Learning in the Lab with Rebecca Roston

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03/18/2021 Added

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Rebecca Roston is an associate professor of biochemistry at University of Nebraska-Lincoln. She takes us through the laboratory process of making soap.

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[00:00:00.214](bright upbeat music)
[00:00:04.430]Hi, my name is Rebecca Roston.
[00:00:05.780]And today we're gonna go into my lab
[00:00:08.010]to learn about making soap, why?
[00:00:10.500]Because this is something that my lab does everyday
[00:00:12.770]not making soap,
[00:00:14.030]but we do end up making soap
[00:00:15.970]out of fatty acids to understand their properties.
[00:00:18.790]And that's because I studied how plants tolerate cold
[00:00:21.510]and membranes are critical to cold.
[00:00:23.665](bright upbeat music)
[00:00:27.080]Natural fats and oils often seem similar in the kitchen,
[00:00:30.040]but they're different up close.
[00:00:31.550]This is the most common coconut oil,
[00:00:33.206]and this is the most common olive oil.
[00:00:35.560]Coconut oil is solid at room temperature
[00:00:37.210]because it's fat stuck well.
[00:00:40.090]Olive oil is liquid because it's fats do not.
[00:00:43.189](bright upbeat music)
[00:00:45.110]When making soap we use lye
[00:00:47.180]or concentrated sodium hydroxide to break up fats.
[00:00:51.760]These long pieces are called fatty acids
[00:00:53.520]because they have a fatty end in gray
[00:00:55.960]and an acid end in red.
[00:00:58.430]Fatty acids are soap, but what is soap?
[00:01:02.610]We suggest pausing here and thinking about what soap is.
[00:01:05.817](bright upbeat music)
[00:01:09.000]Welcome back.
[00:01:09.860]Here's some of the words that we thought of.
[00:01:11.145](bright upbeat music)
[00:01:13.670]The most important of all of these words is 'cleaning'
[00:01:16.430]'cause that's really what defines soap,
[00:01:18.610]but how does soap clean?
[00:01:20.870]Soap forms a structure around fats.
[00:01:25.280]Look, it can trap the fats in a water loving surface,
[00:01:28.310]this lets them get rinsed away.
[00:01:30.480]The structure is called a Micelle
[00:01:32.751](bright upbeat music)
[00:01:34.820]Different fat properties also have
[00:01:36.440]different soap properties.
[00:01:38.230]Pause here and predict.
[00:01:39.800]Will a soap made out of coconut or olive oil
[00:01:42.160]be better at making micelles?
[00:01:44.410]Why? (bright upbeat music)
[00:01:46.580]And will a soap made out of coconut or olive oil be harder?
[00:01:51.110]And why?
[00:01:53.070]You'll find out when you do the experiment.
[00:01:54.857](bright upbeat music)
[00:02:00.620]Starting by weighing out some olive oil, 100 grams oil.
[00:02:06.550]Now that are all oil is ready,
[00:02:08.060]we need to warm it up.
[00:02:09.440]While that's happening,
[00:02:11.530]Zach's getting our lye solution ready.
[00:02:13.385]Do you need 12.47 grams of lye?
[00:02:16.240]That's gonna leave at least five to 8%
[00:02:20.597]of the olive oil unreactive and that's for a reason.
[00:02:23.840]Because, if we made it all into fatty acids,
[00:02:26.630]it would feel pretty terrible on our skin
[00:02:28.300]as it started just upon your skin itself.
[00:02:30.610]Notice how careful Zach's being weighing the lye
[00:02:34.520]into the weigh boat.
[00:02:36.830]He also makes sure
[00:02:37.663]that the spoons stay somewhere safe after he's done.
[00:02:41.170]All of that's gonna be neutralized before discarding.
[00:02:45.560]Both the lye and all the oil
[00:02:48.910]need to be in a format that they can be mixed
[00:02:51.040]before we start.
[00:02:52.390]The lye is currently solid
[00:02:54.060]so we have to put it into an aqueous solution,
[00:02:56.460]that means mixing it with water.
