AprX is a protease produced by psychrotropic bacteria, such as Pseudomonas fluorescens. Ultra heat treatment (UHT) processes kill the bacteria but some AprX protease remains. The residual AprX can digest milk proteins and cause UHT milk to spoil before its use-by-date. PPB Technology can measure AprX activity at levels of concern in raw and processed milk.
Plasmin is a protease endogenous to cow milk. The health and age of cows affects the amount of plasmin in milk. Not all plasmin is removed during UHT processing and, like AprX, the remaining plasmin may spoil UHT products before their use-by-dates. PPB Technology has an assay to measure plasmin activity in raw and processed milk.
Plasminogen is the (zymogen) precursor to plasmin. Plasminogen is produced by the cow and can be converted into plasmin, which damages milk proteins as described above. The plasmin test measures the current level of active plasmin in milk, but not the potential for plasminogen to convert to plasmin over time. PPB Technology can measure the total plasminogen in milk as well as the active plasmin. This may help predict future shelf-life problems.
Thermoduric bacteria form spores under the heating and drying conditions used to make powdered milk. When powdered milk is reconstituted, the spores may germinate and secrete aggressive proteases that degrade milk quality. PPB Technology is developing a test for proteases produced by thermoduric Bacillus spp. If you would like to be involved in pre-commercial trials of a Bacillus protease assay, please contact PPB Technology in confidence.
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