Stability of Membrane‐Sterilized Bovine Immunoglobulins Aseptically Added to UHT Milk

Lyophilized immunoglobulin (IgG) of 56% purity isolated from Cheddar cheese whey was reconstituted with distilled water to a protein content of 60–70 mg/mL. The solution was membrane‐sterilized (0.2 μ.m) and aseptically injected into cartons of UHT milk. This method could be used for fortification of UHT products without denaturing IgG. Concentration of IgG remained constant in milk stored at 4, 25 and 35°C over 5 mo. However, when stored at 25 and 35°C, the milk thinned probably due to residual enzymes in the IgG solution. D values measured between 62 and 80°C for thermal destruction of IgG in UHT milk appeared to confirm shelf life results.