[00:02:58.180]Anytime you mix a solid base with water,
[00:03:00.930]you should do it carefully because it releases heat.
[00:03:04.080]So, we need to start by weighing
[00:03:05.770]out the right amount of water.
[00:03:07.730]Should be 30... 30 Milliliters.
[00:03:10.355]30 Milliliters is the same as 30 grams,
[00:03:12.390]so you can either way or pour out.
[00:03:14.290]Now, when you're mixing a strong base with water
[00:03:19.640]you should do so in a safe place like the hood.
[00:03:22.530]If you don't have a hood available
[00:03:24.570]you should be doing this in as open air, as possible
[00:03:27.900]with as much ventilation as you can.
[00:03:30.090]Open windows if you have them.
[00:03:32.070]Zach's using the sash of the hood to protect his face.
[00:03:35.310]That way no lye can get to his face.
[00:03:38.300]If you don't have a hood,
[00:03:39.520]make sure that you're wearing goggles
[00:03:40.930]or some other appropriate eye protection,
[00:03:43.850]glasses aren't enough.
[00:03:44.994]Periodically as you're adding the lye,
[00:03:47.190]fill the beaker to make sure
[00:03:49.890]that you haven't gotten it too hot.
[00:03:52.580]If it feels hot to the touch,
[00:03:54.170]Wait a few minutes before adding more lye.
[00:03:57.150]So once you've added the lye and it's well mixed in,
[00:04:00.030]it should be warm enough.
[00:04:01.348]But your oil needs to be heated before it's ready.
[00:04:05.470]And Ngoc has already heated the oil.
[00:04:07.172](bright upbeat music)
[00:04:09.240]Bowls should be no warmer than 50 degrees Celsius
[00:04:12.720]and should be at least 35 degrees Celsius
[00:04:15.760]before beginning to mix them.
[00:04:17.600]Do you wanna check those temperatures?
[00:04:18.898]Yes.
[00:04:21.570]As Zach's discovering,
[00:04:22.740]mixing the lye with the water
[00:04:24.360]got it a little bit too warm.
[00:04:26.250]You wanna wait till that cools down before mixing it.
[00:04:28.251](bright upbeat music)
[00:04:30.470]Now that it's down to temperature
[00:04:31.960]you can add a lye into the oil.
[00:04:34.870]The oil should be mixing
[00:04:37.080]when you start.
[00:04:38.870]He's turning on a magnetic stirrer underneath
[00:04:41.270]that's allowing that stir bar to mix.
[00:04:42.810]If you don't have a magnetic stir
[00:04:44.140]you can stir with a spoon,
[00:04:45.640]or preferably a whisk at this point.
[00:04:48.750]As you add in your lye
[00:04:50.150]your oil will quickly become cloudy.
[00:04:54.440]That's the pontification reaction starting
[00:04:56.339](bright upbeat music)
[00:04:57.960]If you're using a stir bar and a stir plate like this
[00:05:01.770]what you'll see is that you can create a strong vortex
[00:05:06.140]and that as your solution thickens like this one
[00:05:09.170]which we started over here,
[00:05:11.172]that divot in the center is gonna start to disappear.
[00:05:14.640]When you see that you can check to see
[00:05:16.210]if it's ready to trace.
[00:05:18.320]This is a soap making term used to describe the thickness,
[00:05:23.800]and the completion of this pontification reaction.
[00:05:26.464](bright upbeat music)
[00:05:27.297]So what you can see is that when Zach picks it
[00:05:29.800]up and drips it down, nothing stays on the surface.
[00:05:34.590]And what that means is it's not yet ready to mix
[00:05:37.210]even though it's quite light
[00:05:38.330]and a lot of the pontification has occurred,
[00:05:40.360]if you poured that now it would still separate
[00:05:42.500]into fats and lye, which is not good
[00:05:47.071]so while this thickens
[00:05:49.130]let's show you what happens at the end.
