Salt draws out moisture when pickling jalapeños, diluting the vinegar solution and toughening the end product. Cooking salt is preferable to table salt, which contains high quantities of iodine, a chemical that darkens and discolors the peppers.
The best vinegar for pickling peppers is of 5 percent acidity. To ensure that the peppers remain crisp throughout the process, add the vinegar cold and cover the peppers with at least 1 inch. For the solution to remain clear, whole spices are better than powdered versions. The maturing process lasts from two to four weeks, and the peppers remain crisp for up to three months.