Fermentation is one of the oldest and most important methods used in the processing of fruits and vegetables for preservation, value addition, and enhancement of sensory and nutritional qualities. It is a biochemical process in which microorganisms such as bacteria, yeasts, and molds convert sugars and other organic compounds present in fruits and vegetables into acids, alcohol, carbon dioxide, and other metabolites under controlled or natural conditions. The fundamental principle of fermentation is the metabolic activity of desirable microorganisms that inhibit spoilage organisms while improving product stability and acceptability. The fermentation process generally begins with the preparation of raw materials, including washing, sorting, peeling, cutting, or shredding of fruits and vegetables to facilitate microbial activity. Salt or sugar may be added depending on the type of fermentation to create favorable osmotic conditions and suppress undesirable microbes. In vegetable fermentation, particularly lactic acid fermentation, anaerobic conditions are maintained to promote the growth of lactic acid bacteria such as Lactobacillus, Leuconostoc, and Pediococcus species. These microorganisms utilize naturally occurring sugars and convert them into lactic acid, which lowers the pH and acts as a natural preservative. Microorganisms play a central role in determining the quality and safety of fermented products. Beneficial microbes dominate the fermentation environment by producing organic acids, bacteriocins, and antimicrobial compounds that inhibit pathogenic and spoilage organisms. Yeasts are primarily responsible for alcoholic fermentation in fruit products such as wines and ciders, where