High-Temp-Short-Time (HTST) Pasteurization – Water or Steam-based, Continuous
Industry: Dairy Product Manufacturing (NAICS 3115) Meats (NAICS 3116)
NAICS 3116 Meats
Process Brief: The process of destroying microorganisms that could cause disease, usually done by applying heat to a food.
Energy source: Steam or hot water
Milk using a Plate Heat Exchanger
The continuous or high-temp-short-time pasteurization process treats the fluid milk using a plate heat exchanger. The heat exchanger unit consists of a stack of corrugated stainless steel plates that are clamed together. The continuous process shortens the heating of milk to 15 seconds at a minimum temperature requirement of about 72 degrees Celsius. In the continuous system, cold milk is poured from the storage tanks into a balance tank. It is then pumped into the regenerator section of the heat exchanger, where preheated milk flowing in a counter current direction is used to preheat the cold raw milk. The raw milk is then forced using a timing pump to the heater section of the system. Hot water on the opposite sides of the plate heats the milk to a required temperature of 72 degrees Celsius. The milk is held at this temperature for at least 15 seconds. The pasteurized milk is then passed through the regenerator section where it heats the incoming raw milk.
Other Solid Products using Surface Contact Steam
USDA researchers from the Eastern Regional Research Center (ERRC) are currently developing a variation on the traditional surface pasteurization method. Previously, killing bacteria on the surface of foods involved quickly heating the food to a high temperature to kill harmful bacteria. This process was effective in destroying food pathogens, but caused thermal damage and a loss of food quality characteristics such as tenderness in meats and color in fruits and vegetables.
The new method being developed for surface pasteurization of solid foods (poultry, meat, fruit, and vegetables), is called vacuum-steam vacuum (VSV) pasteurization and is as effective at destroying food pathogens while preserving food quality characteristics. VSV pasteurization shortens the amount of time that food is subjected to heat by removing a thin layer of air and moisture from the surface of foods, allowing the steam to make direct contact with the bacteria, thus reducing the amount of damage to the food surface.
The entire VSV process occurs in less than one second. The first step in the VSV process is the application of a vacuum to remove air and moisture from the surface of the food. In the second step, steam is applied for a short period of time to kill off pathogenic bacteria.
The final step includes the application of a vacuum to remove condensed steam and to cool the surface to prevent cooking of the food.
In 2001, the vacuum-steam vacuum process received a U.S. patent, but was tested only on poultry and meat products. Since
then, the process has been adapted to effectively treat the surface of citrus fruit (specifically lemons). The current focus is on adapting the process for foods, such as cantaloupes, hot dogs, and vegetables. In addition, researchers are developing the process for emergence into commercial practice.
Since pathogens usually contaminate the surface of solid foods, the VSV pasteurization process effectively kills pathogens
commonly responsible for food borne illness, such as Salmonella, Listeria monocytogenes, Campylobacter, and E. coli 0157:H7.
The kill success varies on the foods treated. Chicken, because of the pathogens associated with it, is the most difficult to make safe. Kills range from 90 - 97percent, whereas kills on lemons range from 90 to greater than 99.99 percent.
Carcass Cleaning - Steam Vacuuming
FMC FoodTech Chicago
200 East Randolph
Chicago, IL 60601
Web site: www.fmctechnologies.com
P.O. Box 5460
3528 Fredericksburg Rd.
San Antonio, TX 78201-0460
Web site: www.garroutte.com
9165 Rumsey Road
Columbia, MD 21045
Web site: www.niroinc.com
Source: Overview GRI-03/0075; Overview photo from http://www.niroinc.com/html/gea_liquid_processing/food_dairy_beverage.html 3/2007; Other Products Surface Pasteurizaiton FMC Graphics from http://www.fmctechnologies.com/upload/jsp-i_spec_final.pdf; Other Products Text from http://fsrio.nal.usda.gov/research/fsheets/fsheet11.pdf 3/2007;