The Science of Food - Lecture 4
Andreia Bianchini Huebner
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01/30/2025
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The Science of Food
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- [00:00:00.000]♪
- [00:00:24.100]Good morning, everybody.
- [00:00:26.400]Once again, welcome to the Science of Food.
- [00:00:29.260]We're here today to discuss about proteins.
- [00:00:32.460]In our last encounter, we talked about the building blocks of molecules that then make
- [00:00:38.980]our food.
- [00:00:40.460]Today we're going to focus in one type of those molecules, which are the proteins.
- [00:00:46.640]And on our plate, we have the structures of proteins, their functions.
- [00:00:51.620]We're going to look at how we can apply those functions into foods to create textures and
- [00:00:58.520]flavors that we are so familiar with.
- [00:01:01.980]And we're going to also learn that in order to do that, to enable the protein to develop
- [00:01:07.060]its best function in foods, most cases they need to be denatured first.
- [00:01:12.680]So we're going to learn about what is denaturation and how we can use that in our favor.
- [00:01:19.360]So proteins are molecules that are made of different families of organic compounds.
- [00:01:27.440]We talked about organic compounds.
- [00:01:27.780]We talked about organic compound families last time we encountered, we met, and they're
- [00:01:35.960]some of them that are going to come together to make a molecule of protein.
- [00:01:40.660]We're going to have a carbon right in the middle.
- [00:01:43.860]So we're talking about organic compounds.
- [00:01:47.060]And then that carbon needs to share four electrons.
- [00:01:51.540]That's what we learned, right, in our previous lecture.
- [00:01:55.440]That carbon is going to share the electrons.
- [00:01:57.040]The electrons with a hydrogen, with a carboxyl group,
- [00:02:03.680]which makes an acid part of that molecule,
- [00:02:06.880]and with an amino group,
- [00:02:08.720]which makes the amino part of that molecule.
- [00:02:10.960]That's why they're called amino acids.
- [00:02:14.020]And then we're going to have this R,
- [00:02:16.020]which is the last group
- [00:02:17.400]that is kind of hanging on to that carbon.
- [00:02:20.320]The R group is going to be really important
- [00:02:22.160]because it's going to give a lot of properties
- [00:02:24.940]to this amino acid.
- [00:02:26.300]The amino acid then is the smallest piece of a protein.
- [00:02:31.040]So if you think of Legos,
- [00:02:32.540]that would be your first little building block.
- [00:02:35.140]And then we can bring them together
- [00:02:37.940]to make our proteins.
- [00:02:40.280]So the amino acid is the smallest part of the protein.
- [00:02:45.280]And that amino acid has that R group, right,
- [00:02:51.360]that I mentioned.
- [00:02:52.360]Depending upon the properties of that R group,
- [00:02:55.560]this amino acid is gonna have chemical properties
- [00:03:00.560]that will enable them to interact
- [00:03:04.340]with other molecules of protein
- [00:03:06.540]and even other molecules in our food.
- [00:03:09.240]So they become really important.
- [00:03:11.180]Some of them are going to be, have like a charge.
- [00:03:16.180]They're gonna either be positively charged
- [00:03:18.920]or negatively charged.
- [00:03:20.780]And that's gonna help them with those chemical interactions
- [00:03:24.820]within the protein and outside of the protein.
- [00:03:28.700]Some of those are molecules like that side group,
- [00:03:33.700]that R group on our proteins.
- [00:03:40.200]They can also be uncharged.
- [00:03:42.900]So they have no charge at all.
- [00:03:45.500]So we call them non-polar.
- [00:03:50.500]So some are gonna be polar charged
- [00:03:52.740]and some are gonna be non-polar charged.
- [00:03:54.820]So what does that mean?
- [00:03:56.460]So let's look at the molecule of water
- [00:03:59.000]to kind of better understand what makes a molecule polar.
- [00:04:03.080]So the molecule of water is one oxygen
- [00:04:06.020]and two hydrogens linked to it.
- [00:04:09.820]So that oxygen, it has a charge of negative two
- [00:04:14.820]and it is, in essence, a larger atom than the hydrogen is.
- [00:04:20.420]So it's a little stronger,
- [00:04:22.980]even though it's sharing
- [00:04:24.540]those two electrons with two hydrogens,
- [00:04:27.460]which are plus one.
- [00:04:29.300]That hydrogen still doesn't have as much power
- [00:04:33.780]to keep that electron that is being shared with the oxygen
- [00:04:37.540]right in the middle.
- [00:04:38.920]So what happens is the oxygen
- [00:04:41.020]slightly pulls that electron towards itself
- [00:04:44.960]because it's stronger than the hydrogen.
- [00:04:47.640]And then the hydrogen has a very slight positive charge
- [00:04:51.400]while the oxygen has a slightly negative charge.
- [00:04:54.260]That makes a compound polar.
- [00:04:58.160]So polar compounds are those with that positive
- [00:05:01.700]and negative charge on one side of the other of the molecule.
- [00:05:06.000]Some of those R groups will have that polarization,
- [00:05:11.000]and some will not.
- [00:05:13.400]If they don't have that polarization,
- [00:05:16.260]then the kind of interactions that they do
- [00:05:20.100]is they can interact among themselves,
- [00:05:23.980]but they cannot interact with polar.
- [00:05:26.980]So polar stays with polar, non-polar stays with non-polar,
- [00:05:32.040]and we're going to see more of that later today.
- [00:05:34.280]On my slide here, I have the chemical structure
- [00:05:37.920]of many of those R groups.
- [00:05:40.360]It's not my goal or expectation that you will memorize them
- [00:05:45.060]or learn about them and be able to draw them by heart.
- [00:05:50.720]The intention is to show you that there are
- [00:05:53.700]different R groups, and some of them have charges,
- [00:05:58.700]which makes them very strong, positively or negatively.
- [00:06:03.000]Some of them are polar, and some of them are non-polar.
- [00:06:07.440]That's the goal.
- [00:06:08.320]If you get that out of this, we're happy, I'm happy.
- [00:06:12.520]Those interactions that are gonna occur among polar
- [00:06:17.520]with other polar molecules, non-polar with other
- [00:06:21.300]non-polar molecules are gonna define
- [00:06:23.420]how our protein is going to exist,
- [00:06:26.260]like the form of that protein.
- [00:06:28.080]And we're gonna see that by looking at the different
- [00:06:30.940]structures of that protein.
- [00:06:33.040]So the protein will have a primary structure.
- [00:06:36.440]What is the primary structure of the protein?
- [00:06:38.840]The primary structure is when two amino acids
- [00:06:41.960]come together to make a little chain.
- [00:06:46.200]So two amino acids will bind together.
- [00:06:49.380]The amino acid of one part of the molecule
- [00:06:53.140]will bind to the--
- [00:06:56.440]so the amino part will bind with the acid part
- [00:07:00.820]of the next amino acid.
- [00:07:04.460]And then they will come together to eliminate
- [00:07:07.420]or to kind of release a molecule of water.
- [00:07:10.500]And then they're going to make a bond.
- [00:07:12.120]That bond-- so the water comes out,
- [00:07:14.920]and a bond is created between that nitrogen
- [00:07:21.140]from one amino acid.
- [00:07:22.860]And the carbon of the next one.
- [00:07:27.840]That is a peptide bond.
- [00:07:29.600]And you can see that here in our slide.
- [00:07:32.740]There's a peptide bond that forms between the carbon
- [00:07:36.600]of one amino acid and the nitrogen
- [00:07:39.620]of the next amino acid.
- [00:07:41.780]And we can keep linking them that way
- [00:07:45.020]until we form a dipeptide, tripeptide,
- [00:07:49.480]and we can increase that and bind
- [00:07:52.580]them to make a chain.
- [00:07:54.980]That peptide bond formed between two molecules,
- [00:08:00.560]and they're going to release the water molecule,
- [00:08:02.920]and they're very strong.
- [00:08:05.160]I'm going to try and represent those peptides using little
- [00:08:09.160]beads here for us today.
- [00:08:11.860]And by putting them together on a pipe cleaner,
- [00:08:15.700]I just made that chain of amino acids.
- [00:08:19.180]And you can see that I used different colors, and the reason
- [00:08:22.300]was because each amino acid is unique because of those R
- [00:08:26.040]groups, so they're going to have different properties.
- [00:08:28.780]So that's why I'm representing them with different colors.
- [00:08:31.380]Each of them will have a different, you know,
- [00:08:33.380]ability to bind with other molecules.