[00:05:51.560]You're gonna pour your soaps into a mold,
[00:05:54.120]and then they're gonna take a while
[00:05:55.350]to finish saponifying.
[00:05:56.550]and you need a check to find out when they're safe.
[00:06:00.050]Ngoc here is going to take some pH strip paper,
[00:06:04.130]and test some soaps that we made last week.
[00:06:07.040]She had a different finger in the water,
[00:06:09.230]put a little bit on the soap
[00:06:10.970]and then gently put that pH paper in.
[00:06:12.890]The color on the pH paper indicates the pH.
[00:06:16.050]As you can see, this one's a eight
[00:06:18.980]maybe a little bit on the neutral side of eight.
[00:06:21.890]Not exactly where you want a piece of soap to be
[00:06:23.940]that soap is ready to use.
[00:06:25.800]In contrast this olive oil soap
[00:06:29.030]which was made more recently,
[00:06:31.750]you see is not quite there yet.
[00:06:33.495]It's a darker color, more like a nine
[00:06:38.420]and that's soaps getting ready to use,
[00:06:40.250]but it's not perfect.
[00:06:41.970]Not at the same time we made this all of oil soap,
[00:06:44.490]we also made two types of soap incorrectly.
[00:06:47.890]In these we didn't let the soap trace.
[00:06:50.990]And what happened was the lye separated out from the oil.
[00:06:56.090]And one of the consequences is
[00:06:57.500]that it destroyed the foil underneath.
[00:06:59.960]And another consequence Ngoc will show you with a pH strip.
[00:07:04.530]That's still a very, very basic piece of soap.
[00:07:07.380]For the longer you leave it
[00:07:08.213]the more ready your soap will be to be soap
[00:07:10.780]because the saponification continues to occur
[00:07:12.900]in the solid form.
[00:07:14.800]And you should make sure
[00:07:15.633]that you do that until your soap is ready.
[00:07:17.400]It should take at least a week
[00:07:18.940]to turn to a fairly neutral pH.
[00:07:23.270]alright and now our soaps that we've been mixing are ready.
[00:07:28.340]The soap on the right has some herbs floating in it.
[00:07:31.100]It's taken about an hour to come to this thickness.
[00:07:34.670]The trace means that you can start to see those blocks
[00:07:37.810]on the top of the surface before they mix in.
[00:07:40.800]That's what you're looking for
[00:07:41.800]to know that your soap is ready.
[00:07:46.800]Adding some extra heat underneath can help.
[00:07:49.280]You can see these hot plates are on
[00:07:51.670]and that's helping that so get to that trace faster.
[00:07:54.140]If you don't have hot plates
[00:07:55.690]you can alternatively use a crock pot and hand mixing.
[00:07:59.306](bright upbeat music)
[00:08:03.480]Make sure you settle it a little bit
[00:08:04.920]to make any air bubbles come to the surface and pop.
[00:08:08.520]If you have been using a stir bar, like we have,
[00:08:10.960]make sure you pour slowly and gently
[00:08:13.490]so the stir bar stays in your beaker.
[00:08:16.100]Those will be solid in just a couple of hours,
[00:08:18.630]but there'll be very basic still.
[00:08:20.810]Right you can't pH test them because they're too oily
[00:08:23.890]for allowing the water solution to get on the paper.
[00:08:28.580]So as soon as your paper sits on top
[00:08:30.780]and can't enter the solution,
[00:08:32.210]that's the first time you can pH it.
[00:08:33.912]When you do that
[00:08:35.823]your pH should be as low as your pH paper chemical.
[00:08:38.740]That's that strong base.
[00:08:40.200]Then over time, it'll lighten up.
[00:08:42.400]Once you bake it back to eight
[00:08:44.080]you can start to use it on your bare hands.
[00:08:46.490]We chose to show you this reaction making soap
[00:08:49.220]because it's very similar to reaction that we do in the lab.
[00:08:51.850]And Zach set up a demonstration here
[00:08:54.670]showing you some of the things we do.
