Quick Answers
We pulled about two gallons of grapes off the vine. I ran them through a juicer and put the juice into gallon jars, sealed them and put them in the refrigerator. The next morning, we opened the fridge and found that it had fermented and ran all over. Can I still make jelly out of this or do I throw it away? Why did this happen? What did I do wrong?
It appears that your grapes did what grapes have been
doing naturally for as long as anyone knows –
fermenting. Even at refrigerated temperatures the
wild-type yeasts that are naturally present on almost
all grapes can grow and convert the sugar in the grape
juice to alcohol. You may also have added yeasts or
other microorganisms to the juice from the juicer, or in
the jugs. Here are some suggestions for preventing this
in the future:
Pay careful attention to the cleaning and sanitizing
of the juicer and jugs you use to store the juice. Wash
all equipment with warm soapy water, then soak the
washed equipment in a sanitizing solution such as
sulfite (see below) or one tablespoon household bleach
in one gallon of water. Allow the equipment to soak for
at least one minute. Do not leave metal parts in the
bleach solution for much longer than one minute, since
bleach water is somewhat corrosive. It is also a good
idea to use gloves to protect your hands from the bleach
water. Allow the equipment to air-dry and use within
about one hour of sanitizing.
Most modern winemakers use sulfite to sanitize
equipment and inhibit the growth of these wild-type
yeasts in juice. Sulfite can be purchased at stores
specializing in home winemaking or brewing, or on the
Internet. The sulfite will come with instructions for
its use.
Another way to prevent fermentation would be to heat
the juice to about 165°F for 15 seconds (bringing the
juice just to a simmer would accomplish the same thing)
and then put in sanitized jars. This is something like
the process of pasteurization used commercially for
juices and milk products.
As for using the juice to make jelly, there is no
safety reason that would prevent you from making jelly
out of the juice. In fact, it is possible to make jelly
out of fully fermented grape juice (wine). (I frequently
make wine jelly at Christmas time. You can put the
finished jelly in cheap wine glasses, seal with
paraffin, tie a ribbon around the stem of the glass and
have a great impromptu gift.) However, the flavor will
be different than you might expect. If you want to try
this, follow the directions for the type of pectin you
like best. I might add just slightly more sugar than the
recipe calls for to take in account the sugar that has
been lost due to the action of yeasts. The process of
cooking the jelly will remove any alcohol from the
juice.
Douglas L. Holt, Ph.D., Chair, Food
Science and Extension Specialist, University of
Missouri-Columbia
Last update: Saturday, June 28, 2008
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