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AgricultureFood ScienceMicrobiologyFood MicrobiologyMicrobial MetabolismMicrobial PhysiologyExtrinsic Factors Affecting Microbial GrowthMicrobial BioenergeticsMicrobial Ecology Of FoodsMicrobial GrowthMicrobial Growth In FoodsMicrobial Toxins In FoodCell Growth RegulationMicrobial Growth InhibitionMicrobial InhibitionMicrobial ToxinsMold Growth InhibitionOsmotic StressPh Effects On GrowthWater Activity Reduction
Decrease in water activity in foods generally reduces microbial growth, including that of bacteria, molds, yeasts, and some parasites and viruses. If other growth factors are less than ideal, reduction of water activity increases growth inhibition. Sporulation seems to occur at a lower water activity level than that needed for growth, therefore, water activity may also affect the shape of organisms and their mobility. The production of microbial toxins is inhibited to varying degrees by reduction of water activity because microbial organisms adjust to osmotic stress by excluding solutes or by accomplishing metabolic tasks in the presence of solutes. Cell growth is determined by the amount of energy left after this task. Heat, pH, oxygen, and chemicals also inhibit microbial growth. (kbc)