Destabilization and off-flavors generated by Pseudomonas proteases during or after UHT-processing of milk

Background: Pseudomonads play a major role in the spoilage of UHT processed dairy products, due to their growth-related protease production in raw milk. Results: To assess the off-flavor generating capacity of these AprX proteases in milk after UHT-processing, six major milk spoiling Pseudomonas groups were investigated. Sensory evaluation of the different processed milk samples showed large differences in the degree of proteolysis related to onset of off-flavors. Nevertheless, it was illustrated that P. fragi has the greatest spoilage potential within the tested Pseudomonas groups, when it comes to generating off-flavors. Conclusions: No clear correlation could be obtained between protein hydrolysis and the presence of off-flavors in UHT milk.