- [00:08:38.180]And a protein will have a very, very long, you know,
- [00:08:42.860]chain of those peptides.
- [00:08:44.920]I just got us started here so you could visualize that.
- [00:08:50.620]Then we go to the secondary stage,
- [00:08:52.020]the very structure of that protein.
- [00:08:53.960]So now what is happening here is this very, very long chain,
- [00:08:59.400]right, it could be all the way here,
- [00:09:01.560]it's going to start to interacting with itself
- [00:09:04.360]in different ways based on what kind of amino acids I have.
- [00:09:10.240]Depending upon the kind of amino acids I have,
- [00:09:13.480]this long chain can interact with itself
- [00:09:17.340]to form two kinds of structure, and as it's forming,
- [00:09:21.740]that structure, the type of bonding
- [00:09:25.740]that is going to help us here, it's called a hydrogen bond.
- [00:09:29.520]So in the primary structure, it was a peptide bond.
- [00:09:32.360]Now on the secondary structure, we have a hydrogen bond.
- [00:09:35.360]What does that mean?
- [00:09:36.520]A hydrogen bond is a weak bond between two molecules
- [00:09:40.200]or regions of a molecule, and they are happening
- [00:09:44.760]because of an electrostatic attraction
- [00:09:47.660]between a positive and a negative part
- [00:09:51.460]of that molecule.
- [00:09:52.900]So usually we're going to have a hydrogen involved.
- [00:09:55.600]That's why it's called a hydrogen bond.
- [00:09:57.860]And then it's going to bind to either a nitrogen, an oxygen,
- [00:10:01.460]or a fluoride, and those are going
- [00:10:04.540]to make the hydrogen bonds of our next structure.
- [00:10:07.700]How can this long chain of peptides here,
- [00:10:12.080]or a peptide chain, interact with itself?
- [00:10:14.720]It can form two types of structures.
- [00:10:17.180]It can either curl like this and make
- [00:10:21.180]a helix, and it could be a very long helix, right?
- [00:10:25.280]It could curl here and just-- we can imagine
- [00:10:28.520]that this whole pipe cleaner was covered in beads,
- [00:10:32.420]so we can make a helix just like that.
- [00:10:37.000]That's called the alpha helix.
- [00:10:40.540]And the way that that helix organizes itself,
- [00:10:44.500]it's that we're going to have each amino acid here.
- [00:10:50.900]So take one amino acid of this chain.
- [00:10:53.260]It's going to seek an amino acid that is four positions down,
- [00:10:59.400]and it's going to bind to it.
- [00:11:01.640]So it's going to twist in a way that's going to, you know,
- [00:11:04.140]it would be a very tight helix here on my beads,
- [00:11:06.880]but you can imagine that.
- [00:11:08.560]So the one amino acid is going to bind to another amino acid
- [00:11:14.020]that is four positions down on this chain.
- [00:11:18.900]With that,
- [00:11:20.620]we're going to have that hydrogen bond
- [00:11:22.880]stabilizing that structure.
- [00:11:28.720]So now what I did was I eliminated the beads,
- [00:11:31.640]but I made it, you know, to kind of imagine
- [00:11:33.860]that we are enlarging our alpha helix.
- [00:11:38.080]The purple hooks here show us our hydrogen bonds,
- [00:11:45.780]and then what happens is all those R groups
- [00:11:48.540]are going to stick out, and that's what I have.
- [00:11:50.340]I have sticking out, see?
- [00:11:52.280]So now we have the alpha helix with the R groups sticking out.
- [00:11:57.520]My polypeptide can also fold itself
- [00:12:02.660]in a beta sheet configuration, which would be pleated sheets
- [00:12:07.160]like this, just going back and forth and zigzagging, right?
- [00:12:11.520]So in that situation, we're also going
- [00:12:14.740]to have hydrogen bonds stabilizing this,
- [00:12:18.400]and what's going to happen is--
- [00:12:20.060]so the polypeptide chain is going
- [00:12:24.540]to line up next to each other, and then the hydrogen bonds
- [00:12:28.100]are going to form in between those backbones.
- [00:12:32.540]And now, if I were to enlarge this structure,
- [00:12:38.080]the hydrogen bonds would stabilize in between,
- [00:12:42.620]and my R groups are going to stick either upwards
- [00:12:46.880]or downwards from that--
- [00:12:49.780]beta sheet.
- [00:12:51.940]So they would go either, you know, up or down.
- [00:12:58.160]And then I'm going to push this one up and this one down.
- [00:13:01.160]So they're going to stick either up or down.
- [00:13:06.260]And those R groups now are going to be
- [00:13:08.860]responsible for helping us create the tertiary structure.
- [00:13:12.600]Why so?
- [00:13:13.440]Because they're free to interact with each other.
- [00:13:16.440]So I could have a molecule that is very long
- [00:13:19.500]and I could even tie these two together, right?
- [00:13:22.500]Because on the same molecule, I could
- [00:13:24.540]have a region that is a beta pleated sheet
- [00:13:28.080]and I could have a region that is alpha helix.
- [00:13:31.440]So now my R groups are going to stick each other
- [00:13:35.280]and I can clamp them together.
- [00:13:39.020]What kind of interactions I could have?
- [00:13:40.880]Two kinds of interaction-- well, not just two kinds,
- [00:13:43.700]but two kinds can be seen here that we haven't talked
- [00:13:47.820]about before.
- [00:13:49.220]Which are those hydrophobic interactions.
- [00:13:53.600]So now every R group that is nonpolar,
- [00:13:59.540]they're going to seek other nonpolar groups
- [00:14:02.540]and they are going to kind of like be
- [00:14:05.360]part of this internal part of the protein.
- [00:14:08.440]So those are going to kind of like seek each other
- [00:14:11.100]and make this protein like the internal parts of it.
- [00:14:15.640]Kind of protecting themselves and shying away
- [00:14:18.940]from everything else that's happening on the outside.
- [00:14:22.620]So they're going to kind of like band together in the middle.
- [00:14:27.320]I'm trying to put these two together here.
- [00:14:30.320]Let's see if I can.
- [00:14:32.120]I'm going to pinch these two together with my little clip.
- [00:14:34.820]See if I can.
- [00:14:39.620]Okay, there we go.
- [00:14:44.160]So see how it's banding and forming this tertiary structure?
- [00:14:48.660]There's one other kind of bond that can help in this tertiary structure, which is
- [00:14:53.900]a disulfide bond.
- [00:14:56.540]So now these are covalent linkages between sulfur-containing R groups.
- [00:15:02.260]So if my R groups here have a sulfur, they are going to bind together and they're very
- [00:15:08.780]strong.
- [00:15:09.780]This disulfide bond, it's very strong and can hold everything together.
- [00:15:17.340]It's like a safety pin.
- [00:15:18.380]In our tertiary structure.
- [00:15:21.620]So a very long polypeptide chain is going to start folding and bending over itself and
- [00:15:27.240]with that we have a tertiary structure.
- [00:15:32.000]Sometimes we can have two of them come together, two chains of amino acids that are already
- [00:15:40.160]folded by themselves.
- [00:15:42.720]They can come together and form a quaternary structure.
- [00:15:48.100]Which is even more complex and they will bind with each other and have a very specific format
- [00:15:57.780]and shape.
- [00:16:00.460]That defines the properties of that protein.
- [00:16:04.420]That tertiary and quaternary structures are the ones that are going to give the protein
- [00:16:11.040]its function, either in our body or in our foods and we're going to look at what our
- [00:16:17.820]proteins are and what are the different kinds of functions that they can have it in a little
- [00:16:21.980]bit.
- [00:16:23.380]What are the sources of proteins in our foods?
- [00:16:26.100]We can get proteins from grains and legumes, so if you are vegetarian or vegan, that's
- [00:16:32.600]how most likely you're going to be acquiring your dose of protein daily.
- [00:16:40.440]There's some legumes and grains that are fairly known for having larger amounts of proteins.
- [00:16:47.540]We have here on the slide a chart that kind of shows us that, for example, soybeans contain
- [00:16:54.660]a decent amount of protein, lentils, peas, those are legumes that contain a decent amount
- [00:17:00.900]of protein, so we could use them as a source of protein for our diet.
- [00:17:07.040]For those that are in a non-restricted diet, most of our proteins usually come from animal
- [00:17:13.800]sources, being meats, fish.
