Microbial spoilage is manifested by a variety of sensory cues such as off-colours, off- odours, off- flavours, softening of vegetables and fruits, and slime. However, even before it becomes obvious, microbes have begun the process of breaking down food molecules for their own metabolic needs. Sugars and easily digested carbohydrates are used first, plant pectins are degraded. Then proteins are attacked, producing volatile compounds with characteristic smells such as ammonia, amines, and sulfides. This may be accompanied by the production of a wide range of metabolites which includes: alcohols, sulphur compounds, ketones, hydrocarbons, fluorescent pigments, organic acids, esters, carbonyls, and diamines
