There are many ways to 'pickle' cucumbers and vegatables. The most common recipes for pickling involve vinegar (distilled or apple cider vinegar) and salt. Both distilled and apple cider vinegar contain acetic acid. So your answer is 'acid.'
Acids eg vinegar
Pickling vinegar and white vinegar are not the same, although they are similar. Pickling vinegar typically contains a higher acidity level, usually around 5-7%, which helps preserve foods effectively. It may also have added flavorings or spices specifically for pickling. White vinegar, on the other hand, is generally used for cooking and cleaning and has a more neutral flavor.
For pickling, it is recommended to use white vinegar or apple cider vinegar. These types of vinegar have the right level of acidity needed for pickling and will help preserve the pickled items properly.
The best vinegar for pickling vegetables is white vinegar or apple cider vinegar, as they have a mild flavor that complements the vegetables well.
Vinegar is used in pickling to create a sour and tangy flavor, preserve the food by creating an acidic environment that inhibits bacterial growth, and help maintain the texture of the pickled food.
Vinegar
The recommended vinegar to water ratio for pickling is typically 1:1, meaning equal parts vinegar and water.
Vinegar
Vinegar is produced by acetic acid producing bacteria during the fermentation of wine, cider, or beer, and is used as a condiment or for pickling.
vinegar (when pickling), salt . . .
The acid typically used in pickling is common household white or apple cider vinegar. Both of these products are food grade.