- [00:17:17.260]Fish and dairy are the main sources of protein.
- [00:17:21.840]So if we look here at the composition of muscle tissue, when we take away the water, which
- [00:17:27.860]accounts for 75%, a big chunk of what is left is protein, 18%.
- [00:17:34.260]So definitely a good source of protein.
- [00:17:36.980]And now that we've learned about the protein structure and all the chemical interactions
- [00:17:41.760]that it can have, let's see how that plays a role in our nutrition.
- [00:17:46.980]And as transport in our bodies and the bodies of animals, and we're going to look at their
- [00:17:53.740]functional properties in food.
- [00:17:55.400]So that's kind of like an overview of what's coming.
- [00:17:58.540]As far as the nutritional value of those proteins, we're not going to spend a whole lot of time
- [00:18:02.840]today because we will have a nutrition module later, so we're going to kind of save all
- [00:18:09.940]of that discussion for later, but what I want to point out is because of that uniqueness
- [00:18:16.700]of amino acids that are part of the protein, some of them we can make it ourselves in our
- [00:18:23.880]body, so we eat protein from plants and animals, we break them down, and we have molecules
- [00:18:34.220]in our body that we're going to be reusing, so some of those amino acids we can build
- [00:18:39.380]ourselves through the foods we eat, and the nutrients that we have circulating in our
- [00:18:46.420]body, those are called non-essential amino acids, because we can build them ourselves
- [00:18:53.520]in our bodies, however, there's some of them that we cannot, we don't have the pathway
- [00:18:59.380]to make them, so if we want them, which we do, because they are essential for our health,
- [00:19:07.320]that's why they're called essential amino acids, we need to acquire them through diet,
- [00:19:11.720]so we need to make sure that the foods that we're eating have these specific amino acids,
- [00:19:16.140]that are essential.
- [00:19:18.780]Some of them are conditionally non-essential, that means that if you are healthy, you might
- [00:19:24.180]be able to build them yourselves in your body, but there are some diseases, conditions or
- [00:19:30.440]some nutritional states that will not allow us to be able to build them, so in those cases
- [00:19:39.940]we have to get them from diet as well, so that's what I'm going to put in front of you,
- [00:19:45.860]is that some amino acids are essential, some are not, those essential we have to acquire
- [00:19:51.740]them through our diets, and it goes all back to the R groups that they have sticking out
- [00:19:58.740]of them.
- [00:19:59.920]So proteins as transport, so this is an important protein that I'm going to bring in front of
- [00:20:07.560]you is myoglobin, you may know this from biology when you study about oxygen being
- [00:20:15.580]transported in our blood, you know from the lungs to the cells and so on and so forth,
- [00:20:22.260]so we use this protein in our bodies, but it also becomes a very important protein for
- [00:20:27.660]us to consider when we're talking about food science because it's a protein that it's part
- [00:20:32.200]of the muscle of the animals that we harvest for food, so in that case that myoglobin,
- [00:20:41.100]which is the protein that we're talking about, it has a very specific part of it.
- [00:20:45.300]And here in our slide, it is colored to be highlighted in different colors.
- [00:20:53.320]So this group here that it's colored is the heme group.
- [00:21:00.860]This heme group is able to carry oxygen, which are colored in green, and it also has an iron
- [00:21:15.020]right in the middle that's colored in red.
- [00:21:17.700]So that iron stays with the heme group, and the oxygen will bind or not to that heme group
- [00:21:26.740]depending upon what's happening in the body.
- [00:21:29.820]So as we have that oxygen being transported from the lungs to the cells, it's going to
- [00:21:35.000]be bound.
- [00:21:36.000]But then once it gets to where it's going, it's released.
- [00:21:40.140]So at some points, oxygen may be part of the molecule.
- [00:21:44.740]Sometimes it may not.
- [00:21:46.740]Why do we care in food science?
- [00:21:48.820]Because if the oxygen is there, the meat is going to have a certain hue.
- [00:21:54.580]If the oxygen is not there, the meat is going to have a different hue as far as pinkish
- [00:22:00.960]or reddish or purplish.
- [00:22:03.780]And when we get to food systems, we're going to see that that is directly correlated with
- [00:22:07.540]the quality of that meat.
- [00:22:09.160]So that's why I'm bringing that in front of you.
- [00:22:11.720]Also different animals will have more oxygen.
- [00:22:14.460]They have more or less of that protein in the muscle, and that's why they are inherently
- [00:22:21.820]more or less colored.
- [00:22:23.960]Think of the flesh of a fish compared to a piece of steak.
- [00:22:29.300]So that's part of it, part of what gives color to that tissue.
- [00:22:37.000]Proteins are also extremely important for us in the foods and our digestive system because
- [00:22:44.180]they serve as enzymes, but in foods that enzyme can have also important functions.
- [00:22:51.240]So we're going to talk about proteins as biological catalysts.
- [00:22:57.000]So what are those?
- [00:22:58.680]So biological catalysts are enzymes, and enzymes are proteins that are able to expedite things.
- [00:23:09.880]So they speed up chemical reactions, they help out.
- [00:23:13.900]So sometimes different molecules would react to each other regardless, but if you have
- [00:23:22.860]a protein hanging around that can help with that, the protein will make that happen faster.
- [00:23:29.940]So we have here in our slide two types of reactions that can be catalyzed by these proteins
- [00:23:40.040]that we call enzymes.
- [00:23:42.000]So we can bring compounds together.
- [00:23:43.620]So we can form compounds with the help of the enzyme.
- [00:23:48.720]So you have here on this diagram in gray we have what looks like a little Pac-Man, right,
- [00:23:56.900]with a double mouth.
- [00:23:58.960]But essentially that's our enzyme, and each of those little mouths are going to be just
- [00:24:05.380]fitted for a particular substrate, for a specific molecule, not any molecule can sit
- [00:24:13.340]in that space, it has to be very specific.
- [00:24:17.140]So then you have that molecule that sits right there, and it fits perfectly.
- [00:24:21.320]Then what that enzyme is going to do is clip that molecule into two other molecules, so
- [00:24:28.480]it's going to help us break those compounds apart.
- [00:24:33.600]So if you're thinking of digestion, that's essential, because we eat foods and we want
- [00:24:38.760]to break them down in smaller compounds that we can actually absorb.
- [00:24:43.060]So in our digestive tract, we have a lot of enzymes that help with the digestion, and
- [00:24:49.060]that's what they're doing.
- [00:24:50.060]But guess what, just like that happens in our digestive tract, sometimes it happens
- [00:24:55.720]in food as well, and it ends up breaking down the food, which sometimes is good, sometimes
- [00:25:01.500]is not.
- [00:25:02.500]We'll see about that.
- [00:25:04.500]Enzymes can also bring molecules together.
- [00:25:07.780]So that's the other half here of our slide, where the enzyme, once again, very specific.
- [00:25:12.780]There's a specific active site where two now molecules have to fit.
- [00:25:18.620]Two very specific molecules will fit in that site, and then the enzyme will stitch together
- [00:25:26.060]those two molecules, will make bonds.
- [00:25:28.420]So then when it's released, you have a larger molecule made up of the two initial substrates.
- [00:25:35.500]So they can bring it together or they can break it apart.
- [00:25:42.500]Proteases receive a very special name depending upon what they act on.
- [00:25:47.320]So if they act on a protein, they're going to be called proteases.
- [00:25:52.340]"Ase" is the suffix that indicates in biochemistry a name of an enzyme.
- [00:25:59.600]So every time you see the three letters, A-S-E, you're talking about an enzyme, a protein
- [00:26:05.820]that either breaks things or brings things together.
- [00:26:09.240]In our case here, I am showing on the slide.
- [00:26:12.220]A polypeptide that was broken down by a protease and amino acids are released.
- [00:26:21.160]If instead of a protein I had a carbohydrate, say for example starch, because that is a
- [00:26:28.420]carbohydrate molecule, the name of the enzyme would be a carbohydrates.
- [00:26:35.820]Carbohydrates is going to break it down into little pieces of sugar.
- [00:26:38.980]And if I had a lipid.
- [00:26:41.940]The name of the enzyme would be a lipase, which then would break it down into fatty
- [00:26:47.860]acids and glycerol.
- [00:26:50.320]So that's the idea.
- [00:26:52.820]Like I said, in some cases it's very positive, it's very desirable to have these enzymes
- [00:27:00.700]present in food.
