Soaking your uncooked chicken in a marinade containing vinegar can add flavor and moisture to it, while also tenderizing the meat. Although marinating the chicken in straight vinegar for more than a few hours could make it tough, instead of tender, it won't spoil it unless you leave it out at room temperature.
Playing It Safe
When it comes to marinating chicken, always do so in the refrigerator, set to 40 degrees Fahrenheit or below, to prevent the meat from spoiling. Place the chicken and the marinade in a food-grade glass, stainless steel or plastic container or resealable bag; the acidic vinegar may react with other types of metal containers. It's perfectly safe to marinate your chicken and other poultry for up to two days in the refrigerator, according to the United States Department of Agriculture. Keeping your chicken in a marinade for longer than two days or marinating chicken that is more than two days old overnight may result in spoiled meat.
Tender, Not Tough
While the acidity of vinegar can break down and tenderize chicken, if it's not balanced with equal amounts of oil and flavorings, your poultry could wind up tough and stringy. Once you've marinated your chicken, cook it to an internal temperature of 165 F to kill any pathogens in the meat. Discard your used marinade or boil it for at least one minute to serve it as a sauce.