Impact of Sodium-based Food Preservatives

Sodium chloride, more commonly known as table salt, serves many functions in foods, imparting flavor, texture, and preservation and providing the essential nutrient sodium to the human body. However, when consumed in excess, elevated sodium intake has been linked to adverse health effects, including hypertension, cardiovascular disease, gastric cancer, obesity, osteoporosis, kidney disease, and Alzheimer's. According to the World Health Organization, an estimated 2.5 million deaths could be prevented annually if global sodium consumption was reduced to recommended levels, from 3,400 to 2,300 mg per day. According to the Centers for Disease Control and Prevention, over 70 percent of sodium consumption comes from processed and packaged foods, as well as restaurant meals like soup, pizza, cured meat, cheese, and other savory dishes. Both domestic and global initiatives exist to actively seek sodium reduction strategies across food categories. In fact, the global sodium reduction ingredients market is projected to grow at a compound annual growth rate of 12 percent from 2022 to 2027.

As a food preservative, sodium has been utilized since at least 2000 BC, though refrigeration and improvements in processing, packaging, transport, and storage have reduced the reliance on high sodium levels to prevent microbial growth. Sodium affects the availability of water in foods, impeding the growth of spoilage and pathogenic organisms and working in tandem with intrinsic (e.g., pH, moisture, preservatives, competing microflora) and extrinsic (e.g., temperature, modified atmosphere packaging) factors to ensure safety and quality of foods. Examples of common sodium-based preservatives are given in Table 1.

Table 1. Common sodium-based food preservatives

Replacement options for sodium chloride can include other salts (e.g., potassium, magnesium, or calcium chlorides, magnesium sulfate, potassium lactate), yeast extract, monosodium glutamate, or naturally high-glutamate extracts (e.g., hydrolyzed vegetable extract, soy sauce, or broths). Depending on the sodium alternative, some can require flavor maskers, e.g., to cover bitter or metallic notes of potassium chloride or sourness of potassium lactate. Dry topical applications (e.g., snack foods) have additionally leveraged microstructure changes in the sodium chloride itself by increasing the surface area either by utilizing salt flakes or round hollow structures to increase saltiness perception. Within dairy powders, reduced lactose whey and hydrolyzed whey proteins have been effectively utilized to reduce sodium by up to 10 percent in macaroni & cheese and provide partial phosphate replacement and fat/moisture retention in meat applications, respectively. Both ingredients provide savory umami notes via naturally occurring dairy minerals such as calcium and phosphate.

Foods are a dynamic system in which formulation changes can impact intrinsic properties and their resultant antimicrobial impact

Foods are a dynamic system in which formulation changes can impact intrinsic properties and their resultant antimicrobial impact. For example, the substitution of sodium chloride with potassium chloride has been shown to increase the antilisterial efficacy of salt in natural cheeses. However, if substituted at a lower use rate due to cost (nearly twice that of sodium chloride) or sensory impact, replacement with water or other fillers can increase available water in the cheese, thereby increasing the probability of listerial or spoilage outgrowth. Similarly, changes in susceptibility to microbial outgrowth when altering preservative use rate can occur in the replacement of sodium lactate with potassium lactate in deli meats and sodium propionate with clean-label alternatives (e.g., cultured wheat) in bakery items. Additionally, the molar equivalent of the salt cation must be accounted for, with a higher use rate of potassium- than sodium-buffered vinegar needed for equivalent delivery of acetate, the active antimicrobial component of these preservatives. Likewise, when reducing or replacing high-sodium food items (e.g., aged or processed cheese) within a formulation, the level of the active component(s) providing safety and quality (lactic acid) must be maintained or accounted for in formulation. Due to these and other nuances, it is imperative to validate formulas for food safety and quality targets via challenge and/or shelf-life studies with appropriate microorganisms and study design.

Due to sodium's multitude of functions within foods, strategies for its reduction must apply a holistic approach to maintain taste, texture, and preservation in application. A hurdle approach whereby layers of safety and quality protection are formulated (via clean-label or conventional sodium replacers) or engineered (via processing or packaging) into the final food product may need to be employed.