Hi all I'm new to home brewing - have two 5-gallon batches under my belt. That said, I've been trying to figure out, but haven't had any luck, on what is the difference between a yeast starter and re-hydrating dry yeast. For the two batches that I've done, I've re-hydrated the dry yeast. Since there's a more complicated recipe that I want to try that requires secondary fermentation and a yeast starter, I would like to know if I can substitute the yeast starter for re-hydrating dry yeast? I'm still not too confident doing a yeast starter yet. However, I would like to know if it's the same thing. The key to a yeast starter is to multiply the yeast count from the Wyeast liquid yeast smack-pack. The same goes when re-hydrating the dry yeast. Is this a correct statement? Otherwise, please provide some knowledge/experience. Really appreciate any help/explanation I can get, so that I can start my next brew. Thanks.
A yeast starter insures you have healthy and already multiplying cells ready to go once pitched into your wort and shortens lag time for fermentation to begin and a less stressed yeast. Rehydrating is a less involved but your cell count is smaller than a starter. Much like a smack pack. These are interchangeable really just time and more contact points for possible contamination. Rehydration or Starters are good practices to have and will produce better beer than straight pitching dry on wort imo. As for secondary fermentation id say skip it moving the beer from a carboy to another you run the risk of infection and or introducing oxygen to your beer once was a recommended practice now not really needed. this will help alot too. http://www.mrmalty.com/calc/calc.html
Not rehydrating decreases your cell count. Starters increase your cell counter. I typically would not make a starter with dry yeast (but I might rehydrate multiple packs and pitch). I typically would make a starter with liquid yeast, using two packs if making a lager. Even for low gravity beers, I'll make a 1 liter starter.
-> Purpose of Rehydration: Conditions the cells of dry yeast (and their walls) so that more of them survive when added to the wort. -> Purpose of Yeast Starter: Increase Cell Count. The two are not interchangeable. Most(?) Dry Yeast manufacturers do not recommend making starters with dry yeast. That's fine, but with some worts, you'll need more than one pack. Dry Yeast packs also (luckily) generally have more cells than liquid packs and vials. With liquid packs and vials, you would never rehydrate (because the cells were never dried). But the lower starting cell count in a liquid pack/vial means that for most worts you'll be better off with making a starter (unless you are making really small batches). For any given volume and gravity of wort, there is some number of yeast cells that you'll want to pitch. Calculators can really help here. The liquid yeast manufacturers will tell you that as long as the pack isn't "expired" (an arbitrary bit of nonsense, since cells are dying off every day, before and after the expiration date), it's good for "X" gallons of wort of up to "Y" gravity. They are correct in the sense that it will make beer, but you won't be pitching at ideal rates, whatever your chosen ideal rate happens to be. Did I mention calculators?
Starter purpose is to make more healthy yeast. Rehydrating is just to bring that dried out yeast back to the living stage. There's 5 times the amount of yeary cells in a dry pack than a snack pack. ALWAYS rehydrate your dry yeast. It's the very least you can I for your yeast/beer.
Most of what was already said is correct. Some of what was said is wrong. Some was just irrelevant. Rehydrating dry yeast and making a starter are two different things. My 2 cents: Ideally, rehydrating dry yeast simply undoes the drying process and the yeast is as good as it was before. In practical terms, that's exactly what it does. There are a number of benefits to rehydrating dry yeast before pitching. The most commonly cited benefit seems to be avoiding the massive kill-off that occurs when it's pitched dry. Some say that 50% of the otherwise viable cells die when you do that, and I won't argue with that number. Contrary to popular myth, however, this will not adversely affect your beer, since there's more than enough in the remaining 50% to do the job. I frequently cite a gasoline analogy (I'm not sure if I thought this up myself) - if it takes 3 gallons of gas to make the round trip to work, then 4 gallons in your tank will get you there just as reliably and efficiently as 8 (this analogy works best if you assume it's a rental car and whatever gas is left in the tank after your trip is lost). That's the situation with dry yeast. Rehydrating doesn't hurt, but it also doesn't help, IMO. That said, peace of mind is a real thing, so I would never advise someone to not rehydrate dry yeast if it enhances confidence. The purpose of a yeast starter is to increase the cell count and/or to ensure the viability of the yeast. Certain styles notwithstanding, underpitching is a bad thing. A starter minimizes this danger. Generally speaking, one smack pack/vial will ferment 5 gallons of a 'normal' gravity wort just fine. The problem is that liquid yeast is more sensitive to storage conditions than dry, so you can never be sure how viable the pack is. Odds are, it's fine (most suppliers and brewers are aware of the need to store it properly, just like the supermarket and the consumer are aware of the need to keep the milk chilled). A starter just improves the already excellent odds. Overpitching is less problematic than underpitching, so we err on the side of more (just as 8 gallons in the tank is typically not problematic). It's important to note that bigger beers need either a starter or multiple vials or packs of dry, since they need more yeast than a single package typically contains. In that case, a starter is necessary, if only from a cost perspective (Yeast is not cheap. Multiple vials are even less cheap).
Since it was mentioned there are indeed online yeast calculators (e.g., Mr. Malty Yeast calculator). These yeast calculators utilize a series of conservative assumptions that will yield an ‘answer’ that you need more yeast cells than is truly needed. To borrow an analogy from mikehartigan, the Mr. Malty yeast calculator will yield an answer that you need 8 gallons of gasoline when a lesser amount is perfectly fine. Some folks will state that overpitching is not an issue and that more is ‘better’. That is not always the case and it could be argued it often is not the case. Overpitching will result in a differing beer than one where the proper amount it is pitched. There are experienced industry folks who actually advocate a slight underpitch. Below is what Dave Logsdon (founder of Wyeast and owner/brewer of Logsdon Farmhouse Ales) states: “There is also an upper limit to how much yeast you should add. Logsdon says, “I try to stay within 20 percent of my ideal pitch rate and I prefer to slightly under pitch rather than over pitch. This causes more cell growth, more esters and better yeast health. Over pitching causes other problems with beer flavor, such as a lack of esters.” Cheers!
Problem is, in many cases you might actually need more than 50% of the yeast cells in a dry yeast sachet to have a healthy fermentation. Such as with high OG beers, or lagers. So it takes 3 gallons round trip but your only using 2 gallons. You'll come up short.
Since the calculators apparently yield an answer that you need more yeast cells than is truly needed, what's your preferred pitch rate, in cells per volume per gravity?
That's what I said (read my post through to the end). If you're hauling gold bars to work, you'll need more gas that day. In that case, either make a starter or pitch another packet of dry (or buy extra gas).
