Question

In 2004 , a casino paid $$\$ 28,000$$ for a grilled cheese sandwich that was purported to have an image of the Virgin Mary on it. The seller had stored the sandwich in a less-than-airtight box for 10 years without decay or the growth of mold. What antimicrobial chemical and physical agents might account for the longevity of the sandwich?

Short answer

The longevity of the sandwich could have been due to a combination of antimicrobial chemical agents like food preservatives in the bread or cheese, the heat used in the grilling process, and environmental factors such as cold, dehydration, and lack of nourishment that could discourage microbial growth.

Step-by-step solution

Identify possible antimicrobial chemical agents

First, think about antimicrobial chemical agents that could have possibly preserved the sandwich. Antimicrobial chemicals are substances that inhibit the growth of microbes. Certain food additives and preservatives, such as sodium benzoate, sodium nitrate, and vinegar, are antimicrobial agents. Some of these could have inadvertently preserved the sandwich.

Identify possible physical antimicrobial agents

Next, physical agents such as heat, irradiation, and drying also act as antimicrobial agents. In the case of the sandwich, it was grilled, which involves the application of heat. This process could have eliminated any microbes on the bread and cheese, hence preserving the sandwich for a while.

Consider the environmental factors

The environmental conditions the sandwich was stored in, even if not perfectly airtight, could have also acted against microbial growth. Cold, dehydration, and lack of nutrients may discourage microbial growth. The cheese sandwich itself does not provide a suitable environment for the growth of most molds.

Key concepts

Chemical Preservatives

Chemical preservatives are vital components in food preservation, ensuring that our food remains safe for consumption over extended periods. When it comes to preventing spoilage and extending shelf life, substances such as sodium benzoate, which can inhibit the growth of bacteria and fungi, play a crucial role.

Similarly, sodium nitrate is another preservative commonly used in the curing of meats, keeping them free from harmful bacteria while also maintaining the desired red or pink color. Vinegar, with its acetic acid content, is a natural preservative found in many pickled products. Its acidic environment is detrimental to many microorganisms and can prevent food spoilage.

Students should understand that chemical preservatives work by creating conditions unfavorable to microbial growth. Preservatives can act by disrupting microbial cell walls, altering the pH level, or interfering with the cell's metabolism. This is how a substance could have helped to preserve the famed grilled cheese sandwich over a decade.

Physical Antimicrobial Agents

Besides chemical means, food preservation utilizes physical antimicrobial agents, which are processes that physically alter or handle food to prevent microbial growth. One common physical agent is heat application, such as grilling, which not only cooks the food but also destroys microorganisms that may cause spoilage or disease.

Other examples of physical antimicrobial agents include irradiation, which uses energy in the form of ionizing radiation to kill or deactivate pathogens, and drying, which removes moisture necessary for the survival of microorganisms. Freezing is another method that considerably slows down the growth of microbes by creating an environment too cold for them to thrive.

In our example of the preserved grilled cheese sandwich, the application of heat through grilling likely played a significant role in its remarkable longevity by initially reducing the microbial load.

Microbial Growth Inhibition

Microbial growth inhibition involves a spectrum of strategies deployed to prevent the proliferation of bacteria, molds, yeasts, and other microorganisms in food. Crucial factors that influence microbial growth include temperature, moisture content, pH levels, and the presence of oxygen.

By understanding these factors, we can control and inhibit microbial growth. Refrigeration, for example, slows down the metabolism of microbes, while drying removes moisture, making it difficult for microorganisms to grow. Acidifying foods through pickling or fermentation creates a low pH environment, which is hostile to many pathogens. In addition, packaging that limits oxygen can help prevent the growth of aerobic bacteria and mold.

Analyzing the casino's grilled cheese sandwich, despite not being stored in a completely airtight container, the environmental conditions and inherent properties of the sandwich could have naturally contributed to inhibiting microbial growth. This includes the low moisture content of the grilled bread and the potential inhibitory compounds within the cheese.