food scale (up to at least 500 g or so and with a resolution of at least 0.2 g, I use the America Weigh Scales SC-2KG-A)
Ice cream maker (I use a Cuisinart ICE-21)
two big bowls
a big fork
pH strips (Whatman pH indicator pH 4.5-10, type CF, Cat. No. 2614 991) (maybe 5-10 total)
a small microwave-safe dish (something other than a shot glass)
a cheesecloth or large handkerchief
Latex gloves (if they're powdered, maybe wash the powder off first)
5 g solid sodium hydroxide (NaOH) (food grade)
8 g solid citric acid (food grade) (if you can get food grade HCl, use that)
400 g Lupin flour (This recipe isn't optimally efficient for flour usage. I didn't end up using all of the protein I extracted, the leftovers can be made into lupin milk)
1 tbsp vanilla extract
80 g granulated sugar
65 g canola oil
1. Suspend 400 g of lupin flour in 3 liters of water. Stir it until there are no clumps
2. Add 4 g of solid NaOH, or however much it takes to get the pH to about 9, use the pH paper to test. Stir the solution so the NaOH is evenly distributed.
3. Cover the solution and let it sit for 1-2 hours, stirring occasionally. The protein in the lupin flour will go into solution, leaving the insoluble carbohydrates (like starch and fiber).
4. Strain off the solids. The solids are useless for ice cream, but I don't throw it away. Instead, I use it as a soup thickener.
5. Precipitate the protein from the liquid fraction by lowering the pH to about 5.5 with 8g citrate. Check with pH paper. Stir it up. You should see the solution becoming cloudy as the protein comes out of solution.
6. Cover the solution and put it in the fridge to settle for 2-3 days (if you leave it for too long it will spoil, so be careful). We need to separate the protein from the liquid (which contains things like soluble carbohydrates). I used a wide container, but the ideal container for this will be as tall and narrow as possible, like a big flower vase or something like that.
7. Decant off the liquid on top, leaving a sludge of protein.
8. (optional) I've found that it seems to help to freeze the decanted protein, and then thaw it, and decant again. Freezing seems to separate the protein from the liquid more and make the protein stick better to itself so it doesn't pour off with the liquid.
9. Determine the percent protein of your sludge. Weigh a small cup or other microwave safe container. Put about 10 g (know the exact amount) of sludge into the container. Microwave the sludge until it is dry. Be careful not to burn it. Weigh it again. Divide the final weight from the initial weight and multiply by 100 to get the percent protein (be sure to not include the weight of the container). In my case, I started with 7.7 g and it was 0.8 g dry. Which is about 10% protein.
10. Adjust the pH of the protein back up to around 6.5-7 by adding NaOH (for me this took 1 g). Stir it up. Most of the protein will go back into solution.
11. Combine protein solution with oil, sugar, and flavor. Depending on your protein concentration, the exact ratios you use will be different from mine. What you want is to end up with a solution of about 5% protein, 10% oil, 10% sugar. I used 515 g of my protein solution (I had about 340 g left over, so I could have made a bigger batch), 12 g (1 tbsp) vanilla extract, 80 g sugar, 65.5 g canola oil. I stirred until the the sugar was all dissolved, and the oil was mostly all emulsified.
12. Pour the solution into the ice cream maker to freeze it into ice cream.
13. Put it in the freezer to set.
|Step 2: lupin flour suspended in water and adjusted to pH 9 with NaOH|
|Step 4: filtering setup to separate solubilized protein (the flow-thru) from fiber (the solids that get trapped in the cloth). I speed the filtering process by detaching it, bunching it up, and twisting to squeeze the liquid through.|
|After step 4: the two fractions. The solids (left), and the protein solution (right). In this picture|
|After step 7: A protein sludge.|
|Step 8: frozen protein.|
|Step 12: The ice cream maker working hard.|
|The final product.|
For my first few efforts, I didn't have an ice-cream maker, but I was unable to get the ice-cream to freeze properly without big crystals, so eventually I broke down and got an ice cream maker, which worked much better than trying to do it manually.
I tried multiple kinds of pH paper but the Whatman 2614 991 gave the clearest results by far.
When letting the protein settle in the fridge, be sure not to forget about it. In an earlier batch, I let it sit too long and it started to get stinky and bad, so I had to throw it out. I really wish I had a centrifuge, but that's not really practical for home use.
Shot glasses are NOT! microwave safe. I ruined two of them trying to use them as vessels for drying lupin protein to determine the percent protein in the solution.
The kind of oil you use is probably not terribly important, as long as it's relatively flavorless (or if you like the flavor), I'm not sure how high melting-point oils like coconut would work, maybe not quite as well.
I had left over protein. I'll talk about what can be done with that in a later blog.
For more detail about optimal protein/sugar/fat ratios, see steps 0046 to 0048 of patent US20080089990.