Which pressurizing fluid is primarily used in the HPP machine at the UNL pilot plant?

In High Pressure Processing (HPP), water is primarily used as the pressurizing fluid due to its unique properties that make it highly effective for food preservation. Water can evenly transmit pressure throughout the product being processed, allowing for uniform treatment. This is crucial in HPP because it helps to inactivate bacteria, viruses, and enzymes without the need for high temperatures, thus preserving the sensory and nutritional qualities of food.

Using water also minimizes potential contamination issues that could arise from other fluids, such as oil or alcohol, which may not be food-safe or could alter the flavor of the food product. Furthermore, water is readily available, non-toxic, and environmentally friendly, making it an ideal choice for food processing applications.

The other options would not be suitable for HPP. Air would not provide the necessary pressure consistently throughout a food product, while oil and alcohol could introduce undesirable properties or safety concerns. Thus, water is the optimal choice for HPP in terms of safety, efficiency, and effectiveness.