Pasteurization without the Heat

Cold pasteurization may be a regulatory non-starter, but kinder, gentler treatments are being commercialized, providing processors alternatives to conventional thermal treatments.

Kevin T. Higgins
Managing Editor, Food Processing

To borrow the language of prize fighting, if food sterilization is a KO, then pasteurization is a TKO — germs and viruses may be dazed and confused, but some will get off the mat and live to fight another day.

Both commercial sterilization and pasteurization are used for food preservation, of course, and both rely on thermal treatment to inactivate all or most bacteria, spoilage organisms and enzymes that degrade products over time. The difference is that sterilization destroys spore formers and renders food shelf stable but also degrades a product’s nutritional value.

With interest in healthy eating growing, that tradeoff tilts the balance in favor of pasteurization, particularly in North America, where a well-established cold chain can maintain product temperatures below 40°F from the point of processing to home consumption.

Dialing down pasteurization’s thermal input would result in even more nutritional foods and beverages with longer shelf lives. Food scientists have researched numerous novel technologies that promise effective but gentle pasteurization: radio frequency, ultraviolet treatment, pulsed electric fields and ultrafiltration, to name a few. The most viable, however, is high-pressure processing (HPP), the now-industrially hardened technology that uses hydrostatic pressure in the 87,000 psi range to essentially squeeze the life out of microbes and viruses without affecting the food itself.

To distinguish HPP from conventional thermal pasteurization, one of the main suppliers of the technology has started referring to the process as “pascalization,” a salute to Blaise Pascal, the 17th Century physicist who lent his name to the measurement of pressure and vacuum. Pressure of the magnitude found in HPP vessels long has been used to squeeze oxygen out of high-performance metals, but it was not until the mid-1990s that the technology was used commercially in food.

The first several machines were purchased by Don Bowden, who went to market with HPP-treated guacamole under the names Avomex and then Wholly Guacamole before selling the business to Hormel in 2011. His first vessel held 17 liters of avocados and ran 20 cycles before a valve failed — then ran another 20 before failing again. Today’s machines hold up to 525 liters and vessels are guaranteed for 100,000 cycles, though valves and seals require more frequent maintenance.

Industry understanding of HPP and the 5-log bacterial reduction it delivers has grown enormously, particularly in North America, where the majority of operating systems can be found. As recently as six years ago, food professionals who visited Bowden’s operation wrestled with process fundamentals.

“They want to see the bubbles coming up, and that’s not the case,” noted Fernando Portales, an engineer at Bowden’s former Fort Worth, Texas, firm. The extended shelf life and food-safety assurance delivered by the technology made the technology popular for ready-to-eat meats, which until recent years accounted for the majority of applications. Now HPP is being applied to wet salads, juices and beverages such as coconut water, where flavor improvements over aseptic processes are driving sales gains.

Continue reading article at Food Processing.