I am brewing a pale ale today and am planning to add some apple cider to it to give it some apple flavor. My plan is to brew about 4 gallons of pale ale and then add 1.25 gallons apple cider. I am thinking I will add the apple cider after fermentation so that it doesn't take away from the flavor. How would this affect my OG and FG? I know it will add fermentables, but my OG is going to be high starting with a low volume so what would adding more volume later do?
Well its not like diluting it straight with water because the cider has a gravity to it as well. You need to check the gravity of your cider before you can start figuring out the math for your change in gravity or dilution in ABV. I would track it based on points. Say you have 3 gallons of 1.050 wort that's 150 points (3*50). Then you add 2 gallons of 1.035 cider, that's another 70 points. So its like having 220 points in 5 gallons, or a 1.044 OG. And to me it doesn't matter much when you add the cider, in the end you are still trying to ferment out the total 220 points, just at different times. (That's not to say that when you add the cider will not effect the flavor profile of the final product. I am just talking points here.) Remember if you are adding hops or other ingredients, you'll be diluting those out too with the addition of cider. And Cider is more fermentable than wort so its tougher to predict FG as well.
From what I've experienced and read about cider it's like just about any other fruit. Treat it like you're making wine. You're going to hit somewhere around 0.99-1.002 depending on the yeast. The OG is never high enough to ramp up the FG by much unless you start adding pounds of sugar. You could go either way on this: http://www.howtomakehardcider.com/fruit-yeast.html I prefer unpasteurized when making hard cider. It shapes up over time (like lots of beers). The pasteurized stuff is a little more stagnant. As the article states, unpasteurized cider is sketchier and will give you the chance of a wild yeast or infection. I use campden tablets to fight this and I've had great success with the raw unpasteurized stuff. To go back to the OP: Would it matter which you choose to blend in a beer that's 1.045? I don't think it would matter much. But, now you know a little more about what you're working with.
Im guessing that your not using apples meant for hard cider? If IMO so granny smith or gravenstein is the best to use, Ive done varietal ciders using granny, fuji, grimes golden, pippin, gravenstein, and gala, my favorite is gravenstein, but they are hard to get ahold of, granny is much easier to come by. IMO 1.25gal of cider in a 5gal batch is going to add next to no flavor. Apple flavor is extremely delicate to begin with, and adding it to a PA with any amount of hoppiness and there will be next to no flavor coming through. Ive tried adding cider to a couple of beers, and the only one that had an apple presence was one where I boiled down the wort to a syrup and adding 4gal of fresh pressed cider to dilute the wort syrup (link to recipe if your interested) Yeast choice will also make a big difference, I would suggest using the WL cider yeast or nottingham
