I keep reading that starters should be made from wort in order to get the yeast used to eating maltose and/or acclimate them to their new environment (your wort). I've not seen this backed up anywhere, just said and propagated around like it's the cold, hard truth. I'm not saying it isn't true and that it didn't stem from somewhere, but I like to know this things for sure.
A little background on sugars:
is a disaccharide, comprised of two glucose molecules.
is a disaccharide, comprised of one glucose molecule and one fructose molecule.
So after doing some digging I cam across a paper talking about glucose repression of maltose metabolism
. This paper gives references of the well documented that when yeast S. cerevisiae are in an environment of a lot of glucose, their ability to process maltose is suppressed. Since maltose is made up of two glucoses, the yeast simply prefers to eat plain glucose over breaking down a maltose and eating that, makes sense right?
What about sucrose? Since sucrose is only 1/2 glucose, how do the yeats handle fructose metabolism? Well this paper
studying metabolism of an S. cerevisiae strain use commercially for making apple wine compared yeast growth and fermentation using glucose, fructose, and sucrose. The results were that yeast growth was fast faster with pure glucose and slowest with pure fructose, and in the middle with sucrose. There was a noted lag time time in ethanol production with sucrose, attributed to the need of the yeast to first break down the sucrose to it's two constituents.
On the topic of sugar type and getting yeast used to eating a certain type, I would say that besides a slightly reduced growth time in pure sucrose, your yeast will likely have little to no problem adjusting to eating the maltose in wort. The other option would be to use corn sugar, which is basically pure glucose (and/or dextrose - which is virtually the same thing, but that's a chemistry topic for you to research yourself
), which would likely give you the fastest yeast growth, though it's anyone's guess if the result would be measurable over a 24 hour period. Due to the glucose supression of maltose metabolism mentioned before, you may find that there is a lag time as the yeast switch gears and begin to process the maltose again. Again, testing is required to determine exactly how much lag time there would be, if any.
Now there are other factors that may make using wort (or close to it) better for your yeast, and those are a little harder to figure out. There are compounds other than sugar in wort, and some of these compounds may be beneficial, such as nitrogen containing compounds, and I don't have any info on those for now. The pH of the starter with just sugar and water will be different from that of wort, which is another important consideration.
My literature review has convinced me that using a wort starter, either extract based or real wort, is definitely
better than using table sugar simply for growing healthy yeast faster. If you're in a pinch you can likely get away with using corn sugar, but I would use yeast nutrient in that starter as well. As I said, this needs to be tested to verify that it'll be effective and not stress out the yeast and yield unsatisfactory results in the final beer.
I'd like to do some real world testing on this, and once I'm a little more settled in my new house I'll look in to doing so.