The effect of heat treatment on γ-glutamyl transferase activity in non-bovine and bovine milk – A comparative kinetic and thermodynamic investigation

Cow's milk with active immunoglobulins againstCampylobacter jejuni: Effects of temperature on immunoglobulin activity

“…However, an analysis of different Igs has not been done in this research. Under normal pasteurisation temperature–time conditions (72°C for 15 s or 63°C for 30 min), previous works showed that Ig activity loss was less than 10%, similar to the results presented in Fig. .…”

“…Values of Z were 5.93°C for this work; 34.7°C for Wehbi et al ; 26.6°C for Dumistrascu et al ; and 6–7°C for Li‐Chan et al (where Z is the logarithmic reduction temperature, in °C).…”

“…It is interesting to see that there is an important difference between activity losses at long treatment times when the temperature is increased from 70 to 72°C. This behaviour has also been observed (at different temperatures) in the case of enzyme deactivation . Authors that have studied the effect of temperature on the stability of Igs in colostrums and milk concluded that the degree of denaturation depends on the type of Ig, as IgA is less resistant to heat treatment, while IgG (the most common Ig in humans and cows) and IgM are partially denatured when treated at 88°C for 15 min .…”

“…Values were obtained in different media, as follows: Li‐Chan et al , in milk; Wehbi et al , α ‐lactalbumin (determination by radial immunodiffusion); Domínguez et al , immunoglobulin in colostrum (ELISA method); Dumistrascu et al , buffalo milk (mean values of immunoglobulin M and immunoglobulin G); Mainer et al , in milk; Domínguez et al , in PBS; Mainer et al , in colostrum; Fukumoto et al , milk + immunoglobulins; and Chen et al , in PBS.…”

“…The kinetic, thermodynamic parameters, the decimal reduction time, D (in seconds) and the logarithmic reduction temperature, Z (in °C) were calculated using the same methodology used by previous authors . The inactivation process for Ig can be described by the general equation: …”