Abstract
This review is focused on the application of surface and volume-sensitive acoustic methods for the detection of milk proteases such as trypsin and plasmin. While trypsin is an important protein of human milk, plasmin is a protease that plays an important role in the quality of bovine, sheep and goat milks. The increased activity of plasmin can cause an extensive cleavage of β-casein and, thus, affect the milk gelation and taste. The basic principles of surface-sensitive acoustic methods, as well as high-resolution ultrasonic spectroscopy (HR-US), are presented. The current state-of-the-art examples of the application of acoustic sensors for protease detection in real time are discussed. The application of the HR-US method for studying the kinetics of the enzyme reaction is demonstrated. The sensitivity of the acoustics biosensors and HR-US methods for protease detection are compared.
Highlights
Milk proteases are of high importance in the digestion of milk proteins, mostly caseins.Among them, the plasmin has a crucial role, because its activity has a substantial effect on the quality of milk and milk products
The sensitivity of the thickness shear mode (TSM) method is compared with those based on high-resolution ultrasonic spectroscopy (HR-Ultrasonic spectroscopy (US)) that are convenient for studying the kinetics of the cleavage of caseins and other milk proteins by proteases in a small volume of approx. 1 mL
It has been demonstrated that surface acoustic methods, such as quartz crystal microbalance (QCM), quartz crystal microbalance with dissipation (QCM-D), TSM and EMPAS, as well as high-resolution ultrasonic spectroscopy (HR-US), are effective tools for the detection of the activity of milk proteases
Summary
Milk proteases are of high importance in the digestion of milk proteins, mostly caseins. The concentration of plasmin in raw milk is in the range of 4–12 nM [2]; the methods of plasmin determination should have sensitivity in order of 1 nM It is important for analysis of the kinetics of casein cleavage by proteases and their time stability. Plasmin and the other protease, trypsin, present in human milk were detected by conventional methods, such as the Enzyme-linked Immunosorbent Assay (ELISA), which is currently the only one commercially available test kit for plasmin detection [4]. The sensitivity of the TSM method is compared with those based on high-resolution ultrasonic spectroscopy (HR-US) that are convenient for studying the kinetics of the cleavage of caseins and other milk proteins by proteases in a small volume of approx. We will explain the principles of detection of proteases activity in a volume using high-resolution ultrasonic spectroscopy (HR-US)
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