The increased use of bulk cooling and storage equipment has made what type of bacteria the primary organisms in raw milk?

The correct answer is psychrophilic bacteria, which thrive at low temperatures, typically between 0°C and 20°C. The increased use of bulk cooling and storage equipment in the dairy industry enhances the cooling process of raw milk, creating an environment where these bacteria can grow and multiply. Psychrophilic bacteria can survive and even flourish in the chilled conditions often found in bulk storage tanks, unlike other types of bacteria that might require warmer temperatures.

Thermophilic bacteria prefer higher temperatures, typically above 45°C, and are less likely to be prevalent in refrigerated environments. Mesophilic bacteria grow best at moderate temperatures (20°C to 45°C) and generally are not as dominant in the cold conditions of bulk storage. Acidophilic bacteria thrive in acidic environments, which is less relevant to the raw milk directly after milking and storage, as the pH of milk is neutral to slightly acidic.

Understanding the prevalence of psychrophilic bacteria helps in maintaining proper milk quality and safety, as these organisms can affect the taste and shelf-life of dairy products.