Thermally inactivated

The activation energy (E) associated with microbial death is larger than the thermal inactivation of chemical compounds in fermentation broths (see Table 24-4). Thus by sterthzing at high temperatures for short times (HTST), overcooking of nutrients is minimized. 

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. 

Edelson-Mammel, S. G. Buchanan, R. L. Thermal inactivation of Enterobacter sakazakii in rehydrated infant formula. J. Food. Prot. 2004, 67, 60-63. 

Solarization process increases soil temperatures up to levels lethal to many plant pathogens and pests and, therefore, direct thermal inactivation is the most important and normally expected mechanism. Some studies on the biochemical bases of sensitivity of organisms to high temperatures hypothesized that heat sensitivity is related to small differences in cell macromolecules, leading to a lethal increase of intra-molecular hydrogen, ionic, and disulfide bonds (Brock 1978). Sundarum (1986) suggested a reduced cell membrane function beyond an upper limit fluidity... 

Benson DM (1978) Thermal inactivation of Phytophthora cinnamomi for control of Fraser fir root rot. Phytopathology 68 1373-1376... 

Coelho L, Mitchell DJ, Chellemi DO (2000) Thermal inactivation of Phytophthora nicotianae. Phytopathology 90 1089-1097... 

Myers DF, Campbell RN, Greathead AS (1983) Thermal inactivation of Plasmodiophora brassi-cae Woron. and its attempted control by solarization in the Safinas Valley of California. Crop Prot 2 325-333... 

Stapleton JJ (1991) Physical effects of soil solarization-thermal inactivation of crop pests and pathogens and other soil changes caused by solarization. In DeVay JE, Stapleton JJ, Elmore... 

Cellulases can also be eliminated fiom a mixture with xylanases by selective thermal inactivation. Cellulases are more thermolabile than xylanases in tiie cdlulolytic systems of the fungus Y-94 (79), T. harzianum 20), and Tkermoascus aurantiacus (77), but not in the Trickoderma reesei system (Biely, P. and Vrsanska, M., Slovak Academy of Sciences, Bratislava, unpublished results). Since cellulase thoixud inactivation causes a significant loss of xylanase also, a more convenient way to eliminate cellulase activity is by selective chemical or biological inhibition or inactivation. There appear, however, to be no reports on the existence of natural inhibitors that would be specific for cellulases. Such inhibitors of amylases and pectinases are known to occur in plants (27). 

Turner, C. (2002). The thermal inactivation of E. coli in straw and pig manure. Bioresource Technol. 96,521-529. 

Klibanov, A.M. (1983) Stabilization of enzymes against thermal inactivation. Adv. Appl. Microbiol., 29, 1-28. 

Tomazic, S.J. and Khbanov, A.M. (1988) Mechanisms of irreversible thermal inactivation of Bacillus -amylases. J. Biol. Chem., 263, 3086-3091. 

Alkaline phosphomonoesterase (EC 3.1.3.1). The existence of a phosphatase in milk was first recognized in 1925. Subsequently characterized as an alkaline phosphatase, it became significant when it was shown that the time-temperature combinations required for the thermal inactivation of alkaline phosphatase were slightly more severe than those required to destroy Mycobacterium tuberculosis, then the target micro-organism for pasteurization. The enzyme is readily assayed, and a test procedure based on alkaline phosphatase inactivation was developed for routine quality control of milk pasteurization. Several major modifications of the test have been developed. The usual substrates are phenyl phosphate, p-nitrophenyl-phosphate or phenolphthalein phosphate which are hydrolysed to inorganic phosphate and phenol, p-nitrophenol or phenolphthalein, respectively ... 

Figure 9.12 Thermal inactivation of Ps. fluorescens AFT 36 proteinase on heating for 1 min in 0.1 M phosphate buffer, pH 6.6 (O) or in a synthetic milk salts buffer, pH 6 ( ) (from Stepaniak, Fox and Daly, 1982).

Additional information <2> (<2> Triton X-100, 0.02%, stabilizes markedly against thermal inactivation [3]) [3]... 

Apparent Temperature Optimum. A rise in temperature has a dual effect upon an enzyme-catalyzed reaction it increases the rate of the reaction, but it also increases the rate of thermal inactivation of the enzyme itself. Like the pH optimum, the temperature optimum may in certain instances be altered by environmental conditions, e.g., pH, type and strength of buffer, etc. The term temperature optimum, therefore, is useless unless the incubation time and other conditions are specified. A more enlightening term is apparent temperature optimum, which indicates that the optimum has been obtained under a... 

Saito, Z., Nakamura, S. and Igarashi, Y. 1970. Milk lipases. VII. Protective effect of substrate on the thermal inactivation of lipases. Dairy Sci. Abst. 32, 3081. 

Thunell, R. K., Duersch, J. W. and Ernstrom, C. A. 1979. Thermal inactivation of residual milk clotting enzymes in whey. J. Dairy Sci. 62, 373-377. 

In general, enzymes can be thermally inactivated by bringing the enzyme-containing solution to 95° to 100°C for 5 min. However, one should always verify that treatment results in complete inactivation (via a check for residual activity), since some enzymes are particularly heat stable. 

The thermal inactivation curve of the enzyme in 0.15 M acetate buffer-0.01 M ethylenediaminetetraacetate (EDTA), pH 5.0, showed that a 50% inactivation was obtained by heating for 20 min at 56° 11). 

Thermal inactivation. All activities were equally susceptible to inactivation by relatively mild heating (37, 41, 45). 

The effects of temperature both on the stability of the enzyme (26, 37, 41, 46) and on the catalytic reaction itself (46, 112) have been studied. The enzyme is considerably more labile to mild heating in the absence of substrates than is microsomal acid phosphatase (26, 37, 4U 46)-Glucose-6-P (26, 136), P, (26), glucose (136), PP, (119, 136), and various amino acids (136) protect to some degree against thermal inactivation as do certain metal chelators which inhibit the reaction (120). 

Detergents labilize the enzyme to thermal inactivation in the absence of substrates (26, 90), while activation by exposure of the enzyme to high pH does not (90). The enzyme appears stable to freezing for several months (137). 

L-Cysteine, o-tyrosine, and L-leucine inhibit and also stabilize enzyme against thermal inactivation. A variety of other amino acids are also effective to some degree in the latter respect... 

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