<P> The Codex Alimentarius Code of Hygienic Practice for Milk notes that milk pasteurization is designed to achieve at least a 5 log reduction of Coxiella burnetii . The Code also notes that: "The minimum pasteurization conditions are those having bactericidal effects equivalent to heating every particle of the milk to 72 ° C for 15 seconds (continuous flow pasteurization) or 63 ° C for 30 minutes (batch pasteurization)" and that "To ensure that each particle is sufficiently heated, the milk flow in heat exchangers should be turbulent, i.e . the Reynolds number should be sufficiently high ." The point about turbulent flow is important because simplistic laboratory studies of heat inactivation that use test tubes, without flow, will have less bacterial inactivation than larger scale experiments that seek to replicate conditions of commercial pasteurization . </P> <P> As a precaution, modern HTST pasteurization processes must be designed with flow - rate restriction as well as divert valves which ensure that the milk is heated evenly, and no part of the milk is subject to a shorter time or a lower temperature . It is common for the temperatures to exceed 72 ° C by 1.5 ° C or 2 ° C . </P> <P> According to a systematic review and meta - analysis, it was found that pasteurization appeared to qualitatively reduce concentrations of vitamins B12 and E, but it did increase concentrations of vitamin A. Apart from meta - analysis, it's not possible to conclude the effect of pasteurization on vitamins A, B12, and E based merely on consultation of the vast literature avalaible . </P> <P> Milk is not an important source of vitamins B12 or E in the North American diet, so the effects of pasteurization on the adult daily intake of these vitamins is negligible . However, milk is considered an important source of vitamin A, and because pasteurization appears to increase vitamin A concentrations in milk, the effect of milk heat treatment on this vitamin is a not a major public health concern . Results of meta - analyses revealed that pasteurization of milk leads to a significant decrease in vitamin C and folate, but milk also is not an important source of these vitamins . However, a significant decrease in vitamin B2 concentrations was found after pasteurization . Vitamin B2 is typically found in bovine milk at concentrations of 1.83 mg / liter . Because the recommended daily intake for adults is 1.1 mg / day, milk consumption greatly contributes to the recommended daily intake of this vitamin . With the exception of B2, pasteurization does not appear to be a concern in diminishing the nutritive value of milk because milk is often not a primary source of these studied vitamins in the North American diet . </P>

Who discovered that microbes make food go off