In the beginning, smoking was not just a way of giving foods an interesting flavor: it was a way of delaying their spoilage. Wood smoke contains many chemicals that slow the growth of microbes. Among them are formaldehyde, and acetic acid (vinegar) and other organic acids, thanks to which the pH of smoke is a very microbe-unfriendly 2.5. Many of the phenolic compounds in wood smoke are also antimicrobials, and phenol itself is a strong disinfectant. The phenolic compounds are also effective antioxidants, and slow the development of rancid flavors in smoked meats and fish.