Potential application of non-thermal atmospheric plasma in reducing the activity of Pseudomonas-secreted proteases in milk

Abstract

Application of non-thermal atmospheric plasma was examined against the activity of Pseudomonas-secreted proteases in milk. UHT milk samples were inoculated with crude extract of Pseudomonas-secreted proteases and treated in atmospheric plasma discharge system. Evaluation of the progress in protein hydrolysis of plasma-treated and non-treated milk samples revealed that the degree of hydrolysis was lower in plasma-treated milk samples. The longer the plasma treatment time, the lower the degree of hydrolysis during storage. Furthermore, plasma-induced changes in milk proteins and volatile compounds were also evaluated. Caseins, whey proteins, aldehydes, ketones, free fatty acids and hydrocarbons were all affected by plasma discharge. The amount of increase or decrease in these components was dependent on the duration of plasma treatment. Overall, this method is a promising approach that could be used to inactivate bacterial hydrolytic enzymes in milk.