Is it possible to stop fermentation

This may seem a bit "off the wall" but I am researching if it is possible to essentially prevent fermentation in freshly squeezed grapes; just the opposite of what is desired in making wine. I realize that in the time it takes to squeeze the grapes and collect and bottle (if one chose those steps in order quickly) would still result in fermentation beginning, but if one wished to stop the fermentation at that stage would it be possible and how?

As someone who filters and does not filter let me input my opinion here... For home use a .45 micron filter (preferrably rated as absolute) is all that is needed for a sterile filtration of an otherwise clear and stable wine. I have used .45 micron Nominal cartridge filters with great success, and I think they are more than adequate for most home winemakers that are looking for a "sterile" filtration. I must point out to avoid confusion that this is not a truly sterile method that I employ (meaning all yeasts are gone) but in practice I have found it to be adequate 99.9 percent of the time. I have also used .2 micron filters and although they certainly due a good job of filtering I didn't see the advantages for my home use, and they tend to blind much faster than the .45 microns.
In regards to the stripping of color or taste I haven't seen this to be true in practice. That is not to say that taste or color is not removed, but generally I would point out that the flavor or color component that a .45 micron filter would remove probably doesn't belong in your wine. With that point stated I still say to each there own. HTH
John Dixon

but after that it will not taste the same as "fresh" grape juice -- the heat/pasteurisation is a huge part of why red wine kits never achieve the same quality!
You finish up with that coked fruit taste!

Boiling should pasteurize the juice and kill the microbes, but the character of the fresh juice will be changed.

Large quantities of potassium metabisulfite can inhibit fermentation, but the quantities needed are so large the juice would not be useful for most applications.

Last year, I froze some fresh juice and reserved it to add back to completed wine to give a higher sugar content. In spite of all of my efforts at filtering and sulfiting, it still re-fermented in the bottle. The problem with most readily available filters is that they don't take out ALL of the yeast....just enough to fool you.

A couple of possibilities come to mind. You could filter the juice with a tight membrane filter and remove all of the native yeast and bacteria. This method requires special equipment and a course filtration will be needed before the membrane filter could be used.

Or, you could pasteurize the bottled juice just before sealing the bottles.
A temperature of 160 - 170 F for two or three minutes might kill the native yeast and bacteria. This method requires special heating equipment and the juice must be mixed in some way to maintain a uniform temperature.

Of course, you could always freeze the juice.

I have read where it is possible to boil the grape must to make something akin to molasses and seal it (I suppose one could add something like potassium metabisulfite as well) and, since no yeast is added, could prevent fermentation. Is this true?

Nominal is a rating method which if I recall is that the average is .45 micron for example. An absolute rated filter will not allow anything larger than .45 through, and is a much more stringent standard. I buy my filter cartridges from Presque Isles, and then nominal .45 10" cartridges are around $35. each, but I dont remember the name. Not that many choices once you look at them on their site.
I have found that if your wine is very clear, or you are prefiltering such as with a 1 micron wound filter then the filters will last for at least a couple hundred gallons or more. HTH
John Dixon

For "coked" read "cooked" !!!!

John, what brand of filter do you use? Is "Nominal" a brand name?