00:46:22.450]yeah, so what do you do when you make that product?
[00:46:26.780]You add some nitrate.
[00:46:27.650]Yes, like biltong, you dip it in apple cider,
[00:46:32.240]Worcestershire and all that,
[00:46:33.133]and you just coat it with salt for a little bit
[00:46:35.470]and then rinse that off and then hang it.
[00:46:37.210]Okay, so you coat it with salt.
[00:46:39.920]What does salt do?
[00:46:41.580]It pulls, debinds.
[00:46:43.490]It binds the water, or pulls the water out.
[00:46:45.500]And then you hang it to?
[00:46:47.510]Dry. Dry.
[00:46:48.660]So you're taking more water out.
[00:46:50.550]So that's how we're preserving that product.
[00:46:52.910]We're reducing the water activity a lot.
[00:46:55.107]And some of those salts also have a
[00:46:58.700]antimicrobial activity.
[00:47:00.450]So they're not only binding the water,
[00:47:02.430]but they're bad for bacteria.
[00:47:03.950]Bacteria don't like it.
[00:47:06.769]So it's a double-wham for bacteria.
[00:47:08.300]Is that where the addition
[00:47:10.440]of the nitrate comes in?
[00:47:11.650]Mmhmm, yes.
[00:47:14.462]It's the preservative.
[00:47:19.320]Question?
[00:47:21.140]My question was regarding botulism in canned goods.
[00:47:24.170]What is the shelf life of a canned good,
[00:47:25.990]and are the expiration dates valid?
[00:47:29.040]Okay, that's a great question,
[00:47:31.440]because there's two different things.
[00:47:33.060]There's the food safety and the food quality of the product.
[00:47:36.430]Right, so if we're talking about food safety,
[00:47:39.420]the process of canning,
[00:47:41.270]and we're gonna learn more about it later today,
[00:47:43.420]we're gonna have a lecture about it.
[00:47:44.960]You're gonna see that it's developed to kill
[00:47:48.400]up to 12 logs of that spore.
[00:47:52.590]Do you guys remember?
[00:47:53.423]One log was 90%, two logs, 99.
[00:47:56.840]How many is 12 logs?
[00:47:58.830]99.99 and we're gonna be here for a while saying nine.
[00:48:03.090]Right?
[00:48:03.923]So it's extremely safe.
[00:48:06.985]If the process is applied correctly,
[00:48:11.320]that product inside of the can
[00:48:13.020]should be safe for a long time.
[00:48:16.180]Safe.
[00:48:17.330]But now, is it gonna be of quality?
[00:48:19.890]There are some microorganisms
[00:48:21.570]that still may survive, believe it or not,
[00:48:24.410]that's more resistant to heat than clostridium.
[00:48:28.720]So they can survive that temperature
[00:48:31.720]that was used to kill the spores of clostridium,
[00:48:34.170]because we're concerned about food safety.
[00:48:37.470]The quality is a good side effect,
[00:48:40.630]that by killing the pathogens
[00:48:42.260]we also killed the spoilage organism.
[00:48:44.500]So that's the good side effect of the processing.
[00:48:47.320]So now the organisms that don't die
[00:48:50.010]because they're more heat resistant,
[00:48:51.800]and you keep that on the shelf.
[00:48:53.820]And let's say that your shelf, if it's in your house,
[00:48:57.940]and it's a room that is temperature controlled,
[00:49:01.400]more or less because you have AC and heating and such,
[00:49:04.930]it might be stable for a while.
[00:49:07.170]But if you're in a warehouse now that in the summer,
[00:49:09.850]the temperature may shoot up to what,
[00:49:12.772]100, 110, maybe inside of that warehouse, more?
[00:49:17.560]Those organisms that survived the heat process
[00:49:21.210]can now grow because they like the heat.
[00:49:23.810]They like the high temperature.
[00:49:25.480]So they're gonna start spoiling the product
[00:49:27.580]in the warehouse, for example.
[00:49:29.880]Beyond that, we have lipids in our foods, right?
[00:49:33.650]We have fats, and those are good, they give us flavor.
[00:49:37.310]A lot of the flavor associated with the food product
[00:49:39.830]is because of the fat that is in there.
[00:49:42.070]With time, that fat starts oxidizing.
[00:49:45.470]So yes, the can may be safe for three years or so,
[00:49:49.640]but will it taste good?
[00:49:51.850]I don't know, depending upon the product,
[00:49:53.500]it may not because that could be oxidized.
[00:49:56.830]Dependent upon the storage conditions
[00:49:58.748]other organisms may grow.
[00:50:01.370]They're not gonna make you sick,
[00:50:03.330]but definitely it may not,
[00:50:07.306]it might not give you an experience
[00:50:08.680]that will lead you to buy back that product.
[00:50:10.790]So that's why the industry is concerned
[00:50:12.890]and put a shelf life and an expiration date,
[00:50:15.410]because they want you to have the best experience
[00:50:17.900]so you go back to the store and buy their product again.
[00:50:28.450]More questions?
[00:50:29.840]Well, this was great, lots of questions.

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Basic Food Microbiology

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