I have bought a gallon of Apple juice fresh off the press. I was told to just leave it 'as is' in a container with an air lock/bubbler and that's all I need do.
I usually brew beer and this all seems too simple to me. Can it be that simple.
You can certainly make great cider that way, but it's hit or miss. I've made probably about 6-8 batches using natural fermentation and my record is about 50/50 great cider/vinegar. A more reliable method is simply to pitch some yeast into it. Almost any yeast will give good results, but I've made my best ciders with WY4766 cider yeast.
I just bottled 5 gallons of cider I made (my first batch last year was excellent, and strong). I've definitely found cider to be easier than beer when it comes to the actual brewing. That said, if you press the cider yourself and/or add in apple picking for 5 gallons worth of cider, you've got a bit of work to do.
The recipe I used was specified by the gallon, but I just scaled it up for 5 (with the exception of the yeast; I only pitch one vial/packet of yeast since they're supposed to be sufficient for [I believe] up to 6 gallons). It's basically an apple wine that you then prime with sugar before bottling. Everything non-apple derived I was able to get from my local brew shop. Here's what I went with...
The cider took longer than most of my beers for the bottle conditioning to take the hard edges off the flavors, but once it did it was very tasty. The regular stirring bit has concerned me some (both in terms of possible infection and so many recipes advocating not aerating once fermentation is underway) but the cider I made was quite good.
Started doing hard ciders (apple, pear, hot pepper, peach, cactus pear, raspberry, pumpkin spice, about 60 gal total to date) last august and have learned a few key things. Using a juicer is just as good as using a traditional cider press. When you use the pressed stuff, you end up having the clarify the hard cider, while juiced apple cider is more clear. The taste between the two cider production methods is not significantly different. You can clarify pressed cider with gelatin just before bottling and it seems to taste just fine.
I've done apples, pears, cactus pears, and peaches and all produced juice with SG's in the 1.050 range that you need for a good hard cider. Even the Mussleman's pasteurized cider (don't use juice, it's too dilute and usually has sorbate added that will inhibit your yeast) from Wally world made a good tasting hard cider and base for some of my freaky brews (made a 1,000,000 scoville unit hot pepper cider that is great with chili or hot wings). Much higher than that SG and the alcohol tends to override the fruit flavor (adjusted my first pear SG to 1.070 and it was almost straight alcohol with no fruit taste). I found that using honey or sorghum to raise the SG for low SG apple juices worked great and gave so good character to the apple cider.
Yeast is important, but not as much with beer. The cheap cotes de blanc or premier cuvee ($0.75 per package) turns out as decent a cider as the more expensive cider yeast from west labs ($5.00 per tube). The primary difference will be in the carbonation during bottling. The red star tends to be more flat than the west labs, but this can be compensated by a larger priming sugar add before bottling). Wyeast 3068 makes a really good apple and pear cider with a little better flavor than the red star varieties, but it is more expensive (less than west labs or saf-brew), about $3 per activator pack. But the advantage here is that with so many more yeast cells, the fermentation takes significantly less time and the fruit flavor comes out faster during aging that with the red star.
As for a recipe, The simplest is for every 5 gallon batch (about 55 pounds of fruit juiced in juicer), add 6 crushed campden tabs to cider and let stand for at least 48 hours. Swirl the carboy hard to let the sulfur dioxide gas to escape, then add 2 Tbl of pectic enzyme, 3 Tbl of yeast nutrient (both have been dissolved into some of the cider) to the carboy and swirl to mix. Check the SG and if it isn't 1.050 add about 2 cups of sorghum or honey (that have been dissolved into some cider) to bring it up. Activate 1 package of cotes de blanc yeast in one cup of non-chlorinated water (Brita filtered or bottled distilled) that has 2 Tbl of sugar dissolved in it. Let the yeast/sugar water mixture stand for about 20 minutes until you see foam starting to form on top. Add the yeast to the carboy and swirl hard for about 5 minutes (a step that I didn't see in other online recipes and learned from my homebrewing soon-to-be-stepson) to introduce air into the cider. Airlock it and let stand out of the light at 65-70 degrees F until the bubble rate in the airlock is less than one per 15 seconds, or until the FG is less than 1.005 (this will be about a 6% abv). Rack into your keg (force carbonating) or priming bucket (traditional bottling). Use the priming sugar calculator (tastybrew.com has a good one) to calculate the amount of sugar to add to the priming bucket then bottle. Should take about 10-14 days to have a nicely carbonated bottled hard cider.
Your best bet is to pitch yeast into it instead of hoping for spontaneous fermentation.
Keep in mind that the sugars in apple juice are completely fermentable. Which means your end result will be a very dry beverage that will taste much like a dry white wine unless you do something to enhance the body. For a 5 gallon batch add 1-2 lbs of DME and a pound or less of 60L crystal malt. This will give you something that tastes much more like commercial cider.
Apples are covered with yeast, and being ground up to make cider really gets that yeast mixed in well. The problem with going wild with cider is that sometimes bruised or wind falls are often also included which improves the flavor of the raw cider, but means some of the apples may have been infected with acetobactor, in which case as the alcohol is being produced by yeast, the acetobactor is just taking the slowly served thank you very much ethanol and turning it into vinegar.