Canning and Fish Packaging Technology

4.6.2.2.F0 Value

Unit 4 - Thermal process for canned foods

4.6.2.2.F_O Value
It is the number of minutes required to destroy a specified number of organisms at 250_oF when Z =18.

F18250 =F_o or F10121.1 =F_o. Z value of 18_oF or 10C_o is assumed for Clostridium botulinum when TDT determinations have not been made for the product under consideration. F_o value is an unit of sterilization.

F_o value of 1 minute means, the sterilizing effect on the product which has been instantaneously heated to 121.1^oC and held for 1 min and instantaneously cooled. In other words, sum of all lethal effects of all time temperature combinations are converted the lethal effect at 121.1^oC, which equivalent 1 minute.

F_o value of Clostridium botulinum is 2.4 minutes. If the sterilizing value of thermal process in terms of F_o value is 2.4 min, it means the most feared organism i.e. Cl. botulinum is destroyed This thermal process is known as minimum botulinum cook which is essential for a low acid food can. While minimum botulinum cook indicates safety from botulinum food poisoning, in most cases, minimum, it is not sufficient to destroy spoilage organisms especially in low acid foods. A much higher process say F_o = 5 to 6 is required for fish cans to destroy the spoilage organisms. In canned corn, a highly heat resistant spoilage organism Bacillus stearothermophilus needs a thermal process equivalent to F_o value of more than 10 to be destroyed.