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Chapter 8 : Fruits and Vegetables
Category: Applied and Industrial Microbiology; Food Microbiology
This chapter focuses on the origin, description, and control of bacterial and fungal spoilage of fruits and vegetables. Plant tissues in fruits and vegetables consist of an assemblage of cells surrounded by a pectic and cellulosic cell wall organized in a network, and a middle lamella rich in pectin cementing together cell walls. Specific factors associated with virulence of microorganisms are the primary mechanisms at the origin of post-harvest spoilage of fruits and vegetables. Postharvest control of temperature, relative humidity, and composition of the gaseous atmosphere aims at reducing the physiological activity of fruits and vegetables by delaying ripening and senescence, consequently prolonging the shelf life. The most suitable temperature, relative humidity, and modified atmosphere for preserving the quality of most fruits and vegetables are now relatively well established. Modified atmospheres reduce microbial spoilage of fruits and vegetables in many instances, although some spoilage microorganisms are not directly inhibited. Decontamination aims at reducing the number of microbial contaminants on the surface of fruits and vegetables, thereby prolonging the time required to develop spoilage. Chlorine at concentrations that will cause several decimal reductions of pathogens in pure water is often slightly more efficient than washing produce with pure water. Chitosan, a compound derived from chitin, has antimicrobial properties when used, for instance, to coat fresh fruits and vegetables for the purpose of regulating gas and moisture exchange.
Important microbial agents of postharvest spoilage of fruits and vegetables a
Approximate pH values and water, protein, and sugar contents of some fresh fruits and vegetables a