This is a very simple and fun ferment. One of these days you will have these three ingredients sitting around and you will just need to try it. It is simply fresh oranges, red onion, and white wine vinegar. You could add garlic and, basically, anything at all to suit yourself. During the fermentation, the orange loses some of its sweetness and the onion gains some. It all becomes extra wonderfully vinegary, in a good, culinary sense.
This is a simple vinegar ferment that anyone can succeed with, without any special tools or equipment. As a wild fermenter these are a great change because they move you away from the salty flavors of brine ferments. You trade the salt for vinegar, in this case a quality culinary white wine vinegar.
Vinegar ferments are far more forgiving than salt ferments. There is no salt proportion to worry about. If a vegetable floats on top for a minute or two, it’s not going to go bad on you. You ought to take all of the usual precautions as you do with a salt fermentation, but your success rate will approach 100% if you do. You also end up with a flavored vinegar as a by-product — an exceptional flavored vinegar.
In your list of “tools” is a boiled rock. This is simply a weight to keep your food underneath the vinegar. Without it, your orange and onion slices will float and risk spoilage. Unlike salt brine solutions, your vinegar-based ferments are far less likely to spoil, but a weight is basically a guarantee against it.
(The photo here does not include the weight and you can see that the whole business just want to float to the top of the vinegar level. Your weight takes care of that problem.)
When it’s ready, use it as a condiment or as you would any pickle. Use the vinegar portion in dressing and sauces. My favorite use is to add it to a tuna salad — tuna, mayonnaise, and a chopped portion of this orange/onion combination is EXCELLENT. It could top a green salad, top or get mixed into a potato salad, or any dish that lends itself to vinegar.
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