- [00:27:01.920]So I'm bringing you here in this slide for consideration three situations in which having
- [00:27:07.980]enzymes are really good.
- [00:27:11.660]So part of our group knows anything about fermented beverages.
- [00:27:17.120]As an example would be beer.
- [00:27:19.120]How do you make a beer?
- [00:27:21.580]Any general knowledge about it?
- [00:27:24.180]Do you want to push the button, Fat?
- [00:27:29.000]Is it through fermentation?
- [00:27:31.000]It's through fermentation.
- [00:27:32.700]That's a great start.
- [00:27:34.040]Fermentation, what does that mean?
- [00:27:36.100]Like what is going to, what has to be there for that to happen?
- [00:27:41.380]Yeast.
- [00:27:42.380]You have to have yeast.
- [00:27:44.380]Sugar.
- [00:27:45.380]Sugar.
- [00:27:46.380]Great point.
- [00:27:47.380]Okay, so you have to have yeast and sugar.
- [00:27:50.920]What usually we use for making beer?
- [00:27:53.560]What is the grain that is mostly used?
- [00:27:55.500]Anybody know?
- [00:27:57.700]Wheat.
- [00:27:59.280]Wheat can be used if it's a wheat beer.
- [00:28:03.300]Barley is another one that can be used, but then usually what we do is we convert the
- [00:28:08.480]barley into malt.
- [00:28:11.100]We use malt to make beer.
- [00:28:13.240]What is the difference between barley and malt?
- [00:28:16.260]Fatima told us that the east likes sugar.
- [00:28:21.160]Which one do you think has sugar?
- [00:28:23.620]The barley or the malt?
- [00:28:26.420]The malt.
- [00:28:28.760]The malt, because that's what we use to make the beer.
- [00:28:32.140]So essentially the malt is the barley that has a lot of complex molecules that were pre-digested
- [00:28:40.820]to make malt, so now things are partially broken down already so the yeast can actually
- [00:28:48.800]use it.
- [00:28:50.020]If I give barley to the yeast, it's probably still going to make beer, but it's going to
- [00:28:58.820]take a long time because the yeast will have to first break that barley down.
- [00:29:06.280]It's going to have to produce a whole bunch of enzymes, it's going to have to digest the
- [00:29:10.540]barley, and then it's going to be able to consume it.
- [00:29:14.400]In food production, we don't have that much time, or we're smart, we use things for our
- [00:29:20.920]benefit, so we help the yeast out by using a whole bunch of enzymes to predigest that
- [00:29:28.120]barley, turning it into malt, which then is used by the yeast.
- [00:29:32.960]During that process, a whole bunch of enzymes will play roles: beta-glucanase, alpha-amylase,
- [00:29:40.260]amyl-glucosidase.
- [00:29:42.480]All of those are going to help chomp it down, so then when the yeast comes, half of the
- [00:29:47.760]work is already done.
- [00:29:49.200]So we can expedite that process.
- [00:29:51.940]One other way that we can use proteins for our benefit is when we are marinating foods,
- [00:29:58.520]especially meats.
- [00:30:00.140]Sometimes we want to make that meat more soft, or we want to add more flavor to it.
- [00:30:06.820]We're going to marinate.
- [00:30:07.980]So if we can use a...
- [00:30:09.980]enzyme that breaks down protein, then we're going to make that meat more tender.
- [00:30:17.860]So that's the idea behind tenderization of meat via marination.
- [00:30:25.160]Usually what we do is we add some seasonings for flavor.
- [00:30:31.720]So if you look at the labels of certain seasoning and marinating powders,
- [00:30:39.700]you're going to find words like bromelain or papain.
- [00:30:46.820]Those are enzymes extracted from plants that can be used in meats
- [00:30:51.760]to make them softer and tender.
- [00:30:54.700]We also use those enzymes to break down plant tissue when we're trying to make juice.
- [00:31:01.260]Because if you're trying to make juice, you want to squeeze as much liquid out of that plant material.
- [00:31:09.420]And you want to make sure that there's no cell walls in your way.
- [00:31:13.740]So if we apply pectinase and beta-glucanase to our fruits,
- [00:31:22.320]then we can break some of those down, and then we can extract the juice easier and with a higher yield.
- [00:31:29.460]So it makes the process more efficient.
- [00:31:33.260]However, we can't have a pro without having a con, right?
- [00:31:36.980]Usually they come together, hand in hand.
- [00:31:39.140]In some instances, those same proteases that help us make the meat tender, if they are
- [00:31:46.700]acting upon meat that is left unchecked, unrefrigerated, it's gonna cause that meat to actually spoil.
- [00:31:55.600]So one example would be fish, it's very, very susceptible to spoilage.
- [00:32:02.060]It can also degrade plant tissue beyond what it's, you know, beneficial.
- [00:32:08.860]In the case there, showing bananas that are way past their ripening point because they
- [00:32:14.960]were pretty much, you know, turning to mush by those enzymes that are part of the plant.
- [00:32:22.960]And one other situation that in food science we encounter quite a bit is browning caused
- [00:32:30.080]by enzymes, enzymatic browning of fruits and vegetables.
- [00:32:35.040]If you ever cut some potatoes to make mashed potatoes,
- [00:32:38.580]you might have experienced some of that.
- [00:32:40.860]If you like eating apples, you might have experienced some of that.
- [00:32:44.140]And there's many others, like avocados, which then when they are turned into
- [00:32:49.300]guacamole, become susceptible to browning.
- [00:32:52.420]And who likes that?
- [00:32:54.460]Nobody, right?
- [00:32:55.140]Like here in the, yeah, nobody wants that to happen.
- [00:32:58.700]So why does it happen in the first place?
- [00:33:02.580]So what is that browning of plants, fruits and vegetables?
- [00:33:08.300]Essentially, what's happening there is the fact that inside of the tissue of those fruits
- [00:33:16.100]and vegetables, we have an enzyme called polyphenol oxidase.
- [00:33:20.800]For short, we call it PPO.
- [00:33:23.120]So that polyphenol oxidase will bring, it will convert substrates, right?
- [00:33:31.500]So it's going to take polyphenols that are also part of the plant tissue and it's going
- [00:33:38.020]to have to use oxygen.
- [00:33:40.360]So you have to have two things meet in that polyphenol oxidase.
- [00:33:46.080]You are going to have oxygen coming in and you're going to have to have polyphenols.
- [00:33:50.500]And then that enzyme is going to transform those into different products.
- [00:33:57.120]Examples would be melanin and others.
- [00:34:01.340]Those compounds have color and that's what browns the tissue of those fruits and vegetables.
- [00:34:07.740]This all happens when that fruit is either cut or mushed.
- [00:34:15.500]Normally, the enzyme and the polyphenols are going to coexist in that plant and they're
- [00:34:22.260]just going to be there and sitting there.
- [00:34:25.080]They will come together when we cut and expose that to the air because then we're cutting,
- [00:34:31.040]we're destroying that structure, so we're now mixing them kind of together inside of
- [00:34:35.880]that plant tissue.
- [00:34:37.460]Biologists and people that work in the area of studying plants, they have tried to understand
- [00:34:48.600]why plants have this polyphenol oxidase and they believe that those brown pigments are
- [00:34:54.860]actually produced by the plant as a defense mechanism against pathogens and herbivores,
- [00:35:03.020]so it's a defense mechanism for the plant.
- [00:35:05.880]But when we see that...
- [00:35:07.180]We don't feel so great about that food anymore, right?
- [00:35:10.240]Even though I assure you it's totally safe to eat, that melanin is not going to make
- [00:35:14.980]anybody sick, but it kind of looks different than you would expect.
- [00:35:20.620]So I can understand the perception of spoilage when essentially it was just a change in color.
- [00:35:29.760]What can we do to reduce that?
- [00:35:32.960]Anybody in the room here has any ideas of maybe something that you have experienced?
- [00:35:36.330]In the past things that tricks and tips and those that are at home can also think about it
- [00:35:41.810]And you know maybe something that your grandma does or your mom does or things that you do
- [00:35:47.450]To reduce that enzymatic activity. Let's think of apples because that's perhaps the easiest
- [00:35:53.210]But you can also think of you know, like I said avocados and potatoes anybody
- [00:35:57.790]Putting them in the fridge, but also when I would take apple slices to lunch
- [00:36:03.290]I looked it up and like putting lemon juice on them
- [00:36:05.830]Helps prevent them from browning as quick
- [00:36:08.690]Fantastic. So Myra has hit two
- [00:36:11.750]temperature like putting in a cold temperature and
- [00:36:15.010]Using lemon juice, which we're you know in food science. We know that that's an acid. So using acids. Okay, awesome
- [00:36:22.890]Anybody has any other idea of things that we could do?
