List several antimicrobial agents and explain their function as food additives.

Sodium benzoate is a widely used food preservative that's particularly effective in preserving acidic foods. Its primary function is to inhibit the growth of potentially harmful microorganisms such as molds, yeast, and some bacteria. You'll often find it in foods like salad dressings, carbonated drinks, jams, and fruit juices. Here's why it's so useful: in acidic conditions, sodium benzoate converts to benzoic acid, which is the active form that suppresses microbial activity.

For example, in carbonated drinks, which typically have a lower pH, sodium benzoate serves to extend shelf life and maintain product quality by preventing the growth of microorganisms that could cause spoilage or foodborne illnesses. It's an important additive because it helps maintain the safety of food without significantly altering its taste, odor, or color.

Potassium sorbate, another prevalent food preservative, operates effectively in a variety of products. Its role is primarily to ward off mold and yeast when added to foods such as cheese, wine, and baked goods. What makes potassium sorbate so essential is that it is highly effective at relatively low concentrations and is non-toxic, which is why it's preferable in many food applications.

For example, when it's added to cheese, potassium sorbate prevents fungal growth on the surface, which is a common spoilage process in cheeses. It's hardly noticeable to the consumer, as it doesn't alter the taste or the quality of the cheese.

Nisin is a unique food additive in the sense that it's a polypeptide produced by fermentation of a bacterium. This antimicrobial peptide is particularly effective against certain bacteria, including heat-resistant spores found in processed cheese and meats. It's a natural preservative that helps prevent spoilage and ensures food safety.

Despite its powerful antimicrobial properties, nisin is metabolized by the human digestive system, which means it's non-toxic for consumers. Thus, it's a favored additive for maintaining the freshness and safety of dairy products without impacting the nutritional or sensory properties of the food.

When it comes to processed meats, sodium nitrite plays a dual role: it not only serves as a preservative to prevent the growth of dangerous bacteria like Clostridium botulinum but also gives cured meats their characteristic pink color. As an antimicrobial agent, its use is crucial in products like bacon, ham, sausages, and hot dogs.

Sodium nitrite helps prevent botulism, a potentially fatal illness caused by toxins from Clostridium botulinum bacteria. Moreover, when it reacts with meat myoglobin, it forms a stable pink color, ensuring the meat retains a fresh and appetizing appearance. While effective, the use of sodium nitrite must be carefully controlled due to concerns over the formation of nitrosamines, which can occur if the preservative is not properly managed.