I have been using home made starch for years and never had a problem with it on my fabric. If you leave it in the bottle for more than a week or two (depending on heat and humidity) it will go moldy. I make a batch, starch my fabric, make my quilt and then wash it. But I've had "quilts in the making" with starched fabric sit around for a few months and never had a problem with it on the fabric.
Here's the recipe I use:
1 cup boiling water
1 cup room temp water
anywhere from 1 tsp. to 1 TBLS. corn starch (the more cornstarch you use, the stiffer your fabric will be)
Put the cornstarch in a 2 cup Pyrex measuring cup (or anything similar that can take boiling water).
Add small amount of cool tap water and stir to dissolve starch.
Add boiling water and stir for one minute
Add room temp water and stir thoroughly
When cool enough, pour into spray bottle.
Shake often while using and use within a week or two.
I love this because it's inexpensive, very easy to make, no perfumes or preservatives and it's always on hand since it only has two ingredients we all have on hand. :D