- [00:36:26.890]Perhaps those are really good ones anything else
- [00:36:32.330]Yeah, so that's another way, but essentially an asset, but yeah different so we could use different types of
- [00:36:44.810]Foods I've heard that some people would put Sprite on their Apple. Why because that's a acidic
- [00:36:52.770]Drink right if you measure the pH of Sprite, it's very low
- [00:36:57.370]You can use lemon juice in any other acids
- [00:37:01.490]So those are great ways that we can prevent that enzymatic activity from occurring
- [00:37:06.970]What we've done here in our class is we actually tested some of those
- [00:37:12.190]one our
- [00:37:15.130]Teaching assistant here prepared for us ahead of time
- [00:37:18.670]different kinds of
- [00:37:21.670]Treatments so remember you know with the scientific method our hypothesis that if we apply one of this interventions
- [00:37:29.370]oxygen
- [00:37:30.650]I'm sorry
- [00:37:32.650]acid
- [00:37:34.350]Refrigeration then our enzymatic browning would be reduced so that could be our hypothesis right if we apply
- [00:37:41.290]acid or
- [00:37:43.470]temperature
- [00:37:44.410]Then our enzymatic browning could be reduced I
- [00:37:48.270]Challenged one when he was doing the experiment. I said how about if we try two different apples
- [00:37:55.070]Do you think here in the classroom that we might get different results or not or what?
- [00:38:00.550]so
- [00:38:01.910]This tell me first off. Let's say if anybody here cares to share
- [00:38:06.850]What is your favorite variety of apple because there's tons available right so?
- [00:38:11.410]Resolutions is your favorite
- [00:38:16.310]Anybody else has a favorite honey crisp honey crisp. I'm with you my I like sour sweet and sour
- [00:38:22.630]It's my two favorite tastes so
- [00:38:24.630]Definitely honey crisp do we think that they would respond the same so I bought at the store
- [00:38:30.050]Fuji and
- [00:38:32.050]Honey crisp, so do you think they?
- [00:38:35.670]Behave the same or not I
- [00:38:39.550]See some heads going
- [00:38:44.330]So probably not right because they they're different, so let's see how the results turn out
- [00:38:51.810]so
- [00:38:53.710]essentially we had some
- [00:38:55.710]control which is the
- [00:38:57.930]fruit with
- [00:39:00.050]No treatment at all and we're going to put here on the plate so you can all see it even for those at our home
- [00:39:07.210]You can see this so this is our I
- [00:39:11.670]Believe this is the fuji Apple
- [00:39:16.890]Actually, I'll take it back. You know what fatima. We have red delicious and honey crisp
- [00:39:23.070]So red delicious your favorite apple and honey crisp so you guys can take this home actually when we're done. They were untouched
- [00:39:30.190]It can be your snack so red delicious. Let's look at red delicious. How does it look like so this was?
- [00:39:37.290]We cut them and we let them sit for how long one did you cut it this morning?
- [00:39:42.790]Yesterday afternoon, and you just left them out
- [00:39:47.310]Yep, so nothing was done to it
- [00:39:50.850]In the bag okay, and that's how they turn out
- [00:39:54.790]Everybody got a good view of that. I'm gonna pour next to it so we can compare
- [00:40:00.530]our Honeycrisp
- [00:40:02.530]So let's see how that one works. I'm gonna use my spoon here kind of make some space
- [00:40:09.150]Okay, and I'm gonna put
- [00:40:12.610]The Honeycrisp
- [00:40:15.790]So what do you think is it any better than our red delicious or not?
- [00:40:21.450]What do you guys think?
- [00:40:25.270]The Honeycrisp are slightly better
- [00:40:29.150]The Honeycrisp is slightly better. I would agree. I'm turning the plate around so you can see this half
- [00:40:34.630]It read delicious this half Honeycrisp. I think the Honeycrisp is a little better
- [00:40:41.290]So let's see now when we applied a different treatment. We immersed some in water
- [00:40:48.130]so I
- [00:40:50.950]Don't know nobody mentioned that potential treatment
- [00:40:54.190]But that's something that we usually do with potatoes right as you're cutting potatoes you immerse
- [00:40:59.070]them in water
- [00:41:01.070]So I'm gonna pour first
- [00:41:03.070]the red delicious and then I'm gonna pour
- [00:41:06.950]The honeycrisp, so just gonna get a few here not all of them
- [00:41:13.570]That's my red delicious
- [00:41:16.330]Not sure if it's too delicious anymore, but anyway like I said it shouldn't change the flavor
- [00:41:23.390]I'm just playing with words. It should still be fine, and that's our honeycrisp
- [00:41:28.510]So
- [00:41:29.030]What do we think?
- [00:41:30.910]Honeycrisp I had yet
- [00:41:32.910]Yes, it's looking a little better. How about water immersion versus doing nothing?
- [00:41:39.490]So that's water immersion
- [00:41:42.210]This is doing nothing
- [00:41:44.430]Did it help some?
- [00:41:46.670]It helps some okay keep that in mind
- [00:41:50.210]We have another one here coming up
- [00:41:53.570]Which is we vacuum packaged the fruits?
- [00:41:59.390]So we went to the pilot plant here at the university, and then we vacuum sealed them and
- [00:42:05.310]Once again just to keep with the order. I'm going to show you the red delicious first
- [00:42:11.190]And we're going to right next to it
- [00:42:19.650]Cutting my package open here. We're going to put the
- [00:42:28.950]So again, which one do we think might be best?
- [00:42:31.430]Flip some here because the skin is kind of hard to if we look just at the skin
- [00:42:38.810]We can see we got to look at the flash. How about that?
- [00:42:41.030]Honeycrisp is still a little better
- [00:42:44.610]Okay
- [00:42:47.890]So now there's
- [00:42:52.210]Lemon juice coming up and that is one of the treatments that you in the classroom mentioned
- [00:42:58.910]as
- [00:43:00.030]Something that would be helpful. Let's see if indeed it was helpful
- [00:43:04.990]That is my red delicious and this is my
- [00:43:12.850]Honeycrisp
- [00:43:16.790]Look at that
- [00:43:19.170]Fantastic, don't you think I think it's awesome the the honeycrisp. We cannot even tell and this was cut
- [00:43:25.510]At 4:00 p.m.
- [00:43:28.870]Yesterday
- [00:43:30.270]Isn't that amazing what the lemon juice can do for you and we have one other product again
- [00:43:35.970]I'm not trying to sell anything here, but I do want to bring up the fact to that in the food industry to help consumers
- [00:43:43.670]Products are available to help with avoiding browning of fruits and vegetables
- [00:43:49.550]There's one product called fresh fruit. I don't know if everybody have seen it grocery store
- [00:43:54.930]You can buy it at the you know produce aisle. It's a
- [00:43:58.830]Powder and if you look at the ingredients is
- [00:44:01.390]essentially ascorbic acid
- [00:44:04.230]Which is the same acid that is in many fruits and vegetables?
- [00:44:07.530]So it's a natural acid that is just put it in the form of a powder that you can sprinkle over your
- [00:44:14.590]Apples to try and keep them fresh
- [00:44:18.170]If you don't have lemon juice you can do that
- [00:44:22.010]And I'm going to pour here
- [00:44:24.770]the honey crisp and the red dill
- [00:44:28.790]That is delicious right next to it
- [00:44:30.790]So what do we think does that work as well?
- [00:44:36.250]It kind of does I don't know if it is as good as the lemon juice I
- [00:44:43.470]Think the lemon juice might be our winner here, right?
- [00:44:48.030]So
- [00:44:51.950]Definitely there's several different things that we can do to help
- [00:44:56.330]with
- [00:44:58.750]Browning or reducing browning eliminating browning in foods and
- [00:45:04.650]Some of the things that we tested here definitely worked
- [00:45:10.410]so if we look at our results if we add
- [00:45:14.150]the lemon juice or some of the other strategies that we tried then
- [00:45:19.390]Browning is reduced in the fruit and therefore the quality remains
- [00:45:25.590]and then we can
- [00:45:28.710]Eat it with any problems right like we're not going to be throwing away because it's not good anymore, so
- [00:45:35.330]We're going to skip here Mike on our
- [00:45:41.650]Padlet on our slido because we already revealed the answers, and I don't know why the back is not
- [00:45:48.590]So just give me a second because
- [00:45:51.950]My back projector. It's not
- [00:45:55.670]Coming back oh
- [00:45:58.670]Did now okay all good, okay?
