Learning in the Lab with Rebecca Roston
University Communication
Author
03/18/2021
Added
11
Plays
Description
Rebecca Roston is an associate professor of biochemistry at University of Nebraska-Lincoln. She takes us through the laboratory process of making soap.
Searchable Transcript
Toggle between list and paragraph view.
- [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)
The screen size you are trying to search captions on is too small!
You can always jump over to MediaHub and check it out there.
Log in to post comments
Embed
Copy the following code into your page
HTML
<div style="padding-top: 56.25%; overflow: hidden; position:relative; -webkit-box-flex: 1; flex-grow: 1;"> <iframe style="bottom: 0; left: 0; position: absolute; right: 0; top: 0; border: 0; height: 100%; width: 100%;" src="https://mediahub.unl.edu/media/16011?format=iframe&autoplay=0" title="Video Player: Learning in the Lab with Rebecca Roston" allowfullscreen ></iframe> </div>
Comments
0 Comments