Numerical Calculation of the Denaturation of Enzymes, Nutritional Proteins, and Occurrence of Browning Reaction in Bottled Milk under Cold Plasma Treatment

The aim of this work, was studying the effect of cold plasma treatment on enzymes and nutritional proteins denaturation, and ocurrance of browning reactions of bottled raw milk. A surface discharge plasma system was used for this purpose. The reactor of this system was a quartz cylinder with a diameter of 1 cm and a height of 25 cm. a steel cover with a thickness of 1 mm and height of 25 cm was used on the inner surface of the reactor and as a high voltage discharge electrode. The liquid inside the bottle (milk) was also considered as neutral electrode. The time of inactivation of catalase, alkaline phosphatase, lipase, peroxidase, and protease enzymes, bovine serum albumin, immunoglobulins, alpha lactalbumin, beta lactalbumin, lysine and thiamine were investigated. The simulation was performed by COMSOL a3.5 software for a two-dimensional geometry. The results showed the deactivation time of catalase, phosphatase, and lipase is highly low while the peroxidase and protease show the longest deactivation time. However the final deactivation time of all enzymes is highly low compared with thermal treatments. The peroxidase diactivated at 0.9 min and protease deactivated at 2 minutes after plasma treatment. The other enzyme deactivation time were 0.5 seconds. Also, the protein and amino acid denaturation time has a significant difference at p< 0.05. The inactivation time of lysine amino acid was shorter than other cases studies in this work, and beta-lactalbumin protein had the longest denaturation time. Also, the time of starting the browning reaction under plasma treatment was 3.4 minutes. It can be concluded that the studied cold plasma condition have no negative effect on proteins and color of milk.