FIGURE 4-1 Examples of the multiple-hurdle method for reducing microbial activity in foods. At the level employed in many foods, individual hurdles may not provide adequate protection from spoilage or pathogenic microorganisms. When multiple hurdles are combined, each hurdle plays a role in reducing microbial activity (displayed as →) until, eventually, the microbial population is so weakened that it cannot cross any further hurdles and the food is protected from spoilage and pathogen survival (letters a, b, and c). If hurdles are insufficient to reduce microbial growth, food products may not be adequately protected (letter d).
NOTE: aw = water activity; Eh = redox potential; F = heating; pH = acidity; pres = preservatives; t = chilling.
SOURCE: Reprinted from Trends in Food Science and Technology, 6(2), Leistner and Gorris, Food preservation by hurdle technology, 41–46, Copyright © 1995, with permission from Elsevier.