HPP Technology, also referred to as high pressure processing, high hydrostatic pressure, or pascalization, is the process by which food and beverages are placed into a vessel which is then subjected to a high level of isostatic pressure, 87,000 psi, which is transmitted by cold water. Products that undergo the HPP process have a reduction in pathogens that cause food borne illness. Because cold water pressure is used, and HPP has a limited effect on covalent bonds, the organoleptic properties of the ingredients are not lost leaving a product that has the same nutritional, taste, and texture of a non-processed product.
High Pressures Processing History
HPP technology goes all the way back to the 17th century with a French scientist Blaise Pascal, who studied the effects of pressure on fluids. Throughout his work, he determined that applying more than 50,000 PSI for around 15 minutes would lead to the inactivation of yeast, mold, and bacteria.
Experiements using high pressure and their effects on microorganisms began in the late 1880s with a focus on milk where it was noted that the process had no effect on the taste of the product. The device used was damaged and the experiments were stopped due to concerns over the effectiveness of the process.
In the early 1900’s a report was published on the effects of pressure to sterizile food products such as fruits, fruit juices, and some vegetables. These test lead to the conclusion that bacterial spores were not killed by pressure but vegetative bacteria were usually killed.
60 years later, around 1970, researchers began to test the effects of pressure on bacterial spores and up until the 1980s, the effects of high pressure microorganisms focused mostly on deep-sea organisms.
Today, high pressure processing has been successful at creating a 5-log reduction in microogranisms that cause food borne illness in a wide range of food and beverage products such as: juices and beverages, meat and poultry, seafood, salsa and guacamole, fruits and vegetables, ready-to-eat meals, wet dalads and dips, and more! One of the first early adopters of the HPP technology was guacamole. The process does not change the products taste, texture, or color and can extend the shelf from approximately 3 days to 30 days.
Instead of the original PSI of 50,000, today’s HPP machines can deliver 87,000 PSI to the product and the hold time varies based on product and desired outcomes.
As determined in the early 1900’s high pressure does not kill bacteria spores so refrigeration of the product is required after undergoing high pressure processing.
How HPP Works
The HPP process begins by loading a vessel with product in its final, flexible, packaging. The vessel is then inserted into to HPP machine where cold water is pumped into the vessel creating isostatic (even) pressure on the product and its packaging. Once the pressure reaches the desired PSI the product is held at that pressure for a few minutes, pressure and hold times vary by product.
During the pressure hold time, pressure is transmitted uniformaly throughout the packaged food disrupting the microbial biochemistry which preserves freshness and increases shelf life.
After reaching the desired hold time, the pressure is released, the vessel is removed from the machine, and then product is dried, inspected, and any labels, extra packaging, or tagging of the product is completed.
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