Can I make and split a yeast starter indefinitely?

[duncan.brown]

Does the pessure canning process help remove any potential infections? That is, if clean & sanitize fully as normal, will the temp, time, & pressure help kill any other "bugs" that may have gotten in to my wort?

Pressure canning gives you sterile wort so you can store it at room temperature for extended periods of time. 20 mins at 250 F is enough to kill all microbes, including botulism spores. Just boiling doesn't kill the the spores. If you make and use the starter wort straight away, simple boiling to sanitize is fine. The yeast will quickly drop the pH to a low enough level where botulism can't grown.

However, if you want to make starters in a batch and keep them on the shelf, you have to use pressure canner to sterilize the wort. If you buy off-the-shelf Propper Starters, they contain are sterilized wort.

It's getting OT, but my process for pressure canning is:

1. Dissolve 6 lbs of DME in 7.64 gal of water at 110 F (which according to Briess is the optimal temperature for dissolving DME). Add a teaspoon of yeast nutrient.
2. Boil for 15 mins to get the gravity to 1.034 and go through the hot break in my kettle. This isn't strictly necessary. Some just add the DME directly to the Mason jars before canning, but boil for 15 mins first gives me less crud in the jars. I also find spooning out the DME gets messy. It's easier to pour the bags into my kettle.
3. After letting the wort cool a bit, fill seven clean (but not sanitized) quart mason jars up to the neck with the hot wort, leaving about 1/4" of air at the top.
4. Put on the lids and screw down the bands. Loosen the band by 1/3 turn as the lids need to be loose in the canner.
5. Put them on the rack in the bottom of the pressure canner. Add hot water (hot so the jars full of hot wort don't crack) to about 1" below the neck of the jars in the canner.
6. Seal the pressure canner. and heat on high gas until steam is continuously vented from nozzle (approximately 25 mins).
7. Vent all air from pressure canner by allowing steam to continuously vent from nozzle for 10 mins. This step is important.
8. Add the pressure canner weight set to 15 psi. Continue to heat on high gas until the weight starts to continuously rock and pressure reaches 15 psi (approximately 15-20 mins).
9. Turn down gas so that the weight is just rocking and cook 20 mins at 15 psi.
10. Turn off gas and allow to cool until pressure is zero (approximately 50-60 mins).
11. Remove weight and allow residual steam to vent.
12. Remove canner lid and carefully remove jars. Hand-tighten the lids.
13. Goto to step 3 and repeat for 7 more cans. 6 lbs of DME fills 35 cans (five canning cycles).
14. Wait for the jars to cool and the lid button to pop in. This shows that a vacuum has been created in the jars and they are sealed.

When jars are completely cool, check the lid seal by removing the screw band and pulling on the lid. The full cycle of heat, vent steam, heat to 250F, hold at 250F, then cool to room temperature sterilizes the cans and, as the cans cool, they create a vacuum inside that seals the lid tight. If the seal is good, the jars can be stored for long periods of time at room temperature. I store them without the screw band as the vacuum keeps the lid on and in the rare case that there is an infection (which shouldn't happen if you canned properly), then the lid will pop and not the jar.

It takes me the better part of a day to make 35 jars of wort, but it's short bursts of activity with plenty of time to do other stuff. 35 jars last me a while and I like the convenience of just dipping in star san and cracking the lids when I make a starter.

 

[NightFlight]

To get back yo your original question.
Of course you can repitch harvested yeast from a previous batch. Use about 1/5 to 1/4 of that yeast cake of a batch of similar size and gravity, as it has grown 4-5 times in quantity.

There is no need to "wash" (rinse is actually the correct term here, unless you use an acid) to separate the yeast from the trub. You could pitch as is. Just keep excellent sanitation.

Do you have to wash a "trub starter" to store it?