The function of acetic acid in vinegar is to serve as the primary acidic component that imparts its sour taste and preservative qualities. Acetic acid, typically present at concentrations of 4-8% in vinegar, acts as a natural preservative due to its antimicrobial properties, inhibiting the growth of bacteria and fungi. Additionally, it is used in culinary applications for flavor enhancement and food preservation, making vinegar a versatile ingredient in both cooking and food processing.