Chapter 3: Factors Affecting the Growth and Survival of Micro-organisms in Foods

Given suitable conditions, exponential microbial growth can quickly achieve very high numbers of organisms, although their increase is eventually limited by some adverse condition. Factors which affect the growth and survival of microbes in food can be intrinsic to the food, such as its composition and structure; its storage environment, such as temperatures or relative humidity; or implicit properties of the micro-organisms themselves, such as growth rate, stress response and microbial interactions. Aspects of processing, such as peeling, cooking and washing, are also an important influence – adding or removing micro-organisms and changing other factors such as nutrient availability. The aggregate result of these ultimately determines which microbes survive, grow or die during processing and storage, giving rise to the product’s microflora. In this chapter individual factors are described along with the physico-chemical basis of their effect on microbial growth and survival. Development of mathematical models relating the effect of multiple factors such as pH, salt content and temperature on microbial growth allows the quantitative prediction of changes in a food’s microflora during storage and their consequences for shelf life and safety.