I'm doing apple caviar using alginate in my apple juice and calcium lactate as my spherification bath. Everything worked out well, the result is amazing, but after one hour my caviar turn out to be flavourless and instead of nice juicy bursting little caviar ball, it was 100% jelly like I was using agar-agar. I did rinse my caviar in fresh water right after the process (not even 2 minutes after the drops hit the bath). How can I keep this from happening?
An issue here is that alginates (in the hydrocolloids) are not great at flavor release. The holes between the molecule structures are pretty small and aromatic and flavor molecules (being larger) get trapped.
Ironically, Agar agar's network structure has large holes and does allow for good flavor release.
As the alginate shell gets thicker (the gel you describe), not only the texture changes, the flavor also gets trapped in the molecules and cannot interact with your taste receptors.
The thickness of the shell's formula (if I recall correctly) is:
L = sqrt(PI * Dca * t)
So beyond Brendan's good suggestions, consider dropping the calcium concentration and increasing time (measured in seconds). The way the gelation reaction works is just like how heat diffuses. So consider doing the cooking for longer at a lower temperature equivalent by running lower concentration and for longer.
As an aside, Martin Lersch has a free ebook called textures which has some tested recipes that might help.
Once the calcium and alginate react the process will continue regardless of whether you rinse them or not. The rinsing will slow the process down but won't inhibit the reaction altogether. In order to ensure liquid centers you will have to heat the spheres to 85°C for 10 minutes (from modernist cuisine). However, you have a ton of calcium going on in your mix between the calcium in the apple juice and the fact that you're using calcium lactate as your setting bath so you are likely going to benefit from a sequesterant like sodium citrate to bind up some of the free calcium ions. I would actually suggest you go with a calcium chloride bath for this type of direct spherification. If you were doing larger spheres I would suggest reverse spherification but that won't do you any good for caviar.