[00:08:57.580]Because we look at plant cold tolerance
[00:08:59.630]and because cold tolerance depends
[00:09:01.030]on membrane fatty acid composition,
[00:09:03.640]we extract using Saponification
[00:09:06.460]membrane fatty acids from leaves,
[00:09:08.740]collected at different temperatures.
[00:09:10.800]Right now, Zach is adding methanolic HCL.
[00:09:14.620]Just like the strong base,
[00:09:17.030]this will saponified the fatty acids in the tissue.
[00:09:20.620]It will also destroy the tissue.
[00:09:23.150]Now, this has to go over to heat up.
[00:09:26.470]Unlike those large beakers
[00:09:27.640]we can't heat this on a stir plate.
[00:09:30.370]So instead, we're gonna use a hot water bath.
[00:09:33.710]Over about 30 minutes.
[00:09:35.217]That's gonna saponify, all the fats in that leaf.
[00:09:39.840]Zach's now holding one
[00:09:40.673]that's been sitting in there for over 30 minutes.
[00:09:44.670]Is he's gonna take it out?
[00:09:46.310]I'll let it cool down.
[00:09:48.390]Now after letting it cool,
[00:09:50.650]Zach's gonna add a organic solvent
[00:09:52.970]to extract the fatty acids from the water.
[00:09:58.390]He's also gonna add salt
[00:10:00.115](bright upbeat music)
[00:10:01.420]in the form of salt water to help improve the extraction.
[00:10:05.170]Just like when you made soap,
[00:10:06.600]it's really important to mix these very carefully.
[00:10:09.920]So Zach's gonna use a vote texture
[00:10:12.240]to make sure that mixing is complete.
[00:10:14.716](bright upbeat music)
[00:10:17.124](motor revving)
[00:10:18.950]It creates a cyclone within the tube
[00:10:22.074]quickly mixing the contents thoroughly.
[00:10:24.646](bright upbeat music)
[00:10:25.720]As you can see it's already starting to separate again.
[00:10:28.740]Zach's gonna take this tube and put it into the centrifuge.
[00:10:32.150](bright upbeat music)
[00:10:36.299]Zach places the tube in,
[00:10:38.280]the centrifuge is spend the two very quickly
[00:10:40.930]increasing the speed of gravity
[00:10:42.490]and allowing the separation to complete.
[00:10:45.290]Here's one that we did already.
[00:10:47.630]Now, the top layer has all of the fats
[00:10:49.460]that were in the leaf.
[00:10:51.580]Zach's gonna take that, a sample of it
[00:10:55.030]into a small vial that we can run on a chromatograph
[00:10:59.790]to understand which fats are present.
[00:11:02.890]He's capping a small bile
[00:11:04.120]to make sure no oxygen gets in to change these fats
[00:11:09.260]before we can read what they are.
[00:11:13.720]Zach adding the sample
[00:11:15.920]into the GC Autosampler now.
[00:11:18.214](motor revving)
[00:11:20.110]That's gonna automatically inject it
[00:11:22.220]and Zach's gonna be able to see what pieces come out.
[00:11:25.730]Here's a typical chromatogram
[00:11:26.960]showing you a lot of different fatty acids.
[00:11:28.880]Fatty acids vary in chain-link
[00:11:30.950]and the number of desaturations.
[00:11:32.690]And here Zach's looking
[00:11:34.360]at a sample that had many different ones.
[00:11:36.750]Plants also typically have many different fat samples,
[00:11:40.030]right there he's looking at one of the fatty acids
[00:11:42.020]most commonly present in coconut oil.
[00:11:47.520]You just saw how my lab uses Saponification
[00:11:50.130]on a daily basis to help understand the fats
[00:11:53.200]that are in plants.
[00:11:55.190]And hopefully in about a week
[00:11:57.060]you'll have your very own bar of soap.
[00:11:58.765](bright upbeat music)

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Learning in the Lab with Rebecca Roston

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