Final answer:
Sugar and salt are used as antimicrobial agents because they reduce the available water in foods, increasing osmotic pressure that dehydrates and inhibits growth of microbes, thus preserving the food.
Step-by-step explanation:
Sugar and salt are used as antimicrobial agents in foods because they capture a food's water and make it unavailable to microbes. By adding high concentrations of these solutes to foods, the water activity is lowered, creating an environment with high osmotic pressure. This process draws moisture away from microbial cells, dehydrating them and inhibiting their growth. Examples of such preservation include honey, which consists mainly of sucrose, and salted meats and fish products.
Microorganisms exhibit varying susceptibilities to osmotic pressure, which is why foods like jams, jellies, and preserved meats can remain safe to eat without refrigeration. However, it's worth noting that certain microbes, particularly molds and yeasts, can withstand these desiccation conditions, potentially leading to food spoilage in some cases.