Log Reduction Value

The efficiency of the filter is evaluated in terms of the titer reduction or log reduction value (LRV). The titer reduction is the ratio of the number of microorganisms in the input suspension to the number of organisms in the effluent. Similarly, the LRV is the log Q of this ratio. The ratio of the difference between the numbers of challenge microorganisms recovered upstream and downstream of the test filter to the average total challenge received by the filter... 

Complementary to the passage, one can also consider the retention of a component as R = 1 - S (also called rejection). Retention can also be either an observed or an intrinsic measurement. Retention is useful in considering retained products during concentration mode operation. Other component separation characterizations include the log reduction value LRV =- logS which is used to characterize high-efficiency separations with permeate products (sterilization). The beta ratio P = I/S is sometimes used in NFF for clarification applications. 

The equation used for determining the microbial log reduction value is derived as follows ... 

The minimum F value is based only on microbial spore destruction. It is believed that F0 = 12 min is a realistic minimum value, since most mesophilic spore-forming micro-organisms have D values <0.5 min at 121°C. Even if Dm = 1.0 min, the spore log reduction value according to Eq. (10) would be 12. ... 

In the past, several terms have been coined to describe the retention efficiency of the filter system beta value, microbiological safety index, reduction ratio, and titer reduction ratio [64,68,72], The log reduction value (LRV) is a filter retention efficiency term that is the logarithm to the base of 10 of the ratio of the number of organisms in the challenge suspension to the number of organisms in the filtrate. 

LRV = log reduction value No = number of organisms in the challenge N = number of organisms in the filtrate ... 

The performance of membranes in bacterial challenge tests is often quantified by a log reduction value (LRV), defined as... 

Dry heat sterilization is used to depyrogenate glassware and other heat-stable mateiials. Temperatures in the range of 250°-325°C rapidly inactivate endotoxin by thermal incineration. The size and mass of a load influence the time required to reach equilibrium within the oven therefore, empirical data are required to verify that desired conditions were achieved. Overkill cycles in the range of 4-6 log reduction values (LRV) are common. A heat exposure of 250°C for at least 30 min provides greater than a 3 log reduction. 

The finer the particles in a mixture the more difficult it is to obtain an appreciable difference in the rates at which they permeate a membrane. Thus, separation of bacteria from a suspension is routinely achieved with log reduction values (LRVs) ... 

The required log reduction values of the antimicrobial soap intended for general consumer use are hotly debated. It is this author s opinion that the reduction values should be at least 1 logio from the baseline value after wash 1 and... 

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