- [00:46:00.890]So we might have to do a cut there
- [00:46:03.590]To fix it we're gonna skip this one
- [00:46:06.970]Tell me when you're ready Mike, okay awesome
- [00:46:10.590]So essentially we were able to test a whole bunch of different things with our little experiment right one
- [00:46:18.290]Was that different varieties of apple will respond?
- [00:46:22.070]Different to different treatments, and you might be asking yourself. Why right?
- [00:46:28.630]Well one of the things that could be the reason is
- [00:46:31.590]the composition of that Apple, so I look and I search on
- [00:46:39.090]Journals in food science, and I found this data set that I thought it was very pertinent to what we're discussing
- [00:46:48.070]So they were evaluating four different varieties of Apple
- [00:46:52.870]Aori 27 L star Fuji and Mellow and they quantified a whole bunch of stuff
- [00:46:58.590]But the ones that I kind of cropped to bring it to you like I kind of cut out of the paper
- [00:47:02.970]Was the polyphenol oxidase activity that tells me how much of that enzyme is?
- [00:47:08.490]Present in the apples and they had four varieties of that Apple and we can see here
- [00:47:14.430]that the polyphenol oxidase
- [00:47:17.790]Activity was always and they tested at three different points in the growth of that
- [00:47:26.010]Apple like initially and then
- [00:47:28.550]As the fruit was completely mature you can see that the our a 27 was the variety with the
- [00:47:35.990]lowest amount of polyphenol oxidase like
- [00:47:39.890]69 compared to Fuji that was over
- [00:47:44.310]1300
- [00:47:46.790]69 verse 1300 so one has a lot more of the enzyme than the other
- [00:47:51.350]one other thing that it was also different in those varieties was the amount of phenols or
- [00:47:58.510]Phenolic compounds I should say so the amount of phenolic compounds was much lower in the awari
- [00:48:06.570]variety
- [00:48:08.390]Versus say the Fuji variety so you have less of the
- [00:48:12.410]Poly phenolic compounds you have a lot less of that enzyme activity
- [00:48:17.570]So of course you end up with a fruit that browns a lot less and the little pictures here
- [00:48:25.890]That I have like four little boxes
- [00:48:28.470]Is the color of the flesh of the fruit?
- [00:48:32.710]After has been graded and left it sitting for 24 hours
- [00:48:37.730]So after 24 hours of grading the Apple the first one is a worry
- [00:48:42.970]Which it hasn't changed much at all while the other ones got very very dark, right?
- [00:48:48.650]And then the paper was describing this a worry Apple as a genetically modification developed in Japan for the purpose of
- [00:48:58.990]Being resistant to browning. So that was the goal of that particular variety and it definitely achieved right that goal
- [00:49:07.030]so one thing that we can kind of bring back to our discussion is that
- [00:49:10.650]If we remove either of the chemicals that are part of that reaction
- [00:49:17.450]We can reduce browning so we can take away the polyphenolic compounds. We can take away the enzyme
- [00:49:23.670]We can also take away oxygen right because that was one other element
- [00:49:28.390]Of our reaction, so if we can remove those we can reduce
- [00:49:33.750]The browning if we can also change the environment where that reaction is happening. We can also
- [00:49:39.510]Change the outcome
- [00:49:42.270]In one example of changing the environment would be for example using a refrigerator
- [00:49:49.050]right
- [00:49:50.790]So how does that work in our examples here?
- [00:49:54.750]We put the apples in water and
- [00:49:58.350]We also vacuum sealed. It wasn't ideal
- [00:50:00.970]I would say based on our results it might have given us a slight positive result
- [00:50:07.230]But it wasn't ideal. What were we trying to do that remove the oxygen from that equation?
- [00:50:13.610]But we weren't quick enough right because you cut the apples
- [00:50:17.150]then you have to put them in the water or you have to put them in a bag and then take to the pilot
- [00:50:21.490]Plant and then vacuum sealed by that time you know it was already doomed so
- [00:50:26.970]our
- [00:50:28.310]apples ended up getting some browning one other way that we can do that it's by adding the citric acetic
- [00:50:35.350]acetic or ascorbic acid so either lemon juice or our Sprite or
- [00:50:40.750]The commercial product that I showed you what are we doing here? We're changing the pH which is essentially we're adding
- [00:50:48.870]Hydrogen ions age plus we're going to circle back to this in a little bit, but just keep that in mind
- [00:50:55.810]the depending upon
- [00:50:58.270]the pH of a solution
- [00:51:00.930]Polyphenol oxidase may be more or less active
- [00:51:05.190]So we can see here on my chart that the line with the little squares is the activity of the polyphenol oxidase
- [00:51:12.870]And depending upon the pH it goes up and then depending upon the pH is going to be very
- [00:51:18.290]Low so in our case what we were doing is we take we took the apples from a situation in where the polyphenol oxidase
- [00:51:25.890]Was active and we moved
- [00:51:28.230]It towards an area where it was not active anymore. Why it was not active. I'll tell you in a little bit so hang on
- [00:51:35.550]Other things that we can do is the temperature
- [00:51:38.990]Some of us are a lot more active in the summertime right while in the winter
- [00:51:45.290]We just want to crawl under the blanket and not do much
- [00:51:49.370]Same thing happens in the universe and molecules in physics
- [00:51:54.450]Molecules are going to have a lot more activity at a higher temperature
- [00:51:58.190]A lot less activity at a lower temperature
- [00:52:02.070]Because of it, that enzyme is going to be a lot more active at a higher temperature
- [00:52:07.490]If we put that in the refrigerator, we're essentially slowing it down
- [00:52:11.870]And we could also, on the opposite end of that spectrum
- [00:52:17.670]We can heat up to the point that we kill it
- [00:52:21.830]Like we essentially cause a denaturation on that protein
- [00:52:25.590]And we're going to talk a little bit more about denaturation
- [00:52:28.150]Here, in a few slides
- [00:52:30.550]So hang on to that word
- [00:52:32.250]But denaturing that protein can also be very helpful to us
- [00:52:38.230]So, now we're going to look at the functional properties
- [00:52:43.770]Of those proteins in foods
- [00:52:46.630]Beyond the enzymatic activity
- [00:52:48.830]So we're going to look at the properties of creating gels
- [00:52:53.510]Foams, giving elasticity to our food
- [00:52:56.550]Because that's going to confer a lot of benefits
- [00:52:58.110]And a lot of texture to our foods
- [00:53:00.810]And we love texture, right?
- [00:53:03.690]A lot of products, we make them to be in the form of a gel
- [00:53:09.550]Or chewy, or crunchy
- [00:53:12.850]That's a big selling point of a product
- [00:53:16.230]It's texture
- [00:53:18.030]So let's look at how proteins can help us
- [00:53:21.430]However, before we look at how proteins can help us
- [00:53:25.830]We first need to understand denaturation
- [00:53:28.070]Because most of the protein's functionality in foods
- [00:53:33.310]Will only come up after they have been denatured
- [00:53:38.110]When they are in their original form
- [00:53:42.110]They don't help us as much
- [00:53:43.490]But as soon as we can take that protein molecule
- [00:53:48.290]Remember, all folded
- [00:53:50.290]As soon as we can open them up
- [00:53:54.030]And break those
- [00:53:58.030]Bonds
- [00:54:00.010]To the point of opening all the way back
- [00:54:03.610]To our initial primary structure
- [00:54:06.410]That's when they have the most activity
- [00:54:09.990]In our foods
- [00:54:11.210]The functionality is going to come out
- [00:54:14.050]So that's why it's important to understand
- [00:54:15.970]How can we achieve that?
