I just collected apple seeds from the cross pollinations that I made earlier this spring. Some seeds I collected as they ripened and others have been piling up in the fridge since September. Following is a short video on collecting seeds and a brief written post.
Once the seeds are extracted, I keep them moist in the refrigerator until planting. Most apple seeds need to be stratified to sprout. That means that they have to experience a certain number of hours below a certain temperature. I don’t know how long, but I know that sitting outside or in a fridge for the winter is enough stratificationization, and that’s all most of us need to know. I'm sure that information is easy to find if you need it. I just have other things I'd rather fill my head with just now. You can also stratify them by simply planting outside, or planting in the flats early and leaving them outside.
I have never dried apple seeds, but it is done. I just haven’t had a need to and I think the germination rate of fresh seeds is probably much better. If you needed to store them for a long time before planting, drying makes sense. The general rule for drying seeds is to dry them at room temperature until thoroughly dry and then store dry in a jar or baggie. Tossing in one of those moisture absorbing silicon packets that come in vitamin bottles doesn’t hurt either. You can also use charcoal for the same purpose, but it should be fresh burned, because it absorbs moisture from the air rapidly under normal conditions.
Each cross or seed variety is kept separate and the bag labeled. The seed parent comes first, followed by X and the pollen parent. If they won’t be stored very long, it’s fine to just put them in a plastic bag or small plastic container or jar. If they will be in there for a while, but not planted until Feb or March, a little damp sawdust can help keep the seeds happy and safe. What you don’t want is for the seeds to sit against wet plastic for any length of time. Sawdust absorbs condensation and keeps the seeds away from the plastic and against a material that breaths a little. If the seeds are harvested in summer and kept till late winter to plant, definitely use some damp sawdust or at least put them in a paper bag inside of a plastic bar or jar. Remember the sawdust should be damp, not wet.
When I get around to it, usually sometime in January or February, the seeds are planted in flats in the greenhouse and then transplanted into the ground, but we’ll get to that stuff when the time comes.