For example, phenolic antioxidants would be present here. Most proteins will be present in the so-called protein-interphase, but also components that fail to dissolve in any of the other two (polar and non-polar) phases, or have a density that would be intermediate between the densities of the polar and non-polar phases (i.e. hemin). Highly non-polar components (lipids), plus components derived through oxidation that are still not soluble in the polar phase, will remain in the non-polar phase. Transient stability of lipid peroxides has been reported numerous times (Reeder and Wilson, 2001 and Takahashia et al., 2001). Here we also report that protein-bound
peroxides LY2835219 manufacturer are transient, having a maximum value at 2–4 h from being subjected to oxygen. Since these samples
were fresh meat kept at −80 °C under vacuum, we have to consider the sample as being kept anaerobic until incubated with access to oxygen at 37 °C. Addition of extra lipids as liposomes did not affect the transient nature of the peroxides. It should be pointed out that, with extended incubation time, the protein became more difficult to resolubilise, in agreement with the fact that protein crosslinking becomes likely when the peroxides decline (Gay & Gebicki, 2002b). When proteins crosslink, meat becomes tougher and the activities of proteases are reduced. Both processes will be negative for meat quality. Incubations at lower pH gave consistently lower hydroperoxide values. The effect was largest on the protein-bound peroxides. Both the kinetics of formation and the stability of peroxides may
Gemcitabine purchase change with lower pH (Gay and Gebicki, 2002b and Reeder and Wilson, 2001). Hemin-catalysed peroxidation is expected to provide more peroxides with lower pH (Gao, Song, Li, & Gao, 2009). The fact that this was not observed here may be due to the fact that the peroxide value had started to decline before 2 h had passed at the lower pH values. The pH effect was also smaller when compared with the effect of incubation time from 1 to 24 h. Addition of liposomes to meat systems is interesting else because the liposomes can mimic cell membranes. The fact that protein-bound peroxides increased the most upon liposome addition, may suggest that the added phospholipids interacted with the liposomes. Similar interactions have been reported and ascribed to electrostatic and hydrophobic interactions (Alipour, Suntres, Halwani, Azghani, & Omri, 2009). It is possible that the effect of multiple washings was partly due to peroxides in the liposomes that were removed, along with other components. However, the effect of washing was nevertheless small and even 10 washes with their removal of peroxides would only explain 1/3 of the increase in protein-bound peroxides upon incubation with liposomes. Five groups of meat homogenates were incubated for 2 h, with or without liposomes.