Table 2. Some highlights of the effects of different processing technologies on the activities of endogenous enzymes

Processing technologies	Proteolytic system	Effect on endogenous proteases	References
High pressure processing	Lysosomal proteases	- Releases and increases the activities of lysosomal proteases	- Jung et al. (2000), Kubo et al. (2002)
		- Increased cathepsin D activities observed in pressure treated (520 MPa, 10°C for 260 s) 2 d post-rigor bovine (Biceps femoris and Longissimus dorsi) muscles throughout storage at 4°C for up to 20 d post-mortem	- Jung et al. (2000)
		- Pressure induced higher endogenous proteolytic activity due to the release of enzymes from lysosomes (between 100–200 MPa), denaturation of muscle proteins and enhanced susceptibility of these proteins to proteolysis	- Ohmori et al. (1991)
	Calpains	- Activates calpains under moderate pressure and with the release of calcium ions from the sarcoplasmic reticulum	- Bessiere et al. (1999), Homma et al. (1996)
Pulsed electric field	Lysosomal proteases	- Releases lysosomal proteases from lysosome	- Faridnia et al. (2015)
	Calpains	- Releases calcium ions which activates μ-calpain	- Alahakoon et al. (2016)
		- Promotes the autolysis of calpains which enhances the proteolysis during aging	- Bhat et al. (2018c), Bhat et al. (2019)
Shockwave processing	Cathepsins	- No improvement in the cathepsin and peptidase activities	- Bolumar et al. (2014)
Ultrasound processing	Calpains	- Releases calcium ions, which activate μ-calpain	- Alarcon-Rojo et al. (2015), Roncalés et al. (1993)
		- Increases calpains autolysis and enhance proteolysis during maturation	- Roncalés et al. (1993), Wang et al. (2018)
	Cathepsins	- Releases cathepsin from lysosomes	- Roncalés et al. (1993)
Thermal processing (Sous vide cooking)	Cathepsins	- Mild heating promotes the activity of cathepsins by rupturing of lysosomes	- Dominguez-Hernandez et al. (2018), Ertbjerg et al. (2012)
		- Cathepsins B+L are most active when being held at 55°C, remain active at 63°C for 19.5 h	- Christensen et al. (2013), Ertbjerg et al. (2012), Wang et al. (2013)
		- Cathepsin H has highest activity at 20°C and lost most of its activity at temperatures above 40°C	- Wang et al. (2013)
		- Cathepsin B+L activity increased at 50°C after one hour of cooking	- Kaur et al. (2020)
	Calpains	- Calpains starts to be inactivated from 55°C and there was no extractable activity at 60°C	- Ertbjerg et al. (2012), Wang et al. (2013)
Electrical stimulation	Calpains	- Early activation of calpains which accelerate muscle proteolysis	- Abbasvali et al. (2012), Ferguson et al. (2000), Lee et al. (2000), Li et al. (2012), Pouliot et al. (2014), Uytterhaegen et al. (1992)
	Lysosomal proteases	- Increases the activity of lysosomal enzymes such as β-glucuronidase, cathepsin C and cathepsin B+L & cathepsin D, in most of the cases	- Dutson et al. (1980), Li et al. (2012), Pommier et al. (1987)