- [00:54:19.210]We can achieve that using different strategies
- [00:54:22.030]What we are trying to do is
- [00:54:24.890]Break the
- [00:54:27.990]Chemical bonds that are happening
- [00:54:29.670]Without destroying that peptide bond
- [00:54:34.250]We want to keep that primary structure
- [00:54:36.970]But everything else we want to open up
- [00:54:39.970]We want to unfold
- [00:54:41.270]Once they are unfolded
- [00:54:43.570]Those proteins are going to be a lot more soluble
- [00:54:46.070]They're going to lose their biological activity
- [00:54:48.870]So any enzymatic browning that's going to happen
- [00:54:51.730]It goes out the window
- [00:54:53.050]We're going to also help increase viscosity of our products
- [00:54:57.950]And we're going to have them act their best
- [00:55:03.450]As far as their functional properties in foods
- [00:55:06.790]So let's look at one agent of denaturation
- [00:55:10.990]The pH that we saw the results on our browning
- [00:55:14.810]The browning of the apple
- [00:55:16.230]We reduced it because of the pH
- [00:55:19.130]But what essentially what we're doing
- [00:55:21.470]Remember that I said when we add an acid to a food
- [00:55:24.590]We're adding hydrogen acid
- [00:55:27.910]Ions, H plus
- [00:55:29.710]So when we start with that protein in solution
- [00:55:33.730]It might be negatively charged
- [00:55:36.150]Like we are showing here in our diagrams, right?
- [00:55:39.610]Like on the slide we're showing a soluble protein
- [00:55:41.890]That is negatively charged
- [00:55:43.370]As I'm adding those H pluses
- [00:55:46.630]What are they going to do?
- [00:55:47.750]They're going to start binding to those proteins, right?
- [00:55:50.970]And they're going to bind in a way
- [00:55:54.330]That they're going to eventually get to a point where
- [00:55:57.870]My protein, instead of being negatively charged
- [00:56:00.790]Is going to be neutral
- [00:56:02.370]I'm going to neutralize
- [00:56:04.150]And the net charge of that protein is going to be neutral
- [00:56:08.790]And then if I continue to add
- [00:56:11.650]Then I'm going to bring that protein back into solution
- [00:56:16.030]Because now I'm going to positively charge it
- [00:56:18.990]So we can go from being in solution
- [00:56:21.770]To out of solution by precipitation
- [00:56:24.690]So that's when it's neutrally charged
- [00:56:27.830]It's where we achieve the isoelectric point of that protein
- [00:56:31.810]That means that the net charge of that protein is zero
- [00:56:35.810]And when that happens, it's going to precipitate
- [00:56:38.810]It's going to coagulate, it's going to be denatured
- [00:56:42.770]And that's what happens when we sour milk
- [00:56:45.810]Essentially, you're getting that protein out of the milk
- [00:56:48.790]Because of the sour, the acid that has been added to it
- [00:56:54.790]Either because we did or because we didn't
- [00:56:57.790]Or because a microorganism did
- [00:57:00.750]And turned that milk sour
- [00:57:02.770]So that's one way
- [00:57:04.770]Another way that we can denature protein is using heat
- [00:57:09.770]So essentially what we're going to do is look at how heat can cause this denaturation
- [00:57:16.770]Once again, the goal here is for our protein to unfold and become denatured
- [00:57:27.750]So it can cause that unfolding, it's going to lead to that opening of the chains
- [00:57:35.750]There are two kinds of denaturation, especially caused by heat
- [00:57:40.730]One is reversible, the other one is irreversible
- [00:57:44.730]So here in our slide, I'm showing you an active protein that is part of milk
- [00:57:49.730]And then if I unfold that because I'm heating it gently, I'm going to cause that protein to become inactive
- [00:57:57.710]And then that protein can refold itself, coming back to a situation where it's now potentially active again
- [00:58:07.710]So that denaturation was reversible
- [00:58:11.690]In some cases, depending upon how much heat I'm applying to that protein
- [00:58:17.690]And now I'm going to use as an example the protein albumin from eggs
- [00:58:21.690]So if I apply heat to that protein, I'm going to cause a denaturation
- [00:58:27.670]That will be irreversible because as that protein is unfolding
- [00:58:34.670]It has very unique R groups that are going to form disulfide bonds
- [00:58:40.670]That are very strong and now even after I cool off, I can undo that
- [00:58:47.670]That is an irreversible change
- [00:58:51.670]So we're going to try and get that going here and we're going to try
- [00:58:57.630]And show that denaturation happening either reversible or irreversible with a demonstration
- [00:59:07.590]So I'm going to explain to you what I have here
- [00:59:10.590]What I have is an egg that we're going to be working with
- [00:59:18.590]And I'm just going to unpack here
- [00:59:20.590]So we have an egg and I have milk and I'm brought to you
- [00:59:27.590]Three types of milk
- [00:59:35.550]Just regular milk that I kept cold without doing anything to it
- [00:59:44.550]Then I took some of that milk and I heated it yesterday in the microwave until it was boiling
- [00:59:52.550]And then I cooled it down in the refrigerator and since then I have been
- [00:59:57.550]Maintaining it cold
- [01:00:00.510]So my hypothesis based on what we are learning here
- [01:00:04.510]Is that my cold milk has my active protein
- [01:00:08.510]My heated milk and cooled
- [01:00:12.510]Will have that active protein as well
- [01:00:16.510]So that protein is not as good
- [01:00:20.510]As far as the functionality because remember that I told you that the functionality of the protein comes
- [01:00:27.510]From the unfolding so that shouldn't be as functional
- [01:00:31.470]But I also have and it's coming in at any second here into the room
- [01:00:36.470]Some milk being heated right now to cause that unfolding
- [01:00:41.470]And that milk will then hopefully show us
- [01:00:45.470]The best functionality for this protein
- [01:00:49.470]So how am I going to be able to show you that because if you look at the
- [01:00:53.470]Containers here there's no difference right
- [01:00:57.470]My cold milk I have the milk that I heated yesterday and now
- [01:01:01.470]We have another milk that was just heated on the microwave
- [01:01:05.470]Right now so it's hot so can you tell which one
- [01:01:09.470]Has functional properties and which one doesn't it's kind of hard to see
- [01:01:13.470]So one way that I'm going to show you that is by
- [01:01:17.470]Frothing the milk anybody likes
- [01:01:21.470]Frothed milk on their coffee I do I only drink coffee
- [01:01:25.470]With frothed milk
- [01:01:27.430]So I'm going to
- [01:01:31.430]Plug in here
- [01:01:35.430]A little frother that I brought from home and
- [01:01:39.430]What I'm going to do is I'm going to froth this hot milk first
- [01:01:43.430]Before it gets cold so I'm going to give it the best chance and I'm going to
- [01:01:47.430]Froth without adding any additional heat because my little frother here I can
- [01:01:51.430]Froth with heat and without today I'm going to
- [01:01:55.430]Froth everything without
- [01:01:57.390]Heat because I'm trying to compare just one thing
- [01:02:01.390]The temperature of the milk right so I'm going to froth
- [01:02:05.390]This one without any additional heat and
- [01:02:09.390]My frother is going it's going to take about a minute and then we're going to pour
- [01:02:13.390]That in a cup here to see how much foam
- [01:02:17.390]I can gain from that milk that was heated
- [01:02:21.390]And hopefully the protein is unfolded
- [01:02:25.390]So
- [01:02:27.350]Hopefully it's going to work as intended
- [01:02:31.350]In the meantime to save us time we're going to be looking at another
- [01:02:35.350]Type of denaturation which is the one for the egg
- [01:02:39.350]So remember that I have my pan
- [01:02:43.350]Here hot and I'm just going to pour the egg in there
- [01:02:47.350]And as you can all imagine what is going to happen over time here
- [01:02:51.350]The egg is going to cook
- [01:02:55.350]The egg is going to get cooked and
- [01:02:57.310]During that cooking process what are we doing is we're opening the
- [01:03:03.310]Chains of that protein like we're opening that folding
- [01:03:07.310]Of the protein but we're also allowing the sulfide bonds to be created
- [01:03:12.310]In a way that is going to
- [01:03:18.310]Going the wrong direction here on my heating
- [01:03:21.310]It's going to become irreversible because that
- [01:03:27.270]The sulfide bond is very very stable and strong
- [01:03:33.270]So
- [01:03:40.270]That's my foam in there
- [01:03:46.270]I'm going to try
- [01:03:51.270]And now I'm going to put the cold milk
- [01:03:57.230]And it's going to froth
- [01:03:59.230]Without any heat I'm not adding any heat to that
- [01:04:03.230]So make sure that you pay attention how this looks like because over time
- [01:04:07.230]You might lose some of that air
- [01:04:11.230]It's not going to hold it forever
- [01:04:13.230]So by the time that we get the third one done
- [01:04:15.230]That might be reduced a little bit but I want you to see
- [01:04:18.230]The texture and how that foam was formed
- [01:04:22.230]In the meantime our pan here is heating our egg not as fast as I designed
- [01:04:27.190]But we can see the color changing already
- [01:04:31.190]For those that are at home you can hopefully see that on the pan
- [01:04:35.190]I will wait just a little more and then I will show it to everybody here in the room
- [01:04:40.190]But I can see that the protein is becoming opaque
- [01:04:44.190]And eventually it will turn white
- [01:04:47.190]And that's when the disulfide bonds happen
- [01:04:50.190]And then I cannot revert that denaturation anymore
- [01:04:55.190]So now that our
- [01:04:57.150]Cold milk has been frothed
- [01:04:59.150]I'm going to pour so we can see
- [01:05:03.150]So what do you think of that?
