Table 2.

Comparison of the sensitivity of acoustics biosensors and high-resolution ultrasonic spectroscopy (HR-US) methods for milk protease detection. QCM: quartz crystal microbalance and EMPAS: electromagnetic piezoelectric sensors.

Acoustic Method	Detection Phase	Substrate	Limit of Detection	Time of Detection	Reference
QCM	surface	Short peptides at gold surface	0.65 nM Plasmin	30 min	[63]
QCM	surface	β-casein at gold substrate	0.1 nM Trypsin 1 nM Plasmin	30 min	[62]
EMPAS	surface	β-casein at gold substrate	0.032 nM Plasmin	30 min	[64]
HR-US	volume	0.1–1% (w/w) β-casein in buffer	0.2 nM Trypsin	15–30 min	[104]
HR-US	volume	0.1–1% (w/w) β-casein in buffer	0.2 nM Plasmin	15–30 min	[120]