Jack Keller dealt with a very similar situation to this in a recent
blog entry.

See http://winemaking.jackkeller.net/wineblognew.asp. Look for
"Fermentation Troubles" under the December 10 entry. It essentially
deals with making a very large starter colony of yeast to add to the
must. If this doesn't reach the desired degree of fermentation, then
add another starter colony when the first one stops.


On Jan 25, 5:28 am, "Joe Sallustio" > wrote:
> > A search of this group on Google yields a number of threads on this
> > subject. It seems that a slow starting and slow fermenting Ribena must
> > is a common thing. It might be best to repitch yeast, if not already
> > done, and let it go. It'll either ferment or rot. No reason to throw it
> > out until you know for sure.I wouldn't throw it out unless the cost is minor but the benzoate is
> going to be an issue. Maybe diluting it enough to get it to start and
> feeding the remaining in might be the best option. If you are
> concerned about spoilage you could take what you have now and freeze it
> in gallon bags; then thaw a gallon at a time to add it back in.
>
> I might start like this.
>
> Take 1/10 of what you have and dilute it with 5 to 10 parts water and
> enough sugar to get that to a SG of 1.070. See if that will ferment.
> If not, find another use for the remaining batch. Assuming it gets
> going, once you have a decent ferment add back into it the same amount
> of Ribena you started with and see what happens. Go slow and keep the
> fermentation temperature over 70 F.
>
> I am making this up; I have no experience doing this by the way...
> That is what I would try if i were you though. You do have to be very
> careful of using anything with preservatives, they are in there to
> retard fermentation among other things but you know that now.
>
> Joe