Oxidases thermal inactivation

RODRIGUEZ LOPEZ J, FENOLL L G, TUDELA J, DEVECE C, SANCHEZ HERNANDEZ D, DE LOS REYES E and GARCIA CANOVAS F (1999) Thermal inactivation of mushroom polyphenol oxidase employing 2450 MHz microwave radiation , J Agric Food Chem, 47 (8) 3028-35. 

If enzyme inactivation is not due to covalent changes in structure, the native active structure can be reformed in immobilized enzymes by refolding from a random coil state (22,27). In fact, if they are attached to the matrix by multiple points, even thermally inactivated multichain enzymes can be reactivated (27). Although such regeneration steps apparently have not been used commercially, their use should be considered in certain cases, especially since in many cases the inactivation may result from adsorption onto the enzyme matrix of components in the process stream. For example, we have found that immobilized sulfhydryl oxidase activity can be regenerated numerous times following treatment of UHT milk by washing with 4 M urea (28). 

Tan, T.-C., Cheng, L.-H., Bhat, R., Rusul, G., Easa, A. M. (2014). Composition, physicochemical properties and thermal inactivation kinetics of polyphenol oxidase and peroxidase from coconut (Cocos nucifera) water obtained from immature, mature and overly-mature coconut. Food Chemistry, 142(0), 121-128. doi http //dx.doi.org/10.1016/ j.foodchem.2013.07.040... 

Fig. 2.37. Thermal inactivation of enzymes of milk, 1 Lipase (inactivation extent, 90%), 2 alkaline phosphatase (90%), 3 catalase (80%), 4 xanthine oxidase (90%), 5 peroxidase (90%), and 6 acid phosphatase...

Substrates, FAD, substrate competitors (n-leucine and benzoate), and the FAD competitors (AMP), all protect the oxidase against thermal inactivation. According to Burton 58), the site of protection by benzoate or AMP is the same as the site of inhibition. 

Van Den Broeck, I., and Hendrickx, M.E. (1998) Effect of pH on pressure and thermal inactivation of avocado polyphenol oxidase a kinetic study. Journal of Agricultural and Food Chemistry, 46, 2785-2792. 

Terefe, N.S., Yang, Y.H., Knoerzer, K., Buckow, R., and Versteeg, C. (2009) High pressure and thermal inactivation kinetics of polyphenol oxidase and peroxidase in strawberry puree. Innovative Food Science and Emerging Technologies, 11, 52-60. 

Cichoric acid is believed to contribute to the immunostimulatory activity, but the compound tends to decompose through enzymatic degradation during extractions (Bauer, 1997) thus, the variability in cichoric acid levels found by many researchers may be due to the extraction methodology and not to the plant species or origin. Bauer (1999b) evaluated the cichoric acid content of six commercially available expressed juice preparations of E. purpurea. The thermally treated preparations had higher cichoric acid than ethanol-preserved preparations. The inactivation of polyphenol oxidase by heat may account for the difference found between heated and nonheated preparations. 

Recently, Willoughby and Spector have broadened the hypothesis by showing that the vascular response to injury depends also on the inactivation of noradrenaline, DOPA and dopamine, and that inhibitors of DOPA decarboxylase or dopamine j8-oxidase reduce vascular permeability in thermal burns in the rat. 

Rapeanu, G., Van Loey, A., Smout, C., and Hendrickx, M. (2005) Thermal and high-pressure inactivation kinetics of polyphenol oxidase in Victoria grape must. Journal of Agricultural and Food Chemistry, 53, 2988-2994. 

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