Food Chemistry and Microbiology Flashcards

A research chef is developing a new shelf-stable cheese sauce. The primary role of the starter culture added during the fermentation process is to:

Answer: Produce lactic acid, which lowers the pH and inhibits the growth of spoilage organisms.

The main function of starter cultures, particularly lactic acid bacteria (LAB), in fermented dairy products is to consume lactose and convert it into lactic acid. This acidification process lowers the pH, which is critical for coagulating milk proteins to form the curd and, most importantly, creating an environment that prevents the growth of pathogenic and spoilage microorganisms, thus ensuring food safety and extending shelf life.

Which of the following statements most accurately describes the key chemical difference between the Maillard reaction and caramelization?

Answer: The Maillard reaction involves a chemical reaction between amino acids and reducing sugars, whereas caramelization involves only the breakdown of sugars.

The fundamental distinction between these two non-enzymatic browning reactions is the reactants involved. The Maillard reaction is a complex series of reactions between amino acids (the building blocks of proteins) and reducing sugars, requiring heat. This reaction creates a wide array of savory and complex flavor compounds. Caramelization, in contrast, is the thermal decomposition or pyrolysis of sugar molecules alone at a higher temperature, resulting in sweet, nutty, and sometimes slightly bitter flavors.

A culinary R&D team is creating a hollandaise sauce concentrate. To ensure a stable product, they must incorporate an effective emulsifier. Which naturally occurring component in egg yolks serves this function?

Answer: Lecithin

Lecithin, a phospholipid found in high concentrations in egg yolks, is a powerful natural emulsifier. Its molecules have both a hydrophilic (water-attracting) end and a lipophilic (oil-attracting) end. This structure allows lecithin to surround microscopic oil droplets, preventing them from coalescing and separating from the water-based components (like vinegar or lemon juice), thus creating a stable emulsion like hollandaise or mayonnaise.

During a quality control check of a new batch of ready-to-eat chicken salad, the presence of Listeria monocytogenes is detected. Why is this particular pathogen a significant concern for this type of product?

Answer: It is capable of growing at refrigeration temperatures.

Listeria monocytogenes is a major concern in ready-to-eat foods like deli meats and salads because it is a psychrotroph, meaning it can survive and multiply at cold temperatures, including standard refrigeration (around 40°F/4°C). This allows it to proliferate during storage, increasing the risk of listeriosis, a serious infection, especially for vulnerable populations.

A research chef is developing a marinade to tenderize a tough cut of beef. The marinade includes pineapple juice, soy sauce, garlic, and ginger. The tenderizing effect is primarily due to the action of what?

Answer: An enzyme in the pineapple juice called bromelain.

Fresh pineapple juice contains bromelain, a protease enzyme that breaks down protein molecules. When used in a marinade, bromelain denatures the collagen and muscle fibers in meat, resulting in a more tender texture. While acids can also tenderize, the enzymatic action of bromelain is significantly more potent in this context.

Which of the following microorganisms is a virus, is highly contagious, and is a leading cause of foodborne illness outbreaks often linked to ready-to-eat foods handled by infected workers?

Answer: Norovirus

Norovirus is the leading cause of foodborne illness in the United States and is a highly contagious virus, not a bacterium. It is frequently transmitted through ready-to-eat foods that have been contaminated by an infected food handler, often due to improper handwashing. Salmonella, E. coli, and Clostridium are all bacteria.