- [01:05:06.150]I hardly can see any frothing at all
- [01:05:09.150]On the cold milk
- [01:05:11.150]When with the hot milk I can definitely see the little bubbles
- [01:05:15.150]And I can see the texture there
- [01:05:18.150]Now let's see how our heated milk
- [01:05:21.150]But then cooled
- [01:05:23.150]So essentially it would be
- [01:05:25.150]Taking the milk protein
- [01:05:27.110]Inactivating it but then letting it sit in the refrigerator
- [01:05:30.110]So we can reform again
- [01:05:32.110]Let's see if we can bring it back
- [01:05:34.110]To its original configuration
- [01:05:37.110]So once again
- [01:05:40.110]We'll let it froth
- [01:05:42.110]For a minute here
- [01:05:44.110]And then we'll pour our last
- [01:05:46.110]And by then
- [01:05:48.110]Our egg is not going to be completely cooked
- [01:05:51.110]But we can definitely see differences
- [01:05:54.110]So I will show everybody
- [01:05:57.070]In a little bit here
- [01:05:59.030]So now that our milk finished frothing
- [01:06:04.030]So we got some of that foam
- [01:06:10.030]But maybe not as big bubbles
- [01:06:12.030]As we had with the original one
- [01:06:14.030]That had never been heated
- [01:06:16.030]So our heating
- [01:06:18.030]Maybe the fact that yesterday
- [01:06:20.030]I heated to the point of boiling at home
- [01:06:22.030]It denatured some of the protein
- [01:06:25.030]And some got
- [01:06:27.030]Refolded but not all of them
- [01:06:29.990]So we definitely have
- [01:06:31.990]Some of that refolding happened
- [01:06:33.990]But not as much
- [01:06:35.990]Because like I said
- [01:06:37.990]I heated to the point of boiling
- [01:06:39.990]And I want to show everybody at home
- [01:06:41.990]That our pan here going with our egg
- [01:06:44.990]It's definitely like cooking
- [01:06:46.990]And turning white
- [01:06:48.990]Which again is another indication
- [01:06:50.990]Of a denaturation
- [01:06:52.990]And that one I can guarantee you
- [01:06:54.990]Is not going to be reversible
- [01:06:56.990]So now that some time
- [01:06:58.990]Has passed and we have completed
- [01:07:00.990]Our activity here with the reversible
- [01:07:02.990]And irreversible denaturation
- [01:07:04.990]Of the proteins
- [01:07:06.990]I want to bring us back
- [01:07:08.990]And focus on the milk again
- [01:07:10.990]Just to do a final
- [01:07:12.990]Evaluation of the results
- [01:07:14.990]So even though when I was
- [01:07:16.990]Frothing the milk
- [01:07:18.990]That had been heated yesterday
- [01:07:20.990]And sat in the refrigerator
- [01:07:22.990]Overnight it seemed
- [01:07:24.990]Like it was holding a lot of
- [01:07:26.950]Air
- [01:07:28.950]Shortly after
- [01:07:30.950]It was let it sit
- [01:07:32.950]All that air was released
- [01:07:34.950]From the
- [01:07:36.950]Product just
- [01:07:38.950]Like the air was released
- [01:07:40.950]From the cold milk
- [01:07:42.950]That was never touched
- [01:07:44.950]So that shows to me
- [01:07:46.950]That that protein
- [01:07:48.950]Did indeed return
- [01:07:50.950]To its original shape
- [01:07:52.950]And was not able
- [01:07:54.950]To hold that air
- [01:07:56.910]However the milk
- [01:07:58.910]That was heated right before
- [01:08:00.910]We frothed
- [01:08:02.910]Definitely was
- [01:08:04.910]More denatured
- [01:08:06.910]Held the air inside
- [01:08:08.910]And was able to with those
- [01:08:10.910]Shear forces from the
- [01:08:12.910]Frothing machine
- [01:08:14.910]Hold the air the longest
- [01:08:16.910]So we can see that functionality of the protein
- [01:08:18.910]As its best
- [01:08:20.910]On the heated milk
- [01:08:22.910]That was frothed
- [01:08:24.910]Rather than cold
- [01:08:26.870]Or milk that had been heated and cold
- [01:08:28.870]Afterwards
- [01:08:30.870]So pressure can also denature
- [01:08:32.870]Proteins and there is a
- [01:08:34.870]Technology called high pressure
- [01:08:38.870]Processing that can be used
- [01:08:40.870]To denature proteins
- [01:08:42.870]And we're going to talk more about that when we talk about
- [01:08:44.870]Food processing
- [01:08:46.870]Shear by mixing things
- [01:08:48.870]By beating like when we beat
- [01:08:50.870]Eggs when we beat whipped cream
- [01:08:52.870]That definitely can open
- [01:08:54.870]Up and unfold those
- [01:08:56.830]Proteins can help with
- [01:08:58.830]That so as we have
- [01:09:00.830]That protein now unfolded
- [01:09:02.830]Open how can we use it
- [01:09:04.830]To change the texture of
- [01:09:06.830]Foods we can create gels
- [01:09:08.830]Because that protein could be
- [01:09:10.830]In solution now
- [01:09:12.830]And then as it
- [01:09:14.830]Combines itself
- [01:09:16.830]With you know
- [01:09:18.830]Different strands of that protein we can
- [01:09:20.830]Trap water and
- [01:09:22.830]That's what we do in gelatin sausages
- [01:09:24.830]And yogurts we're trapping
- [01:09:26.790]Liquids inside of that
- [01:09:28.790]Network we can also
- [01:09:30.790]Trap air inside
- [01:09:32.790]Of the network so essentially
- [01:09:34.790]We frothing our milk
- [01:09:36.790]We were shearing the proteins
- [01:09:38.790]They open up and then
- [01:09:40.790]Air went inside
- [01:09:42.790]And got trapped and that's why we
- [01:09:44.790]Created that foam
- [01:09:46.790]We can also do that by
- [01:09:48.790]Preparing a dough
- [01:09:50.790]Like if you are
- [01:09:52.790]Preparing bread
- [01:09:54.790]You can be
- [01:09:56.750]Working on that dough
- [01:09:58.750]And opening some of the
- [01:10:00.750]Proteins that are present in
- [01:10:02.750]The wheat
- [01:10:04.750]Especially those called gluten
- [01:10:06.750]Proteins so the gluten
- [01:10:08.750]Proteins will be denatured
- [01:10:10.750]As we are working
- [01:10:12.750]That dough and then
- [01:10:14.750]We can open them up and they can
- [01:10:16.750]Rearrange themselves
- [01:10:18.750]So the gluten protein will form
- [01:10:20.750]A network that then can
- [01:10:22.750]Trap air and then when
- [01:10:24.750]We bake the bread we get those
- [01:10:26.710]Air bubbles inside
- [01:10:28.710]Of the product
- [01:10:30.710]Proteins can also help
- [01:10:32.710]Us with emulsification
- [01:10:34.710]And that's when we are using the protein
- [01:10:36.710]To bring together things that
- [01:10:38.710]Otherwise would be immiscible oil
- [01:10:40.710]And water we're going to have a chance to
- [01:10:42.710]Explore emulsifiers
- [01:10:44.710]In our next lecture so I'm going
- [01:10:46.710]To keep it short here
- [01:10:48.710]Today and with
- [01:10:50.710]The emulsifier then is that
- [01:10:52.710]Compound that helps the oil
- [01:10:54.710]To be suspended in water or
- [01:10:56.670]Water to be suspended in oil
- [01:10:58.670]And that's
- [01:11:00.670]All we had for today and
- [01:11:02.670]I'll see you all next time
- [01:11:04.670]Bye bye
- [01:11:06.670]Thanks for watching!
- [01:11:08.670]Thank you.
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