The instructions for both Oz Tops and E-Z Caps say that after brewing put the bottle in the refrigerator to stop the fermentation. This does NOT kill the yeast. As long as there is live yeast present in the liquid, there is a chance that the fermentation can start up again. Cooling the liquid just slows down the yeast to the point where fermentation is not noticeable. It’s kind of like putting the yeast into hibernation. If the liquid warms up and there is live yeast and sugar present, fermentation (and the production of alcohol and carbon dioxide) will begin again. If you bottle your wine and it starts fermenting again, you could blow out a cork (messy, but fun!), burst your plastic bottle (messy, no fun), or burst your glass bottle (messy and dangerous). To avoid this, kill the yeast.
There are 4 ways to do this in 3 categories:
Starvation, Poison, and Cooking.
Last to first, cooking kills the yeast.
That's the whole idea behind Pasteurization. You cook it by raising the temperature of
your wine well above the level that yeast can survive (usually 150-160 degrees F) and
keep it there for a period time, about 10 minutes. But, it changes the flavor of the
beverage in ways that aren't always predictable.
Starvation works very well.
The yeast eats the sugar and produces alcohol and CO2 until there isn't any more sugar
to eat. The yeast then dies of starvation. This lack of sugar is what produces a "dry"
wine, and is a very natural process. After the yeast is dead, you can go back and
sweeten the wine to your taste without fermentation starting again.
One way of poisoning the yeast is a natural process, the other is not. Different yeast cultures, or strains of yeast, have different levels of alcohol tolerance, meaning they can coexist with alcohol up to a certain point. After that, the alcohol kills (poisons) the yeast. Some yeast, like beer and ale yeast can only tolerate up to about 6 or 8% alcohol. Most wine yeast can stand up to about 10-12% alcohol, while some Champaign yeast can live up to about 18% alcohol. The forth way to kill the yeast also poisons it. Adding Sulfites or Sorbates to the wine will also kill the yeast. This is the way most commercially produced wine is stabilized, but it presents 2 problems. By adding chemicals to the wine, it changes the flavor. Maybe not much, but some. The other concern is a lot more important. Some people are allergic to the sulfites that are used to kill the yeast. If you do use sulfites to kill the yeast, make sure you tell everyone who tries your beverage that it contains sulfites. Be sure to label the bottles as well.
I personally prefer to let the wine "brew out" by letting the yeast either die of starvation or alcohol poisoning. I don't have to worry about re-fermentation popping open my wine before I'm ready to drink it, or that my friends will swell up like Violet from Willie Wonka and the Chocolate Factory.