Recent Advances in High Pressure Food Processing Equipment and Equipment Requirements to Meet New Process Needs

Foods preserved by high pressure processes (HPP) are sold in Japan, the United States, and Europe. HPP technology is used to pasteurize low acid solid and liquid foods such as oysters, hams, and guacamole and to extend refrigerated shelf-life. HPP technology can commercially sterilize liquid and solid acid products such as fruit juices, salsa, and cut tomatoes. Product sales have reached millions of pounds per year. New processes have been developed to sterilize low acid foods using a combination of heat and pressure. Foods at temperatures of 90 to 1000C can be compressed to 600 to 700 MPa for one or more cycles and thus heated uniformly by compression heating in the range of 111 to 121 0C. Decompression brings the product back to its starting temperature for final cooling. This application provides a high-temperature-short-time sterilization process for low acid foods and thus preserves fresh product quality. Commercial HPP foods require rapid cycling of equipment and maximum use of the pressure vessel volume. These requirements have been met in commercial, semi-continuous, liquid food treatment systems. A single 25 liter pressure vessel can cycle 15 times per hour with a three minute product hold at a pressure of 580 MPa. This vessel operating 5000 hours per year can treat over four million pounds of liquid food. Batch equipment designed to cycle over 12 times per hour with a three minute product hold at 680 MPa is under construction. All units manufactured for the HPP treatment of foods use stainless steel contacting parts, potable water as the compression fluid, and are designed to have a safe cycle life of over 100,000 cycles at 580 MPa. Equipment used for the HPP treatment of food must have an up-time in excess of 90% and must be capable of repair and maintenance by food process line technicians. Ease of access and ease of seal and wear part replacement is required. Equipment must meet cleaning and sanitation requirements of the FDA and the USDA if used to treat meat containing products. Pressure chamber volume use in batch systems must be optimized. Even one additional package per cycle at 12 cycles per hour and 5000 hours per year can yield 60,000 additional packages. High cycle rates require automatic package handling systems for loading packages into carriers and for loading and unloading carriers at the pressure vessel. The operation of high pressure food processing equipment must integrate with a specified food packaging and package handling system as it is desirable to have the high pressure processing system as an integral part of the total food processing and packaging system.