Non-Thermal Technologies for Dairy Processing

Changing consumer trends have fueled the increasing interest of dairy product manufacturers in developing “non-thermal” dairy processing technologies. Specifically, customers want products that are safe, minimally processed, fresh-like, nutritious, and devoid of synthetic food additives, says Aubrey Mendonça, PhD, an associate professor in the department of food science and human nutrition at Iowa State University in Ames.

“Demand increased since the COVID-19 pandemic began, as consumers moved toward foods and beverages that help to strengthen immunity and improve overall health,” says Errol V. Raghubeer, PhD, senior vice president of microbiology and food technology at JBT Corporation’s Avure Technologies, which manufactures high pressure food processing equipment in Middletown, Ohio.

Although traditional “thermal” milk processing technologies such as heat pasteurization, ultra-high temperature (UHT) treatment, canning, and dehydration have been used for several decades to ensure microbial safety and extend dairy products’ shelf life, these processes can cause degradation of heat sensitive bioactive and nutritional components, and undesirable changes in the properties of treated dairy products that detract from “fresh-like” characteristics. “More health-conscious consumers prefer to consume dairy products made from raw milk,” Dr. Mendonça says.

Thermal technologies use heat treatments to achieve fluid milk safety by killing any microbial contaminants present; however, the temperatures used can also cause changes in protein structure and functionality as well as the activity of bioactive compounds, including vitamins and minerals in dairy products, says Maneesha S. Mohan, PhD, associate professor and endowed chair in dairy manufacturing in the dairy and food science department at South Dakota State University in Brookings. For example, whey proteins in milk start to denature above 150ºF and form covalent bonds with sugars and other proteins, which affects the flavor, color, bioactivity, and functionality, causing changes such as gelling, enzyme coagulation, and sedimentation of individual components and the overall product.

Some non-thermal technologies for dairy processing ­include high-pressure processing (HPP), pulsed electric fields (PEF), and ultraviolet (UV) light processing. “These technologies do not rely on high temperatures (i.e., temperatures greater than 50oC) to achieve the ultimate goal in food processing—which is to maintain food safety and quality during shelf life,” says Federico Harte, PhD, a professor of food science at Pennsylvania State University in University Park.

Many of the non-thermal technologies have either been commercialized in the past decade or are in the research phase prior to commercialization, Dr. Mohan says. Many are effective in inactivating microorganisms and pathogens in dairy and other food products.

Here’s a look at some of the newer, non-thermal technologies, how they work, and their advantages and disadvantages.

High-Pressure Processing

HPP involves placing packaged foods in a pressure vessel and filling it with water as the pressurizing fluid. High pressure, typically 600 MPa, is generated by a pair of intensifiers by pumping more water into the closed pressure vessel. Foods are held at the targeted pressure for a specified time before releasing pressure, says Alvin Lee, PhD, associate professor in the department of food science and nutrition at the Illinois Institute of Technology in Chicago and director of the Center for Processing Innovation at the Institute for Food Safety and Health in Bedford Park.

During compression, physiological and biochemical processes within microorganisms are affected, resulting in their inactivation, Dr. Raghubeer says. However, product nutrients and bioavailable compounds are largely unaffected because covalent bonds aren’t affected at these pressures. This results in fresh-tasting, nutrient-rich products.

Zifan Wan, PhD, an assistant professor in the School of Agriculture at the University of Wisconsin in Platteville, concurs, and adds that HPP treatment leads to enhanced quality because the process doesn’t affect heat-sensitive compounds (e.g., vitamins, simple sugars, and volatile flavor compounds). Therefore, it doesn’t result in non-enzymatic browning and loss of flavor and nutrients.