For many foods, reducing the sodium content of the product should not create food safety or spoilage concerns. Such foods include frozen products, products that are sufficiently thermally processed to kill pathogenic organisms (e.g., canned foods), acidic foods (pH < 3.8), and foods in which water activity remains low when sodium is removed (e.g., foods with low water activity due to high sugar content) (Reddy and Marth, 1991; Stringer and Pin, 2005). For other foods, reducing sodium content has the potential to increase food spoilage rates and the presence of pathogens. For these foods, product reformulation, changes in processing, and changes in handling may be required to ensure that the product has an adequate shelf life and to prevent pathogen growth. Such efforts do incur additional costs and require careful attention to ensure that new formulations and processes are sufficient to ensure product safety. These issues are discussed further in Chapters 6 and 8.
Foods using sodium as a hurdle to retard microbial growth and survival present a reformulation challenge, since changing the sodium content alters the impact (or height) of the water activity hurdle. Changing this single hurdle may impact the safety and quality of the food because other hurdles that are present (pH, temperature, etc.) may work only in combination with the original sodium level. To maintain a safe, good-quality product, reformulation may have to include the introduction of additional hurdles or an increase in the impact of existing hurdles. If such additional measures are not taken during sodium reduction efforts, the remaining products may not be stable. For example, in cured meats, reducing the sodium content (by removing both salt and sodium nitrite) could allow for rapid growth of lactic acid bacteria and action by proteolytic microorganisms, resulting in a product that spoils more rapidly (Roberts and McClure, 1990; Stringer and Pin, 2005). In some foods, pathogen growth, rather than spoilage, may become a concern.
There is speculation that some past salt reduction efforts may not have adequately accounted for the need to adjust additional hurdles to microbial growth. In the United Kingdom, salt reduction efforts in chilled, ready-to-eat foods were cited as one factor that may have contributed to an increase in the incidence of listeriosis from 2001 to 2005 (Advisory Committee on the Microbiological Safety of Food, 2008). Listeriosis is caused by Listeria monocytogenes, which has a high thermal stability and is able to grow and survive at refrigeration temperatures and elevated salt levels (Zaika and Fanelli, 2003). To decrease the risk of listeriosis, a draft report of the United Kingdom’s Advisory Committee on the Microbiological Safety of Food called on the Food Standards Agency to work closely with food